River Adur Catchment Flood Management Plan

September 2008

Environment Agency i River Adur Catchment Flood Management Plan (September 2008)

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Environment Agency ii River Adur Catchment Flood Management Plan (September 2008) Foreword

I am pleased to be able to introduce the River Adur Catchment Flood Management Plan.

Past flood events remind us of the hardship that flooding can cause, especially in the built environment. They also reveal the challenges we face when confronted by the forces of nature. Our aim is to reduce the risk to people, property and the environment. We do this by taking action to manage and reduce the likelihood and consequences of flooding. This is known as ‘flood risk management’.

This plan will allow us to understand and describe how the catchment behaves and what the most sustainable flood risk management policies may be over the next 50 to 100 years. We can then use this direction to plan the most acceptable measures to manage flood risk for the long term.

We will use the Catchment Flood Management Plan to guide our future investment in flood risk management. We hope that our public and private partners will find it useful in their decision making, especially where it can guide the planning of land use.

I look forward to working with you so that we target our efforts and precious resources in a better way.

James Humphrys Solent and South Downs Area Manager

Environment Agency iii River Adur Catchment Flood Management Plan (September 2008) Contents Foreword ...... iii Contents ...... iv List of tables...... vi List of figures ...... viii 1 Introduction...... 1 1.1 Background...... 1 1.2 Aims and scope ...... 2 1.3 Policies ...... 3 1.4 Links with other plans ...... 4 1.5 Involving others ...... 9 2 Catchment overview ...... 12 2.1 Definition and extent of the Adur catchment ...... 12 2.2 Topography...... 14 2.3 Geology and hydrogeology...... 16 2.4 Geomorphology ...... 18 2.5 Soils ...... 19 2.6 Land use and land management...... 20 2.7 Hydrology...... 28 2.8 Natural and Historic Environment...... 31 2.9 Communities and the local economy ...... 44 3 Current flood risks and management ...... 49 3.1 History of flooding...... 49 3.2 Sources and probability of flooding ...... 51 3.3 Consequences of flooding ...... 64 3.4 Summary of flood risk...... 77 3.5 Existing flood risk management...... 80 4 Future flood risk ...... 90 4.1 Introduction ...... 90 4.2 Future scenarios...... 94 4.3 Assessment of future flood risk ...... 95 4.4 Summary of Flood risk at key locations...... 105 5 Catchment objectives ...... 109 5.1 Introduction ...... 109 5.2 Catchment opportunities and constraints ...... 109 5.3 CFMP objectives ...... 111 6 Policy appraisal ...... 122 6.1 Introduction ...... 122 6.2 Policies for the River Adur catchment ...... 138

Environment Agency iv River Adur Catchment Flood Management Plan (September 2008) 7 Delivering the CFMP ...... 162 7.1 Action Plan...... 162 7.2 Consequences of our policies ...... 188 7.3 Monitoring, review and evaluation...... 189

Glossary of terms...... 191 List of abbreviations ...... 208 References...... 212

Environment Agency v River Adur Catchment Flood Management Plan (September 2008) List of tables

Table 1.1 - Summary of consultation during the development of the CFMP ...... 10 Table 2.1 - Adur CFMP catchment overview...... 14 Table 2.2 - Future housing figures...... 27 Table 2.3 - Development plan proposals...... 27 Table 2.4 - Summary of SSSIs ...... 34 Table 2.5 - Landscape character summary...... 35 Table 2.6 Main species rich habitat groups...... 37 Table 2.7 - Freshwater Fish Directive designated reaches...... 39 Table 2.8 - Water quality baseline data...... 41 Table 2.9 - Population size data ...... 46 Table 3.1 - Selected historic flood events ...... 49 Table 3.2 - Flood sources and risk summary ...... 62 Table 3.3 - Communities currently at risk from river flooding...... 65 Table 3.4 - Social vulnerability of properties affected by the 1% annual probability flood event ...... 66 Table 3.5 - Social vulnerability of areas affected by other sources of flooding ...... 66 Table 3.6 - Population currently at risk from river flooding...... 67 Table 3.7 - Summary of depths of flooding during the 1% annual probability flood event...... 67 Table 3.8 - Number of properties at risk from other sources of flooding...... 68 Table 3.9 - Summary of flood sources and locations at risk in the River Adur CFMP area...... 69 Table 3.10 - Baseline flood damages...... 71 Table 3.11 - Properties and infrastructure currently at risk of flooding...... 73 Table 3.12 - Area of designated sites currently at risk of flooding ...... 74 Table 3.13 - Environmentally designated sites affected by the 1% annual probability flood event ...... 74 Table 3.14 – Historic Environment sites affected by the 1% annual probability flood event...... 75 Table 3.15 - Vulnerable features of the historic environment...... 76 Table 3.16 - Summary of flood risk for key communities ...... 77 Table 3.17 - Typical annual maintenance activity ...... 83 Table 3.18 - Major flood alleviation schemes ...... 84 Table 3.19 - Flood alleviation measures around Brighton and Hove ...... 86 Table 3.20 - Fluvial flood warning areas ...... 88 Table 4.1 - Changes in flood damages for the urban development analysis (1% annual probability fluvial event)...... 91 Table 4.2 - Changes in flood damages in 50 years time for the climate change analysis (1% annual probability fluvial events) ...... 92 Table 4.3 - Changes in flood damages in 100 years time for the climate change analysis (1% annual probability fluvial events) ...... 93 Table 4.4 - Main impacts of future flood risk ...... 95

Environment Agency vi River Adur Catchment Flood Management Plan (September 2008) Table 4.5 - Residential properties potentially at risk from flooding in the future ...... 96 Table 4.6 - Social vulnerability of people affected by the 1% annual probability flood event ...... 97 Table 4.7 - Population potentially at risk from flooding in the future ...... 97 Table 4.8 - Summary of depths of flooding during the 1% annual probability flood event 100 years in the future ...... 98 Table 4.9 - Number of properties at risk of other sources of flooding ...... 99 Table 4.10 - Estimated flood damages for the future scenario ...... 100 Table 4.11 - Properties and infrastructure at risk of flooding in the future ...... 103 Table 4.12 - Area of designated sites at risk of flooding the future ...... 104 Table 4.13 - Environmentally designated sites affected by the 1% annual probability flood event ...... 104 Table 4.14 – Historic Environment sites affected by the 1% annual probability flood event...... 105 Table 4.15 - Summary of future flood risk for key communities ...... 106 Table 5.1 - Catchment objectives, opportunities and constraints...... 113 Table 5.2 - Policy appraisal objectives, targets and indicators ...... 118 Table 6.1 - Flood risk management policies...... 124 Table 6.2 - Policy appraisal forms ...... 124 Table 6.3 - Generic responses ...... 125 Table 6.4 - Policy unit justification ...... 139 Table 7.1 - Summary table of action plan...... 163 Table 7.2 - Summary of CFMP policy consequences ...... 188

Environment Agency vii River Adur Catchment Flood Management Plan (September 2008) List of figures

Figure 1.1 - Catchment location ...... 2 Figure 1.2 - Context of CFMP within wider planning framework ...... 5 Figure 2.1 - Main features in the Adur CFMP catchment...... 13 Figure 2.2 - Catchment topography...... 15 Figure 2.3 - Channel slope of the River Adur (Main River only)...... 16 Figure 2.4 - Geology summary of the Adur CFMP catchment ...... 17 Figure 2.5 - Soil types in the Adur CFMP catchment ...... 19 Figure 2.6 - SPARQ land cover classification ...... 21 Figure 2.7 - Proportion of SPARQ land cover types...... 22 Figure 2.8 - Agricultural land classification...... 23 Figure 2.9 - Proportion of land under each ALC grade ...... 24 Figure 2.10 - Location of main urban areas, towns and villages...... 26 Figure 2.11 - Main watercourses in the River Adur CFMP catchment ...... 29 Figure 2.12 - Hydrographs for the River Adur (1% annual probability fluvial flood event) ...... 30 Figure 2.13 - Landscape designations ...... 32 Figure 2.14 - Environmentally designated sites ...... 33 Figure 2.15 - Landscape character areas ...... 36 Figure 2.16 - Main species rich habitat groups ...... 38 Figure 2.17 - Location of scheduled monuments ...... 43 Figure 2.18 - Administrative areas within the River Adur CFMP area...... 45 Figure 2.19 - Social vulnerability of the Adur CFMP area ...... 48 Figure 3.1 - Flood outline for the 0.1% annual probability flood event...... 52 Figure 3.2 - Flood outlines: 10%, 1% and 0.1% annual probability flood events (Adur East Branch) ...... 54 Figure 3.3 - Flood outlines: 10%, 1% and 0.1% annual probability flood events (Adur West Branch) ..... 55 Figure 3.4 - Flood outlines: 10%, 1% and 0.1% annual probability flood events (Lower Adur) ...... 56 Figure 3.5 - Flood outlines: 10%, 1% and 0.1% annual probability flood events (Ferring Rife)...... 57 Figure 3.6 - Flood outlines: 1% and 0.1% annual probability flood events (Teville Stream)...... 58 Figure 3.7 - Flood depths for the 1% annual probability flood event...... 59 Figure 3.8 - Surface water flooding in Findon ...... 61 Figure 3.9 - Flood damages for the 1% annual probability fluvial flood event ...... 72 Figure 3.10 - Raised defences relevant to the CFMP ...... 82 Figure 3.11 - Fluvial flood warning areas ...... 87 Figure 4.1 - Change in the 1% annual probability flood damages under future scenarios ...... 101 Figure 4.2 - Distribution of flood damages for the 1% annual probability flood event under the future scenario in 2106 ...... 102 Figure 6.1 - Location of policy units...... 123 Figure 6.2 - Policy units and selected policies ...... 138

Environment Agency viii River Adur Catchment Flood Management Plan (September 2008) Executive summary

Welcome to the River Adur Catchment Flood Management Plan (CFMP). This document gives an overview of the flood risk in the River Adur catchment and sets out our preferred plan for sustainable flood risk management over the next 50 to 100 years.

This is a summary of the River Adur Catchment Flood Management Plan. Using a Catchment Flood Management Plan (CFMP) we, the Environment Agency, will work with our partners and members of the public to agree how we will manage flood risk in the future. The overall aspirational aims of the CFMP are to improve the well being of people living in and visiting the area, and to protect and enhance the environment through appropriate and sustainable flood risk management. Policies and guidance in this plan will help us to decide how best to manage the risk of flooding in our catchments. Climate change, rises in sea level, urban development, and land management will all have a major influence on these decisions.

We hope to use this document to make sure that policies and plans that affect land use planning, rural development, agriculture, transport, recreation, nature conservation, landscape character and the historic environment in our catchments take into account flood risk management. We want public authorities to work together better and to work with local communities to look at the effects of future changes on flood risk. We will continue to promote sensible and sustainable development that works with nature and the assets that are of value and importance to the area. Working together in this way, Our Our Vision we will help to reduce the effects of flooding on our communities, the economy and our environment as well as reducing the chance of flooding due to climate change in the future.

It is vital that all our partners and the community support our policies. So far, we have received wide ranging and informative contributions from many different groups and individuals. We hope that interest and support for this plan will continue.

The rivers that make up this Catchment Flood Management Plan are the River Adur and its tributaries, the Ferring Rife, and the Teville Stream. The catchments of these streams and rivers stretch from the coast to the High Weald in the north and from Rottingdean in the east to Littlehampton in the west. The catchments lie in the counties of West Sussex and East Sussex. Catchments are the areas of land that drain into a particular river or stream and rivers are naturally at the heart of these areas. A number of our historic county and district boundaries follow these rivers and their catchment boundaries (usually marked by the highest hills in an area) and many of our homes and businesses have a close relationship with these features.

Flow characteristics of the rivers change with different topography and geology. There are significant groundwater components in the headwaters and narrow valleys of the chalk escarpment. Where geology and soils are impermeable there are denser river networks, broad valleys and active floodplains. The tidal influence has a major bearing on the character of the lower parts of the River Adur and extends to Bines Green on the Adur West Branch and to Shermanbury on the Adur East Branch.

Landscape is varied from the flat coastal plain, the distinctive steep scarp slopes of the South Downs and the gently rolling hills of the Low Weald. Much of this countryside is recognised for

Environment Agency ix River Adur Catchment Flood Management Plan (September 2008) its environmental and cultural value, with the South Downs being an Environmentally Sensitive Area (ESA) as well as a proposed National Park. There are also many valuable natural habitats in the area, often related to rivers or wetlands.

The majority of the CFMP area is covered by arable land and managed grassland. The coastal areas are more urban and several important urban centres are concentrated within the coastal plain to the south. The distribution of land use is reflected in the flooding mechanisms and distribution of flood risk across the study area.

The area is home to around 550,000 people. These communities include Brighton and Hove, Worthing, and Shoreham, with smaller towns at the base of the South Downs, such as Upper Beeding, Bramber, and Steyning. The north east of the CFMP area includes the urban area of Burgess Hill and smaller towns of Henfield and Hassocks along the edge of the north-facing scarp slope of the South Downs. These towns, as well as many smaller towns and villages, contribute to the regional economy and are focal points for many of the visitors to the region every year. The character and the services provided through these centres, as well as the surrounding countryside, are vital to the future prosperity of the area. Effective and appropriate flood risk management will form an integral part of preserving and improving the social, economic and environmental assets of the area.

The River Adur catchment experiences flooding from rivers, groundwater, sewers, and surface water runoff. Flooding can also occur from the sea but this is dealt with in Shoreline Management Plans (SMP). The CFMP is closely linked to the Beachy Head to Selsey Bill SMP. There are a number of places where local flooding from rivers is a problem, and this is made worse by the influence of the tide, which can add considerably to already high water levels in rivers and streams. Surface water flooding is also a problem, particularly in places like Burgess Hill and Hassocks where it can be caused by under capacity or blockages in the urban drainage network. Surface water runoff from the South Downs has caused flooding in Worthing, Brighton and Hove, and is often referred to as ‘muddy flooding’ due to the quantity of soil washed into the urban area. Occasional blockages can also occur in other urban areas within the CFMP area, resulting in unexpected localised flooding of roads and property.

Groundwater flooding also occurs in the catchment and affects urban areas including Brighton and Hove, Worthing, and Lancing. Previous groundwater flood events have resulted in numerous properties being flooded and the closure of major transport routes.

Table 1 shows the estimated number of people at risk from fluvial flooding for the 10%, 1% and 0.1% annual probability fluvial flood events. The population at risk has been inferred from the number of residential properties at risk using the assumption that each household contains an average of 2.39 occupants, based on the regional average for the South East (National statistics census data 2001). Table 1 also includes estimates of the number of people at risk from surface water and groundwater flooding, based on records of historic flooding incidents.

There is limited information available for the Teville Stream, and as such the current and future flood risk in the area is uncertain. It is likely that there are a greater number of people at risk from fluvial flooding in Sompting and East Worthing area than indicated in Table 1. More detailed study of the Teville Stream is required to improve understanding of the watercourse and flood risk.

Environment Agency x River Adur Catchment Flood Management Plan (September 2008) Table 1 – Number of people currently at risk of flooding in the River Adur CFMP area Communities currently at risk in the River Adur CFMP area Number of people Number of currently at risk from people CFMP area Key fluvial flooding currently Source of flooding sub-division communities at risk 10% 1% 0.1% from other sources • Fluvial • Surface Water Burgess Hill, Less than • 5 29 1,288 Adur East Hassocks Under capacity and 48 Branch blocked drainage systems. Less than Wivlesfield • Surface Water 0 0 0 24 Adur West Isolated • Fluvial 0 0 36 Unknown Branch properties • Fluvial People at Steyning, • Surface Water risk – Bramber, Upper • 7 217 246 Under capacity and number Beeding blocked drainage unknown Lower Adur systems • Fluvial People at Shoreham and • Surface Water risk – 0 2 822 Lancing • Tidally influenced river number flooding unknown Brighton and • Surface Water More than 0 0 0 Hove • Groundwater 50 Ferring, Ferring Rife • Fluvial Durrington, More than and Teville • Surface Water 5 124 1,200 Sompting, East 2 Stream** • Worthing Groundwater More than TOTAL - 17 372 3592 120 Note: Number of residential properties x 2.39 occupants (based on Table 3.3) Source: National statistics census data 2001 **Information uncertain due to insufficient data to model Teville Stream

Capital schemes and maintenance costs in the CFMP area are focused largely on coastal and tidal defences. However, there has been considerable investment in river defences, particularly associated with the Lower Adur. These works include flood defence embankments. Brighton and Hove council has been working with others to establish farming practices around the city aimed at reducing surface water runoff from the South Downs. In some locations there are earth dams and retention ponds that store runoff from the South Downs and reduce flooding to properties.

We assessed future flood risk by developing models to look at how predicted changes in our climate, land use, and increased urban growth would affect flooding in the catchment. Of these, we found that climate change will cause the most significant increase in future flood risk. Our changing climate is predicted to cause more frequent and more severe rainfall events and to increase sea levels. This means that the effects of climate change will be most significant in the Lower Adur area where our broadscale models show damages increasing from £0.4 million in 2006 to £80 million in 2106 during a 1% annual probability flood event.

Environment Agency xi River Adur Catchment Flood Management Plan (September 2008) Table 2 details the number of people at risk in the future in the key communities. As the effect of climate on other sources of flooding is less certain, and more difficult to quantify, only broad estimates of the number of people at risk from other sources of flooding in the future have been included in the table below.

Table 2 – Number of people at risk of flooding in the River Adur CFMP area in the future Communities at future risk in the River Adur CFMP area Number of people at Number of risk from fluvial people flooding in the future potentially CFMP area Key Source of flooding at risk sub-division communities from other 10% 1% 0.1% sources in the future • Fluvial Burgess Hill, • Surface Water Between 48 Hassocks, • 5 598 1,315 Adur East Under capacity and and 160 Wivlesfield Branch blocked drainage systems. Between 24 Wivlesfield • Surface Water 0 0 0 and 80 Adur West Isolated • Fluvial 0 0 36 Unknown Branch properties • Fluvial People at Steyning, • Surface Water risk – Bramber, Upper • Under capacity and 10 268 268 number Beeding blocked drainage likely to increase Lower Adur systems People at • Fluvial risk – Shoreham and • Surface Water 14 4199 4199 number Lancing • Tidally influenced river likely to flooding increase Brighton and • Surface Water Between 50 0 0 0 Hove • Groundwater and 500 Ferring, Ferring Rife, • Fluvial Durrington, More than Teville • Surface Water 5 141 1,219 Sompting, East 5 Stream • Worthing Groundwater Between TOTAL - 34 5,206 7,037 120 and 750 Note: Number of residential properties x 2.39 occupants (based on Table 3.3) Source: National statistics census data 2001

Increased surface water flooding is another predicted effect of climate change. This is of particular concern in Brighton and Hove where the likelihood of rapid flowing flood waters increase, posing a potential threat to life. The increased stormy conditions are expected to bring an associated increase in localised sewer flooding throughout the catchment. The urban areas of Worthing, Burgess Hill, and Shoreham are likely to experience an increase in surface water and sewer flooding in some localised areas. We are unsure of how climate change will affect groundwater flooding and this is the subject of current research projects. Future flood risk in Brighton and Hove is uncertain and there is a clear need for further study to improve understanding of surface water, urban drainage and groundwater flooding mechanisms in the

Environment Agency xii River Adur Catchment Flood Management Plan (September 2008) area. The study should also consider the potential change in flood risk in the future, and if unacceptable how this could be mitigated.

The predicted increase in flood risk may result in benefits to wetland biodiversity in the floodplain. There may be particular opportunities to expand and enhance areas such as the River Adur water meadows and Wyckham Wood SNCI and the inter-tidal areas of the Adur valley and estuary. There are no sites designated as Special Protection Areas (SPAs), Special Areas of Conservation (SACs), or Ramsar within the CFMP area and as such an appropriate assessment is not required. Appropriate assessments are required for European sites, and aims to ensure that the plan will not have adverse effects on the integrity of sites designated under the Habitats Directive.

Certain features of the environment, or aspects of the local community or economy, can not only lead to effective ways of managing flood risk in the area, they can also benefit the catchment in other ways. We have identified a number of these ‘opportunities’, including those that:

• Enhance the character of the landscape and increase amenity opportunities for recreation, tourism and leisure activities. • Help meet national biodiversity action plan (BAP) targets. • Work with the High Weald AONB Joint Advisory Committee to achieve the targets set in the High Weald AONB Management Plan to maximise the opportunities for natural processes to reduce flooding through the adoption of river restoration policies, whilst enhancing landscape character. • Move towards more natural rivers and drainage networks, as outlined within PPS25, will mean we can achieve more efficient and sustainable water management, whilst enhancing landscape character. • Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Partridge Green and Steyning and between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity. • Influence the coastal defence strategy, along the Lower Adur, Teville Stream and Ferring Rife, to improve the sustainability of flood risk management in the this area. • Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Brighton and Hove, Worthing, Shoreham, and Burgess Hill). • Reduce flood risk and improve water quality by promoting and encouraging the use of SuDS in the proposed urban developments in Brighton and Hove, Worthing, Shoreham, and Burgess Hill. • Investigate the feasibility of incorporating the Teville Stream into the Floodline Warnings Direct service by installing new level gauges on the Teville stream. • Continue local authority and Environment Agency support of the Flood 1 project in relation to groundwater flooding. • Develop a flood warning system for groundwater flooding. • Continued practice and development of the Emergency Response Plan in Brighton and Hove, Worthing, Shoreham, and Burgess Hill. • Reduce surface water run-off and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices (e.g. those set out by Brighton and Hove City Council). • Support the existing flood defence measures in relation to surface water flooding, such as bunds and storage provided by Brighton and Hove City Council. • Potential for improving the current defences, for example possible installation of demountable or temporary defences in Shoreham and Burgess Hill.

Environment Agency xiii River Adur Catchment Flood Management Plan (September 2008) • Improvements in the efficiency of channel and flood defence maintenance processes. • Effective and efficient use of developer contributions for flood risk management. • To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing the run-off rate.

We have also identified constraints within the catchment, which may limit certain opportunities, or reduce the benefits available as follows:

• Government and international legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive. • Existing urban development may prevent reinstatement of natural river processes. • Individual homes and properties are currently at risk of flooding. • Transport links in the catchment are a vital part of the communication network regionally, nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032. • Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance. • Historic development and some heritage designations in Steyning, Bramber and Upper Beeding present permanent physical obstructions. • Presence of protected species with specific water level, water quality and habitat requirements, for example in the Adur Estuary SSSI. • Location of electricity pylons adjacent to the Lower River Adur (currently protected by existing defences). • No degradation of existing fish passage and habitat. • Visual impact of flood risk management activities within the proposed National Park or Areas of Outstanding Natural Beauty. • Steep catchments of the South Downs result in rapid run-off and quick responses to rainfall events. • A suitable level of productivity from agricultural land needs to be retained. • Changes to flood risk management can affect the landscape, its character and value as an amenity. • CFMP objectives and policies must complement those of the Shoreline Management Plan (SMP) that affect the CFMP area. • Available funding for the initial set up of new flood risk management schemes. • Older flood defence structures are likely to be costly to maintain. • Limited available information on surface water and groundwater flood damages.

We have set objectives for the catchments within the River Adur CFMP area based on specific issues, features or problems that relate to flooding, taking into account the opportunities and constraints identified. The objectives for the CFMP area are:

Environmental

• Restore rivers and floodplains to a naturally functioning state where feasible. • Protect and enhance nationally and internationally important species and habitats.

Environment Agency xiv River Adur Catchment Flood Management Plan (September 2008) Social

• Ensure the impact of flooding on people and property does not significantly increase in the future (for example due to climate change). • Ensure the disruption caused by flooding to transport and critical infrastructure does not significantly increase in the future (for example due to climate change). • Reduce the impact of muddy flooding.

Economic

• Ensure flood damages do not significantly increase in the future (for example due to climate change). • Ensure that river channel and flood defence maintenance expenditure is appropriate to the economic damage of flooding.

We and our partners have developed policies to manage flood risk in the future. These policies set out our vision for a more sustainable, cost effective and natural approach to managing flood risk in our catchments. The policies are:

1. No active intervention (including flood warning and maintenance). Continue to monitor and advise.

2. Reduce existing flood risk management actions (accepting that flood risk will increase over time).

3. Continue with existing or alternative actions to manage flood risk at the current level (accepting that flood risk will increase over time from this baseline).

4. Take further action to sustain current scale of flood risk into the future (responding to the potential increases in flood risk from urban development, land use change, and climate change).

5. Take further action to reduce flood risk (now and/or in the future).

6. Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, (which may constitute an overall flood risk reduction, for example habitat inundation).

We have selected the most appropriate policy for various parts of the catchment (referred to as ‘policy units’) by using an appraisal process, which is based on how well the policy helps achieve the catchment objectives. We have considered current and future flood risk to people and property, flood risk management practices, and environmental benefits when selecting policies. In some instances the policy selected in a policy unit also has positive benefits in terms of flood risk for adjacent policy units. The policy units shown in figure 1 are numbered 1 to 9, and each unit is colour coded according to which policy we have selected.

Environment Agency xv River Adur Catchment Flood Management Plan (September 2008)

Figure 1 – Policy units and selected policies

Apart from the recommended policies, the other most important part of this CFMP is the Action Plan, found in chapter 7 of this report. To make sure that the policies are implemented, we have agreed a set of actions, not just for us but also other organisations. These actions include completing new studies to identify the best way forward, reviewing our current maintenance activities through the development of System Asset Management Plans (SAMPs), improving flood warning, and working with other organisations to help reduce flood risk. We will need to take some action in the short-term. Other long-term actions will be necessary for the lifetime of the plan. Some actions depend on others being complete and so will not happen straight away.

Environment Agency xvi River Adur Catchment Flood Management Plan (September 2008) 1 Introduction In this section we explain what a Catchment Flood Management Plan (CFMP) is, what it will achieve, and how it fits into the overall flood risk management process.

1.1 Background

Flooding is a natural process that can have a major impact on lives, communities, the economy, and the environment. We cannot prevent floods, but we can prepare for them. Our aim is to reduce the risk to people and property, and to deliver environmental benefits consistent with sustainable development. We do this by taking action to reduce the likelihood and consequences of floods. This is known as ‘flood risk management’.

Flood risk is a combination of two parts; the chance (or probability) of a particular flood event happening and the impact (or consequence) it would have if it did happen. Flood risk management can reduce the impact of flooding by influencing development in flood risk areas; by warning people when floods might occur; by responding rapidly and effectively to emergencies; and by reducing the chance of flooding happening by managing land, river systems and flood defences.

The Department for Environment, Food and Rural Affairs (Defra) has overall responsibility for flood risk management in England. Its aim is to reduce flood risk by:

• discouraging inappropriate development in areas at risk from flooding; • encouraging adequate and cost effective flood warning systems and flood emergency arrangements; and • encouraging adequate technically, environmentally, and economically sound and sustainable flood defence measures.

A Catchment Flood Management Plan (CFMP) is a planning document we develop together with other main decision-makers within a river catchment. We are developing CFMPs for the whole of England and Wales, each one covering either a single large catchment or a number of smaller catchments combined to form a single study area. They will set out the policies we will adopt to manage flood risk in each area for the next 50 to 100 years. This means we need to take account of the increased likelihood of flooding, which in the CFMP area may be considerable, as a result of the combined effect of expected changes in our climate and rising sea levels.

The CFMPs consider all types of flooding, whether from rivers, sewers, groundwater, or surface water. CFMPs are based on a standard approach to make sure they provide a consistent assessment of flood risk and policy options. They also cover tidal flooding from rivers and estuaries (flooding influenced by changes in sea levels as well as river flows) but not flooding from the sea (coastal flooding), which is covered by Shoreline Management Plans (SMPs). The two sets of plans meet at the existing SMP boundary, with no gap in between them.

Environment Agency 1 River Adur Catchment Flood Management Plan (September 2008) 1.2 Aims and scope

The location and extent of the River Adur CFMP is shown in figure 1.1.

Figure 1.1 - Catchment location

The main aims of the River Adur CFMP are:

• to reduce the risk of flooding and harm to people, the natural, historic and built environment caused by floods; • to work with natural processes so that flood risk management brings benefits and contributes effectively to sustainable development; • to inform and support planning policies, statutory land use plans and implementation of the Water Framework Directive.

Environment Agency 2 River Adur Catchment Flood Management Plan (September 2008) The CFMP achieves these aims by setting policies for managing flood risk in the area now and in the future. These policies must take into account the likely impacts of changes in climate and the effects of land use and land management. They will bring a range of environmental and social benefits and contribute towards sustainable development.

We have prepared the CFMP by:

• assessing current and future flood risk from all sources (rivers, sewers, groundwater, and surface water) within the area, by understanding the likelihood and impact of flooding and the effects of current methods of reducing risk. The scale of risk should be measured in economic, social, and environmental terms; • identifying opportunities and constraints within the area for reducing flood risk through changes in land use, land management practices, and/or flood risk management; • finding ways to work with natural processes to maintain, restore, or enhance natural and historic assets (including biodiversity); • working out priorities for studies or projects to manage flood risk within the area and making ourselves, other operating authorities, local authorities, water companies or other key groups responsible.

We have devised specific catchment objectives during the study to provide the framework to develop and appraise sustainable policies.

The results of the hydraulic modelling carried out for the study, including any flood outlines developed, do not replace any existing information we may hold on flood risk in a particular area and are not intended to be used under Section 105 of the Water Resources Act 1991.

1.3 Policies

CFMP policies are driven by the extent, nature, and scale of current and future flood risk across the whole catchment, with the overall aim of reducing flood risk by meeting specific CFMP objectives. The policies aim to set the right approach to managing the overall flood risk within the catchment. Within many catchments it is not possible to reduce flood risk everywhere so we need to understand where the greatest risks are, and why they are there, before choosing which policies to implement. We have to decide where we need to take further action to reduce flood risk, where we will simply need to sustain the current risk, and where we may have to accept that the risk will increase.

The CFMP shows the broad areas where these actions should be applied. These areas are known as ‘policy units’ and it is here that we will set policies to manage the level of flood risk. During policy appraisal we assess catchment objectives and possible future changes to address the level of risk. There are only a limited number of policies that we can apply. There are six pre-defined policies we can choose from to apply to different parts of the CFMP area. These are:

Policy 1 - No active intervention (including flood warning and maintenance). Continue to monitor and advise. We may select this policy for natural catchments where the river is connected to its floodplains and flooding has positive effects, for example, it is good for habitats). We may also select this policy where we recognise that the harm posed by flooding is not high, nor will it be in the future. In these instances, we would not envisage costly interventions to manage low risks.

Environment Agency 3 River Adur Catchment Flood Management Plan (September 2008) Policy 2 - Reduce existing flood risk management actions (accepting that flood risk will increase over time). We may select this policy for places where current and future risks do not warrant as much intervention (for example on maintenance) and it is clearly not worth continuing. Here, we can allow the risk of flooding to increase naturally over time. Following this policy, where we have assets in place now, we may look at the options and timing of withdrawing or retreating flood defences in our Asset Management Plans.

Policy 3 - Continue with existing or alternative actions to manage flood risk at the current level. We may select policy 3 where the risks are currently managed appropriately and where the risk of flooding is not expected to increase significantly in the long term. We may need to review if what we are doing currently is the best way of managing the risk in the longer term, but we are confident that the risks do need managing. This policy may lead to reviewing the flood warning services, or how we manage assets that may be in place.

Policy 4 - Take further action to sustain the current level of flood risk into the future (responding to the potential increases in risk from urban development, land use change and climate change). We may select policy 4 in places where the risk is currently managed appropriately, but risk is expected to rise significantly in the long term. In these circumstances, we would need to do more in the future to reduce the increase in risks.

Policy 5 - Take further action to reduce flood risk. This policy is about reducing the risk where the existing flood risk is too high. We need to take action in the short term to reduce this level of risk.

Policy 6 - Take action to increase the frequency of flooding to deliver benefits locally or elsewhere (which may constitute an overall flood risk reduction, e.g. for habitat inundation). We can apply this policy either locally to a flooding problem, or some distance away where flooding is not a problem. However, the principle behind policy 6 is that we transfer flooding to places where it can bring benefits, which reduces the risk in areas where it is a problem. This may mean that we can restore floodplains and improve habitats, reducing the negative impacts of flooding elsewhere within the catchment. This may also include changing the way we use the land to hold water within that part of the catchment for longer, reducing flood risk elsewhere.

1.4 Links with other plans

Developing CFMPs and Shoreline Management Plans (SMPs) will help us to reduce flood risk and bring about a range of benefits. These benefits include the environmental objectives identified in River Basin Management Plans under the Water Framework Directive. The European Commission has recently passed a new directive on assessing and managing flood risk (the Floods Directive). The Floods Directive aims to reduce the risk to human health, the environment and economic activity associated with floods. Under the Directive, flood risk maps, flood hazard maps, and Flood Risk Management Plans (FRMPs) will have to be prepared. These will sit alongside the River Basin Management Plans prepared under the Water Framework Directive. The FRMPs we prepare in the future will build on our Catchment Flood Management Plans and Shoreline Management Plans.

The CFMP represents the first ‘tier’ in the strategic flood risk management process, providing the overall framework within which we can carry out more detailed assessments of flood risk, such as strategy plans. Local Authorities are also currently completing strategic flood risk assessments. These assessments cover smaller areas and so are generally better able to

Environment Agency 4 River Adur Catchment Flood Management Plan (September 2008) address local issues, opportunities, and constraints, although there are places where it is more appropriate for the CFMP to recommend specific flood risk management measures.

A key relationship for the CFMP, shown within figure 1.2, is the link with the land use (spatial) planning process. This relationship operates at two levels, with a strong link to the Regional Spatial Strategies and a slightly weaker, but still important, link to the Local Development Frameworks. The other significant external link is to rural land management plans.

Figure 1.2 - Context of CFMP within wider planning framework

Statutory plans, strategies, programmes and studies: The many statutory strategies and plans highlight the area’s existing and future pressures or objectives. We looked at the policies and objectives concerning water management in these plans that could affect or be affected by our CFMP. In particular, we looked for constraints and opportunities that we would have to consider when developing our flood risk management policies. The following are particularly important:

• Regional Spatial Strategies for the South East – Aim to contribute to the achievement of sustainable development in South East England over the next 20 years. The main topics

Environment Agency 5 River Adur Catchment Flood Management Plan (September 2008) covered are housing, transport, employment and the environment. The flood risk management policies chosen within the CFMP will need to be inline with the RSS. • Regional Sustainable Development Frameworks for the South East – The aim of the Regional Development Framework is to clarify what sustainable development means for the South East of England and how this contributes to sustainable development of the country. It is intended to provide a common reference point for sustainable development to help guide the work of agencies and organisations. The CFMP will complement the Regional Sustainable Development Framework. • East Sussex and Brighton and Hove Structure Plan 1991-2011 saved policies – The role of this structure plan is to set out a broad picture of what state East Sussex and Brighton and Hove should be in fifteen years time, together with policies and proposals that can be implemented to achieve this. From September 2007 the majority of this document expired, however, a number of policies were saved by approval of the Secretary of State and are therefore still statutory and relevant to the CFMP. • West Sussex Structure Plan 2001-2016 – This document forms part of the Development Plans that set out the local planning authority’s policies and proposals for the development and use of land in the area. From October 2007 only policies that have been saved by approval of the Secretary of State will be relevant to the CFMP. • Regional Forestry and Woodlands Framework for the South East: Seeing the Wood for the Trees – Sets out a framework for the future development of woodlands and forestry in the South East. It is based on four themes and develops outcomes that would be encouraged for the region. There are opportunities within the CFMP to enhance the development of this framework. • The Water Framework Directive (2000) – The Water Framework Directive requires all inland and coastal waters to reach “good status” by 2015 by establishing a river basin district structure with demanding environmental objectives that incorporate all aspects of the water environment. The CFMP will need to comply with the requirements of the Water Framework Directive. • Future River Basin Management Plans – These are required within the Water Framework Directive. They will form an integrated management document for whole water body systems incorporating surface water run-off to estuaries and the sea. The CFMP will contribute to and be integral to the River Basin Management Plan that covers the River Adur catchment. • The Floods Directive (2007) – This Directive is designed to help European Member States prevent and limit floods and their damaging effects on human health, the environment, infrastructure and property. The Directive came into force in November 2007. The CFMP will be inline with the Floods Directive. • Making Space for Water: Urban flood risk and integrated drainage – This document provides an holistic approach to flood risk, taking into account all sources of flooding and reflecting other relevant government policies inline with the Water Framework Directive. Flood risk management should reduce the threat of flooding to people and property while delivering the greatest environmental, social and economic benefit consistent with sustainable development principles. The CFMP must comply with the flood risk and coastal management policies and accommodate potential opportunities to improve current flood risk management and to encourage sustainable urban drainage. • Local Development Frameworks (LDFs) – The LDF contains local development documents that outline how planning will be managed in the area. The River Adur CFMP will take account of the proposed urban development areas when selecting the most appropriate policy for future flood risk management. Strategic Flood Risk Assessments (SFRA) form one of the documents which support the LDF and provide information about flood risk within Local Authority boundaries. The majority of local authorities within the Adur CFMP study area have completed or are close to completing SFRA, these include, Arun District Council, Adur District Council, Worthing Borough Council, Horsham District

Environment Agency 6 River Adur Catchment Flood Management Plan (September 2008) Council, Lewes District Council, Brighton and Hove City Council, and Mid-Sussex District Council. • Area of Outstanding Natural Beauty management plans – Management plans for an AONB set out local authority policy for the AONB. It will be used to assess how the responsible organisations fulfil their management duty to have regard for the conservation and enhancement of the area. The CFMP will reflect the AONB management plans. • Planning Policy Statements (including PPS25) - Prepared by Government following public consultation, PPS explain statutory provisions and provide guidance to local authorities and others on planning policy and the operation of the planning system. Their content must be taken into account within local authority development plans and have an important bearing on development and land use. In particular the CFMP will support the guidance and policies of PPS25 Development and Flood Risk. • The Wildlife and Countryside Act (1981 as amended) – The principal mechanism for the legislative protection of wildlife in Great Britain. The act covers the protection of wildlife (birds and some animals and plants), the countryside, National Parks, and the designation of protected areas and public rights of way. The CFMP recognises the protected areas and seeks to identify potential opportunities that would enhance these areas. • The Countryside and Rights of Way Act (2000) – This Act provides for public access and enjoyment of the countryside whilst providing safeguards for landowners and occupiers. It includes greater protection to SSSIs and better management arrangements for AONBs. As such the CFMP will need to comply with this legislation. • Habitats Directive (as transposed into UK law by the Conservation (Natural Habitats) Regulations (1994 as amended)) – The Habitats Directive provides for the designation and protection of ‘European sites and protected species’ including SACs and SPAs. The CFMP will need to be inline with the Habitats Directive with regard to the environmental designated sites within the CFMP area. • The Freshwater Fish Directive – This Directive requires certain designated reaches of water (watercourses, lakes or reservoirs) to meet quality standards that should enable fish to live or breed in the designated water body. There are two categories identified; salmonid fish (salmon and trout) and cyprinid fish (coarse fish), different standards are set for the two categories. The CFMP must comply with the standards set as a result of this Directive for any designated water body within the area of the CFMP.

Non-statutory plans, strategies, programmes and studies: There are a number of non-statutory plans, strategies and programmes that set priorities for flood risk protection and improvement. The following are particularly important:

• Beachy Head to Selsey Bill Shoreline Management Plan (First Review) – This plan addresses the risk of flooding to people and the historic and natural environment along the coastline. The CFMP objectives must be inline with the objectives outlined within the SMP. The SMP also identifies potential opportunities for intertidal habitat creation. • Adur and Ouse Catchment Abstraction Management Plan (March 2005) – The plan outlines the sustainable management of water resources in the catchment, including water allocation and abstraction licensing. • Directing the Flow: Priorities for future water policy (November 2002) – In order to implement the Water Framework Directive future water policy should respect environmental limits, productivity, abstraction, health, pollution, land use planning, climate change and recreation. The CFMP should consider opportunities for identifying diffuse water pollution issues from agricultural and urban sources, improved understanding of the catchment and future land use planning and for returning watercourses to a more natural state. • High Weald AONB Management Plan (March 2004) – The management plan addresses the maintenance and enhancement of the landscape character of this area. It includes the

Environment Agency 7 River Adur Catchment Flood Management Plan (September 2008) restoration of naturally functioning river catchments and the protection of sandstone outcrops. The chosen CFMP policy must retain the landscape character, consider the impact on the sandstone outcrops and protect and enhance BAP priority species and habitats. There are opportunities to reduce flood risk through the restoration of functional floodplains and to improve public understanding and awareness of the benefits of river restoration. • South Downs Management Plan (October 2007) – The management plan incorporates policies to reduce stress from abstraction, mitigate rising demand in water resources, prevent drying out of chalk streams and low flows, reduce soil erosion and water pollution and mitigate increasing flood severity and frequency. The CFMP needs to consider increased storage elsewhere in the catchment to alleviate abstraction pressures, threats of pollution to surface and groundwater as a result of flooding events and future constraints of National Park status of the South Downs AONB. There are opportunities to improve river flow, reduce flood risk in vulnerable areas or increase inundation of water compatible sites through floodplain and wetland restoration. • UK Biodiversity Action Plan (BAP) (1994) and Local BAP for Sussex (1997) – The UKBAP and local BAP identify priority habitats and species within the catchment. The protected species and environmentally designated habitats are to be maintained and enhanced by preventing loss and damage to existing habitat while promoting new areas of habitat and improving quality through suitable flood risk management activities. • Local Environment Agency Plan (LEAP) – The LEAP provides a holistic approach to environmental management and is seen as the key mechanism for prioritising actions arising from BAPs. The CFMP will consider the potential contribution of riverine systems and habitats identified within the LEAP as an objective within the CFMP.

In addition to the above plans, strategies, programmes and studies there are also fisheries action plans, tourism strategies, Natural England natural area profiles, Countryside Agency Landscape Character Assessments, Environmental Stewardship Schemes and emergency response plans that shall be consulted as part of the CFMP process.

There are also a number of studies and research projects being undertaken to better understand groundwater and surface water flooding. These include:

• Flood1 Research Project (Bureau de recherches Géologiques et Minières, Brighton University, and British Geological Society) – the Flood1 Research Project is an EU INTERREG IIIA funded collaborative project that aims to investigate the role of groundwater in flooding on chalk catchments by providing a more detailed understanding of processes in the undersaturated zone of the Chalk aquifer of southern England and Northern France. The project aims to develop monitoring techniques for groundwater in the saturated and undersaturated zones, and to produce more appropriate methodologies and tools for forecasting groundwater flood events over longer timescales than is currently possible. It is of particular relevance to the CFMP as one of the study sites is near Patcham, Brighton, where groundwater flooding occurred in 2000. • Flood Defence Assessment of Downland Flooding (2001, Brighton and Hove City Council) – this report compiles historical records of flooding in areas around Brighton and Hove, asses the effectiveness of existing flood defences, and investigates potential options for flood risk management. • Flooding and soil Erosion at Rottingdean (1987, Brighton and Hove City Council) – this report was compiled by the University of Sussex and considers two extreme surface water runoff events in the Rottingdean area. The report makes recommendations for reducing flood risk including land use planning and land management options.

Environment Agency 8 River Adur Catchment Flood Management Plan (September 2008) CFMP boundaries do not necessarily coincide with other administrative boundaries. The CFMP will take account of the interests of a number of authorities and other groups within or overlapping the CFMP boundary.

This plan will be used by:

• us to direct our investment in activities to manage flood risk (for example strategic planning, asset management and flood event management) and support other activities within the catchment (for example river basin management planning under the Water Framework Directive); • regional and local government authorities to inform spatial planning, sustainability appraisal/strategic environmental assessment and emergency planning; • internal drainage boards and water companies to help them plan in the wider context of the catchment; • Government and government departments to help plan future funding and policy development; and • the public to improve its understanding of flood risk and integrated flood risk management.

1.5 Involving others

We cannot reduce flood risk across England and Wales on our own. The main organisations and decision makers in a catchment must work together to plan and take action to reduce flood risk. The CFMP has been developed by a steering group with representatives from the following organisations:

• Adur District Council • Arun District Council • Brighton and Hove City Council • Defra • Environment Agency • Horsham District Council • Mid Sussex District Council • Natural England • Southern Water • West Sussex County Council • Worthing Borough Council

The steering group guided the development of the CFMP, consulting key individuals and organisations, providing technical guidance on wider issues, and reviewing results from the project. A wider group of consultees also helped develop the draft plan (see Appendix A). It is inevitable that given the great number of interested parties not everyone will be able to agree with some of the difficult decisions that the steering group need to make.

Developing a CFMP can take over 18 months. This allows for public consultation so that we can tell people what we are doing and receive comments and suggestions on the plan. Table 1.1 shows how we gathered information and consulted and worked with important groups and organisations for this CFMP. The key issues raised by others in the CFMP process are summarised below the table.

Environment Agency 9 River Adur Catchment Flood Management Plan (September 2008) Table 1.1 - Summary of consultation during the development of the CFMP CFMP Consultation CFMP How we Who we Date Consultee Key Issues Our Response Stage consulted consulted

At the start of the inception stage meetings held with Project Team to January Inception report delivered according to CFMP rolling discuss Project Team - 2004 programme. approach of the CFMP, consultation Inceptionstage and steering group involvement.

Scoping Project Team January workshop Further development of catchment understanding and review and - 2006 held. of hydraulic model output. Stakeholders

Scoping report public consultation period. Report available on April 2006 Environment Stakeholders to June - Comments on all aspects of the scoping report received. Agency and public

ScopingStage 2006 website, main libraries and advertised in local newspapers.

September Steering group Review of policy unit boundaries and application of flood risk Project Team - 2006 meeting held. management policies.

Public Confirmation required as to Hassocks is within Policy Unit consultation which policy unit Hassocks 2 with Burgess Hill. August period. Draft Mid Sussex is located in. 2007 to CFMP Stakeholders District We also welcome the November available on and public Council Questions raised regarding questions and interest 2007 Environment System Asset Management regarding integrated drainage Agency Plans and Integrated studies and System Asset website, main drainage strategy. Management Plans libraries and The Council feels that it is advertised in important that the current Henfield We welcome the support for local floodplains are properly Parish Council flood risk management. newspapers. maintained to reduce the

Main Stage risk of flooding in the future. Helpful comments regarding implementation of policy 6 We welcome the support for and the requirements for additional flood risk more detailed studies on management studies, where West Sussex creation of habitats, Teville feasible. County Stream, and tidal Council vulnerability. Majority of suggested changes to text have been Some suggested changes to implemented. the text in the CFMP were made.

Environment Agency 10 River Adur Catchment Flood Management Plan (September 2008) CFMP Consultation Majority of suggested changes to text have been Some suggested changes to implemented. the text in the CFMP were made. The action plan has been adjusted to suggest The council feel the continuation with the Brighton and recommendations from the recommendations taken Hove City Downland flooding report forward from the Downland Council have been taken as far as Flooding Report. currently possible. The lead organisations are Suggest clearer roles should identified in the action plan, be established in the action and it may be suitable for plan working groups to be set up to co-ordinate the implementation. We welcome the support for flood risk management, urban drainage strategies, and cross group working.

We have taken into Pressure of future consideration the pressure of development. future development in Burgess Burgess Hill Hill when assessing future Town Council Rapid runoff rates flood risk and have taken into - Planning and consideration the high priority Transport The need for cross group of addressing current and Committee working and consideration of future runoff rates, particularly the impact of updates to for new development. other documents. Catchment Flood Management Plans are likely to be reviewed every 6 years or more often if required. During this review any new documents will be included in the CFMP. September Final CFMP published. Document available on Environment Agency website, main libraries and advertised in local 2008 newspapers.

The main points resulting from the CFMP consultation stages are listed below:

• Clarification on how an integrated urban drainage strategy would be developed and who will lead on it. • Concerned that the current floodplains are properly maintained to reduce the risk of flooding in the future. • Suggestion that the CFMP is updated on a regular basis and taken into account in future studies. • Consideration of surface water, urban drainage and groundwater flood risk aspects.

We have acknowledged, considered, and taken actions where necessary to all the consultation responses received throughout the CFMP process to date, however, due to the extent and variability of queries and issues raised not all of the responses, or actions undertaken as a result, have been listed within the CFMP. Where suggested changes to text and figures have been made these have all been considered and the report altered accordingly.

We have discussed the policies and actions presented in the CFMP through project team meetings and discussions with stakeholders to keep them informed and involved in the decisions reached.

Environment Agency 11 River Adur Catchment Flood Management Plan (September 2008) 2 Catchment overview This section describes the main physical, biological and cultural aspects of the area covered by the CFMP. It also highlights those features, initiatives and policies that may provide opportunities or constraints on how we manage flood risk.

2.1 Definition and extent of the Adur catchment

The River Adur CFMP covers 118 km of main rivers in the following catchments:

• Lower Adur • Adur East Branch • Adur West Branch • Ferring Rife • Teville Stream

The catchment boundaries, shown on figure 2.1, are largely topographical, marking the limit of the area where water lying on the ground will flow downhill toward the stream that drains the catchment. It follows that any rain falling on the CFMP area that runs off the ground will (apart from losses, due for example to water supply abstractions or evaporation) drain to the sea through one of these rivers or streams.

The total area covered by the CFMP is approximately 600 km2, of which only 16% is urban and the rest is either farmed or open countryside. The catchment extends from Littlehampton to Rottingdean on the coast and inland to Horsham and Haywards Heath in the north. Several administrative boundaries are covered by the catchment, mostly within West Sussex as well as a small part of East Sussex. The CFMP area includes Adur District, Borough of Worthing and parts of the district councils of Horsham, Arun and Mid Sussex as well as most of the City of Brighton and Hove.

The CFMP develops policies to manage flooding from rivers, groundwater and surface water but not coastal flooding (flooding directly from the sea), which is addressed through Shoreline Management Plans (SMPs). The coastline within this CFMP study area is covered by the Beachy Head to Selsey Bill SMP. The boundary between these plans and the CFMP is generally on the coast except for the River Adur, where it is at the A259 road bridge. The long- term plan for all the SMP policy units along the coastline of the Adur CFMP boundary recommends ‘hold the line’. The current policy and lengths of the coast over which the SMP applies are shown on figure 2.1.

Apart from the coastal plain which is heavily built up, including Littlehampton, Worthing, Shoreham, and Brighton and Hove, the catchment is mostly characterised by rural and agricultural land use, with several small settlements, villages and towns scattered throughout. There are several major A-roads passing through the catchment, linking the coastal towns with London, and the A27 which links the main areas along the coast. Figure 2.1 provides an overview of the catchment and shows the catchment boundary, the river network, main urban areas and transport links.

Environment Agency 12 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.1 - Main features in the Adur CFMP catchment

The area contains several sites of environmental and landscape importance, including the Sussex Downs and High Weald Areas of Outstanding Natural Beauty (AONB), the South Downs Environmentally Sensitive Area (ESA) and the proposed South Downs National Park, which crosses the catchment from west to east. There are also several Sites of Special Scientific Interest (SSSIs) in the area. These are discussed in more detail in section 2.8.

Table 2.1 summarises the main features of each of the main river reaches in the River Adur CFMP catchment.

Environment Agency 13 River Adur Catchment Flood Management Plan (September 2008)

Table 2.1 - Adur CFMP catchment overview Catchment overview Watercourses River Adur, Ferring Rife, and Teville Stream Source of main rivers/streams High Weald, Low Weald and South Downs River Adur East Branch to Mock Bridge, Shermanbury Tidal limit River Adur West branch to Bines Bridge Length of main rivers 118 km Ranges between 600 mm in coastal areas to 975 mm in the upper parts of Average annual rainfall the catchment Geology Weald Clay, Chalk and Upper Greensand Urban area 93 km2 (16%) CFMP area sub-division Assets Adur East Adur West Teville Lower Adur Ferring Rife Branch Branch Stream Area (km2) 163.4 123.3 252.8 35.6 24.7 Population 64,164 15,506 315,239 88,033 63,605 Grade 1 0 0 0.5 3.7 0.6 Agricultural Grade 2 8.0 0.7 7.7 4.1 1.7 land Grade 3 118.5 84.0 112.6 5.3 3.6 classification (km2) Grade 4 30.2 38.6 60.3 0.4 2.3 Grade 5 0.3 0 2.9 0 0 Residential properties 26,847 6,488 131,899 36,834 26,613 Commercial properties 2,563 464 12,904 1,851 3,011 A-class roads (km) 90.8 30.4 186.9 31.6 28.9 Railway (km) 13.7 5.3 29.0 7.6 4.6 National Park (proposed) 2 14.4 0 161.7 5.9 8.8 (km ) Sites of Special Scientific 2 1.9 0 6.4 0 0.2 Interest (SSSI) (km ) Scheduled Monuments 5 4 104 1 1 (SM) Listed Buildings 648 285 1723 142 144 Registers Battlefields 0 0 0 0 0 Registered Historic Parks 2 1 6 0 0 and Gardens World Heritage Sites 0 0 0 0 0 Areas of Outstanding Natural Beauty (AONB) 34.8 0 137.4 3.7 8.4 (km2) Sites of Nature Conservation Importance 3.0 2.8 8.4 2.8 2.4 (SNCI) (km2) Environmentally Sensitive 2 2.9 0 122.2 3.8 8.7 Area (ESA) (km )

2.2 Topography

The topography of the catchment is dominated by the South Downs chalk escarpment to the south, beyond which the land gently descends into the low-lying coastal plain. The northward face of the South Downs scarp is steeper and overlooks the Low Weald, a broad, low-lying vale punctuated by higher drier outcrops of limestone or sandstone. The northwest part of the Environment Agency 14 River Adur Catchment Flood Management Plan (September 2008) catchment is characterised by the sandstone ridges and valleys of the High Weald, as shown in figure 2.2.

Figure 2.2 shows that the majority of the main River Adur flows through the Low Weald where gradients are generally flat. However, some of the upstream tributaries of the Adur East Branch do originate in the High Weald where the ground elevations are more than 200m AOD. The tributaries of the Adur West Branch only reach ground elevations of approximately 100m AOD. Where these two branches of the River Adur meet, the ground elevations are considerably lower, at only approximately 3m AOD. The Lower Adur has a very low gradient, with elevations that range from only 3m AOD at the confluence with the two branches down to 0m AOD at the coast. The gradients of the West Branch, East Branch and Lower River Adur main rivers are shown in figure 2.3. The Teville Stream and Ferring Rife are located on the coastal plain to the west of the River Adur with maximum ground elevations that reach only 5m AOD and 8m AOD respectively.

Figure 2.2 - Catchment topography

Figure 2.3 clearly shows the difference in the channel slopes of the East and West Branches of the River Adur compared to the Lower Adur.

Environment Agency 15 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.3 - Channel slope of the River Adur (Main River only)

The channel slopes of the River Adur contribute to the timings of the flood flows. The Adur East Branch takes approximately eight hours between the peak of the rainfall and the peak of the flood in the river, just above the confluence. Whereas the Adur West Branch is slightly slower, taking approximately ten hours before it reaches the peak of the flood flow after a rainfall event (see section 2.7 for more details).

These physical characteristics of the River Adur play an important role in the highly valued landscape character of the area. The topography, as well as the geology, directly affects the hydrology of the catchment and how it responds to rainfall, as discussed in sections 2.3 and 2.7. The topography can also indicate potential locations for future flood risk management options, for example the broad flat floodplain areas of the Lower Adur could provide a suitable location for flood storage. This will be discussed further in sections 5 and 6.

2.3 Geology and hydrogeology

The area has a diverse geology, reflected in the landforms illustrated in figure 2.4. The geology within the CFMP area is dominated by the features of the High Weald, Low Weald and the South Downs (as shown in figure 2.2), all of which have a significant influence on the flooding characteristics of the catchment.

There is a clear link between areas of higher ground and more porous layers, in particular the chalk of the South Downs and the sandstone of the High Weald. In the permeable areas of the South Downs, the soils are generally well drained (see section 2.5) and the streams respond to seasonal groundwater variations and high levels of surface run-off from the open landscape during intense rainfall events. The chalk formation is an important aquifer and forms a significant water resource, widely abstracted for public use.

Environment Agency 16 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.4 - Geology summary of the Adur CFMP catchment

These areas are in contrast to the less permeable geology of the Low Weald, which occupies the majority of the upper catchment. Underlying this area is a band of impermeable Weald clay where drainage is poor with overlying soils subject to prolonged water logging. Here, the mudstones and clay, with corresponding clay soils, result in a very different hydrological response, with a much higher percentage of the rainfall ending up as run-off. This results in the area responding rapidly to rainfall.

The chalk layers of the South Downs are covered by generally shallow and well-drained topsoils. These allow rainfall to quickly seep into the chalk aquifers below. The chalk within the study area is classified on our Vulnerability Map as a highly vulnerable major aquifer, due to the overlying thin soils. A characteristic of the South Downs is the spring line along the escarpment. Rain soaks through the shallow soils of the Downs into the chalk and may emerge at the base of the scarp slope as springs, eventually giving rise to tributaries such as the Honeybridge Stream, Black Sewer, Herrings Stream and Woods Mill Stream. The relatively high level of groundwater and springs in these strata is an important part of river flows Environment Agency 17 River Adur Catchment Flood Management Plan (September 2008) throughout the catchment, with chalk-fed streams responding to seasonal variations in groundwater levels. Some groundwater flooding can occur in the chalk valleys to the north and the south of the Downs.

2.4 Geomorphology

The watercourses in the Adur catchment have been heavily modified by man over time, through land drainage and flood defence activities. Natural processes have also played a significant part in shaping the landscape, particularly at the shoreline. For example, the River Adur and neighbouring River Arun once shared a single outlet to the sea near Lancing. The drift of the shore shingle pushed the River Adur eastwards to its present location at Shoreham, whilst the River Arun now enters the sea at Littlehampton.

Geomorphological processes can be relevant to flood risk management in several ways. Sedimentation can influence channel capacity, erosion can damage flood defences and riverbanks, and historic channels can indicate potential flood pathways.

The geomorphology of the coast is comparatively simple, consisting of a shingle or sand beach generally moving eastwards under the process of longshore drift. Where the tidal inlets and rivers discharge to the sea (for example at the rivers Adur, Arun, Ouse and Cuckmere) the currents interrupt the eastward drift of beach sediment so that beaches tend to build up to the west of the harbour mouths and erode on the east.

The geomorphology of a river and its floodplain is determined by a number of factors. Principally, these factors include geology and topography. Softer geological units, such as chalk and sandstone, tend to be eroded more rapidly by a river, which can result in a continually changing watercourse. Harder geological units take longer to erode, and therefore the river channel tends to remain within a single or only slightly varying course.

Steep slopes tend to be associated with high velocity river flow. During times of high rainfall the steep slopes and consequent run-off from the upper catchment increases the system’s energy and river levels respond rapidly. These high flow rates can cause bed and bank erosion.

The geology and land use within the river catchment contributes to the type and amount of sediment load within a river. Soil erosion has been identified as an issue in parts of this CFMP area, in particular areas south of the South Downs where run-off, associated with increased growing of autumn-sown cereals, is a problem. During rainfall events, the soil is eroded and carried to the river channel by surface run-off or overland flow. The soil removed from the South Downs can cause a large build up of sediment within the river thus reducing river capacity and causing more frequent flooding within the floodplain. Gifford Associated Consultants (1997, in Bray et al., 2004) estimated the suspended sediment load of the River Adur (delivering into the sea at Shoreham) as 2,800 cubic metres per year.

This sediment process does occur naturally in lowland watercourses, but can be amplified by excess sediment created by poor land management practices. Flooding in this way can benefit the environment. The natural features created by the sediment can provide valuable habitats for aquatic species. (We discuss land management and soil erosion issues in section 2.6).

Without the series of water level control structures sited along the river, there would be very little water in the channel in the upper reaches of the River Adur. Water level control structures are the most significant modification to this section of the River Adur. Downstream of the structures, river levels rise as water is released, increasing the chance of bed scouring due to Environment Agency 18 River Adur Catchment Flood Management Plan (September 2008) the increased flow. Increased flow can also result in the undercutting of river banks as stronger flows erode the outside banks of meander bends. Bank erosion protection works have been undertaken in some locations in the form of timber toe protection and stone-filled wire baskets known as gabions.

Human intervention or natural processes can significantly alter river geomorphology. The river will adapt to this by flooding, increasing or decreasing its sediment load, or by altering its path. This must be considered during flood risk management, as intervention within the floodplain or on the river will affect the river’s regime up or downstream.

2.5 Soils Soil characteristics have a significant impact on how the different parts of the area covered by the CFMP respond to rainfall. The distribution of soil types is shown in figure 2.5 and is influenced by the geology and topography of the area, although over much of the catchment farming practices and drainage have altered the natural characteristics.

Figure 2.5 - Soil types in the Adur CFMP catchment

Environment Agency 19 River Adur Catchment Flood Management Plan (September 2008) In the northeast part of the catchment, silty soils over sandstone prevail. These impermeable clay and slowly permeable soils in the steep areas of the upper catchment can result in rapid run-off, causing river levels to rise rapidly. These provide suitable conditions for the applications of SuDS as a flood risk management solution.

In the central and remaining upper catchment the dominant soil type is seasonally wet loam to clayey soils over shale. There is a narrow band of loam over sandstone in the west and seasonally wet deep clay soils in the east running across the southern part of the Low Weald. Soils in this area become easily water logged and are poorly draining which prolongs water logging.

The South Downs have mainly shallow silty soils over chalk. This area is free draining and allows rainfall to quickly get into the underlying chalk aquifers. However, on the steeper slopes there are poorly draining silty soils, which cause water to run off the slopes more quickly and contribute to surface water flooding in parts of the catchment.

The River Adur channel itself is characterised by seasonally wet deep clay soils with low permeability and is therefore poorly draining. Silty or fine sandy loams exist along most of the coastal section of the catchment. These soils are generally well drained.

2.6 Land use and land management

The catchment is mainly rural with only 18% of the land classed as urban (using the Spatial Pressures Analysis of River Quality [SPARQ land cover classifications]). Population density is greatest at the coastal fringe within the urban areas of Worthing, Brighton and Hove, and Shoreham. Inland, the principal urban areas are Burgess Hill, Hassocks, Steyning and Upper Beeding. The central and lowland areas include many scattered villages and the population density is approximately five people per hectare.

2.6.1 Land types We have used two methods to describe how land is used in the CFMP. These are the SPARQ land cover classification and the Agricultural Land Classification (ALC).

Environment Agency 20 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.6 - SPARQ land cover classification

The SPARQ land cover dataset is based on information supplied by the National Soil Resources Institute (NSRI). The SPARQ land cover types within the CFMP are shown in figure 2.6 and the proportion of each land cover type is summarised in figure 2.7. Most of the CFMP area is either covered by arable land (30%) or managed grassland (45%). 18% of the CFMP area is urban and 6% is forestry or woodland. There is no data for the remaining 1%. The main urban areas are described in section 2.9.

Environment Agency 21 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.7 - Proportion of SPARQ land cover types

The ALC provides a method for assessing the quality of farmland to help make informed choices within the planning system about how it will be used in the future. Grades are related to climate, topography, drainage, soil characteristics and other site factors. The ‘best and more versatile land’ is defined as Grades 1 and 2. Grade 3 agricultural land varies in how it can support agriculture, ranging from moderate to poor. Much of the Grade 3 in this CFMP is moderate. Grades 4 and 5 are poor (ODPM, 2004). The ALC grades indicate the different types of agricultural land uses possible based on the quality of the land. They do not represent the actual land use within the catchment. Figure 2.8 shows the ALC grades within the River Adur CFMP area.

Environment Agency 22 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.8 - Agricultural land classification

The majority of the land in the Adur CFMP area (56%) is classified as Grade 3, with 22% classified as Grade 4, and small areas of higher and lower quality grades. Grade 3 and 4 land is dispersed fairly evenly throughout the catchment area. Small areas of Grade 2 overlie areas of Greensand and Gault geology, particularly west of Henfield and at the base of the southern slopes of the South Downs near Worthing. There are only very small pockets of Grade 1 land, surrounding the upper reaches of the Ferring Rife and Teville Stream, and Grade 5 land exists along the level tops of the South Downs. Figure 2.9 shows the areas of land classified in each ALC grade.

Environment Agency 23 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.9 - Proportion of land under each ALC grade

2.6.2 Land management How the land is used affects the chance of flooding. This is because it affects the amount of rainfall that runs off the land. For example, developed areas are heavily paved and so rainfall cannot soak into the ground. Rainfall then runs off into rivers and streams much faster, and this increases the chance of flooding in urban areas. Unless it is carefully managed, urban development may have a significant impact on local flooding. The main urban development issues relevant to the River Adur CFMP relate to the housing requirements of the South East Plan. Redevelopment on previously developed land is encouraged as opposed to development on Greenfield (previously undeveloped) land. We discuss future development further in section 2.6.3.

Changes in agricultural practices and rural land use can also have an impact on flood risk. Cropping and livestock management practices have the potential to impact on the structure of the soil. This impact is greatest when machinery or livestock have access to the land when the soil hydrological cycle is at or approaching its wettest season. Degraded soils are less able to absorb rainfall. This can result in higher run-off, causing soil erosion. Soil erosion can then increase flood risk as sediment blocks ditches and drains. Higher levels of sediment can damage habitats such as fish spawning grounds.

Poor agricultural land management practices include river bank trampling by farm animals, poor ploughing regimes in upland catchments, changes in crop type and poorly timed cropping practices. More recent trends such as using larger harvesting and cultivation machinery, and increased densities of livestock densities are likely to damage the soil even more. More sensitive land management can reduce these problems by adjusting agricultural practices to retain more soil. Problems may increase if cropping and rainfall patterns alter due to climate change.

Environment Agency 24 River Adur Catchment Flood Management Plan (September 2008) Flooding has been caused or exacerbated by land management practices within the Adur catchment. The areas affected in the past include Sompting, Patcham, Bevendean, Woodingdean, Ovingdean, Westdene and Mile Oak. The practice of growing winter cereal crops on the South Downs near to the affected areas is considered to be a major contributory factor. Seed drilling takes place between September and November and results in land vegetation cover of less than 30% at the time when most rain falls. Other factors, which increase runoff, include removing field boundaries, including hedgerows, and also using the steepest slopes, which have been ploughed downslope.

More recent reforms to the Common Agricultural Policy (CAP) have driven new initiatives to manage the land in a more environmentally sensitive way. There has been a shift from intensive farming practices to more sustainable environmentally based approaches. Various Defra agri-environment schemes could potentially improve land management practices within the CFMP area. These include Environmental Stewardship Scheme (replaces Countryside Stewardship Schemes), Woodland Grants Scheme, Farm Woodland Premium Scheme, Hill Farm Allowance, and the Organic Farming Scheme.

The main areas where land management could have impacts on run-off are:

• Upper catchments - where improved farming and land use practices could improve infiltration and water retention and reduce run-off rates and soil erosion. • Middle reaches – where creating wetlands could provide flood storage areas and improve the environment by trapping sediment and providing new habitats. • South Downs – where improved farming and land use practices on the steeper slopes could improve infiltration and reduce run-off rates. Selective crop choice could also provide additional benefits.

There are a number of Environmental Stewardship Schemes (ESS) currently operating in the Adur CFMP area. Areas of land adjacent to the upper reaches of the Adur East and West Branches are target areas for Stewardship Schemes.

This riverside land contains many features of interest, including areas of wet grassland, extensive ditch systems, mires and wet woodland. The valleys are linked to the wider countryside through extensive networks of hedgerows and the rew (or shaw) woodlands. A notable change is underway at the Knepp Castle estate, which has an ongoing river restoration project on the River Adur linked to an ESS (formerly CSS).

We also need to consider current land uses when proposing changes in the flooding regime, for example there are two landfill sites near Small Dole, which may be vulnerable to flood water if the river was naturalised. Areas such as this would need careful consideration as part of a more detailed feasibility study.

2.6.3 Urban development Urban areas are confined largely to the coastal towns of Brighton and Hove, Shoreham, and Worthing. There are a number of smaller inland towns dispersed throughout the CFMP area, such as Burgess Hill, Hassocks and Steyning, as shown on figure 2.10. The historical development of the shoreline has been strongly influenced by defence structures and reclamation in low-lying areas. This reclamation was made possible by a series of coastal and secondary flood defences, particularly along the river valleys. You can appreciate the potential flood hazard within these low-lying areas once you realise that much of this land is more than 1.5m below mean high water spring tide levels. Any breach of these defences could cause extensive flooding.

Environment Agency 25 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.10 - Location of main urban areas, towns and villages

Approximately 754,000 people live in West Sussex and this figure is expected to rise to 800,000 by 2016 (WSCC 2006). This is indicative of the population pressure on the CFMP area where the current population is estimated at around 480,000. Approximately half of these people live in Brighton and Hove, and a significant proportion of the rest are also concentrated in and around the coastal conurbations.

Under the new planning system, introduced by the Planning and Compulsory Purchase Act (2004), the CFMP catchment falls within the South East Plan area. A Draft South East Plan has been developed by the South East England Regional Assembly (SEERA) and covers a range of planning issues including housing, transport, economy and the environment. The South East Plan is scheduled to be adopted during 2008 and it will become the Regional Spatial Strategy (RSS) up until 2026. Until the RSS is adopted the Structure Plans for West and East Sussex will remain in place to guide future development.

As elsewhere in England, proposed levels of new housing development within the catchment represent a significant pressure for change. The structure plans for East Sussex and Brighton and Hove (1999 – 2011) and West Sussex (2006 – 2016) already propose significant future Environment Agency 26 River Adur Catchment Flood Management Plan (September 2008) housing increases within the CFMP area. However, the South East Plan requires annual increases in new housing to meet the predicted demand.

Table 2.2 shows the predicted future housing growth rates for the seven council areas in the River Adur CFMP area based on the proposals set out in Policy H1 of the draft South East Plan.

Table 2.2 - Future housing figures South East Plan proposed housing figures 2006 - 2026 Number of houses District/Strategic Annual development area Total average Adur 130 2,600 Arun 465 9,300 Horsham 620 12,400 Worthing 200 4,000 Brighton and Hove 550 11,000 Mid Sussex 705 14,100 Lewes 220 4,400 Source: Policy H1 of the South East Plan

The proposed annual average housing is greatest for Mid Sussex, which includes, Burgess Hill. Burgess Hill has sites where potential for future development has been identified by Mid Sussex District Council. As such there is potential for a future increase in flood risk in Burgess Hill due to urban development.

It is difficult to take account of future urban growth in the context of the CFMP because the current planning strategy is only looking ahead 20 years, whereas the CFMP has a 50 to 100 year time horizon. The future housing rates from the new RSS (not yet finalised), which apply to the CFMP area, are slightly increased from the existing Structure Plan rates. Government policy encourages the expansion of existing urban centres and villages (including reusing previously developed land), although potentially there could be development of new towns beyond the 2026 planning horizon within the South East Plan. Table 2.3 details the development plan proposals in the Adur CFMP area.

Table 2.3 - Development plan proposals Development plan proposals in the Adur CFMP area Plan or strategy Plan name Characteristics type New growth and development strategy focussing on housing, transport, economy and the environment. Encourages the development of more multi-centred structure within the region.

Regional Changes to number of houses needed for the coastal sub-area; South East Plan Sub-Regional Spatial housing plan is to provide 28,900 new homes a year in the South Strategy Strategy East between 2006 and 2026.

In Sussex coast sub-region the focus is on improving the economy to reduce deprivation and bring its economic performance closer to the regional average. Regional This RPG covers the period up to 2016. Urban areas should be Planning RPG9 2001 the main focus for development. Emphasis on sustainable Guidance development. (RPG)

Environment Agency 27 River Adur Catchment Flood Management Plan (September 2008) Proposes 1,800 new homes a year for East Sussex.

Close regard to the overall aim of setting a more environmentally sustainable context.

East Sussex and Brighton & Key features of regional spatial development include maintaining Hove Structure Plan 1991-2011 London's role as a world city and a change in the balance of development from areas to the west of London to the Thames Gateway. Protection of the Sussex AONBs is identified as an important Structure aspect of planning in the region. Plans

Proposes 2,890 new homes a year for West Sussex. Aim that the county continues to retain a network of small to West Sussex County Council medium-sized towns and villages, with strong rural focus. Structure Plan 2001-2016 Three main elements to the Plan: 1. Regenerate the coast. 2. Support and encourage economic growth in the rest of West Sussex’ particularly in the north east of the county around Crawley/Gatwick. 3. Meet the local needs of rural communities. The Adur District Local Plan Annual average housing rate (2001-16) - 115 1996-2006

Horsham District Local Plan Annual average housing rate (2001-16) - 620 1997-2006

Local Mid Sussex Local Plan (to 2006) Annual average housing rate (2001-16) - 680 Plans* Arun Local Plan 2003-2011 Annual average housing rate (2001-16) - 580

Worthing Local Plan 2003 Annual average housing rate (2001-16) - 280

The Brighton & Hove Local Plan Annual average housing rate (2006-16) - 260 adopted July 2005 * All currently being progressively replaced by Local Development Documents (LDDs) within a Local Development Framework (LDF).

2.7 Hydrology

The climate of the Adur CFMP area is typical of south east England, with lower rainfall and longer hours of sunshine than the national average. Annual average rainfall is largely related to the topography of the area and ranges from 600 mm a year on the coastal plain to 975 mm a year on the higher ground of the South Downs and High Weald.

The River Adur CFMP catchment covers an area of approximately 600 km2 in Sussex and includes the River Adur and its tributaries, the Ferring Rife and Teville Stream. The study area has been divided into five hydrological sub-catchments reflecting these main rivers and their hydrological characteristics. These are:

• Adur East Branch • Adur West Branch • Lower Adur • Ferring Rife and • Teville Stream

Figure 2.11 shows these hydrological units and the main watercourses, together with the main flow, level and rainfall gauging stations.

Environment Agency 28 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.11 - Main watercourses in the River Adur CFMP catchment

The Adur East Branch drains 167 km2 of the 600 km2 CFMP area. The upper parts of this catchment (notably the High Weald) are drained by a relatively dense network of small streams. Some of these small tributaries respond fairly rapidly to rainfall and run-off arrives at the main river relatively quickly. The main tributaries in this catchment are Pook Bourne Stream and Herrings Stream, which flow through Burgess Hill and Hassocks respectively. Approximately 3 km of the main river from the confluence with the Lower Adur and the Adur West Branch, upstream to Shermanbury, is influenced by the tide.

The Adur West Branch drains 143 km2 and includes the major tributaries Nuthurst Stream and Honey Bridge Stream as well as approximately 10 km of the main River Adur. This catchment is predominantly rural with some scattered villages and isolated properties. The confluence with the Adur East Branch and Lower Adur lies to the west of Henfield and south of Partridge Green. The tide continues to influence the river for approximately 1 km upstream of the confluence up to Bines Green.

The Lower Adur is the section of the River Adur flowing from the confluence with the East and West Branches through Steyning and Upper Beeding to the coast at Shoreham. This entire

Environment Agency 29 River Adur Catchment Flood Management Plan (September 2008) section of the River Adur is influenced by the tide. The major tributaries in this reach are Tanyard Stream, Black Sewer and Woods Mill Stream. Steyning and Upper Beeding are at risk of flooding from these rivers. There are no rivers or streams in the Lower Adur sub-catchment that flow through Brighton and Hove.

The Ferring Rife and Teville Stream both drain the flat coastal plain areas adjacent to Worthing and the steep slopes of the South Downs to the north of these catchments. The Ferring Rife to the west discharges into the sea and is tide-locked during certain periods. The banks of the Ferring Rife have been raised upstream of the outfall to store water during these periods and additional flood storage is provided by two lagoons on the western bank. The Teville Stream discharges into the sea via Brooklands Lake.

The CFMP area has varying ground slopes, annual rainfall, soil types, geology, landuse, and sub-catchment sizes. The way that a catchment responds during a storm event depends on these factors. The type and duration of a storm that causes the most flooding in a particular location is called the ‘critical duration’ and this varies throughout the catchment. For example, on the Adur East Branch, a short period of heavy rainfall will cause the most severe flooding. However, in other areas a long period of lighter rainfall will cause the most extensive flooding, for example in the Lower Adur catchment. Four critical storm durations that best represent these characteristics have been applied to the broadscale models to determine the resultant flows and flooding extents.

Figure 2.12 shows the estimated flow hydrographs for the 1% annual probability fluvial flood event at five locations in the Adur catchment. We obtained these using the Flood Estimation Handbook (FEH) Rainfall Runoff method. The locations to which the hydrographs relate are shown on figure 2.11.

Figure 2.12 - Hydrographs for the River Adur (1% annual probability fluvial flood event)

Figure 2.12 shows the scale and range of flood flows throughout the upper Adur catchment, and highlights the relative timing of the flood peak flow progression down the catchment.

Environment Agency 30 River Adur Catchment Flood Management Plan (September 2008) Hydrograph 1 shows the flows in the upper reaches of the Adur West Branch. The catchment is largely rural and less steep than the East Branch, and so it responds slower to a rainstorm, taking approximately 12 hours to reach its peak.

Hydrograph 2 shows the flows in the lower reaches of the Adur West Branch, by which stage the flow is more than 120 cubic metres a second. It takes approximately 20 hours for this arm of the River Adur to reach its peak.

Hydrograph 3 shows the flows in the upper reaches of the Adur East Branch. This part of the catchment responds relatively fast to a rainstorm, which reflects the catchment’s geology and topography and is partly due to the greater percentage of urban land cover. It takes less than five hours to reach its peak.

Hydrograph 4 shows a similar response to hydrograph 3 and is located on the upper Adur East Branch, with a relatively quick response to a heavy rainfall event (approximately seven hours). Again, this is due to the land cover, topography and geology of the area.

Hydrograph 5 shows the flow in the Adur East Branch. The total discharge from the eastern branch is significantly less than the Adur West Branch (indicated by comparing the area under the two hydrographs) and the peak flow is slightly lower (approximately 115 cubic metres a second). The rate of response is more rapid, taking around 15 hours to reach the peak in the Adur East Branch compared with around 22 hours in the Adur West Branch.

We have not included hydrographs for the River Adur below the confluence, as this part of the river system is tidally influenced. Similarly, we have not presented a hydrograph for the Ferring Rife as it is very small compared to the hydrographs for the River Adur, and is complicated by tide locking.

Broadscale modelling (see section 3.2 for more details) helps us to understand the flood processes in the catchments and helps us begin to understand how we might mitigate against flood risk. For example, slowing the water down in one of the tributaries may benefit downstream by altering the timing of the flood peaks from the two River Adur Branches and thus reducing the flood peak in the Lower Adur.

2.8 Natural and Historic Environment

2.8.1 Biodiversity Figure 2.13 shows that the character of the landscape of the catchment is of considerable value, with both the High Weald and South Downs designated as Areas of Outstanding Natural Beauty (AONBs). Much of the South Downs is also classified as an Environmentally Sensitive Area (ESA). There are proposals to upgrade the South Downs to National Park status, reflecting the increased value attached to the wider landscape.

Environment Agency 31 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.13 - Landscape designations

Figures 2.13 and 2.14 show the types, distribution, and extent of designated sites within the catchment. Biodiversity varies across the CFMP area, with the lower part of the catchment showing more diversity in terms of both species and habitats. These areas are generally associated with the nationally important environmentally designated sites, such as the Adur Estuary SSSI. Many areas of ecological importance are principally related to coastal and chalk grassland features as demonstrated by the distribution of SSSI sites along the southern dip slope of the South Downs, with a relatively small area of the Lower Adur estuary designated as a SSSI. Areas to the north of the CFMP area and at the coastal fringe are limited in environmental quality, largely due to historic agricultural practices and associated land drainage activity along with urban development along the coastal fringe.

Environment Agency 32 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.14 - Environmentally designated sites

The Adur CFMP catchment encompasses eight SSSIs, designated because of their ecological or geological importance. These SSSIs do not require a Water Level Management Plan (WLMP) to be prepared. The vast majority of SSSI land is in good condition and meets the Public Service Agreement (PSA) targets whereby 95% of SSSIs in England are to be brought into favourable condition by 2010. The SSSIs, the habitats protected, and their quality, are summarised in Table 2.4. Only the Adur SSSI is affected by the 1% annual exceedence probability fluvial flood event.

The Adur Estuary SSSI represents one of the most significant areas of saltmarsh habitats between Pagham Harbour in the West and Sandwich Bay in the East. This habitat supports unusual plant and wildlife and part of the site is also a managed RSPB Reserve. Across the CFMP area habitats of particular concern include heathland, ancient woodland, chalk grassland and grazing marsh, which have declined in area and status in the recent past.

Environment Agency 33 River Adur Catchment Flood Management Plan (September 2008)

Table 2.4 - Summary of SSSIs Summary of Sites of Special Scientific Interest in the River Adur CFMP area Area of Site Name Feature description SSSI in CFMP area Located to the west of Shoreham on the River Adur. This site represents large areas of saltmarsh and inter-tidal mudflats. These habitats support unusual Adur Estuary estuarine plant communities and a number of wading 0.6 km2 birds. A natural flow regime will help to conserve the features of this site; therefore it is likely that periodical flooding will have a beneficial effect in this SSSI. Situated on the scarp slope of the South Downs. This site is of both geological and biological importance. Three nationally uncommon habitats are represented 2 Beeding Hill to Newtimber Hill 3.2 km at this site which supports a rich community of invertebrates. Devil’s Dyke, the best know example of a dry chalk valley is located on this site. This coastal site comprises the length of chalk cliffs stretching from Brighton to Newhaven and includes the wave cut platform at the cliff base. Although the Brighton to Newhaven Cliffs main interest of the site is geological some rare and 0.6 km2 uncommon plants grow on the cliff face. This site is unlikely to be affected by fluvial, surface water or groundwater flooding. This site is located on the steep chalk escarpment of the South Downs and is dominated by a nationally uncommon woodland type. There are also areas of chalk grassland, another habitat that has a restricted 2 Chanctonbury Hill 0.8 km distribution nationally. The site supports a rich community of breeding birds. This site is unlikely to be affected by fluvial, surface water or groundwater flooding. This site is an ancient hill fort site situated on chalk. The main biological interest of the site centres on the Cissbury Ring areas of unimproved chalk grassland, a habitat type 0.8 km2 which has become rare nationally through being under constant threat from agricultural improvement. This extensive site lies on the chalk escarpment and dip slope of the South Downs. The nationally uncommon chalk grassland dominates much of the 2 Clayton to Offham Escarpment 1.1 km site but woodland and scrub is better represented here than on other chalk sites in East Sussex. The site supports a rich community of breeding birds. This site is on Weald Clay and contains a range of grassland types which have resulted from the wide Ditchling Common variation in drainage conditions. Variable drainage 0.6 km2 and past management of the site have led to a diversity of habitats. The chalk downland of this site is rich in flowering Wolstonbury Hill plants and includes a number of uncommon species. 0.6 km2 Woodland is established in parts of the site. Source: www.naturalengland.org.uk

Although there are no sites of international importance for nature conservation, i.e. Special Protection Areas (SPAs), Special Areas of Conservation (SACs) or Ramsar sites, within the catchment, there are numerous Sites of Nature Conservation Importance (SNCIs) designated Environment Agency 34 River Adur Catchment Flood Management Plan (September 2008) in local plans. Many of these have a wetland component and there are opportunities to enhance these sites and help meet the national Biodiversity Action Plan (BAP) targets.

The Local Biodiversity Action Plan (BAP) for Sussex includes action plans for coastal and floodplain grazing marsh, saltmarsh, chalk grassland and heath, and several other habitats present within the catchment. As farming became more intensive towards the middle of the 20th Century, large areas of the river floodplains lost wildlife, which depended on traditional grazing marsh along with the rivers and associated wetland habitats, particularly around the South Downs. Efficient drainage now means there is less winter flooding and numbers of waterfowl and over-wintering waders have declined as a result. Water abstraction and pumped drainage have also had a profound effect on ecologically valuable systems by reducing or polluting the water in groundwater and rivers respectively.

2.8.2 Landscape Character and Natural Habitats (Joint Character Areas) There are five Joint Character Areas (JCA) as described by Natural England that cover the study area. These include the Low Weald and the South Downs, and to a lesser degree, the South Coast Plain, High Weald, and Wealden Greensands as shown in figure 2.15. The total area of each JCA within the catchment is listed in table 2.5. The JCAs reflect the geology, topography, natural systems and processes, and the wildlife in the different parts of the catchment. These classifications recognise the unique and highly contrasted landscape of the River Adur catchment. JCAs are not designated sites but are a widely recognised spatial framework, used for a range of applications, including the targeting of Defra's Environmental Stewardship Scheme, and informing local assessments of landscape character. Each JCA has its own individual character and identity, even though it shares the same overall characteristics with other areas of the same type of landscape.

Table 2.5 - Landscape character summary Adur CFMP landscape summary

Joint Character 2 Area (km ) % of CFMP area Area High Weald 56 9.3% Wealden 8 1.3% Greensand Low Weald 279 46.5% South Downs 199 33.2% Coastal Plain 58 9.7%

High Weald The northeast corner of the CFMP area lies within the High Weald. This Natural Area is one of the most densely wooded areas in England (also demonstrated by the SPARQ land cover in figure 2.6). There is abundant semi-natural ancient woodland as well as chestnut coppices and conifer plantations. Open water habitats include numerous ‘hammer ponds’ originating from the Wealden iron industry and various ornamental lakes in landscaped parks. Nature conservation features of local significance are considered to be ancient and/or species-rich hedgerows, rivers and streams, standing open water and wet woodland. Roads and settlements located along ridge lines, traversed with a dense network of small, narrow, and winding lanes which link scattered villages, hamlets and farms.

Environment Agency 35 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.15 - Landscape character areas

Low Weald The northwest and central CFMP area is dominated by the Low Weald; an area of low-lying and gently undulating clay vales creating a more enclosed small-scale character. The landscape here is a mixture of fields and hedgerows, well mixed with woodland. Surface water features are more frequent, with an abundance of ponds and small streams with associated sparse pockets of wet woodland habitat. The character is predominantly rural with scattered small settlements and villages. The central catchment of the Low Weald contains noticeably fewer habitat types and has poor natural habitat cover. Rivers within the Low Weald form deep incisive valleys with some wet grazing meadows and pockets of wet woodland. This contrasts with the drier upland areas. Lack of habitat is due to intensive farming and associated drainage works, and the historical modification of the river channel.

Environment Agency 36 River Adur Catchment Flood Management Plan (September 2008) Wealden Greensand There is a small pocket of this landscape type near the western edge of the CFMP area. The upper Greensand escarpment includes steep ‘hanger’ woodlands, open heath, river valleys, sunken lanes and small pastures. In this landscape Lowland heath is the most characteristic habitat. This habitat was once very abundant across the Greensand ridge, but is now concentrated in West Sussex, Hampshire and the western areas of Surrey. Heathland is now nationally and internationally rare and is a threatened habitat.

South Downs The chalk outcrop of the South Downs rises gently from the coast with a characteristic north- facing scarp and distinctive chalk cliffs forming at the coast. The landscape is of rolling arable fields and heavily grazed grassland with a few scattered villages and farmsteads. Natural habitat areas are more abundant within the South Downs than the adjacent Low Weald, with areas of coastal and floodplain grazing marsh associated with the River Adur valley and a narrow band of varying habitat types along the dip slope of the chalk block, which lies within the Beeding Hill to Newtimber Hill SSSI.

Coastal Plain The eastern edge of this type of landscape falls within the CFMP area, the most significant presence is to the west of the CFMP area tapering out near Shoreham. The major urban areas of Worthing, and Brighton and Hove dominate this area. This LCA is exposed to south-westerly winds, with relatively warm temperatures and high quality soils resulting in a long growing season and intensive farming. Large arable fields dominate the extensive and treeless lower plain. The lower plain is cut by southward-flowing streams, known locally as ‘rifes’, which have seasonally dry headwaters over the upper plain and into the Chalk dip slope of the South Downs. The most eastern parts of the South Coast Plain lie in the dip slope of the South Downs along the A27/M27 corridor. The urban development of the coastal strip between Bognor Regis and Brighton and Hove has had a major impact on landscape and wildlife habitats.

Each LCA, and their associated features and natural processes, give rise to a range of associated habitats, shown in figure 2.16. The approximate areas of different habitats within the catchment are set out in table 2.6, which shows that around 9% of the catchment has natural habitat cover. These habitats support important communities of plants and animals, some of which are nationally or locally rare and protected. BAP priority species in the River Adur CFMP area include the otter, great crested newt and pipistrelle bat. Details of priority habitats and species are contained within Appendix B.

Table 2.6 Main species rich habitat groups Main species rich habitat groups in the Adur CFMP area Natural habitat Approx area (km2) % of total catchment Inter-tidal habitats (mudflats and 0.6 0.1 saltmarsh) Species rich (unimproved and semi- 14.9 2.5 improved) grassland Woodland (broad-leaved and mixed) 40.1 6.7 TOTAL CFMP AREA 55.5 9.2% (Source: West Sussex County Council)

Environment Agency 37 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.16 - Main species rich habitat groups

The South Downs is already protected by the Sussex Downs Joint Committee through its AONB status. It is currently in the process of being designated as a National Park under the National Parks and Access to the Countryside Act 1949, as amended by the Environment Act 1995. National Park status will give the South Downs greater protection through special powers under this designation.

2.8.3 Fisheries The Freshwater Fish Rivers Directive (78/659/EEC) and Freshwater Fish Lakes Directive (78/659/EEC) require certain designated stretches of water (rivers, lakes or reservoirs) to meet quality standards that should help fish to live and breed. These directives are recognised under the Water Framework Directive (WFD), which will replace them in 2013. At present, there is no

Environment Agency 38 River Adur Catchment Flood Management Plan (September 2008) Fisheries Action Plan prepared for the River Adur or its tributaries, however significant stretches are designated. Designations of appropriate freshwater rivers and lakes fall into two categories: those suitable for Salmonids (fish that prefer clear faster flowing water such as Salmon and Trout but also Grayling) and those suitable for Cyprinids (fish suited to slower flowing deeper water including Carp, Tench, Bream, Roach, Chub and Minnows). Table 2.7 details designated reaches and their classes in the Adur CFMP catchment.

Table 2.7 - Freshwater Fish Directive designated reaches Designated reaches Water body Source Location Class Environment Adur – East Branch Burgess Hill Stow - Source Cyprinid Agency

Environment Adur – East Branch Shermanbury Place – Wyndham Farm Cyprinid Agency

Environment Adur – East Branch Wyndham Farm – Twineham Green Cyprinid Agency

Environment Copyhold Stream confluence – Burgess Hill Adur – East Branch Salmonid Agency Stow Environment Twineham Green – Copyhold Stream Adur – East Branch Salmonid Agency confluence

Environment Adur – West Branch Extension - Source Cyprinid Agency

The Adur CFMP catchment has a good mixed population of other (coarse) fish and the River Adur and its tributaries are used extensively for coarse fishing. Coarse fish use most of the tributary streams as either spawning areas or nursery areas before moving to the main river and tributaries.

Coarse fish have been stocked, including specimens of Tench, Bream, Carp, Chub and Rudd. Flounders, Eels, Grey Mullet, Sand Smelt and Bass are present in the Adur estuary during summer and autumn. The only large fish recorded as native to the freshwater part of the river is the Brown Trout, a non-migratory Salmonid, which occurs widely throughout the Adur catchment. (Native rudd and bream may also be present.)

Out of bank river flow may cause fish to be displaced, stranding them in old water meadows and drainage ditch networks. Flooding can also impact on still water fisheries and fish farms within the floodplain as fish can be washed out of lakes and ponds into the river. This is of particular concern if non-native species are introduced to the river system. Spring flood events can impact upon fish migration as Cyprinid and Salmonid juvenile fish can be washed out of the watercourse or washed above structures, where they can become trapped when levels drop again. Sediment washed into rivers during flood events can affect gravels and smother spawning and nursery areas. Future flood risk management options present an opportunity to help preserve and enhance fisheries to benefit angling and the environment.

2.8.4 Tourism and recreation The coastal towns of Worthing, Littlehampton, Shoreham, and Brighton and Hove are popular tourist destinations. The coastline between Hove and Saltdean attracts a variety of people from naturalists to holidaymakers. Extensive sailing and water sports facilities are available, particularly at Shoreham. The angling and Trout fishing offered by the River Adur, its tributaries and the still water bodies within the catchment are a major attraction. The historic sites and Environment Agency 39 River Adur Catchment Flood Management Plan (September 2008) estates such as Chanctonbury Ring, Knepp Castle and Hickstead are also very popular all year round. The unique and invaluable countryside of the South Downs as well as the Weald attracts horse-riders, ramblers and many other sightseers.

The inland villages and the character of the surrounding countryside provide charm that attracts visitors from the coast, London and beyond. There is an extensive rights of way network including the Coastal Link, an important pedestrian, bridle and cycle path along the River Adur, which also includes a prominent sculpture trail. The Sustrans cycle route (No 79) runs along the eastern bank of the River Adur. The Link joins Shoreham to the South Downs where it connects with the South Downs Way and the Downs Link, both long distance bridle and cycle paths.

2.8.5 Surface water quality The Water Framework Directive (WFD) aims to improve water quality. Currently general water quality is assessed each year through the General Quality Assessment (GQA) scheme. This looks at the biological, chemical and nutrient quality of a watercourse.

The water quality of the River Adur and its main tributaries is variable and is detailed in table 2.8. The river’s ecology is highly sensitive to changes in flow in the upper headwaters of the western branch, upstream of Burgess Hill, and on the eastern branch and all of the smaller tributaries. This includes notable Chalk stream habitats at various sites on the scarp slope of the Brighton Chalk aquifer. The ecology in the lower reaches and tidal stretches is generally less sensitive to freshwater flows.

Routine monitoring shows that surface water quality within the Adur catchment is generally good. However, the disposal of wastewater continues to cause shortfalls in river water quality. Drought conditions experienced in recent times have contributed to this problem as the receiving watercourses have less flow to dilute discharges from wastewater treatment works (WWTW). There are quality concerns associated with the large Goddards Green WWTW discharge to the Adur East Branch, which would naturally have much lower summer flows downstream of this point. Upstream of the WWTW, urban drainage has been identified as the main cause of poor water quality. Pollution incidents and diffuse pollution also affect the quality of surface water. Meeting future water quality objectives and making water quality improvements, relies on sufficient flows being available in the catchment’s rivers and streams.

Recent GQA results (2001-2004) show water quality in the Adur CFMP catchment is typically ‘fairly good’ or ‘fair’, graded C and D respectively.

There are several outstanding water quality issues that affect the CFMP area, including:

• Diffuse pollutants from urban areas and roads entering the watercourses affect water quality. In areas of urban growth it is going to become more important to manage pollution better. • Run-off from agricultural land (such as fertilisers, herbicides and pesticides) has a significant impact on the nutrient levels in the surrounding watercourses. • Increased sediment from soil erosion caused by surface water run-off and also from scour within river channels. This can damage fish spawning habitats by smothering gravels; increase the costs of providing drinking water; and increase the need for river maintenance activity.

We aim to improve water quality where possible and the CFMP must make sure that the plan and flood risk management policies and actions do not adversely affect water quality. There is also an opportunity for flood risk management to include features, such as creating wetlands, which both improve water quality and help to manage flood risk. There will be improvements in Environment Agency 40 River Adur Catchment Flood Management Plan (September 2008) water quality after the first stage of a £3 million scheme at Steyning Wastewater Treatment Works is completed.

2.8.6 Groundwater quality The WFD also has a requirement to protect groundwater and groundwater-fed environments. New flood risk management schemes will need to take into account any environmental measures needed to comply with the Directive and eventual groundwater quality objectives (which will consider resources and quality). These objectives will have to be accounted for when choosing future flood risk management policies.

Water companies use the chalk aquifers of the South Downs extensively for public water supply, providing high quality drinking water that has allowed the coastal towns, such as Brighton and Hove, and Worthing, to develop. This is a finite resource; most of the groundwater is fully utilised through existing abstraction licences and water resources may be a factor affecting future development plans for the area.

We closely monitor all abstractions from groundwater sources and rivers as well as effluents discharged from sewage treatment works. In this area the chalk aquifer is considered to be at risk from diffuse pollution and from over abstraction or flow regulation. Overall, the aquifer is classed as being at risk of not meeting the Water Framework Directive conditions.

Nitrate levels are used as a general indicator of groundwater quality because they are one of the few factors with long data records. Nitrate comes mainly from agricultural sources and is subject to controls under the EC Nitrate Directive. Much of the area in this catchment is also designated a Nitrate Vulnerable Zone (NVZ). Groundwater in the Chalk aquifer is naturally of very high quality, however increasing nitrate levels are of concern and are being closely monitored. Table 2.8 details the water quality baseline data.

Table 2.8 - Water quality baseline data Water quality baseline in the Adur CFMP catchment Topic Source Trend Adur East –Very high phosphates, moderately low nitrates. Adur West – Very high nitrates and phosphates. Environment Lower Adur – No data. Agency 2006. River Ferring Rife – No data. quality (GQA) data Teville Stream – No data. & maps 2002-04. Steyning classified as a sensitive area with regard to reducing phosphorous. Adur West – Biology similar to that expected for an unpolluted river. Adur East – Biology varies from worse than expected for an Environment River Quality unpolluted river downstream of the WTW to fairly good in the Agency 2006. River (GQA): uppermost reaches. quality (GQA) data Chemical and Lower Adur (freshwater tributaries) - Generally similar to that & maps 2003-5. Biological expected for an unpolluted river, but Black Sewer worse than expected in places. Ferring Rife & Teville Stream – No data. The water quality of the River Adur and its main tributaries varies. The river’s ecology is highly sensitive to changes in flow in the upper headwaters of the western branch above Burgess Environment Hill and on the eastern branch and all of the smaller tributaries. Agency 2003. Adur This includes notable chalk stream habitats at various sites on and Ouse CAMS. the scarp slope of the Brighton chalk aquifer. The ecology in the lower reaches and tidal stretches is generally less sensitive to freshwater flows.

Environment Agency 41 River Adur Catchment Flood Management Plan (September 2008) Environment River Quality RE4 Target compliant: sections of Adur West, Lower Adur. Agency 2006. River Targets RE3 Target compliant: River Adur East RE2 Target compliant. quality 2003-05.

Environment Source Protection Zones cover two large areas of the South Agency 2006. Downs (the Adur valley splits the zone), a smaller isolated area Groundwater around Keymer, and a very small area to the west near the area source protection of Ashington. Groundwater zones. vulnerability BGS1995. South Downs: Major aquifer (with soils of high leaching Groundwater potential). Vulnerability Map South Downs is classified as a high risk major aquifer. Sheet 45.

Environment Low flow is assessed on the western branch of the River Adur at Agency 2003. Adur Hatterell’s Bridge and on the eastern branch at Sakeham. Adur Low flows and Ouse CAMS assessed as having water available in the upper areas but not 2003. available from the chalk block across the lower catchment. Estimated potential annual suspended sediment input to coastal waters from the Adur is 20,000 – 26,000 tonnes a year. This is SCOPAC 2006. reduced by flow barriers and diverting high flows, so actual Sediment Sediment Transport quantities of fine sediment input are approximately 2,600 tonnes load Study. a year. The river does not contribute a significant gravel (bed load) input due to the restricted source area and upstream and in-channel storage of any gravel entering the system.

2.8.7 Historic environment This section highlights key historic environment features in the Adur CFMP area. For this CFMP, we have considered the following:

• Scheduled monuments - There are 115 scheduled monuments in the Adur CFMP area. These are legally protected under the Ancient Monuments and Archaeological Areas Act 1979. Any works affecting a scheduled monument or its setting requires the consent of the Secretary of State for the Department of Culture, Media and Sport.

• Listed buildings - There are 2942 listed buildings in the Adur CFMP area. There are three grades of listed buildings, although all are designated for their national importance: Grade I = buildings of exceptional interest Grade II* = particularly important buildings of more than special interest Grade II = buildings of special interest warranting every effort to protect them.

• Registered historic parks, gardens and battlefields - There are 9 registered historic parks and gardens in the Adur CFMP area, and no registered historic battlefields.

• Non-designated historic environment assets - Not all nationally important historic environment assets are designated. Other features may be known and recorded on the Local Authority Historic Environment Record (HER). Additionally, there may be unknown features of significant interest, particularly buried archaeological remains. These are particularly likely to occur in deeply alluviated floodplains. As the CFMP is a high level strategy document, data from the HER have not been considered as they are too detailed for this study and contain tens of thousands of sites, most of which are not considered to be of national importance. However, these data will be considered, and

Environment Agency 42 River Adur Catchment Flood Management Plan (September 2008) the views of local authority and Archaeological Trust archaeological officers sought at more detailed stages of flood risk management planning.

People have been living in the Adur CFMP area since ancient times and the area is very rich in historical features, including defensive sites, burial mounds and field boundaries. Important historical features include medieval bridges and water level control structures, including old water meadows and mills. There have been many discoveries of Palaeolithic and Mesolithic artefacts along the Adur valley, reflecting the significance of the river in patterns of human settlement and activity. Notable areas of historical significance include Bramber Castle, Bramber (former port), Knepp Estate, St Mary’s House (c.1470) close to an old area of Steyning, Beeding, and the Saltern mounds in the lower floodplain. The catchment has many areas of heritage value with over 100 Scheduled Monuments (SMs). These are shown with Registered Parks and Gardens, and listed buildings in Figure 2.17. Scheduled Monuments and Registered Parks and Gardens vulnerable to flooding are labelled in Figure 2.17.

Figure 2.17 - Location of scheduled monuments

Environment Agency 43 River Adur Catchment Flood Management Plan (September 2008) There are a number of designated sites around Steyning and Upper Beeding that lie in and around the floodplain. Climate change may result in more of these sites being affected by flooding. If flooding occurs more often in the future and is more severe it may lead to the loss or damage of historic environment assets. In the lower catchment, Saltern mounds are a legacy from the medieval salt extraction industry and are considered to be at risk from the effects of increased flooding, sea level rise and siltation.

Historic environment assets and their settings may also be vulnerable to damage resulting from flood risk management schemes, in particular those requiring construction of defences. Objects of archaeological importance can potentially be affected by changes in flood risk management activities. When the environment within which an object or building is located changes, the object’s condition will change, often deteriorating, until it reaches a balance with the new conditions. Changes in flooding patterns, flood duration and water quality, for example, could all potentially have an impact on historic objects and buildings sited on or submerged within the floodplains of the Adur CFMP area. The alteration of water levels may impact upon historic resources, for example altering the preservation environment of buried archaeology or causing structural damage to historic buildings. It is an offence under the 1979 Ancient Monuments and Archaeological Areas Act to deliberately flood land in, on or under which there is a scheduled monument.

Our policies and plans will consider the potential effects on these important historic sites and objects of archaeological significance. There may be opportunities to improve the setting of some historical sites, for example Knepp and Bramber castles.

2.9 Communities and the local economy

2.9.1 Community Environmental constraints have preserved the rural character of the area and local communities are therefore either located around small, close-knit villages and farmsteads or concentrated in the larger urban centres. The South East is a relatively wealthy part of the country and this is generally reflected in the local communities, infrastructure and services of the catchment. However, there are significant levels of social deprivation in parts of the city of Brighton and Hove and also the neighbouring Adur district. Around 550,000 people live in the River Adur CFMP area. Most of these people live either on the coastal plain, in towns such as Worthing and Shoreham and the city of Brighton and Hove, or in inland towns such as Burgess Hill, Steyning and Upper Beeding. Smaller settlements, for example Hassocks, Henfield, and Partridge Green, are scattered across the catchment.

There are seven administrative areas within, or partially within, the Adur CFMP area, as shown on figure 2.18. These are:

• Adur District Council • Arun District Council • Brighton and Hove City Council • Horsham District Council • Lewes District Council • Mid Sussex District Council • Worthing Borough Council

Environment Agency 44 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.18 - Administrative areas within the River Adur CFMP area

2.9.2 Demographics Table 2.9 shows the current population of each of the administrative areas and population density (people per km2) in the CFMP area.

Brighton and Hove has the highest population density, with approximately 3,000 people per km2. The demographic pattern across Sussex is one of a rapidly ageing population. Table 2.9 shows that all administrative areas have higher percentages of people of pensionable age or over, than the national average. Ageing populations place specific demands on public finances but also contribute to the local economy through their purchasing power. Population ages and distributions may have implications for flood risk management in terms of vulnerable groups at risk.

Environment Agency 45 River Adur Catchment Flood Management Plan (September 2008)

Table 2.9 - Population size data Population and statistics, 2004 Total Percentage of Proportion People Population population population (%) Region / Area of CFMP 2 per total percentage Aged District (km ) 2 Of pension area (%) (km ) (thousand) change under 1 age or over 1981-2004 5 Adur District 7 42 1418 59 1.1 5.3 23.2 Arun District 5 221 654 144 21.7 5.2 24.7 Brighton and 13 83 3047 252 6.2 5.2 17.3 Hove City Horsham 43 530 235 125 24.3 5.6 19.9 District Lewes 4 292 320 93 18.3 5.1 26.0 District Mid Sussex 22 334 384 128 9.2 5.7 19.6 District Worthing 6 32 3015 98 5.9 5.4 25.2 Borough South East - 19,069 425 8,110 12.0 5.6 19.1

England - 130,281 385 50,094 7.0 5.7 18.5

1 Pension age is 65 or over for men and 60 or over for women. (Source: Office for National Statistics, 2004)

In relation to the hydrological units (see figure 2.11), the Lower Adur is the most highly populated. This is due to the densely populated areas of Brighton and Hove. The Teville Stream and Ferring Rife catchments are also densely populated, with Worthing Borough having the second highest population density.

2.9.3 Economy The CFMP area has two types of economy:

• The rural South East – a rural area with well-established market and county towns, which provide a focal point around which economic activity may cluster and spread. • The coastal South East – a less prosperous periphery, with large urban areas offering strong economic potential alongside coastal towns that have had mixed success in reinventing themselves (SEEDA 2006).

The local economy has grown since the mid 1990s due to an increase in financial services, new media and advanced engineering industries (Brighton and Hove AIF 2003). Public sector and service industry jobs also provide a major source of employment. The tourist economy, associated with the South Downs and the cultural sectors at the coastal fringe, are central to the social and economic vibrancy of the area.

In the South East region there are nine major centres of economic activity known as the South East ‘Diamonds for Investment and Growth’. The Adur CFMP area includes two of the nine areas; Gatwick and Brighton (Gatwick being a larger area incorporating Burgess Hill and a relatively small area to the north of the catchment). In general, economic strategies within the catchment are divided by an urban focus corresponding to the ‘Diamond’ areas with an emphasis on regeneration and development of existing urban areas, and rural focus elsewhere. The emphasis for rural areas is to develop sustainable income for the farming community, linking to the agri-environment schemes and improved management of the landscape (this will also help to protect and enhance the tourist industry). The issue of flood vulnerability is Environment Agency 46 River Adur Catchment Flood Management Plan (September 2008) particularly important when considering the constraint it may pose to economic regeneration and associated development proposed for the region anticipated within the RSS.

2.9.4 Critical infrastructure The CFMP area contains regionally, nationally and internationally important infrastructure including transport links, hospitals, emergency response centres, electricity sub stations, sewage treatment works, schools and telephone exchange buildings. These services are located throughout the CFMP area, although they tend to be more concentrated within the coastal fringe, including Brighton and Hove, Shoreham, and Worthing. There is also important infrastructure in the Lower and Eastern Adur sub-catchments, including the urban area of Burgess Hill.

The A259 and A27(T) east to west routes across the south of the catchment link all the local coastal towns and the city of Brighton and Hove. The A23 and A24 are main roads running north to south within the catchment, and the A272 forms an important east-west link further north. There are two rail routes, one connecting London to the south coast via Burgess Hill, and another route running east to west along the coastal plain. Shoreham airport is located close to the west bank of the Adur estuary near Lancing and is a major base for flying activities on the South Coast.

Some of these sites and services are all highly vulnerable to flooding. The impact on the local and regional areas will be significant and will cause disruption if any of these services are affected by flooding.

2.9.5 Vulnerability to flooding We have assessed how vulnerable the population is to flooding by using the Flood Hazard Research Centre’s Social Flood Vulnerability Index (SFVI). The SFVI is a national dataset that covers the whole of England and Wales and categorises the vulnerability by enumeration district based on the latest survey information. The factors used to define vulnerability to flooding are:

• elderly (over 75 years of age); • lone parents; • long-term sick; • financial deprivation (unemployment, overcrowding, non-car ownership, non-home owning).

Vulnerability has been categorised into five bands, where category 1 represents low vulnerability and category 5 represents high vulnerability. Figure 2.19 illustrates the social vulnerability based on this dataset for the Adur CFMP area.

Environment Agency 47 River Adur Catchment Flood Management Plan (September 2008)

Figure 2.19 - Social vulnerability of the Adur CFMP area

Figure 2.19 clearly shows that the majority of the Adur CFMP area is of an average vulnerability (category 3), with significant areas in category 4, which represents a slightly higher flood vulnerability index. The most vulnerable areas are small parts of Brighton and Hove, Worthing and Hassocks, all of which are in category 5. This means that flooding in these areas will have higher social consequences than in other parts of the CFMP area.

Environment Agency 48 River Adur Catchment Flood Management Plan (September 2008) 3 Current flood risks and management Flood risk is the combination of the likelihood of a flood occurring and the damage caused when it does. This section discusses the history of flooding in the Adur CFMP area, examines its probability and consequences and finally describes how we currently manage the risk of flooding.

3.1 History of flooding

Few of the rivers and streams flowing through the CFMP area are in their natural state; they have almost all been modified by man at various times and for a variety of different reasons. Table 3.1 presents a brief summary of some of the notable flood events over the past 100 years. We have drawn this information from our archives of historical floods, information provided by the Local Authorities within the CFMP study area, fire brigade records, media and academic papers, and the British Hydrological Society’s Chronology of British Hydrological Events (www.dundee.ac.uk/geography/cbhe).

Table 3.1 - Selected historic flood events Summary of main historic flood events in the Adur catchment Event Details date Heavy rains caused flooding of the Adur valley from Ashurst, Partridge Green, Henfield, and 1911 Steyning to Bramber. Lower floors of properties were inundated with floodwater (November). 1925 Widespread flooding of Adur valley. 1958 Patcham – surface water flooding of roads Highway and road flooding widespread throughout catchment. Properties flooded in Lancing and Worthing (October/November). 1960 Mile Oak – groundwater flooding in gardens Patcham – block of flats affected by groundwater flooding 1960s Properties flooded by water from a ditch in Bevendean 1964 Small scale flooding, property and roads affected in Worthing and Lancing. Road flooding at Worthing, Wivelsfield and properties flooded at Hurstpierpoint and Keymer 1965 (November/December). 1966 Roads and fields flooded at Cuckfield and Bolney (February). Widespread flooding across catchment - Ashurst, Bramber, Coombes, Shipley, Twineham, 1974 Upper Beeding, West Grinstead, Lancing and Steyning. A281 closed at Henfield (11-14 November). Flooding in Burgess Hill, Ashurst, Clayton, Cuckfield, Ditchling, East Preston, Ferring, Findon, Fulking, Shipley and Henfield. Surface water flooding at Steyning High Street, river flooding at Steyning affected some properties. Road flooding at Burgess Hill. Shopping area in Findon covered in an inch of silt. Shoreham airport access disrupted. Kimp Barn Lane flooded, cutting off access to properties and the sewage treatment works (22-23 November). Environment Agency 49 River Adur Catchment Flood Management Plan (September 2008) Summary of main historic flood events in the Adur catchment Event Details date Patcham - surface water flooding of roads Coolham Road flooded (June). 1976 Mile Oak – surface water runoff flooding (properties inundated – number unknown) 1977 Properties flooded in Ashington. 1979 Flooding in Henfield, Burgess Hill and Ashington. 1980 Buildings flooded in Worthing (September). Ferring Rife floods many properties. Sewers also backed up. 1980 Several properties flooded in Steyning and the High St was closed (October). 1981 Ferring Rife floods roads and properties. Properties damaged by surface water runoff from the South Downs in Bevendean. Estimated 1983 2 properties flooded. Properties flooded in Brighton by run-off from agricultural land. Surface water flooding in Findon. Serious flooding in Rottingdean caused by surface water runoff from the South Downs – houses flooded up to 1.4m deep. Two surface water runoff flood events occurred, with up to 66 properties flooded during the first, and 8 during the second. 1987 Woodingdean – damage to property from agricultural runoff. Flooding in Ovingdean, damage to property – likely source was surface water Mile Oak – surface water runoff flooding (properties inundated – number unknown) Bevendean – highway flooding from surface runoff A27, Lewes Road (Elm Grove area) – 2 residential properties flooded by surface water runoff (some incidents included basement flooding) Properties damaged by surface water runoff from the South Downs in Bevendean. Estimated 1988 2 properties flooded. Patcham – 1 commercial property affected by groundwater flooding 1991 Properties damaged by surface water runoff from the South Downs in Bevendean Properties damaged by surface water runoff from the South Downs in Bevendean 1993 Flooding in Ovingdean, damage to property – likely source was surface water Heavy run-off from the downs flooded property in Sompting and North Lancing. Extensive surface water flooding around Lancing and Shoreham. 1994 Mile Oak – cellar flooding (commercial property) Durrington, Sompting, Lancing – groundwater flooding some properties affected Patcham – surface water flooding Patcham – approximately 5 properties affected by groundwater flooding 1995 Rottingdean – Longhill School flooded by surface water runoff Fire brigade records for Brighton and Hove indicate at least 25 call outs in October, and 36 in 2000 November related to heavy rainfall, surface water, and groundwater flooding. These included cellar flooding in Mile Oak and Patcham to depths between 2 and 4 ft. Flooding in Sayers Common and Steyning. Severe flooding in Bramber following overtopping of defences on the main river. Groundwater flooding A27, resulting in surface water run-off in Brighton. Brighton to London railway closed. Groundwater flow at Chilgrove, Brighton. Basements flooded to up to 1.3m deep. Springs emerged and lasted for two weeks (December). Patcham – groundwater flooding; A23 flooded (closed); 15 properties flooded (ground floor), additional 5 properties with basements flooded. Sewer flooding caused by surcharging due to rainfall event – roads flooded. Bevendean – surface water flooding; Over 25 properties flooded, including houses, commercial properties, school and community centre. Flood depths of 0.5 to 1 m reported. Surcharging sewers also caused flooding. Environment Agency 50 River Adur Catchment Flood Management Plan (September 2008) Summary of main historic flood events in the Adur catchment Event Details date Lewes Road, Brighton – groundwater flooding (for 2 week period) closed two lanes causing traffic disruption. Woodingdean – surface water runoff causing ‘muddy flooding’ in gardens. Ovingdean - surface water flooding of at least one property Westdene – Pond overflowed flooding two gardens on four occasions, up to depths of 10 cm. Mile Oak – Runoff from farmland caused flooding on more than two occasions, ponding at a road junction to a depth of 1m, inundating two houses. On one occasion a cellar (commercial property) flooded to a depth of 1.3 m. Garden flooding to depths of 0.33 m is also reported. 9 roads were severely affected. Groundwater flooding in Brighton (February). 2001 Bevendean - surface water flooding; residential roads. Deep surface water and highway drainage flooded Findon. Depth from 1-1.8m recorded. 2002 A24 disrupted with almost a metre of flood water at Kingswood (March). Surface water flooding in Burgess Hill affected 8 residential properties and a number of 2004 commercial buildings. Wivelsfield also affected by drainage problems and surface water run- off (May). 2005 Heavy rainfall caused surface water flooding in Brighton and East Sussex (August).

There are over 150 records of surface water and/or sewer flooding in Worthing, Sompting, Lancing, and Shoreham from more recent times to some dating back to 1960. Some events affected properties, others just roads, and in some instances the information does not specify the receptor.

Although there is a relatively large collection of historic records available for the study area these vary in quality from professional studies and reports to anecdotal accounts. As such the level of detail provided in the CFMP regarding historic events varies depending on the source of information.

3.2 Sources and probability of flooding

The main sources of flooding in the River Adur catchment are rivers (fluvial), groundwater, impaired drainage causing surface water ponding, as a result of run-off from the land, from overloaded drainage networks and from tidally influenced processes. The degree to which these occur at the same time contributes to the severity of flooding. Flooding from the sea is not covered by this CFMP, but is addressed in the Shoreline Management Plan and the Coastal Defence Strategy that are produced separately. The influence of the tide on fluvial flooding is considered through using a Mean High Water Spring tidal cycle in the assessment of fluvial flooding.

We have produced flood risk maps for the whole of England and Wales and you can find these on our website. They show the extent of extreme flooding in the form of Flood Zone 2 and Flood Zone 3. Flood Zone 2 is defined as land with a 0.1% (1 in 1,000) or higher annual probability of being flooded from rivers and the sea. Flood Zone 3 shows areas with a 1% (1 in 100) or higher annual probability of being flooded by rivers or a 0.5% (1 in 200) or higher probability of being flooded by the sea. The map of Flood Zone 2 for the area covered by the CFMP is shown on figure 3.1.

The Flood Map is based mainly on information about flooding from rivers and the sea; the two main sources of flooding throughout the country. It does not include information about flooding from groundwater (water emerging from the ground where the water table is high) or from

Environment Agency 51 River Adur Catchment Flood Management Plan (September 2008) surface water (water collecting on or flowing over the surface before soaking into the ground or entering a watercourse). These are the other two important sources of flooding in the River Adur CFMP area.

Figure 3.1 - Flood outline for the 0.1% annual probability flood event

The 1% annual probability flood event is also described as the 1 in 100 year event. It is important to understand that a 1 in 100 chance of flooding in any one year does not mean that this level of flooding will happen once every 100 years. Nor does it mean that if the flood has not happened for the previous 99 years, it will happen this year. A flood of this severity could occur more than once in any given year, or occur two years in succession.

When discussing flood ‘risk’ we look at the combination of the chance (or probability) of a particular flood happening and the impacts (consequences) that would result. Only by examining both the chance and the impacts collectively can we gauge the scale of flood risk and assess its importance to people, property, infrastructure and wildlife. The CFMP process will look at the scale of changes in flood risk across the whole catchment. The occurrence of flooding from different sources and the assessment of risk are described in section 3.2.1 to 3.2.5 and summarised in table 3.2 at the end of this section.

Environment Agency 52 River Adur Catchment Flood Management Plan (September 2008) 3.2.1 River flooding The shape of the catchment and the nature of the rainfall event dictate the extent and depth of flooding. Water levels can also be significantly influenced by the presence of structures such as weirs and culverts. These can hold back river flow or constrict the space available in which the water can flow. There are two distinct types of river system in the CFMP area. One is the River Adur, which collects water draining from the High and Low Weald and the north slope of the South Downs, then flows to the sea along a relatively long channel that cuts through the South Downs. The other river system comprises the two small coastal rivers (Ferring Rife and Teville Stream) that drain the southern slope of the South Downs. They are much shorter and discharge to the sea through a tidal outfall and lake respectively.

To assess and quantify the level of flood risk for this CFMP, we used computer models to simulate river flows and estimate flooding. The models provide an indicative flood outline and also include estimates of flood depth. From these models, we can estimate the number of people at risk from flooding, what the economic damage to property might be and how the environment is affected, for example, impacts on designated sites. We have used a modelling system called TuFlow, which allows us to build a model relatively quickly, that covers a wide area of the catchment. The model covers the River Adur from Shoreham to Burgess Hill and Hassocks on the Adur East Branch and up to Coolham on the Adur West Branch. A small model was also built for the Ferring Rife from the coast up to the A2032 crossing with Yeoman Road. The level of detail within the models is appropriate to the aims of a CFMP, however it has been possible to include more detail where required, in order to represent an important feature. This includes flood defence walls, embankments, and other structures, which we make every effort to incorporate in the model as accurately as possible within the limitations of a broadscale model. The results of the models should not be compared to, or replace, more detailed studies we have carried out such as strategies or flood mapping studies.

We have divided the River Adur CFMP area into five hydrological sub-catchments that can be studied in more detail. These sub-catchments are the Adur East Branch, Adur West Branch, Lower Adur, Ferring Rife and Teville Stream and are shown in figure 2.11 (see section 2). Figures 3.2 to 3.5 show indicative flood outlines for the 1% and 10% annual probability flood events in the sub-catchments based on the broadscale modelling carried out for the CFMP. These flood outlines take account of existing raised flood defences. These figures also show the 0.1% flood outline taken from our Flood Zone maps (which does not take into account flood defences). Figure 3.6 shows the 1% and 0.1% flood outlines in the Teville Stream area taken from our Flood Zone maps only, as we do not have modelled data for the Teville Stream.

Environment Agency 53 River Adur Catchment Flood Management Plan (September 2008) Adur East Branch

Figure 3.2 - Flood outlines: 10%, 1% and 0.1% annual probability flood events (Adur East Branch)

The Adur East Branch above its junction with the Lower Adur and Adur West Branch drains the low permeability Sandstone of parts of the High Weald and the impermeable Weald Clay of the Low Weald. It therefore responds relatively rapidly to heavy rainfall, since most of the water runs fairly quickly off the land into the network of ditches and streams. The upper reaches of the Adur East Branch and two of its main tributaries, Pook Bourne Stream and Herrings Stream, flow through the urban areas of Burgess Hill and Hassocks, where river flows tend to remain largely within the channel, although lack of channel capacity (particularly if made worse by blockages) can cause localised flooding. Figure 3.2 shows that there are only small increases in the flood outline from the 10% to the 1% and 0.1% annual probability flood events in the rural areas, where we have modelled. However, in Burgess Hill and Hassocks there is a more noticeable increase in flood outline, with more properties at risk of flooding in the urban areas from the 0.1% annual probability flood event compared to the 1% annual probability flood event.

Environment Agency 54 River Adur Catchment Flood Management Plan (September 2008) Adur West Branch

Figure 3.3 - Flood outlines: 10%, 1% and 0.1% annual probability flood events (Adur West Branch)

Streams flowing into the Adur West Branch drain parts of the Low Weald and flow through predominantly rural landscapes, with no major urban areas at risk of flooding. River flows tend to remain largely within the channel or to flood recognised areas of functional floodplain. Flooding mainly affects agricultural land. There are a limited number of properties affected by river flooding; most of these are isolated farms or settlements. The flood risk does not increase with increased severity in this area.

Environment Agency 55 River Adur Catchment Flood Management Plan (September 2008) Lower Adur

Figure 3.4 - Flood outlines: 10%, 1% and 0.1% annual probability flood events (Lower Adur)

The Lower Adur is the largest sub-catchment of the CFMP area, comprising the River Adur tidal reach from the river mouth at Shoreham up to the confluence where the River Adur splits east and west, just northwest of Henfield. Figure 3.4 shows that the urban areas of Steyning, Upper Beeding and Bramber are at risk of flooding from the 1% and 0.1% annual probability flood events and a small section of Bramber is at risk from the 10% annual probability flood event. South of Steyning and Upper Beeding the raised embankments provide protection to most of the area from river flooding during the 10% annual probability flood event and the 1% annual probability flood event through Shoreham. Figure 3.4 shows that the Shoreham area is at risk from the extreme flood events (0.1% annual probability flood event), a combination river and

Environment Agency 56 River Adur Catchment Flood Management Plan (September 2008) tidal flooding. It should be noted that the risk of flooding from the sea is greater in Shoreham than from river flooding, and that flooding from the sea is covered by SMP. .

Ferring Rife

Figure 3.5 - Flood outlines: 10%, 1% and 0.1% annual probability flood events (Ferring Rife)

The Ferring Rife drains part of the southern slope of the South Downs and flows through the urban areas of Durrington and Ferring. The flood extents are fairly narrow and the flows are largely confined to the main river channel, which is shown on figure 3.5. There is little flood risk from the 10% annual probability flood event, which only increases slightly for the 1% annual probability flood event. Ferring and Durrington are more at risk from the extreme flood events (0.1% annual probability flood events), shown in pink in figure 3.5.

Environment Agency 57 River Adur Catchment Flood Management Plan (September 2008) Teville Stream

The Teville Stream flows between the urban areas of East Worthing and Sompting, draining part of the southern slope of the South Downs and the low-lying area on the coastal plain, before entering the sea via Brooklands Lake. A number of properties in the low-lying areas are potentially at risk from river flooding from both the 1% and 0.1% annual probability flood events. This data is based on our Flood Zone maps only.

Figure 3.6 - Flood outlines: 1% and 0.1% annual probability flood events (Teville Stream)

The extent of fluvial flooding and the potential consequences are uncertain for the Teville Stream. Although broad conclusions may be drawn, the lack of sufficient data to model the watercourse limits the analysis that can be completed in the CFMP.

Flood depths are available from the models of the River Adur and Ferring Rife. These are shown in figure 3.7 and illustrate relatively shallow depths and low velocities in the East and West Adur branches. Within the Lower Adur flooding is of moderate depth and medium velocity. Along the Ferring Rife flooding is moderate in depth but velocities are expected to be low. Further research is required to establish flooding depths and velocities in the Teville catchment.

Environment Agency 58 River Adur Catchment Flood Management Plan (September 2008)

Figure 3.7 - Flood depths for the 1% annual probability flood event

3.2.2 Tidal flooding The tidal Adur is the section of river that is influenced by the tide. It extends from Bines Bridge on the Adur West Branch and Shermanbury on the Adur East Branch downstream to the river mouth at Shoreham and is influenced by the tide throughout this length. Flooding can be caused by a combination of high tides and high river flows, which, on their own, may not cause any out of bank flow. There are flood defence embankments on both sides of the River Adur along the whole of this section. Flood risk along this section is caused by water breaching or overtopping the embankments on either side of the Lower Adur or when high river levels in the channel prevent the drainage from small tributaries. Water levels in the tidal reach are increased by high river flows coming down the River Adur and high spring tides and surge tides coming up the estuary. The protective harbour arm at Shoreham reduces the severity of surge tides travelling up the river. The incoming tide has less influence on water levels the further it is from the river mouth.

Tidal flooding of the main coastal streams (Teville Stream and Ferring Rife) is controlled via tidal flaps that prevent tidal waters from entering the streams where they discharge to the sea.

Environment Agency 59 River Adur Catchment Flood Management Plan (September 2008) However, the effect of the tides are noticed when, during high tides, freshwater from the streams is unable to drain away and can back up in the channels.

In areas at risk of flooding from the sea a typical flood risk assessments will consider a flood event with a 0.5% annual exceedence probability event. This more severe event is used to account for the greater consequences associated with flooding from the sea. The CFMP considers both the probability and consequences of flooding using the 10%, 1% and 0.1% fluvial flood events as specified in CFMP guidance. The CFMP does consider the influence of the tide on fluvial flooding through using the Mean High Water Spring as the peak of the tidal cycle used at the downstream end of the CFMP river models. Flooding from the sea is covered by the Beachy Head to Selsey Bill SMP.

3.2.3 Surface water flooding Surface water flooding features throughout the catchment but is a particular concern in urban areas where floods occur rapidly in response to heavy rainfall events. This type of flooding can occur when water is unable to drain away due to drains being at capacity or blocked with debris. Flooding can also be caused by rapid surface runoff from the surrounding countryside, and is often referred to as muddy flooding, due to the quantity of debris carried in the flood waters. In general, surface water flooding is the most frequent cause of flood event but the floodwaters are generally shallower and can last for shorter durations than other types (usually a few hours).

The most serious surface water flooding in the catchment occurs in Brighton and Hove, and Worthing. The large proportion of hard-surfaces and steep topography of Brighton and Hove leads to fast runoff rates that can flood properties, roads and gardens. Although relatively infrequent, the flooding of basements is a particular danger to life with anecdotal reports of flooding to depths of a metre occurring within 4 hours. Heavy rainfall events in 2000 caused flooding in some basement properties including properties in the Lewes Road and Patcham areas of Brighton and some parts of Mile Oak and Portslade. Records of historic surface water flooding incidents are kept by Brighton and Hove City Council, who have also commissioned a number of reports on surface water flooding incidents and flood risk management around the city. Historic records document incidents of surface water flooding back to the 1950s, and identify communities in Brighton and Hove most at risk.

Surface water runoff from agricultural land, with exposed soil, on the South Downs has also caused many ‘muddy flood’ events, particularly in the urban fringe areas of Brighton and Worthing. Changes in farming practices from pasture to arable resulted in an associated increase in flooding and erosion. In 1987, two separate run-off events caused flooding of up to 1.4m deep in houses in Rottingdean; the first event affected 66 properties, second affected 8 houses. This risk of flooding has been successfully reduced in some areas though changes in land management (such as arable reversion and the retention of winter stubble) and through the creation of earth dams to hold back run-off. After the 1987 event Brighton Council erected a series of earth dams and lagoons to reduce flooding in Rottingdean. The areas of Bevendean, Woodingdean, Ovingdean and Westdene were also affected by this type of flooding during the winter 2000/2001.

Elsewhere in the catchment, downland runoff also affects parts of Findon. Past muddy flood events in this area have disrupted road traffic passage and flooded some houses. The most notable event in recent years was in 2002 when flood waters up to one metre deep prevented traffic movement on the busy A24. Many of these effects have now been successfully mitigated through the Council’s efforts to secure more sensitive land management, however runoff from the Downs is still a potential source of flooding.

Environment Agency 60 River Adur Catchment Flood Management Plan (September 2008)

(Source: www.findonvillage.com/0594_findon_flooding.htm) Figure 3.8 - Surface water flooding in Findon

Burgess Hill experiences flooding once or twice a year from surface water. This is most severe in the east of the town where water is slow to drain away out to the west of the railway line. During some of the worst surface water flooding in 2004, approximately 8 houses and gardens were inundated to up to one metre with the water remaining for a few hours. In addition, a number of commercial buildings were affected and passage along one of the busy two east/west routes in the town was also difficult.

Parts of Wivelsfield are also affected by surface water flooding with reports of some properties being flooded six times in the past ten years. One of the recent events in May 2004 resulted in flooding of up to half a metre in localised areas affecting some houses, businesses and roads, with the most notable traffic disruptions occurring due to flooding of the B2112.

This information has been gathered from Brighton and Hove City Council, Worthing Borough Council, Burgess Hill Town Council, East Sussex Fire Service and internet searches.

3.2.4 Sewer flooding Sewer flooding occurs when sewage is unable to drain away in sewerage pipes but emerges from manholes or toilets usually due to the systems being overloaded with floodwaters. This form of flooding brings with it the additional hazards of spreading diseases and the dirty waters being particularly distressing for people to deal with in their homes.

In Brighton and Hove, storm water in the area is mostly drained via the sewers. The old permeable infrastructure can become inundated with groundwater when groundwater levels rise and the system can become overloaded in storm conditions. This has lead to a mixture of sewage spilling into the streets at several locations in past events, such as Preston Park and Patcham in winter 2000/2001. Areas of Portslade also suffered sewer flooding in 2002 after a rainfall event.

Environment Agency 61 River Adur Catchment Flood Management Plan (September 2008) Other parts of the catchment are subject to this type of flooding including some areas in Burgess Hill, Shoreham, and Worthing. Historical problems with sewer flooding in Durrington have been rectified through improvements to drainage infrastructure.

This information has been gathered from Brighton and Hove City Council, Worthing Borough council, Burgess Hill Town Council, East Sussex Fire Service and internet searches.

3.2.5 Groundwater flooding In the Adur catchment, flooding from groundwater occurs in areas with chalk geology. This affects the populations of Brighton and Hove, Shoreham, Lancing, and Worthing. Groundwater levels respond slowly to rainfall events but once levels are high enough, springs emerge at the surface and can remain for months.

As most of Brighton and Hove is built on underlying chalk geology, many areas of the city are susceptible to groundwater flooding. Based on the significant groundwater flood events in the past 100 years, groundwater flooding is estimated to occur every 1 in 20 years (BBV 2001). The most severe groundwater flooding experienced in Brighton and Hove, occurred in winter 2000/2001 which resulted in the closure of the London to Brighton railway line and parts of the busy A23. Many properties were also flooded, with properties in Patcham, Mile Oak and Lewes Road amongst the most severely affected. In Patcham 15 properties experienced flooding of their ground floor, and an additional 5 properties had basements flooded.

In Worthing, the northern parts of the town experience groundwater flooding, with springs occurring in Durrington and East Worthing when groundwater levels are high. During the 1993/1994 floods, some gardens were flooded by up to 3 feet of water. The A27 is also affected by high groundwater levels and in 2000/2001 flooding of this road, which is the main East/West coastal route across Sussex, lead to severe disruption.

This information has been gathered from Brighton and Hove City Council, Worthing Borough Council, Burgess Hill Town Council, East Sussex Fire Service and internet searches. In 2004 Defra completed a Groundwater Flooding Scoping Study, which aimed to provide information on the scale, distribution and nature of groundwater flooding. The report states that the Environment Agency held 20 reports of groundwater flooding within the Sussex Area of Southern Region. Within this area the Defra report identified 83,481 properties located within the emergence envelopes of the predicted groundwater emergence maps. The potential groundwater emergence zone is based on reported observations of groundwater flooding, and there is high confidence in the maps within this area.

3.2.6 Flood sources and risk summary Table 3.2 provides a summary of the sources of flooding and locations at risk within the Adur CFMP study area.

Table 3.2 - Flood sources and risk summary Flood sources and locations CFMP area sub- Flood source and mechanism Locations at risk division Burgess Hill and Hassocks – lack of channel Fluvial flooding. capacity can cause localised flooding. Adur East Surface water flooding from run-off in Burgess Hill and Hassocks - road and Branch the urban areas. property flooding. Surface water flooding generated from Wivelsfield – run-off from fields in Woods run-off from agricultural land. Green area affecting roads and properties. Environment Agency 62 River Adur Catchment Flood Management Plan (September 2008) Flood sources and locations CFMP area sub- Flood source and mechanism Locations at risk division Surface water flooding generated from Road drainage problems at West Grinstead, Adur run-off from agricultural land. including the A272. West Branch Run-off from highway drainage and Henfield suffers from highway drainage surface water. problems. Bramber, Upper Beeding, Ashurst, Henfield Fluvial flooding from the River Adur and Steyning – flooded regularly in the past, and its tributaries. defences exist, however these have been overtopped during extreme flows. Downland ‘muddy’ flooding affecting parts of Brighton, Bevendean, Woodingdean, Surface water flooding generated from Ovingdean and Rottingdean. Roads run-off from agricultural land. affected, clean up costs quite high and damage to land by soil erosion. Lower Surface water flooding from run-off in Roads affected in Steyning and Upper Adur the urban areas. Beeding. Shoreham and Shoreham airport affected by Fluvial and tidally influenced fluvial high river flows and tides overtopping flooding from the River Adur. defences. Patcham – Properties flooded, A23 closed and railway lines closed, Lewes Road – 2 Groundwater, surface water and lanes closed of 4 lane carriageway, persists sewage flooding. for weeks. Mile Oak – properties, car parks, and gardens flooded. Lancing - partial closure of A27. Roads and properties flooded from Ferring Fluvial flooding from Ferring Rife. Rife. Tidally influenced fluvial flooding from Tide-locking caused properties and Ferring Ferring Rife. agricultural land around Ferring Rife to flood. Rife Durrington – groundwater flooding, and Groundwater, surface water and Downland ‘muddy’ flooding affecting Findon. sewage flooding. Surface water (possibly combined with sewer flooding) in parts of Worthing Potential for flooding of commercial and residential properties adjacent to the Teville Potential for fluvial flooding from the Stream particularly when groundwater levels Teville Stream. are high. Further research needed to Teville establish extent of potential flooding and risk. Stream Sompting and North Lancing affected by groundwater flooding. Parts of East Worthing Groundwater and surface water and Broadwater. Surface water flooding flooding events recorded in Worthing town centre and Worthing hospital. Sources: CFMP broadscale modelling (see section 3.3 for more details on modelling results) (Locations listed above can be found on figure 1.1 or figure 2.10)

Environment Agency 63 River Adur Catchment Flood Management Plan (September 2008) 3.3 Consequences of flooding

In section 3.2 we looked at the probability and sources of flooding. In this section we discuss the consequences of flooding at these locations and elsewhere, using results from broadscale models.

We developed two broadscale ‘hydraulic’ models to simulate the fluvial flooding that would occur in the River Adur and Ferring Rife catchments during storms of different magnitudes. We used standard Flood Estimation Handbook (FEH) techniques to derive the inflows (mainly from surface water but also from groundwater) to the river system at various points throughout the catchment and to determine how these flows will vary with time. We developed sets of inflows to represent storms with a range of probabilities of occurrence, from 20% to 0.5% each year (once every five years to once every 200 years on average).

Each broadscale model simulates the movement of the inflowing water down the river channel, taking into account its shape and steepness (together with a number of other variables, such as bed roughness) and the presence of any major structures (bridges, culverts etc.) that could affect the movement of water. The models simulate details of the floodplain characteristics in each case, including flood embankments. The model can tell us when the flow is likely to spill out of the main channel, where flooding is likely to happen, how deep the flooding is likely to be and how long the water is likely to stay in flooded areas.

The output from these ‘hydraulic’ models can be represented as a series of maps showing the maximum depth of water that will occur at each place in the catchment during floods with a different chance of happening. When compared to maps showing agricultural land use and property locations, we have used these flood depths to estimate the economic value of the damage that is likely to occur as a result of flooding. By combining the estimated economic losses during floods with different probabilities of occurrence we have been able to determine the average loss that is likely to happen each year (the ‘annual average damage’) in a particular area or over a catchment as a whole.

These broadscale computer models, are based on a number of simplifying assumptions and data that is relatively coarse. This is necessary to avoid making the models too cumbersome and time-consuming to run but means that, although the results give a good indication of how the catchment as a whole is likely to respond to flooding, they often do not represent the flooding of detailed areas of individual properties accurately. This is not a concern for the CFMP given its scope and objectives.

We work out the impact of flooding on people, property and the environment by looking at the 10% and 1% annual probability fluvial flood events from the broadscale modelling, and the 0.1% annual probability flood extent from the Flood Zone 2 outline. The Flood Zone outline assumes no flood defences and includes flooding from rivers and the sea.

A quantitative comparison of flood extents is restricted by differences in the geographical coverage of the different sources of the flood outlines. The 10% and 1% outlines produced by the broadscale models are available for fewer rivers than the 0.1% flood outline obtained from the Flood Zone maps. However, using all three outlines provide an indication of the level and change in flood risk.

Following feedback from the scoping stage, the broadscale models have been updated. This means that the damage results have changed slightly from the scoping stage. Models have not been developed for other sources of flooding, such as groundwater or surface water. Consequently we do not have models or maps that show flood risk, and cannot calculate Environment Agency 64 River Adur Catchment Flood Management Plan (September 2008) economic damages or quantify flood risk caused by these or other sources of flooding, except from historic records and reports. Where possible, based on historic records we have given an indication of flood risk from other sources. We also do not have enough data to build a model for the Teville Stream. Therefore, we have not been able to calculate damages for this catchment. It is one of our priorities to collate data and to gain a better understanding of flood risk in the Teville catchment. The models we do have are very important for the CFMP as it shows us how sensitive the catchment will be to changes in the future.

3.3.1 Risks to people and the community At the household and community level, flooding can cause personal distress, poor health and damage to property and possessions, as well as disrupting people’s daily routine. Some sectors of the population are particularly vulnerable to flooding and are likely to have greater difficulty in coping with the after effects. Table 3.3 summarises the communities at greatest risk from fluvial flooding from a range of annual probability flood events (10%, 1% and 0.1%). The 10% and 1% annual probability flood events are based on model results with defences, however the 0.1% annual probability flood event is based on the without defences scenario.

Table 3.3 - Communities currently at risk from river flooding Communities currently at risk in the River Adur CFMP area CFMP area sub- Number of residential properties at risk Key communities division 10% 1% 0.1% Adur East Branch Burgess Hill, Hassocks 2 12 539 Adur West Branch Isolated properties 0 0 15 Steyning, Bramber, Upper Beeding 3 91 103 Lower Adur Shoreham 0 1 344 Ferring Rife and Ferring, Durrington, Sompting, East 2 52 502 Teville Stream* Worthing TOTAL - 7 156 1503 *Information uncertain due to insufficient data to model Teville Stream

Flooding can lead to health impacts including physical effects in the short term and psychological effects in the short and long term. The scale of these effects depends on numerous factors including social vulnerability, the nature of the flooding and post-flood activities (Defra, 2004). For the Adur CFMP, we have assessed how vulnerable the population is using the Flood Hazard Research Centre Social Flood Vulnerability Index (SFVI). The baseline SFVI is described in section 2.9. Table 3.4 provides an indication of the number of properties in each SFVI category located in the floodplain.

The East, West, and Lower Adur areas generally have people with a medium vulnerability classification, however in the urban areas, such as Hassocks and Lancing, there are pockets with higher vulnerability. In parts of Shoreham and Worthing vulnerability is low to medium, with pockets of high vulnerability in Ferring, parts of East Worthing, and Sompting.

Table 3.4 indicates that the majority of people at risk of flooding in a 1% annual probability event are of medium to high vulnerability. Areas adjacent to the Teville Stream have SFVI classifications of 2, 3, and 4, with the majority being 3 and 4. As such although the extent of flooding on the Teville is not certain the people who could be at risk generally have a medium to high vulnerability.

Environment Agency 65 River Adur Catchment Flood Management Plan (September 2008)

Table 3.4 - Social vulnerability of properties affected by the 1% annual probability flood event Number of properties in each SFVI classification CFMP area Social flood vulnerability classification* Key communities sub-division SFVI 1 SFVI 2 SFVI 3 SFVI 4 SFVI 5 Adur East Burgess Hill, Hassocks 0 2 10 0 0 Branch Adur West Isolated properties 0 0 0 0 0 Branch Shoreham, Steyning, Lower Adur 0 0 74 17 0 Bramber, Upper Beeding Shoreham 0 0 1 0 0 Ferring Rife Ferring, Durrington, and Teville 0 0 42 10 0 Sompting, East Worthing Stream** TOTAL - 0 2 127 27 0 *Vulnerability has been categorised into 5 bands where 1 represents the lowest and 5 the highest.) **Information uncertain due to insufficient data to model Teville Stream

Areas that have experienced surface water and ground water flooding are listed in table 3.5. The table provides an indication of the SFVI category of the areas which have been affected historically by surface water, sewer or groundwater flooding.

Table 3.5 - Social vulnerability of areas affected by other sources of flooding SFVI classification for areas at risk from other sources of flooding Communities at risk from other Social flood vulnerability classification sources of flooding Generally medium to high vulnerability, some areas to Burgess Hill, Wivelsfield, Hassocks north west of Burgess Hill at lower vulnerability. Rottingdean, Ovingdean, Woodingdean Generally medium to high vulnerability Bevendean Generally at high vulnerability Lewes Road area, Brighton Generally at high vulnerability Westdene, Patcham Generally medium to high vulnerability Generally medium to high vulnerability, some areas to Mile Oak north of area at lower vulnerability. Sompting, Lancing, East Worthing Generally medium to high vulnerability Ferring, Durrington, Findon Generally medium to high vulnerability Steyning, Bramber, Upper Beeding, Generally medium to high vulnerability Ashurst, Henfield Generally medium to high vulnerability Generally low to medium with a pocket of slightly higher Partridge Green, West Grinstead vulnerability to the south west of Partridge Green

The boundaries of the CFMP and flooding rarely coincide with enumeration districts, which makes it difficult to determine the number of people affected by flooding. The population at risk has therefore been inferred from the number of residential properties located within each flood outline using the assumption that each household contains an average of 2.39 occupants, based on the regional average for the South East (National statistics census data 2001. Table 3.6 shows the number of people at risk from a range of annual probability flood events (10%, 1%, and 0.1%).

Environment Agency 66 River Adur Catchment Flood Management Plan (September 2008)

Table 3.6 - Population currently at risk from river flooding Number of people currently at risk CFMP area sub- Key Communities 10% 1% 0.1% division Adur East Branch Burgess Hill, Hassocks 5 29 1,288 Adur West Branch Isolated properties 0 0 36 Steyning, Bramber, 7 217 246 Lower Adur Upper Beeding Lancing, Shoreham 0 2 822 Ferring, Durrington, Ferring Rife and Sompting, East 5 124 1,200 Teville Stream** Worthing TOTAL 17 372 3592 Note: Number of residential properties x 2.39 occupants (based on Table 3.3) Source: National statistics census data 2001 **Information uncertain due to insufficient data to model Teville Stream

Tables 3.3 to 3.6 clearly show that the Lower Adur and Ferring Rife areas are where the most properties and people are at risk from the 1% annual probability fluvial flood event. The Adur East Branch, Lower Adur and Ferring Rife are all at risk from the extreme, 0.1% annual probability fluvial flood events. None of the catchments are at high risk from a 10% annual probability flood event with less than ten people and properties affected in each sub-catchment. It should be noted that these results only include fluvial flooding events and do not include any flooding from the sea. (Flooding from the sea poses the greatest risk to life in the Adur catchment and this risk is addressed in Shoreline Management Plans and the Coastal Defence Strategy.)

The Adur East Branch and Teville Stream areas have the highest social flood vulnerability, with parts of Burgess Hill, Hassocks, Sompting and East Worthing falling in the high vulnerability grade 4 and therefore increasing the social consequences of a flood event in these urban areas.

Certain types of flooding can be directly hazardous to people. Shallow, slow moving floodwater presents very little threat to life, whereas deep and fast flowing flooding is more hazardous and could present a threat to life. Table 3.7 shows the number of properties affected at different flood water depth ranges for the 1% annual probability flood event.

Table 3.7 - Summary of depths of flooding during the 1% annual probability flood event Number of properties and depth of flooding for the 1% annual probability flood event CFMP area Key Communities 0.0 to 0.5m 0.5m to 1m 1m to 2m More than 2m sub-division Adur East Burgess Hill, 11 1 0 0 Branch Hassocks Adur West Isolated properties 0 0 0 0 Branch Steyning, Bramber, 42 45 4 0 Lower Adur Upper Beeding Lancing, Shoreham 1 0 0 0 Ferring, Durrington, Ferring Rife and Sompting, East 36 16 0 0 Teville Stream** Worthing TOTAL 90 62 4 0 Source: broadscale hydraulic modelling **Information uncertain due to insufficient data to model Teville Stream

Environment Agency 67 River Adur Catchment Flood Management Plan (September 2008)

It is clear that most properties affected by the 1% annual probability flood event would be flooded to a depth of less than one metre. There are a small number of properties located in Bramber on the Lower Adur floodplain where flood depths of between 1m and 2m are estimated for a 1% annual probability flood event and could increase the flood hazard in these locations.

For non-fluvial sources of flooding, the greatest risk to people is found in Brighton and Hove City where there are reports of surface water runoff flooding within the city and in the suburbs. Rising groundwater can cause flooding for long durations and if it occurs in basements may threaten life where the water is deep. All types of flooding are made more hazardous and distressing when contamination with raw sewage occurs. Table 3.8 identifies the locations in the River Adur CFMP area that are at risk from other sources of flooding and the approximate number of properties at risk, based on historic records of flooding.

Table 3.8 - Number of properties at risk from other sources of flooding Communities currently at risk from other sources flooding Approximate CFMP sub- Locations at Risk Flood source number of catchment properties at risk Burgess Hill, Wivelsfield, Adur East Surface water flooding and Hassocks (Hurstpierpoint Up to 30 Branch urban drainage system, and Keymer) Cuckfield, Bolney, Surface water None recorded Henfield Adur West Partridge Green, Ashington, West Surface water flooding Number unknown Branch Grinstead Steyning, Bramber, Upper Beeding, Ashurst, Surface water flooding Number unknown Shoreham Rottingdean, Surface water flooding Less than 10, (66*) Ovingdean, Woodingdean Surface water flooding 1 Bevendean Surface water flooding 25 Lower Adur Lewes Road area, Surface water flooding 2 Brighton Westdene, Surface water flooding 2 Surface water, urban drainage Patcham system, and groundwater 15 flooding Groundwater and surface water Mile Oak 3 flooding. Sompting, Lancing, Groundwater and surface water Number unknown Findon, Worthing flooding. FerringRife and Groundwater, urban drainage Durrington More than 2 Teville Stream system Ferring, Findon, Worthing Surface water flooding Number unknown TOTAL - More than 146 Source: Brighton and Hove City Council, Worthing Borough Council, and Mid Sussex District Council *Brighton Council erected dams and lagoons to store runoff and reduce flooding after the 1987 event, therefore the current number of properties at risk is considered significantly less than 66.

Table 3.9 provides an overall summary of the sources of flooding and the flood risks to people and key communities in the River Adur CFMP area.

Environment Agency 68 River Adur Catchment Flood Management Plan (September 2008)

Table 3.9 - Summary of flood sources and locations at risk in the River Adur CFMP area Flood sources and locations Characteristics* CFMP area (based on a 1% annual probability Locations at risk Flood source and mechanism SFVI sub-division flood event) Depth Duration Velocity Cuckfield, Bolney Surface water Shallow Short Low Fluvial flooding – lack of channel capacity can cause localised flooding. Shallow Short Low Burgess Hill and Hassocks Surface water flooding from run-off in the urban areas - road and property Shallow Short Low Mainly medium Adur East flooding. with high Surface water flooding generated from run-off from agricultural land – run-off vulnerability in Branch Wivelsfield Shallow Moderate Low from fields in Woods Green area affecting roads and properties. parts of Fluvial flooding from the River Adur and its tributaries – flooded regularly in the Hassocks past, defences exist, however these have been overtopped during extreme Moderate Moderate Medium Henfield flows. Run-off from highway drainage and surface water - highway drainage problems. Shallow Short Low Surface water flooding generated from run-off from agricultural land. - Road West Grinstead Shallow Short Low Adur West drainage problems at West Grinstead, including the A272 Medium Branch vulnerability Partridge Green, Ashington Surface water flooding generated from run-off from agricultural land Shallow Short Low Fluvial flooding from the River Adur and its tributaries -– flooded regularly in the Bramber, Upper Beeding, past, defences exist, however these have been overtopped during extreme Moderate Moderate Medium Ashurst, and Steyning flows. Brighton and Hove – Surface water flooding generated from run-off from agricultural land. - Mainly medium Westdene, Bevendean, Downland ‘muddy’ flooding affecting properties in some areas, roads affected, Moderate Moderate Medium with small Woodingdean, Ovingdean, clean up costs quite high and damage to land by soil erosion. pockets of high Rottingdean, and Findon. vulnerability in Steyning and Upper Lower Surface water flooding from run-off in the urban areas - Roads affected Shallow Short Low parts of Lancing Adur Beeding. and small Shoreham and Shoreham Fluvial and tidally influenced fluvial flooding from the River Adur - high river flows Moderate Moderate Medium pockets of low airport and tides overtopping defences vulnerability in Groundwater, surface water and sewage flooding.– A23 closed and railway lines parts of Patcham Moderate Long Medium closed, Lewes Road – 2 lanes closed of 4 lane carriageway, persists for weeks. Shoreham Groundwater, surface water and sewage flooding – properties, car parks, and Mile Oak Moderate Long Medium gardens flooded. Lancing Groundwater, surface water and sewage flooding – partial closure of A27. Moderate Long Medium

Environment Agency 69 River Adur Catchment Flood Management Plan (September 2008)

Flood sources and locations Characteristics* CFMP area (based on a 1% annual probability Locations at risk Flood source and mechanism SFVI sub-division flood event) Depth Duration Velocity

Fluvial flooding from Ferring Rife - Roads and properties flooded Moderate Medium Low Mainly low to Ferring Tidally influenced fluvial flooding from Ferring Rife – flooding to properties and Moderate Short Low medium with agricultural land around Ferring Rife small pockets of Surface water flooding Shallow Short Low high vulnerability Durrington Groundwater Moderate Long Medium in Ferring Ferring Rife Findon, Worthing Surface water flooding Moderate Moderate Medium and Teville Medium to high Potential for fluvial flooding from the Teville Stream - potential for flooding of Stream Broadwater, East More research is required to in Sompting and commercial and residential properties adjacent to the Teville Stream when Worthing, Sompting establish flood risk. mainly medium groundwater levels are high vulnerability in Parts of Broadwater, East East Worthing Worthing, Sompting, with small Lancing, and Findon. Groundwater and surface water flooding Shallow Short Low pockets of low Worthing town centre and and high Worthing hospital. vulnerability.

*KEY Water depth: Water velocity: Shallow <0.3m, moderate 0.3-1m, deep >1m Low <0.5m/s, medium 0.5-1.5m/s, high >1.5m/s

Flood duration: SFVI: Short <3 hours, moderate 3-6 hours, long >6 hours Low grades 1 and 2, medium grade 3, high grades 4 and 5 N.B estimates have been made for other sources of flooding where data is not available, based on descriptions in the historic records.

Environment Agency 70 River Adur Catchment Flood Management Plan (September 2008)

3.3.2 Risks to property and infrastructure We have used the modelled flood outlines and the associated flood depths (for the 10% and 1% annual probability fluvial flood events) to produce a set of flood damage costs. We calculated the damage costs using the Modelling and Decision Support Framework (MDSF) software package, which uses the flood outlines and depth data produced by the broadscale modelling. This has given us a value for the current baseline condition flood damages within the catchment. We have included the damages to both property and agriculture in these calculations and then combined them to show the total damages for each of the modelled catchment sub-divisions. The resulting damage assessments are set out in table 3.10.

Table 3.10 - Baseline flood damages Baseline flood damages for a 10% and 1% annual probability flood events and annual average damages Flood damages to Flood CFMP area properties (£ million) damages to Total damages Key communities sub-division agricultural (£ million) Residential Commercial land (£ million) 10% annual probability flood event Adur East Burgess Hill, 0.1 0 0.04 0.14 Branch Hassocks Adur West Isolated properties 0 0 0.02 0.02 Branch Shoreham, Lower Adur Steyning, Bramber, 0 0 0.03 0.03 Upper Beeding Ferring Rife and Ferring, Durrington 0.1 0 0 0.1 Teville Stream** TOTAL 0.2 0 0.09 0.29 1% annual probability flood event Adur East Burgess Hill, 0.3 0 0.05 0.35 Branch Hassocks Adur West Isolated properties 0 0 0.02 0.02 Branch Shoreham, Lower Adur Steyning, Bramber, 2.8 0.2 0.09 3.09 Upper Beeding Ferring Rife and Ferring, Durrington 1.6 0 0 1.6 Teville Stream** TOTAL 4.7 0.2 0.16 5.06 Annual average damages Adur East Burgess Hill, 0.02 0 0.01 0.03 Branch Hassocks Adur West Isolated properties 0 0 0 0 Branch Shoreham, Lower Adur Steyning, Bramber, 0.1 0 0.01 0.11 Upper Beeding Ferring Rife and Ferring, Durrington 0.1 0 0 0.1 Teville Stream** TOTAL 0.22 0 0.02 0.24 **Information uncertain due to insufficient data to model Teville Stream

The higher levels of damages for the Lower Adur sub-catchment reflect the large numbers of residential and commercial properties at risk in the towns of Steyning, Upper Beeding, Bramber, and Shoreham. The low damage values for the Adur West Branch sub-catchment result from the catchment being sparsely populated and predominantly rural in nature, with lower risks of flooding to property and consequently lower flood damages. The damage value Environment Agency 71 River Adur Catchment Flood Management Plan (September 2008) of £0.02 million for the 10% and 1% annual probability flood events is entirely from agricultural damages.

Figure 3.9 shows the range of damages over the whole CFMP catchment, calculated for the current baseline conditions. The sub units for this map are each 0.25. We selected this grid size because the individual squares are small enough to show the areas where significant flood damages will occur, but large enough to show the relative extent of each category of damage.

Figure 3.9 - Flood damages for the 1% annual probability fluvial flood event

The colour coding is graded from yellow to brown for increasing flood damage. These flood damages are based on a 1% annual probability fluvial flood event but do not take into account damages caused solely by groundwater or surface water flooding. A Mean High Water Spring tide has been assumed as the downstream tidal boundary for all of the baseline model runs.

Environment Agency 72 River Adur Catchment Flood Management Plan (September 2008)

Figure 3.9 clearly shows the areas where flood damages occur to properties and/or agriculture as a result of a 1% annual probability fluvial flood event. The higher damages, shown by the darker colours, are predominantly in the urban areas where there are likely to be more properties affected by flooding due to the higher housing densities, for example in Steyning, Ferring and Bramber. There are no damages shown for the Teville Stream as we do not currently have enough information to model this watercourse.

The number and type of properties exposed to flooding have been assessed from the National Property Dataset for a number of probability fluvial flood events, and are summarised in table 3.11. This table also indicates the main infrastructure at risk.

Table 3.11 - Properties and infrastructure currently at risk of flooding Properties and infrastructure at risk CFMP area sub-divisions and annual probability flood event Property/ Ferring Rife and infrastructure Adur East Branch Adur West Branch Lower Adur Teville Stream** type 10% 1% 0.1% 10% 1% 0.1% 10% 1% 0.1% 10% 1% 0.1% Residential 2 12 539 0 0 15 3 92 447 2 52 502 properties Emergency 0 0 0 0 0 0 0 0 1 0 0 1 services Hospitals 0 0 0 0 0 0 0 0 2 0 0 0 Education 0 0 0 0 0 0 0 0 0 0 0 0 Sewage treatment/ wastewater treatment 1 1 1 0 0 0 0 0 0 0 0 0 works/ chemical works Electricity sub 0 0 0 0 0 0 0 0 3 0 0 0 stations Other commercial 0 0 39 0 0 2 10 21 110 0 0 23 properties Main roads 0.3 0.4 3.2 0.4 0.5 2.1 0.6 0.9 3.3 0.1 0.1 0.7 (km) Railways (km) 0 0 0.3 0 0 0.1 0 0 0 0 0.0 0 Agricultural grade land 3.2 4.2 7.1 1.9 2.3 5.9 4.1 8.6 9.2 0 0 0.3 (km2) **Information uncertain due to insufficient data to model Teville Stream

The extent of risk to property and infrastructure reflects the distribution of the urban areas within the CFMP catchment, with the greatest risks for the 1% annual probability fluvial flood event concentrated in the Lower Adur sub-catchment, which include the larger villages of Steyning, Bramber, and Upper Beeding.

The greatest non-fluvial flood risk affecting infrastructure comes from groundwater. Groundwater flooding during 2000 caused major disruption to travel when parts of the Lewes Road (A27), A23 and the main London to Brighton railway line was closed. Surface water flooding tends not to last as long as groundwater flooding but can still cause significant disruption. Flooding can close roads and cut off access to infrastructure such as sewage treatment works. Flooding to schools, shops and commercial properties from all sources of flooding causes disruption. Environment Agency 73 River Adur Catchment Flood Management Plan (September 2008)

Damages were estimated in the Flood Defence Assessment for Downland Flooding Report in Brighton for the 2000/2001 floods. Combined damages in Patcham, Bevendean, Lewes Road, Woodingdean, Ovingdean, and Mile Oak have been estimated by the report in excess of £425,000 based on standardised flood damages at January 2001 prices. The report also estimates costs due to traffic disruption on the Lewes Road and A23 were over £40,000.

3.3.3 Risks to the environment The environmental and landscape designated sites are documented in section 2.8 along with the general impacts of flooding on these sites. The designated sites exposed to flooding and their collective areas, within the Adur CFMP area, are summarised in table 3.12.

Table 3.12 - Area of designated sites currently at risk of flooding Designated sites currently at risk of flooding Area of combined designated sites (km2) Designated site 10% 1% 0.1% SNCIs 0.3 3.3 4.4 LNRs 0 0 0.1 SSSIs 0 0.6 0.6 National Park 0.4 5.1 6.9 (proposed) AONBs 0 1.5 3.4 ESAs 0 1.6 3.1 SMs 2 9 15

Of all the nationally environmental designated sites (SSSIs) in the whole of the Adur CFMP area, only the Adur Estuary falls within the 1% annual probability fluvial river flood outline, the details of which are shown in table 3.13. However, there are six SNCIs (3.3 km2) that fall within the 1% annual probability fluvial flood event, the River Adur Water Meadows and the Ferring Rife and Meadows having the greatest area within the floodplain. The Kneppmill Pond SNCI falls partially within the 1% annual probability flood extent and significantly within Flood Zone 2. Table 3.13 - Environmentally designated sites affected by the 1% annual probability flood event Environmentally designated sites affected by river flooding Site name Feature description Description of flooding Impact of flooding A natural flow regime will help Located to the west of to conserve the features of this Shoreham on the River Adur. site, therefore it is likely that This site represents large periodical flooding will have a Adur The impact of areas of saltmarsh and inter- beneficial effect in this SSSI. Estuary flooding is generally tidal mudflats. These habitats (SSSI) positive. support unusual estuarine Excluding the area of the site plant communities and a which covers the river itself, number of wading birds. the area within the 1% flood extent is 0.6 km2.

Flood risk management activities may have a negative or positive impact on these environmental sites. Flooding in some areas can create or enhance existing wetland habitats by providing suitable conditions for threatened species of flora and/or fauna. Or flooding could introduce new species that may not have existed in the area previously. So there are opportunities to positively affect the condition of sites through flood risk management activities. For example, a new flood storage wetland may also help improve water quality and reduce

Environment Agency 74 River Adur Catchment Flood Management Plan (September 2008) flood risk to nearby urban areas. For most wetland sites in the Adur catchment, flooding is beneficial as the periodic inundation of water is a natural and necessary part of their environment.

Flooding has the potential to cause physical damage to all aspects of the historic environment, whether designated or not. In particular, flooding, and flood risk management activities can cause:

• Erosion of archaeological earthworks, buried sites and standing buildings/structures caused by repeated flood events or by changes in water flow.

• Erosion of parts of historic battlefields; or registered parks and gardens, resulting damage to planting schemes, trees, designed landscape features and structures

• Damage to the integrity of listed buildings, their construction materials, interior and exterior decoration and significant interior features.

• Degradation of preserved organic archaeological and palaeoenvironmental evidence resulting from changes in groundwater flow and chemistry, including pollutants. Where ground water levels are lowered to reduce flood risk, this could cause the deterioration of organic remains through the drying out of deposits and introduction of oxygen leading to bacterial decay.

• Impacts on the setting of sites by construction of flood protection measures (banks, barriers).

• Disturbance and loss of buried archaeological deposits caused by the construction of flood protection structures and associated works.

There are 115 scheduled monuments within the CFMP area, 2942 listed buildings, 9 registered parks and gardens, and no historic battlefields. Very few of these lie within the one per cent annual probability flood extent as shown in table 3.14.

Table 3.14 – Historic Environment sites affected by the 1% annual probability flood event Historic Environment sites affected by river flooding Designation Total number of sites affected Total number of sites within by flooding the Adur CFMP study area Scheduled Monuments 14 115 Listed Buildings 6 2942 Registered Historic Parks and 0* 9 Gardens Historic Battlefields 0 0 *(based on Broadscale modelling, Knepp Castle and Heaselands within Flood Zone 3 on non modelled reaches))

Table 3.15 shows vulnerable features of the historic environment, including Scheduled Monuments (SMs), within the 1% annual probability fluvial flood outline. Scheduled Monuments are protected from deliberate or preventable flooding (unless authorised). Many historic bridges and listed buildings of cultural heritage importance are also protected. Villages and historic market towns are also important to communities and the economy in the CFMP area and are often sited close to rivers where there is a risk of flooding.

Environment Agency 75 River Adur Catchment Flood Management Plan (September 2008)

Table 3.15 - Vulnerable features of the historic environment Historic environment within 1% annual probability fluvial flood outline

Key feature of * SM Location Watercourse Vulnerability historic environment 250m east Bramber Castle

Saltings field • Siltation from river and estuary 220m north sediments. Saltern Mounds Yes Beeding Bridge Lower Adur • Increase flood depth, duration (multiple sites) and frequency. Group north St • Sea level rise. Peters Church (near Upper Beeding) • Flooding of grounds, increased Bramber castle Yes Bramber Lower Adur flood extent with climate change. • Increase flood frequency, depth Upstream West Knepp Estate Yes Adur West and duration. Grinstead • In Flood Zone 2. Shoreham Airfield • Tidal flooding. Yes Shoreham Adur Estuary Dome trainer • At risk of tidal flooding. The Malipins Yes Shoreham Adur Estuary • At risk of tidal flooding. (medieval building) Shoreham Old Fort Yes Shoreham Adur estuary • Tidal flooding. Cowfold • Increase flood frequency, depth, Moated site at Ewhurst Stream Yes Ewhurst extent. Manor confluence • Runoff. with Adur East • Increase flood frequency, depth, extent. Moated site at Headwaters Yes East of Bolney • Runoff. Raggetts Wood Adur East • Not mapped but close to watercourse. Listed building: • St Mary’s House and Gardens at • Tidal and fluvial flooding risk. Beeding Bridge • Increase flood frequency, depth, • St Mary's Lodge No Beeding Lower Adur extent. • The Old Priory

• Yew Tree Cottage

Listed buildings: • The Malthouse, • fluvial flooding risk. Mockbridge Between Lower • Increase flood frequency, depth, • Mockbridge No Partridge Green Adur/Adur extent. House and Henfield Estuary

*SM = Scheduled Monument

Some designated historic environment features are located within close proximity to rivers and streams as a result of their function, such as bridges, mills, and other associated water management structures. The CFMP objective relating to the historic environment seeks to ‘protect and enhance significant historic environment assets and their settings’, however it is Environment Agency 76 River Adur Catchment Flood Management Plan (September 2008) possible that the location of some of the features discussed above (historic bridges, mills etc) may constrain some Flood Risk Management options.

3.4 Summary of flood risk

Table 3.16 provides a summary of flood risk to the key communities in the River Adur CFMP catchment. We have assessed flood risk as high, medium and low at each location. This assessment is based on the combination of the impact of flooding on a location (or receptor) and the likely frequency of occurrence. One of the best measures of this is the annual average damage (AAD) figure, which is derived from estimated flood damages for a range of flood probabilities. We have also taken into account factors such as the 10%, 1% and 0.1% annual probability flood events, the flood depths and flow velocities as these can increase the level of flood hazard.

Table 3.16 - Summary of flood risk for key communities2 Summary of flood risk Flood risk location (key Flood source Assessment of flood risk community) Less than ten properties are at risk of flooding from fluvial flooding and surface water flooding from the 1% annual probability flood event in Burgess Hill. However, there are approximately 300 properties at risk from an extreme flood event (0.1% annual probability flood event), with approximately 700 people at risk.

People and properties at risk of More frequent, less severe flooding (10% annual probability flooding from fluvial flooding from fluvial flood event) is unlikely to cause flooding to people the River Adur East Branch and and properties in this area. the Pook Bourne Stream, a

tributary running through Burgess The depth of the floodwater is generally shallow (less than Hill. 0.5m) with flow velocities less than 0.5m/s, so flood hazard

is assessed as low. Burgess Hill Burgess Hill also suffers from

surface water flooding from the Annual average damages for fluvial flooding in Burgess Hill urban and road drainage systems. is less than £5,000 and for the 1% annual probability fluvial

flood event flood damages are estimated as £0.01 million Blocked drainage systems in and are therefore assessed as low. Burgess Hill cause localised

flooding to properties in the urban There is no critical infrastructure at risk of flooding from the areas. 10%, 1% or 0.1% annual probability fluvial flood events.

Historic flooding reports suggest up to 24 people at risk from surface water and urban drainage system flooding.

The overall hazard and disruption is assessed as low and therefore the current flood risk is assessed as low.

The broad definitions for the parameters contained in Table 3.16 are: 2 Damages Low: AAD < £0.5 million, and 1% annual probability flood damages < £1 million Medium: AAD between £0.5 million and £1 million, and 1% annual probability flood damages between £1 million and £5 million High: AAD > £1 million, and 1% annual probability flood damages > £5 Water velocity Low: <0.5m/s, medium: 0.5 -1m/s, high: >1.5m/s Water depth: Shallow: <0.3m, moderate: 0.3 – 1m, deep: >1m Environment Agency 77 River Adur Catchment Flood Management Plan (September 2008)

Summary of flood risk Flood risk location (key Flood source Assessment of flood risk community) As in Burgess Hill, less than ten properties are at risk of flooding from fluvial flooding and surface water flooding from the 1% annual probability flood event in Hassocks. However, there are approximately 250 properties at risk from an extreme flood event (0.1% annual probability flood event), with approximately 600 people at risk.

A small alleviation pond (Keymer Pond) is located to the west of Hassocks and attenuates the peak flows of one of People and properties at risk of the tributaries running though Hassocks. flooding from fluvial flooding from the Herrings Stream running Flooding is generally short lived and relatively shallow (less through Hassocks. than 0.5m deep). However, because of the surrounding hills, inundation of floodwater may be relatively fast, Hassocks also suffers from although the ground is not considered steep enough to Hassocks surface water flooding from the result in dangerously high water velocities. urban and road drainage systems. Annual average damages for fluvial flooding in Hassocks is Blocked drainage systems in less than £2,000 and for the 1% annual probability fluvial Hassocks cause localised flooding flood event flood damages are estimated as £0.05 million to properties in the urban areas. and are therefore assessed as low.

There is no critical infrastructure at risk of flooding from the 10%, 1% or 0.1% annual probability fluvial flood events.

Historic flooding reports suggest up to 24 people at risk from surface water and urban drainage system flooding.

The overall hazard and disruption is assessed as low and therefore the current flood risk is assessed as low. Less than ten properties are at risk of flooding in Wivelsfield. The flood waters are shallow and have low velocities. A small number of properties,

local road and land are affected Wivlesfield Historic flooding reports suggest up to 24 people at risk by surface water flooding in from surface water and urban drainage system flooding. Wivlesfield.

Because of the low disruption and hazard the flood risk is assessed as low. The risk of flooding is very small in this area, with little Road drainage problems affected disruption caused. No properties are affected and flood West the A272 and B2135, causing damages are minimal. Grinstead minor road and land flooding

around West Grinstead. Current flood risk is assessed as low.

Environment Agency 78 River Adur Catchment Flood Management Plan (September 2008)

Summary of flood risk Flood risk location (key Flood source Assessment of flood risk community) There are no properties currently at risk of flooding from the 10% annual probability flood event and less than 20 properties at risk from the 1% annual probability flood event.

The Adur Esturary SSSI in within the 1% flood extent, however the impact of flooding is generally positive.

There are raised embankments along the River Adur through Shoreham that provide some protection for the lower probability flood events so flood damages are lower for the more frequent flood events in Shoreham. Shoreham is also affected by

tidally influenced flooding from the Annual average flood damages and damages for the 1% River Adur as the water overtops annual probability flood event for fluvial flooding in Shoreham and the raised embankments. Shoreham are estimated as less than £5,000. Lancing

Surface water flooding from Shoreham and Lancing are also affected by surface water overland flow affected properties, flooding from run-off generated from the steep slopes of the land and Shoreham Airport. South Downs. The surface water is pumped to the River Adur in times of flooding, but water can take weeks to subside in extreme events. Agricultural land is worst affected, with some disruption to the airport, highways and gardens nearby. Surface water flooding is experienced approximately 1 in every 10 years.

The overall disruption and hazard from fluvial flooding and surface water flooding in Shoreham and Lancing is currently assessed as low, therefore the current flood risk is assessed as low. There are 91 properties at risk of flooding during a 1% (AEP) fluvial flood event influenced by a mean high water spring tide.

There are historically important environmental assets at risk of flooding in this area.

People and properties at risk of The raised embankments along the River Adur provide flooding from the River Adur. The some protection for the lower probability fluvial flood events, river channel reaches its capacity so damages are lower for the more frequent flood events. and then burst its banks. Steyning, The embankments are likely to be overtopped by an

Upper Beeding exceptionally high tide or the combination of a high tide and Steyning and Upper Beeding are and Bramber very high river flows. also at risk of surface water

flooding and flooding due to under Flood depths vary from 0.1m to 1.6m, but the velocity of capacity and blocked drainage floodwaters is generally low to medium (less than 1m/s). systems.

Historic flooding reports suggest people are at risk from surface water flooding, however the number is unknown.

Because the risk of high river flows alone is low, the overall flood risk is assessed as low.

Environment Agency 79 River Adur Catchment Flood Management Plan (September 2008)

Summary of flood risk Flood risk location (key Flood source Assessment of flood risk community) Approximately 50 properties are currently at risk of flooding from the Ferring Rife from a 1% annual probability flood event, which results in flood damages of approximately £1.6 million. However annual average damages are estimated as less than £0.1 million and therefore assessed as low. People and properties in Ferring and Durrington are a risk of Floodwaters are generally shallow (less than 0.5m) with Ferring and flooding from the Ferring Rife and flow velocities of less than 0.5m/s, so flood hazard is Durrington also from surface water and currently assessed as low. groundwater flooding. There are records of surface water and groundwater flooding in this area. At least to properties were affected.

Both disruption and hazard are assessed as low and therefore the current flood risk is assessed as low. There was insufficient information to model flooding from People, properties and roads at the Teville Stream and therefore the number of people at risk from flooding from the Teville risk of flooding is unknown. Stream, surface water flooding

from overland flow and Sompting and There are records of surface water and groundwater groundwater flooding. Worthing flooding in Worthing and Sompting, and although properties

have been affected the number in unknown. Combined surface water and

fluvial flooding in the urban areas Both disruption and hazard are assessed as likely to be low are the greatest risk in this area. and therefore the current flood risk is assessed as low. There are numerous records of historic flooding in Brighton and Hove, which have affected approximately 114 properties and caused significant disruption to major rail People, properties, and and road transport routes in 2000. Brighton and infrastructure at risk from surface

Hove water, groundwater and urban Although the 2000 flooding caused significant disruption, drainage system flooding. such extensive events are infrequent. Both disruption and hazard are therefore assessed as likely to be low and therefore the current flood risk is assessed as low.

3.5 Existing flood risk management

We not only manage flood risk through physical defences such as embankments and river walls, but also by flood forecasting and flood warnings, raising public awareness about flood risk, and keeping river channels and culverts clear of vegetation and other debris. We also manage flood risk indirectly by advising against inappropriate development within the floodplain, which may cause flooding or make it worse. When development cannot be avoided, we can reduce the risk to people and property by advising on appropriate and sustainable flood resilient design.

Since the Environment Agency was set up in 1996, we have supervisory powers over flood risk management within England and Wales. We also coordinate our plans and actions with a number of other organisations, in particular the emergency services, the Highways Agency and local authorities, as well as the general public. In the area covered by this CFMP we also act as an Internal Drainage Board (IDB), with responsibility for land drainage issues.

One of the aims of the River Adur CFMP is to challenge some of the more traditional methods of flood risk management by looking at more sustainable ways of reducing flood risk. There may be opportunities to restore sections of the floodplains, which would increase the flood Environment Agency 80 River Adur Catchment Flood Management Plan (September 2008) storage capacity of the catchment and reduce the flood risk to downstream areas such as Steyning, Bramber, Upper Beeding, and Shoreham, and it would also enhance the biodiversity of the area by introducing wetland areas. In addition to this careful land use management on the South Downs could reduce surface water flooding to the suburbs of Worthing, and Brighton and Hove, and enhance the AONB.

3.5.1 Flood mapping, data management and development control We provide information on flood risk in the form of the internet based flood map. The flood map shows places that would be affected by flooding from rivers or the sea if there were no defences. We have an ongoing programme of updating the flood map with new and improved information. We also undertake more detailed flood mapping, and in 2005 the Adur Flood Risk Mapping Study was completed. Detailed flood risk mapping involves detailed hydrological and hydraulic modelling studies to produce flood extents and levels, which are used to provide development control advice. In some areas detailed studies have not yet been completed and the information available is limited to the broadscale Flood Zones. One such area is the Teville Stream where the extent of fluvial flooding and the potential impacts of flooding are consequently less certain.

The flood extents shown on the flood map refer to the Flood Zone 2 and Flood Zone 3 as defined in Planning Policy Statement 25 (PPS 25). Although we will normally object to development on the floodplain, we recognise that there are circumstances when other planning considerations can outweigh flooding implications. We then make every effort to make sure that appropriate measures to reduce flood risk, including emergency arrangements, are included in the design and implementation of the development proposal. In some cases we will maintain our objection. In this way, we seek at a local level to influence, and with time, reduce the risk of flooding across the country. We also seek to influence development at a strategic level through the Regional Assemblies and it is intended that the policies developed through the CFMP will be used in the development of Local Development Documents.

We provide information about the possible extent and likelihood of flooding across the country through our flood risk maps, which you can view on our website. They show land within the Flood Zone 2 and Flood Zone 3 boundaries and whether the land is at risk of fluvial or tidal/coastal flooding. Figure 3.1 shows the land falling within Flood Zone 2 within the area covered by the CFMP.

We also have direct control over activities that may affect watercourses and the floodplain. According to the Water Resources Act 1991 and local byelaws, anyone wishing to carry out work in, over, under or within 8 metres from the top of the bank of a main river, or 5 metres from an Internal Drainage Board watercourse needs consent from us. Under the Land Drainage Act 1991 and byelaws, any proposal to construct works within any other watercourses also needs our consent.

Although we do not hold maps of flooding from other sources, local planning authorities are developing Strategic Flood Risk Assessments as part of the Local Development Frameworks. SFRAs summarise flooding from all sources, bring together records of flooding, to better understand flood risk.

We also work with local authorities to make sure that new developments incorporate sustainable drainage systems (SuDS) wherever possible. These surface water systems are designed with three objectives in mind:

• to control the quantity of run-off from a development;

Environment Agency 81 River Adur Catchment Flood Management Plan (September 2008)

• to improve the quality of the run-off; • to enhance the nature conservation, landscape and amenity value of the site and its surroundings.

SuDS can be designed to fit all developments, from hard surfaces to soft landscaped features, as there are many design options available. Implementing SuDS contributes significantly towards achieving sustainable development.

3.5.2 Flood defence assets A National Flood and Coastal Defence Database (NFCDD) is used to hold all information on flood defence assets, known as structures and defences. We inspect these assets each year and report on their condition for the NFCDD. Structures and defences are built to help reduce the chance of flooding. The assets are owned, operated and maintained either by us, local authorities or privately.

Currently there are no major concerns with the general condition of the raised defences on the River Adur north of the A259 road bridge. The raised defences relevant to the CFMP are shown in figure 3.10.

Figure 3.10 - Raised defences relevant to the CFMP Environment Agency 82 River Adur Catchment Flood Management Plan (September 2008)

Effective operation and maintenance of control structures and defences is a key element of flood risk management. Riparian landowners have certain rights and responsibilities for the watercourse flowing through or adjacent to their property. Mill and weir owners have particular responsibilities to maintain and operate structures and fulfil any obligations under land drainage byelaws. Under the Water Resources Act 1991, we have permissive powers to maintain and improve main rivers for the efficient passage of flood flow and the management of water levels.

As well as operating the assets during flood events and maintaining them as necessary, we carry out capital schemes to construct new defences, repair defences that have deteriorated or to improve ones that no longer provide an adequate standard of protection. We have to justify both maintenance and capital expenditure taking economic, technical, environmental and social issues into account, comparing the costs of carrying out the work with the benefits (in particular the damage that will be avoided). If we cannot show that there is a strong business case for a proposed scheme, we will not be able to obtain the national funds to implement it.

Our maintenance programme ensures that river channels and culverts are kept clear of excessive vegetation and other debris that can cause blockages. Historic practices of continuous desilting and dredging have ceased in order to avoid ecological damage and to promote biodiversity. The need for this management activity is now more carefully considered and is only carried out when necessary.

Table 3.17 details typical annual maintenance activities carried out in the River Adur CFMP area.

Table 3.17 - Typical annual maintenance activity Annual maintenance activities and costs in the River Adur CFMP area Approximate CFMP area annual Watercourses Maintenance activity sub-division maintenance cost River Adur East Branch, Chess Stream, Cowfold Stream, Grass cutting, weed cutting, Adur East Shermanbury Mill Stream, cutting back overhanging £70,000 Branch Herring Stream, Pook Bourne branches, and debris removal. Stream River Adur West Branch, Adur West Honeybridge Stream, Nuthurst Grass cutting and weed cutting. £35,000 Branch Stream Lower Adur, Black Sewer, Grass cutting, weed cutting, Woods Mill Stream, Wyckham cutting back overhanging Lower Adur £130,000 Farm Stream, Northover Sewer, branches, channel desilting and Tanyard Stream debris removal. Ferring Rife Grass cutting and weed cutting, and Teville Ferring Rife £210,000 debris removal and inspections. Stream

We also have a programme of maintenance and improvements for Environment Agency owned assets in order to manage the risk of flooding. This includes larger capital schemes carried out by our maintenance teams (Operations Delivery) or framework contractors. The annual maintenance budget for the River Adur CFMP area is currently £467,000, which includes internal drainage board work.

We use various measures to reduce flood risk. These range from installing hard defences in the form of embankments and walls, to creating designated storage areas. We also manage Environment Agency 83 River Adur Catchment Flood Management Plan (September 2008) flood risk through the provision of a flood warning service. In the past, we modified channels to increase flow capacity, although historically this type of activity was associated with navigation and agriculturally related drainage works and not flood protection. Table 3.18 details the major flood alleviation schemes undertaken within the catchment.

Structures and defences can only protect against a specific flood level and their condition will deteriorate over time. The standard of protection (SoP) therefore relates to the actual height of a wall or capacity of a pump and its physical condition. In the past we have concentrated on assessing the individual SoP given by a structure or defence. Now we recognise that we need to look at how they perform alongside neighbouring or associated structures and in combination with other flood management options such as flood warning or returning floodplain areas to more natural conditions. The standard of protection that the schemes have been designed to provide, is noted within table 3.18.

Table 3.18 - Major flood alleviation schemes Flood alleviation schemes Location and Standard of Organisation construction Defence schemes/structure protection responsible date Adur tidal embankments (approximately 19km in length) from the river mouth to Bines Green/Shermanbury. The defences consist of earth banks with chalk rubble revetments, Standard of which line the channel. Provides protection to protection properties in Shoreham, Steyning, Upper ranges Tidal Adur Beeding and Bramber (approximately 2600 between the Environment (construction properties). It is at, or above target condition. 20% and 0.5% Agency date unknown) annual Secondary defences (counterbanks) are also probability flood in place. These run at right angles from the events. river and their purpose is to restrict flooding to a smaller, area if the raised flood embankments are overtopped.

Bevendean Flood detention basins South Downs No data. No data 1950s (Bevendean). Worthing Environment Brooklands lake storage area. No data. (Unknown) Agency Worthing Worthing 7 balancing ponds, Worthing. No data. (Unknown) Borough Council Environment Ferring Flood storage area in Ferring. No data Agency

Approximately 2600 properties would benefit from the defences along the Adur during a 0.1% annual probability fluvial flood event. The defence assets are generally considered to be in a condition fit for purpose, with a residual life of approximately 10 to 20 years. The Adur CFMP area does not contain many large purpose-built flood alleviation schemes. There are no significant stretches of raised bank on the River Adur above the Lower Adur, however there are a number of river control structures designed to retain water during the drier summer months. These structures have implications for flood risk management as they present an obstruction to flow. Therefore, stop boards are removed in the winter months to allow larger river flows to pass through the channel.

The most significant defences along the River Adur are the raised embankments along the tidal reaches of the river. The Rivers Arun to Adur Coastal Defence Strategy has superseded the Environment Agency 84 River Adur Catchment Flood Management Plan (September 2008)

Shoreham Adur Tidal Walls consultation document, but still has the preferred option of raising and improving the West Bank up to the A27. It is anticipated that the main River Adur Strategy will not started until 2010.

Other Flood Risk management schemes include eight designated flood storage areas within parts of Worthing and Shoreham. These are:

• Brooklands Lake East Worthing • Ferring Pond Goring-by-Sea • Longcroft Park (North) West Durrington • Longcroft Park (South) West Durrington • Northbrook Pond West Durrington • Northbrook College Pond West Durrington • Pond Lane Balancing Pond Durrington • Westlake Gardens West Tarring

Brooklands Lake, the largest storage area, is located near the seafront at the eastern edge of Worthing Borough. The Teville Stream flows into the lake and forms the last link in a strategic land and surface water drainage system, which is reported to account for 30% of Worthing Borough’s drainage requirements. In addition the lake also receives a significant amount of drainage from the adjoining Adur District. These storage areas are crucial in buffering the effect of tide-locking. Tide-locking occurs when the tide is in or during high tides when control structures between the land and the sea prevent seawater entering the land. During this time, the structures also prevent water draining from the land discharging out to sea and so this water builds-up behind the structure on the landward side.

There are also surface water retention bunds near Bevendean which were constructed in the 1950s (BB&V, 2001) and designed to slow down run-off from the South Downs and prevent surface water flooding. Brighton and Hove City Council are responsible for maintaining the structures. Other measures have been added including a ditch, bank, and coppice to try and reduce runoff from the fields north of Bodiam Close. Since the 2000/2001 flooding the existing dams have been rebuilt and enlarged.

As a result of storms and flooding in 1987 a number of flood alleviation measures were implemented around Mile Oak. A series of dams were constructed across the valley floor and fields were left in grass to reduce runoff. More recently some engineering works have been completed in Cockroost Hill area of Mile Oak.

There are a number of other embankments which have been constructed to alleviate flooding in Brighton. In addition to structures, Brighton and Hove City Council has been working to implement land management practices to reduce runoff from the fields adjacent to the city, in areas such as Bevendean and Falmer. As part of the councils support for the groundwater flooding ‘FLOOD1’ research project, they have allowed the establishment of a groundwater monitoring site on farmland to the west of the A23. There may be potential to use this site as part of a groundwater flood warning system in the future. The councils Emergency Planning Office also monitor and disseminate within the council severe weather warnings. Work is being undertaken in the city to replace and upgrade sections of the sewerage network.

A flood defence structures inspection carried out for Brighton and Hove City Council in 2003 lists a number of structures around the city and their condition. These are listed in table 3.19.

Environment Agency 85 River Adur Catchment Flood Management Plan (September 2008)

Table 3.19 - Flood alleviation measures around Brighton and Hove Flood alleviation measures Comments from Condition Description of flood Location Assessments in 2003, 2006 Owner alleviation measure and 2007 Rottingdean - New Five embankments to slow No evidence of erosion or Brighton & Barn Valley surface water runoff slippage, however holes in Hove City structure from burrowing Council animals could increase risk of breach Rottingdean - Ditch and embankment with Good Condition - No evidence Brighton & Longhill School soakaways of erosion or slippage Hove City Council Bevendean - Earth embankment 3m wide, Good Condition - No evidence Brighton & Walmer Crescent 10 metre long of erosion or slippage Hove City Council Bevendean - Bodiam Series of three earth Good Condition - No evidence Brighton & close embankments, at the end of of erosion or slippage Hove City balancing ponds. Soakaways Council Bevendean - Bank and ditch around lower Bank has been breached by a Brighton & Kenilworth Close reaches of a field footpath in one location. Hove City Council Moulsecoomb/ Ditch and bund situated at Not assessed - Ditch requires Brighton & Bevendean - the foot of a field clearing, although some Hove City Wheatfield Way evidence of erosion was Council observed Ovingdean - Earth bund 50 m long and 3 Good condition except for one Brighton & Bulstrode Farm m wide. section which had been Hove City (Ovingdean Road) damaged by excavations. Council Mile Oak Embankments Good Condition - No evidence Brighton & of erosion or slippage Hove City Council Westdene - Millcroft ‘dew’ pond which provides Not assessed – however Brighton & storage for runoff, bund storage capacity of pond notes Hove City downstream of pond to be small. Council between it and properties. Coldean - Wolseley Earth bund with ditch directly Good Condition (upstream Brighton & Road upstream of it. face and ditch not assessed) - Hove City No evidence of erosion or Council slippage

Southern Water Services are carrying out a series of improvements across the catchment to address sewage and surface water flooding problems, most notably in Brighton and Hove, and Worthing.

3.5.3 Flood incident management One of the ways we manage flood risk is through ‘flood incident management’. This involves flood forecasting, flood preparedness, emergency planning with our professional partners, operating a flood warning service and raising public awareness with associated campaigns.

The UK’s first integrated multi-channel warning system, providing flood warning and information to the public, professional partners and the media (Floodline Warnings Direct) is now operational. The next phase of implementation will be to provide on-line registration so that our customers can have access to their details and ensure they are kept up to date. In the River Adur CFMP area 1,199 properties have signed up to the Floodline Warnings Direct service. Environment Agency 86 River Adur Catchment Flood Management Plan (September 2008)

Our Flood Warning service provides information to the public, professional partners and the media. It means we can warn those people at risk, reducing the financial and personal cost of flooding from rivers and the sea. It is an efficient and adaptable system that we can extend as we need to. The service currently relies on members of the public registering on to the system. There are six fluvial flood warning areas within the catchment as shown on figure 3.11, which provides warning to properties in the River Adur CFMP area. Table 3.20 identifies the flood warning areas and the number of properties covered by each.

Figure 3.11 - Fluvial flood warning areas

By the end of 2008 it is anticipated that these flood warning areas in the River Adur CFMP area will be altered to provide flood warning to ‘communities’ rather than whole areas. This will also Environment Agency 87 River Adur Catchment Flood Management Plan (September 2008) involve the inclusion of further flood warning areas including Burgess Hill.

Table 3.20 - Fluvial flood warning areas Fluvial flood warning areas in the River Adur CFMP area Number of Properties Number of properties Registered for Flood covered Area Name Area Description Warning Residential Business Residential Business The Upper Ferring Rife at North Ferring Upper Ferring Rife at extending from 226 9 145 3 North Ferring Northbrook College to the railway line at Ferring The Lower Ferring Rife at South Ferring Lower Ferring Rife at including areas from 36 1 65 3 South Ferring south of the railway line down to Ferring Beach River Adur West River Adur West Branch from Coolham Branch (from to Bines Green 8 1 9 2 Coolham to Bines including the Nuthurst Green) Stream The River Adur East River Adur East Branch from north of Branch (from Burgess 9 0 8 2 Burgess Hill to Chates Hill to Henfield) Weir west of Henfield The River Adur from the confluence of the East and West River Adur (from branches at Henfield, Henfield to Upper 83 6 107 7 to the A283 Steyning Beeding) by-pass including Upper Beeding and Bramber The River Adur from downstream of the A283 Steyning by- River Adur from pass at Bramber to downstream of Upper the railway at North Beeding to Norfolk 1434 144 780 68 Lancing and Norfolk Bridge at Shoreham- Bridge at Shoreham- by-Sea by-Sea, including western Old Shoreham TOTAL 1957 1199 N.B. The number of properties covered by the flood warning service is greater in some instances than those identified at risk from fluvial flooding because the numbers presented here include properties at risk from coastal flooding.

Flood Wardens can help promote awareness of flood risk in local communities; make local preparations for flood emergencies; and assist the emergency services if another flood strikes. All of this improves emergency readiness for wardens and their neighbours. However there are currently no Flood Wardens in the Adur catchment. Other measures that can be taken by local residents at risk of flooding include purchasing flood protection products to make their homes more resilient to flooding. Flood protection products aim to stop water getting into the home and Environment Agency 88 River Adur Catchment Flood Management Plan (September 2008) include temporary door guards or waterproof render. Other measures aim to reduce damage if water does enter the home, such as water-resistant walls and floors or raising electrics.

The flood warning service provides an important contribution to flood risk management. However, it is less effective where the catchment responds quickly to individual storm events and it also does not provide warnings of groundwater or surface water flooding. The system relies on individuals registering for the service and taking effective action themselves against the threat of flooding to reduce flood damage. The numbers in table 3.20 illustrate how in some areas people have registered an interest in receiving flood warnings even where they are not at risk, and as such some of the ‘properties registered figures’ are greater than the number of people at risk. Registration for flood warnings is not as complete in the Lower Adur downstream of Upper Beeding and Upper Ferring Rife warning areas, compared to the Upper Adur reaches and the Lower Ferring Rife. There is currently no fluvial Flood Warning Service for the Teville Stream.

The lead times for Flood Warning are more than two hours on all reaches of the River Adur and although short they are considered adequate. However, on small flashy rivers, such as those in the upper catchments, ‘triggers’ for flood warning sometimes use a combination of rainfall and level data to give greater lead times. But this carries a level of uncertainty due to the inherent difficulties in relating rainfall to flood events. At present we make use of data from a range of sources including:

• the hydrometric network shown in the previous section (figure 2.11); • HYRAD rainfall radar; • weekly soil moisture information; • Meteorological Office weather forecasts and warnings.

The River Adur Flood Forecasting model was produced in 2006, and is used to predict the water levels in the river. The model performance will be reviewed in the future after a longer duration of operational use. We will become better at forecasting flooding with new technology and by continuing to gather data.

Environment Agency 89 River Adur Catchment Flood Management Plan (September 2008)

4 Future flood risk In section 3, we looked at the areas currently at risk from flooding and estimated the cost of damages. In this section we look to the future and try to show how flood risk may change over the next 50 to 100 years.

4.1 Introduction

Having set a baseline for flood risk within the CFMP area, we now need to consider how the catchment may respond to any future changes. This will help us set the right policies, strategies and actions to meet the needs of flood risk management both now and for the next 50 to 100 years.

We have taken into account three main ‘drivers’ or influences on changes in the catchment:

• urban development, both in the catchment and river corridor; • climate change (including sea level rise); • change in land use and land management practice.

We have investigated these changes individually through sensitivity tests carried out during the scoping stage of the project, using broadscale models of the principal rivers and streams within the CFMP area. However, following feedback from the scoping stage the broadscale models have since been updated and therefore the damages have changed slightly from the scoping stage. The scoping stage models, however, still give us a good understanding of which of the drivers have a significant effect on the catchment. Tables 4.1 to 4.3 show the independent effects of these changes. We have estimated these changes by working out the differences between the flood damages that would arise under the current baseline conditions (see section 3) and those sustained under future conditions looking at two time horizons, 50 years and 100 years into the future, for the 1% annual probability fluvial flood event.

Sensitivity to urban development Although the catchment is largely rural, development pressures to meet demand for housing within the South East will inevitably result in some urban growth.

We have incorporated urban growth into the broadscale models (see section 3.3), and assumed that an increase in future development will result in increased run-off. For the model, future urban development was represented by a change in the urban extent parameter, for the 50 year horizon this parameter was increased by a factor of 1.17 and for the 100 year horizon by a factor of 1.2. These increases are based on predicted urban growth areas set out in the South East Plan. This is a ‘worst case’ approach and does not allow for the likelihood that any future development will attenuate its surface water discharge to an equivalent ‘greenfield’ rate.

Within the Adur catchment, the predicted increase in urban growth relative to the catchment area is relatively small and, as a result, the impact on flooding at the catchment scale is small, as shown in table 4.1.

Environment Agency 90 River Adur Catchment Flood Management Plan (September 2008)

Table 4.1 - Changes in flood damages for the urban development analysis (1% annual probability fluvial event) Flood damages for urban development Urban development (50 Urban development (100 % change CFMP area Baseline years time) years time) Key between 50 sub- damages % increase % increase Communities Damages Damages years and division (£) from from (£) (£) 100 years baseline baseline Adur East Burgess Hill, 0.31 million 0.31 million 0 0.31 million 0 0 Branch Hassocks Adur West Isolated 0.02 million 0.02 million 0 0.02 million 0 0 Branch properties Shoreham, Steyning, Lower Adur 3.09 million 3.22 million +4 3.46 million +12 +8 Bramber, Upper Beeding Ferring Rife Ferring, and Teville 1.65 million 1.65 million 0 1.73 million +5 +5 Durrington Stream** TOTAL 5.1 million 5.2 million +3 5.5 million +9 +6 **Information uncertain due to insufficient data to model Teville Stream

The catchment as a whole is not particularly sensitive to this level of change in urbanisation, with less than a 10% increase in future damage values from the baseline case over the next 100 years.

Our assessment does not include the impact of any additional building or infrastructure being placed in the floodplain in the future. It is assumed that this will be prevented by appropriate development control, however if it were to occur, the cost of flood damage could increase significantly, depending on the nature of the development (economic and social value) and the depth and frequency of flooding.

As the impact of urban development will be localised, and not significant at a catchment scale, we have not used urban development trends and their effects on future flooding as part of the future scenario.

However, Burgess Hill was identified in section 2.6 as an area where future flood risk may increase due to urban development. Urban development has been taken into consideration in the appraisal of flood risk in the Burgess Hill area.

Sensitivity to climate change Although we cannot accurately predict the effects of climate change, we expect it will result in wetter winters with more frequent and more severe storms. This has been simulated by increasing flow volumes used within the hydraulic model by 20% for both the 50 and 100 year time horizons. This is the accepted approach for ‘typical’ catchments in the UK and is being carried out in this standard way across all CFMPs in England and Wales.

The downstream boundary used for the modelling study was a mean high annual spring tidal cycle over several days. Sea level rise was assessed as 6mm a year for the Sussex coast (at the time the modelling was carried out). This is the combined result of the southern England land mass sinking and rising sea levels due to global warming (that is continental ice caps melting and thermal expansion of the oceans). To represent future sea level rise, this tidal boundary was scaled to increase the maximum still water level by 300mm for the 50 year timescale and by 600mm for the 100 year timescale. The climate change figures used were

Environment Agency 91 River Adur Catchment Flood Management Plan (September 2008) the accepted approach for ‘typical’ catchments when the scoping stage broadscale modelling was carried out. Since the scoping stage was completed new climate change guidance has been released which suggest that for a 100 year time scale, sea level may rise by almost 1 m. Therefore the results from the broadscale model in the tidally influenced areas are likely to have under predicted the increase in flood risk and damages in the future. However the impact of the additional sea level rise is not likely to be that significant when compared to the increased flooding already predicted when sea levels are raised by 600mm.

Results from the broadscale modelling show climate change (including sea level rise) to be the most significant factor in future flood risk within all the catchments, which make up the CFMP area. This trend is supported by the damage values in tables 4.2 and 4.3, where there is a catchment-wide predicted increase in damages to properties and agriculture of approximately 80% for increased river flows, and nearly 900% for sea level rise. The greatest increase in damages due to increased flows occurs in the Lower Adur around Shoreham, Steyning and Upper Beeding, and in the Adur East Branch catchment, where the urban areas of Burgess Hill, and Hassocks are located.

Predicted future sea level rise results in a potentially very large increase in flood damage in the Lower River Adur. Our modelling indicates more than 1,000% increase in the cost of flood damage resulting from a sea level rise of 6mm per year for 100 years. This significantly higher increase in damages resulting from sea level rise is due to the tidal influence and the large number of properties that are located in the coastal areas where the water levels have increased.

Tables 4.2 and 4.3 clearly show what damages could be expected in the catchment if a large storm event was to occur across the CFMP area in the future.

Table 4.2 - Changes in flood damages in 50 years time for the climate change analysis (1% annual probability fluvial events) Flood damages for climate change Increased inflows (50 Sea level rise (50 years years time) time) CFMP area Baseline Key % sub- damages % increased Communities Damages increased Damages division (£) from (£) from (£) baseline baseline Adur East Burgess Hill, 0.31 0.31 0.9 million +290 0 Branch Hassocks million million Adur West Isolated 0.02 0.03 0.02 +50 0 Branch properties million million million Shoreham, Lower Steyning, 3.09 4.66 12.60 +51 +308 Adur Bramber, million million million Upper Beeding Ferring Rife and Ferring, 1.65 1.77 1.73 +7 +5 Teville Durrington million million million Stream** 14.7 TOTAL 5.2 million 7.4 million +140 +280 million **Information uncertain due to insufficient data to model Teville Stream

Environment Agency 92 River Adur Catchment Flood Management Plan (September 2008)

Table 4.3 - Changes in flood damages in 100 years time for the climate change analysis (1% annual probability fluvial events) Flood damages for climate change Increased inflows (100 Sea level rise (100 years time) years time) CFMP area Baseline Key % % sub- damages Communities Damages increased Damages increased division (£) (£) from (£) from baseline baseline Adur East Burgess Hill, 0.31 0.31 million 2 million +645 0 Branch Hassocks million Adur West Isolated 0.03 0.02 0.02 million +50 0 Branch properties million million Shoreham, Lower Steyning, 6.55 48.26 3.09 million +112 +1,462 Adur Bramber, million million Upper Beeding Ferring Rife and Ferring, 1.96 1.75 1.65 million +19 +6 Teville Durrington million million Stream** 10.5 50.3 TOTAL 5.1 million +205 +893 million million **Information uncertain due to insufficient data to model Teville Stream

The impact of climate change on other sources of flooding is not certain. Current predictions suggest more intense rainfall in the future. This could lead to increase surface water flooding in the next 50 to 100 years.

Climate change research indicates winters may be generally wetter and summers substantially drier for the whole of the UK. The direct effect of climate change on groundwater resources depends upon the change in the volume and distribution of groundwater recharge. If drier, warmer summers lead to the seasonal deficits in the moisture content of soils extending into the autumn, the winter groundwater recharge season may be shortened. This could be compensated, at least to some extent, by an increase in winter rainfall. However, aquifers are recharged more effectively by prolonged steady rain, which continues into the spring, rather than short periods of intense rainfall. In the long term, groundwater recharge may reduce but the greater variability in rainfall could mean more frequent and prolonged periods of high or low water levels. Essentially the impact of climate change on groundwater flooding is very uncertain.

We have not modelled surface water or groundwater flooding and therefore do not have flood damages to quantify this potential increase in risk. However an indication of current damages has been taken from the Flood Defence Assessment of Downland Flooding Report (BBV, 2001).

Sensitivity to change in land use and land management We have explored the drivers for change in land use and land management to assess the likely conditions in the future. In doing this we considered pressure to intensify agriculture and increase productivity from the land, which would be likely to increase run-off rates. Throughout our assessment of this catchment, we have found no strong evidence for this driver and therefore we have not included land use change within the future scenario.

Environment Agency 93 River Adur Catchment Flood Management Plan (September 2008)

The alternative scenario where pressure to change farming practices and land use that will reduce run-off rates from the land, such as increasing forest cover or different field patterns, ploughing, cropping, or stock densities are also considered, but this is dealt with as a possible flood risk management ‘response’ (see section 5.2 for further details).

4.2 Future scenarios

In section 4.1 we described how we tested the sensitivity of the CFMP area to changes in the three factors, or ‘drivers’. We tested each factor by itself to see its individual effect. In reality, however, changes in these factors will occur in combination. To assess flood risk under future changes we developed a ‘future scenario’, which combines the factors, to produce our best assessment of likely conditions in the future. We used this future scenario to develop and test how different CFMP policies perform against this likely future situation.

We found flood risk in the River Adur CFMP catchment was sensitive to climate change (both increased flows and sea level rise). Urban development and changes to land use and land use management have very little negative impact on flood risk. We have, therefore, used combined climate change conditions (increased inflows and sea level rise) as our ‘future scenario’ to provide a picture of flood risk in the future and to test the CFMP policies. We have combined the factors in different amounts, to represent different timescales into the future. We have done this to provide a picture of flood risk in 50 years time (2056) and 100 years time (2106).

Since the development of the broadscale model for the River Adur CFMP, during the Scoping stage, new guidance has been produced by Defra on how climate change should be taken into account. The method of predicting future river flows has not changed from those used in this study. However, the new Defra guidance (October 2006) includes greater sea level rise figures. For the River Adur CFMP this means that the sea level rise in 100 years time should be 300mm greater than the 600mm used by the broadscale model. The following tables have not been adjusted to account for the new sea level rise guidance, however, consideration has been given to the potential impact the new sea level rise might have in the policy appraisal.

We used simulated flood extents and depths from the broadscale models to predict the cost of flood damages. This gives us a ‘future baseline’ against which we can test a number of flood risk management responses.

We have run modelling simulations for a range of flood events of different magnitudes, from a relatively small 20% annual probability flood event that has a chance of occurring around once every five years, up to a far less frequent but significantly larger 0.5% annual probability flood event. Other flood events we used to complete the picture were the 10%, 4% and 1% annual probability fluvial flood events.

All the different model runs used the same tidal boundary of a mean high annual spring tidal cycle over several days with the relevant sea level rise increases. We used the results from scenario modelling together with ‘generic responses’ to assess future policies and to see if they can meet the flood risk management needs of the catchment. We discuss these generic responses in more detail in section 6. In this section we focus on the main factors for future change.

The future scenario needs to include some of the possible ways of managing flood risk such as defences, structures and maintenance regimes. As one of the main reasons for developing this future scenario is to provide a future baseline to test different policy options for flood risk management, the scenario we use as a future baseline must assume there will be ‘no change’ Environment Agency 94 River Adur Catchment Flood Management Plan (September 2008) in flood risk management. This means that the current level of defences and standards of protection (based on current flood event return periods) will stay the same in the future.

As with the baseline model results, we recognise the limitations of the broadscale model results and the MDSF software. These factors are not a concern for the CFMP as the damage figures are only indicative and are used as a tool to help us identify where damages are likely to change most in the future.

4.3 Assessment of future flood risk

Modelling the future scenario has allowed us to assess flood risk in the future, providing a snapshot of 50 years and 100 years from now, that is approximately 2056 and 2106. This helps us understand the flood mechanisms and how flood risk is likely to change in the future. It also gives us an indication of the rate at which we can expect these changes to occur. Table 4.4 summarises the main impacts of the future flood risk on the hydrological sub-catchments. Table 4.4 - Main impacts of future flood risk Summary of catchment wide impacts of the future scenario CFMP area Impact sub-division Flood damages along the East Branch of the River Adur increase as a result of climate change. The extent of the modelled risk areas does not increase very much. For the 1% annual probability fluvial flood event, the damage figures only increase from the current baseline of approximately £0.31million up to £0.45 million by 2056 and up to £0.52 million by the year 2106.

For the 10% annual probability event the number of properties at risk 100 years into the future does not increase, and for the 0.1% annual probability event a small increase in the number of properties at risk is predicted. A much greater change is observed for the Adur East 1% annual probability event. branch

It is expected that due to the nature of the flooding in the urban areas of Burgess Hill and Hassocks, more extreme rainfall and the predicted urban growth proposed in the South East Plan, could have a significant impact on the frequency of surface water flooding at a more local scale. There are likely to be up to 500 properties at risk of flooding in Burgess Hill and Hassocks in the future. This could be from combined fluvial, surface water flooding and urban drainage problems. However, we have not modelled surface water flooding and therefore do not have flood damages to quantify this potential increase in risk. The Adur West Branch catchment appears not to be sensitive to our future change scenario. We have found very little serious flood damage in this catchment, with only agricultural land affected by the 1% annual probability fluvial flood outline under both Adur West current conditions and in the future. This flood risk remains low for the 0.1% annual Branch probability flood event with only damages occurring to agricultural land. There are opportunities in the catchment area to provide flood storage and attenuation to flood peaks to help reduce the flood risk in downstream locations such as Steyning, Upper Beeding and Shoreham. The Lower Adur is the catchment that has proved to be most susceptible to future change. Flood damages for the 1% annual probability fluvial flood event, in 100 years time, have shown an increase of 26% from the baseline. The flood extent increases in the future from a current area of 0.04km2 to 3.2km2 in the future. We have also Lower Adur assessed the tidal flooding in this sub-catchment, which shows a very large increase of more than 1,000% from the current baseline. However, there is little increase in flood risk for the more frequent, less severe flood events (10% annual probability flood event), with the flood damages only estimated at £0.2 million in the future.

Environment Agency 95 River Adur Catchment Flood Management Plan (September 2008)

Apart from the uncertainty in predicting groundwater flooding in the future, we do not expect the increase in flooding in the Ferring Rife catchment to be dramatic. The extent of the modelled flood risk areas does not increase very much for the 10%, 1%, and 0.1% annual probability flood events. For the 1% annual probability fluvial flood event, the damages only increase around 3% from the baseline for the 50 year horizon and 11% for the 100 year horizon. Due to the limited data available for the catchment, the impact of climate change on fluvial flooding from the Teville Stream is uncertain. Ferring Rife However it is likely that flood risk will increase in the Teville Stream catchment in the and Teville future. Stream

The impact of future flooding in this catchment is uncertain, but it is predicted that a combination of groundwater flooding, surface water runoff and/or urban drainage system flooding could result in a high risk flood event flooding the low-lying urban areas of Sompting, Lancing, and parts of Worthing. It is also predicted that climate change will increase this risk, however, the extent to which this increase affects the people, property and environment in these areas is unknown.

4.3.1 Future flood risk to people and the community Our broadscale modelling has indicated that the flood risk on the Lower Adur will increase dramatically in the future from fluvial and tidal flooding. At Shoreham there is a significant increase in the number of properties affected if the river overtops its banks, as the predicted flood extent covers an extensive area of low-lying urban development. This flood extent is unlikely to alter significantly with the new climate change guidance sea level rise predictions. Table 4.5 shows the potential number of residential properties at risk from flooding, 100 years in the future.

Table 4.5 - Residential properties potentially at risk from flooding in the future Number of residential properties at risk now and in the future CFMP area Current Baseline Future Baseline Key communities sub-division 10% 1% 0.1% 10% 1% 0.1% Adur East Burgess Hill, 2 12 539 2 250 550 Branch Hassocks Adur West Isolated properties 0 0 15 0 0 15 Branch Steyning, Bramber, 3 91 103 4 112 112 Lower Adur Upper Beeding Lancing, Shoreham 0 1 344 6 1757 1757 Ferring Rife Ferring, Durrington, and Teville Sompting, East 2 52 502 2 59 510 Stream** Worthing TOTAL - 7 156 1503 14 2428 2944 **Information uncertain due to insufficient data to model Teville Stream

For some communities the future number of properties at risk has been estimated based on a combination of model results and Flood Zones. A qualitative assessment of Flood Zone 2 in the future was completed based on geographic features that restrict the extent of the floodplain.

As discussed in chapter 3, flooding can lead to health impacts including physical effects in the short term and psychological effects in the short and long term. For the future scenario in the Adur CFMP, we have assessed how vulnerable the population is using the Flood Hazard Research Centre Social Flood Vulnerability Index (SFVI). As such we are assuming the vulnerability of areas will be the same in the future as the current baseline. There is no information available to determine how the vulnerability of the communities at risk of flooding

Environment Agency 96 River Adur Catchment Flood Management Plan (September 2008) will change in the future. Table 4.6 provides an indication of the number of properties in each SFVI category who live in the floodplain.

Table 4.6 - Social vulnerability of people affected by the 1% annual probability flood event Number of properties in each SFVI classification CFMP area Social flood vulnerability classification* Key communities sub-division SFVI 1 SFVI 2 SFVI 3 SFVI 4 SFVI 5 Adur East Burgess Hill, Hassocks 0 2 130 118 0 Branch Adur West Isolated properties 0 0 0 0 0 Branch Steyning, Bramber, Upper Lower Adur 0 0 95 17 0 Beeding Lancing, Shoreham 0 0 1453 304 0 Ferring Rife Ferring, Durrington, and Teville 0 0 45 14 0 Sompting, East Worthing Stream** TOTAL - 0 2 1866 560 0 *Vulnerability has been categorised into 5 bands where 1 represents the lowest and 5 the highest.) **Information uncertain due to insufficient data to model Teville Stream

Properties at risk in a 1% annual probability event throughout the CFMP study area are generally within the medium to high vulnerability classification.

Areas that have experienced surface water and ground water flooding are listed in chapter 3, table 3.5. The table provides an indication of the SFVI category of the areas which have been affected historically by surface water, sewer, or groundwater flooding.

We have worked out the number of people at risk from the number of residential properties located within each flood outline assuming that each household contains an average of 2.39 people. This is based on the regional average for the South East (National statistics census data 2001), as there is no specific data available on future population figures. Table 4.7 shows the number of people at risk from a range of annual probability flood events (10%, 1% and 0.1%).

Table 4.7 - Population potentially at risk from flooding in the future Number of people potentially at risk from future flooding CFMP area Current Baseline Future Baseline Key communities sub-division 10% 1% 0.1% 10% 1% 0.1% Adur East Burgess Hill, 5 29 1288 5 598 1,315 Branch Hassocks Adur West Isolated properties 0 0 36 0 0 36 Branch Steyning, Bramber, Lower Adur 7 217 246 10 268 268 Upper Beeding Lancing, Shoreham 0 2 822 14 4199 4199 Ferring Rife Ferring, Durrington, and Teville Sompting, East 5 124 1200 5 141 1,219 Stream** Worthing TOTAL - 17 372 3592 34 5206 7037 Note: Number of residential properties x 2.39 occupants (based on Table 3.3) Source: National statistics census data 2001 **Information uncertain due to insufficient data to model Teville Stream Environment Agency 97 River Adur Catchment Flood Management Plan (September 2008)

Tables 4.5 and 4.7 clearly show that the Lower Adur is the area where the most properties and people will be at risk of flooding in the future. In Shoreham and Lancing there is a significant increase in risk from the current basecase where only 2 properties are at risk from the 1% annual probability flood event. The Adur East Branch also shows a significant increase from 12 properties at risk in the current basecase from the 1% annual probability flood event up to 250 in the future.

Properties at risk in Burgess Hill and Hassocks increase in the future, with a greater number at risk to greater depths of flooding. Although slightly more properties are at risk in Steyning, Bramber and Upper Beeding, the depths of flooding do not generally increase, and in some areas decrease slightly, which may be due to the changing flood mechanisms as defences overtop. However, through Shoreham significantly greater areas are at risk of flooding and in some areas depths are greater than 2 metres. Table 4.8 shows the number of properties at risk at different depth ranges for the future 1% annual probability flood event.

Table 4.8 - Summary of depths of flooding during the 1% annual probability flood event 100 years in the future Number of properties and depth of flooding for the 1% annual probability flood event 100 years in the future CFMP sub- More than Key community 0.0 to 0.5m 0.5m to 1m 1m to 2m catchment 2m Adur East Burgess Hill, Hassocks 180 35 35 0 Branch Adur West Isolated properties 0 0 0 0 Branch Lower Adur Steyning, Bramber, Upper 71 37 4 0 Beeding Lancing, Shoreham 314 544 899 2 Ferring Rife Ferring, Durrington, and Teville 40 16 3 0 Sompting, East Worthing Stream** TOTAL 783 668 977 Source: broadscale hydraulic modelling **Information uncertain due to insufficient data to model Teville Stream

The increase in flooding and depths in Shoreham and Lancing is not flooding directly from the sea, but as a result of predicted sea level rise in the future causing the water to back up the River Adur and overtop the river embankments, flooding low lying land behind the defences. Future flood risk management actions will need to take account of this potential significant increase in flood risk in Shoreham and Lancing. The more recent climate change guidance for sea level rise will probably result in little change in the numbers of property at risk, but may result in greater depths of flooding, increasing the flood hazard.

More people are likely to be affected by increased surface water flooding due to predicted wetter winters with more frequent and more severe storm events. This may be of particular concern in Worthing, and Brighton and Hove where incidents of flooding may become more widespread and more frequent. There is also potential for an increase in surface water flooding and urban drainage problems in Burgess Hill and Hassocks. Note that these have not been included in the flood damage calculations presented, in the next section of this chapter, as we have not been able to model these sources of flooding.

Surface water flooding is likely to become more frequent and severe in the future due to the effects of climate change. This is likely to lead to some properties being flooded more frequently in localised areas and an increase in travel disruption. Table 4.9 identifies the

Environment Agency 98 River Adur Catchment Flood Management Plan (September 2008) potential increase in number of people at risk from surface water, groundwater and urban drainage flooding in the future, compared to the current baseline. The number of properties at risk in the future has been estimated based on historic records, location of properties in relation to the likely pathway of flood water, a 30% increase in peak rainfall intensity (FCDPAG3) and development pressures.

Table 4.9 - Number of properties at risk of other sources of flooding Communities at risk of other sources flooding now and in the future Approximate number of CFMP sub- Locations at Risk Flood source properties at risk catchment Current baseline Future baseline Burgess Hill, Surface water flooding Adur East Wivelsfield, Hassocks Between 30- and urban drainage Up to 30 Branch (Hurstpierpoint and 100 system Keymer) Cuckfield, Bolney, Surface water None recorded Unknown Henfield Partridge Green, Adur West Number Number likely Ashington, West Surface water flooding Branch unknown to increase Grinstead Steyning, Bramber, Number Number likely Upper Beeding, Surface water flooding unknown to increase Ashurst, Shoreham Less than 10, Between 10 - Rottingdean, Surface water flooding (66*) 100 Ovingdean, Surface water flooding 1 Between 1-20 Woodingdean Between 25- Bevendean Surface water flooding 25 Lower Adur 50 Lewes Road area, Surface water flooding 2 Between 2-5 Brighton Westdene, Surface water flooding 2 Between 2-5 Surface water, urban Between 15- Patcham drainage system, and 15 20 groundwater flooding Groundwater and Mile Oak 3 Between 3-10 surface water flooding. Sompting, Lancing, Groundwater and Number Number likely Findon, Worthing surface water flooding. unknown to increase FerringRife Groundwater, urban and Teville Durrington More than 2 More than 2 drainage system Stream Ferring, Findon, Number Number likely Surface water flooding Worthing unknown to increase Between 150- TOTAL - More than 146 500 Source: Brighton and Hove City Council, Worthing Borough Council, and Mid Sussex District Council *Brighton Council erected dams and lagoons to store runoff and reduce flooding after the 1987 event, therefore the current number of properties at risk is considered significantly less than 66.

Table 4.9 shows that the number of people affected by surface water and urban drainage flooding in the future will increase slightly in most places. The impact of climate change on groundwater flooding in the future is very uncertain, and as such we have assumed that the number of people at risk in the future will not increase. However, consideration should be given to areas identified at risk from groundwater flooding in the planning process when allocating

Environment Agency 99 River Adur Catchment Flood Management Plan (September 2008) land for development, to ensure the number of people in areas at risk is not increased in the future.

4.3.2 Future flood risk to property and infrastructure The predicted changes in flood damage estimates for 1% and 10% annual probability fluvial flood events and the annual average damages, to both properties and agricultural land, over the next 100 years, is shown in table 4.10.

Table 4.10 - Estimated flood damages for the future scenario Estimated flood damages in 100 years time Flood damages to properties Flood damages Total CFMP area (£ million) to agricultural damages (£ sub-division Key communities Residential Commercial land (£ million) million) 10% annual probability flood event Adur East Burgess Hill, 0.1 0 0.04 0.14 Branch Hassocks Adur West Isolated properties 0 0 0.02 0.02 Branch Shoreham, Lower Adur Steyning, Bramber, 0.2 0 0.05 0.25 Upper Beeding Ferring Rife and Teville Ferring, Durrington 0.1 0 0 0.1 Stream** TOTAL 0.4 0 0.11 0.51 1% annual probability flood event Adur East Burgess Hill, 0.5 0 0.05 2 Branch Hassocks Adur West Isolated properties 0 0 0.02 0.02 Branch Shoreham, Lower Adur Steyning, Bramber, 62.0 19.3 0.1 81.4 Upper Beeding Ferring Rife and Teville Ferring, Durrington 1.8 0 0 1.8 Stream** TOTAL 64.3 19.3 0.17 83.77 Annual average damages Adur East Burgess Hill, 0.03 0 0.02 0.08 Branch Hassocks Adur West Isolated properties 0 0 0 0 Branch Shoreham, Lower Adur Steyning, Bramber, 11.5 3.7 0.01 15.2 Upper Beeding Ferring Rife and Teville Ferring, Durrington 0.1 0 0 0.1 Stream** TOTAL 11.63 3.7 0.03 15.33 **Information uncertain due to insufficient data to model Teville Stream

Modelling the future scenario has allowed us to assess flood risk in the future providing a snapshot of both 50 and 100 years from now, that is approximately 2056 and 2106. This gives us an indication of the rate at which we can expect these changes to occur. Figure 4.1 provides an indication of how flood risk will change over time throughout that period, giving the damages in £million for each of the CFMP sub-catchments at their current estimated level, 50 Environment Agency 100 River Adur Catchment Flood Management Plan (September 2008) years from now, and 100 years from now. Figure 4.1 shows that the flood damages will increase only slightly in the future across most of the CFMP area with Adur East Branch showing a steady increase into the future, and only the Lower Adur showing a significant change due to climate change.

Figure 4.1 - Change in the 1% annual probability flood damages under future scenarios

The projected damages in 100 years time are shown in figure 4.2. It shows how flood damages in some areas will only increase slightly in the future, such as the Ferring Rife, whilst other areas change quite dramatically, such as the Lower Adur. The increased damages in the Lower Adur 100 years into the future are related to the predicted increase in sea level rise. These damages may be higher with the new climate change guidance.

Environment Agency 101 River Adur Catchment Flood Management Plan (September 2008)

Figure 4.2 - Distribution of flood damages for the 1% annual probability flood event under the future scenario in 2106

Environment Agency 102 River Adur Catchment Flood Management Plan (September 2008)

Table 4.11 summarises the number of properties and infrastructure at risk from this future flooding for the CFMP catchment as a whole.

Table 4.11 - Properties and infrastructure at risk of flooding in the future Properties and infrastructure at risk CFMP area sub-divisions and annual probability flood event Property/ Adur West Ferring Rife and infrastructure Adur East Branch Lower Adur Branch Teville Stream** type 10% 1% 0.1% 10% 1% 0.1% 10% 1% 0.1% 10% 1% 0.1% Residential 2 250 550 0 0 15 10 1,869 1,869 2 59 510 properties Emergency 0 0 0 0 0 0 0 1 1 0 0 1 services Hospitals 0 0 0 0 0 0 0 2 2 0 0 0 Education 0 0 0 0 0 0 0 0 0 0 0 0 Sewage treatment/ wastewater treatment 1 1 1 0 0 0 0 0 0 0 0 0 works/ chemical works Electricity sub 0 0 0 0 0 0 0 3 3 0 0 0 stations Other commercial 0 0 40 0 0 2 10 110 110 0 0 23 properties Main roads 0.7 1.1 3.2 0.9 1.1 2.1 0.6 7.0 7.0 0.2 0.2 0.7 (km) Railways (km) 0 0 0.3 0 0 0.1 0.1 1.8 1.8 0 0 0 Agricultural grade land 3.6 4.5 7.1 2.0 2.4 5.9 5.4 11.3 11.3 0 0 0.3 (km2) **Information uncertain due to insufficient data to model Teville Stream

Surface water flooding is likely to become more frequent and severe in the future due to the effects of climate change. This is likely to lead to some properties being flooded more frequently in localised areas and an increase in travel disruption. We are unclear about how groundwater flooding will change in the future and support current research on the subject.

4.3.3 Future flood risk to the environment The impact of future changes to flood risk on designated historic environment assets within the 1% annual probability flood extent are considered in this section. The sites currently at risk were identified in Chapter 3.

Table 4.12 shows a summary of the area’s environmental and landscape designation sites that fall within the 10%, 1% and 0.1% annual probability future flood outlines, looking 100 years ahead. In the future, the area of environmental and landscape designations affected does not increase significantly.

Environment Agency 103 River Adur Catchment Flood Management Plan (September 2008)

Table 4.12 - Area of designated sites at risk of flooding the future Area of designated sites at risk of flooding for the total catchment Area of combined designated sites (km2) Designated site 10% 1% 0.1% SNCIs 2.4 3.8 4.4 LNRs 0 0 0.1 SSSIs 0.6 0.6 0.6 National Park 2.5 5.4 6.9 (proposed) AONBs 0 1.7 3.4 ESAs 0 1.7 3.1 SMs 4 12 15

In the future, the wetland sites on the Adur floodplain will be exposed to a greater frequency of flooding. This could have both positive and negative effects. The increased salinity of floodwaters that is likely to occur due to sea level rise and a greater influence of the tide up the tidal Adur, could have a negative impact on some freshwater sites. However, the increase in frequency of flooding also presents opportunities to increase the area of wetland habitats such as floodplain grassland, reed bed and wet woodland. The creation and expansion of such habitats would improve the biodiversity value of the Adur catchment and contribute to national Biodiversity Action Plan (BAP) targets.

There may be the potential to expand the wetland habitats associated with the River Adur Water Meadow SNCI. There are ten SNCIs (3.8 km2) that fall within the future 1% annual probability fluvial flood event including; the River Adur Water Meadows; Widewater Lagoon, Lancing; Ferring Rife and Meadows; and the River Adur Water Meadows and Wyckham Wood.

The likely future increase in salinity of the tidal Adur may also provide the opportunity to expand inter-tidal habitat of the Adur Estuary SSSI through flood risk management as described in table 4.13.

Table 4.13 - Environmentally designated sites affected by the 1% annual probability flood event Environmentally designated sites affected by current and future flooding Area of site in 1% annual probability flood Site name event Impact of future flooding Current Future baseline baseline In the future, through considering environmentally beneficial flood risk management, there is potential for a greater area of the SSSI to be affected by flooding. The likely future increase in salinity of the tidal Adur may also provide the opportunity to expand inter-tidal Adur Estuary 2 2 1.8 km 1.8 km habitat (a valuable habitat that is the reason for the (SSSI) Adur Estuary SSSI designation)

A natural flow regime will help to conserve the features of this site, therefore it is likely that periodical flooding will have a beneficial effect in this SSSI.

Environment Agency 104 River Adur Catchment Flood Management Plan (September 2008)

Multiple benefits to people and the environment could be achieved by allowing more of the Adur floodplain to store floodwaters, and creating wetland habitat in the process, that could reduce flood risk to people in Shoreham and Steyning.

There 115 scheduled monuments within the CFMP area, 2942 listed buildings, 9 registered parks and gardens, and no historic battlefields. A number of these lie within the future 1% annual probability flood extent as shown in table 4.14.

Table 4.14 – Historic Environment sites affected by the 1% annual probability flood event Historic Environment sites affected by river flooding Designation Total number of sites affected Total number of sites affected by flooding in the current by flooding in the future baseline baseline Scheduled Monuments 14 15 Listed Buildings 6 8 Registered Historic Parks and 0* 2 Gardens Historic Battlefields 0 0 *(based on Broadscale modelling, Knepp Castle and Heaselands within Flood Zone 3 on non modelled reaches)

The majority of scheduled monuments at risk of flooding both now and in the future are in the Upper Beeding area. Knepp castle and the moated site at Ewhurst Manor, located in the West and East Adur sub catchments respectively, are also partially at risk both now and in the future. The number of scheduled monuments at risk in the future increases by one, with the Shoreham airfield dome trainer being within the future 1% annual probability flood extent. Scheduled Monuments are protected from deliberate or preventable flooding (unless authorised). Many historic bridges and listed buildings of cultural heritage importance are also protected. Villages and historic market towns are also important to communities and the economy in the CFMP area and are often sited close to rivers where there is a risk of flooding. It is possible that the location of some of the historic features discussed above may constrain some Flood Risk Management options.

4.4 Summary of Flood risk at key locations

In section 3 we examined the sources and mechanisms of flood risk in each of the CFMP catchment areas. Now that we understand how flooding is likely to change under our future scenario, we can predict how flood risk will change in these areas in the future.

Table 4.15 shows how flood risk will change in the future for each of the key communities in the CFMP area. As for the current baseline (see section 3.4), the assessment is based on the combination of the impact of flooding on the location and the likely frequency of flooding. One of the best measures of this is the annual average damage (AAD) figure, which is derived from estimated flood damages for a range of flood probabilities. We have also taken into account factors such as the 10%, 1% and 0.1% annual probability flood events, the flood depths and flow velocities as these can increase the level of flood hazard. We have assessed the future flood risk as high, medium and low at each location.

Environment Agency 105 River Adur Catchment Flood Management Plan (September 2008)

Table 4.15 - Summary of future flood risk for key communities3 Summary of future flood risk Flood risk location (key Assessment of future flood risk community) In the future there are up to an estimated 350 properties at risk from a 1% annual probability flood event from fluvial flooding and surface water flooding in Burgess Hill and Hassocks.

The broadscale modelling shows limited change in the depth and velocities of the floodwaters in these urban areas (less than 0.3m and 0.5m/s respectively). However, the flood extent is likely to increase by over 100% when a combined fluvial and surface water flood event occurs. Properties that currently flood are likely to flood more frequently in the future.

Burgess Hill and Hassocks Urban growth in the Burgess Hill area has been identified in the South East Plan, which is likely to result in more surface water and urban drainage problems. It has not been possible to quantify this in damages figures, however it is likely to lead to greater disruption and higher damage values.

The broadscale modelling shows that there are also no environmental or landscape designations that will be affected by future flooding.

Our assessment of future flood risk in this area changes from low to medium. Flood risk in Wivlesfield is predominantly from surface water flooding, which has not been modelled.

We have assessed the impact of the future scenario in this area and we Wivlesfield believe that there will be a minimal increase.

It is likely that the extent and frequency of flooding will increase slightly in the future, however this increase will not be enough to change the flood risk assessment, which remains as low. The flood risk in Shoreham and Lancing increases significantly in the future as a result of climate change, in particular due to sea level rises. The flood extent has increased from approximately 0.04km2 to approximately 3.2km2 in the future in this area.

Shoreham and Lancing The increased flood extent increased the number of properties at risk from less than 10 to nearly 2,000 for a 1% annual probability flood event with an associated increase in flood damages from £3.1 million to £81.4 million. Annual average damages in the future are estimated as £10 million and therefore are assessed as high risk.

3 The broad definitions for the parameters contained in the following table are: Damages Low: AAD < £0.5 million, and 1% annual probability flood damages < £1 million Medium: AAD between £0.5 million and £1 million, and 1% annual probability flood damages between £1 million and £5 million High: AAD > £1 million, and 1% annual probability flood damages > £5 Water velocity Low: <0.5m/s, medium: 0.5 -1m/s, high: >1.5m/s Water depth: Shallow: <0.3m, moderate: 0.3 – 1m, deep: >1m Environment Agency 106 River Adur Catchment Flood Management Plan (September 2008)

There is an increase in the extent of critical infrastructure at risk of flooding during the future baseline scenario, including Shoreham airport, three electricity sub-stations and a police station. Major transport links are also affected, with the A27, A259 and the railway line all at risk of flooding by the 1% annual probability flood event.

Flood depths in Shoreham also increase significantly with some areas at risk of depths up to 2.2 metres.

The increased sea levels in the future are likely to result in increased flooding frequency in Shoreham, with properties being flooding more often.

The increase flood depths, extents and frequency of flooding in the future changes the flood risk in Shoreham from low to high. Our broadscale modelling has shown that future flood risk in Steyning, Upper Beeding and Bramber does not increase significantly. Flood damages for the 1% annual probability flood event only increase from £2.9 million to £3.7 million in the future. There is also minimal increase in the number of properties affected from 91 for the current 1% annual probability flood event up to 112 for the future 1% annual probability flood event. This number is not likely to increase much more for the Steyning, Upper Beeding and 0.1% annual probability flood event. Bramber Although the flood extents and frequency remains largely unchanged in the future the flood depths are likely to increase, with flood depths in the future estimated up to 2 metres in Steyning, Upper Beeding and Bramber.

As the flood risk is unlikely to increase significantly in the future our flood risk assessment remains as low. The broadscale modelling has shown that damage levels within the Ferring and Durrington area are relatively insensitive to any changes in flood flows that do occur, with an increase from £1.65 million to only £1.69 million by the year 2050 and £1.83 by the year 2100 for the 1% annual probability fluvial flood event. The average annual flood damages are only expected to increase from £0.07 million to £0.11 million.

Water depths are likely to increase by less than 5cm which causes a slight increase in damages. The velocities and duration of flooding and areas prone to flooding are likely to remain unchanged. Therefore, we assess the hazard to remain unchanged from the current conditions Ferring and Durrington into the future.

Figure 4.1 shows the rate of change to be relatively slow over the next 50 years, and then looking forward towards the 100 year timescale, the rate of change is slightly more noticeable.

The broadscale modelling also shows that there are no environmental or landscape designations that will be affected by future flooding in the Ferring Rife catchment.

Flood risk will increase only marginally as a result of the small increase in damages due to a small increase in flood extent. Although there is a slight increase in flood risk in the future, our assessment of the risk is low. Environment Agency 107 River Adur Catchment Flood Management Plan (September 2008)

Flooding in this catchment is caused by a combination of surface water, groundwater and fluvial river flooding. Due to limited data availability we have not created a broadscale model for the Teville Stream. So, we do not have reliable data on which we can base flood extents, depths and damages for this catchment.

It is expected that flood extent and flood damages will increase in the future, and with the low lying urban areas in Sompting, long duration flooding will become more frequent and damaging. Sompting and Worthing Flood hazard will remain largely the same, as flood depths are not expected to increase significantly in the future.

The scale of disruption could increase as a result of more frequent flooding of roads and properties.

Flood risk will increase due to climate change, however we are uncertain about how much it will increase. Based on our current knowledge we assess the flood risk in the future to be low to medium. There are numerous records of historic flooding in Brighton and Hove, which have affected approximately 114 properties and caused significant disruption to major rail and road transport routes in 2000.

Although the 2000 flooding caused significant disruption, such extensive events are infrequent. No modelling has been undertaken for Brighton and Hove sources of flooding other than fluvial; as such the assessment of future flood risk in this area is uncertain. However climate change guidance suggests the surface water flooding may increase and urban drainage systems will be under increasing pressure. Both disruption and hazard are assessed as likely to be low in the future when considered in the context of other flooding issues within the study area. Therefore the future flood risk is assessed as low.

Environment Agency 108 River Adur Catchment Flood Management Plan (September 2008)

5 Catchment objectives Having looked at the possible future changes to the catchment in section 4, in this section we outline the objectives that will bring sustainable flood risk management and wider benefits to the catchment.

5.1 Introduction

As outlined in section 1, this CFMP will help achieve the main aims and policies set out in EU directives and Government policy and guidance. In keeping with these aims and policies, we have suggested the following targets for the River Adur Catchment Flood Management Plan:

• To reduce the risk of flooding and harm to people, the natural, historic and built environment caused by floods. • To maximise the opportunities to work with natural processes and to deliver a range of benefits from flood risk management and make an effective contribution to sustainable development. • To support the delivery of relevant EU directives, Government and other external organisations’ policies and targets. • To promote sustainable flood risk management. • To inform and support planning policies, statutory land use plans and implementation of the Water Framework Directive.

The overall objective of the flood risk management policies in this CFMP is to help meet these targets. To achieve this, we have developed objectives for the catchment that reflect these targets and allow us to measure how effective our policies are (see section 6). The objectives set within the CFMP take into account the issues, opportunities and constraints identified through this report.

5.2 Catchment opportunities and constraints

5.2.1 Opportunities for sustainable flood risk management Opportunities arise when certain physical features, or social or economic characteristics present ways of managing flood risk more effectively whilst also benefiting the catchment in other ways. We have identified a number of opportunities for the River Adur catchment from the studies carried out, the information gathered, and through consultation. These are:

• Enhance the character of the landscape and increase amenity opportunities for recreation, tourism and leisure activities. • Help meet national biodiversity action plan (BAP) targets. • Work with the High Weald AONB Joint Advisory Committee to achieve the targets set in the High Weald AONB Management Plan to maximise the opportunities for natural processes to reduce flooding through the adoption of river restoration policies, whilst enhancing landscape character. • Move toward more natural rivers and drainage networks, as outlined within PPS25, will mean we can achieve more efficient and sustainable water management, whilst enhancing landscape character.

Environment Agency 109 River Adur Catchment Flood Management Plan (September 2008)

• Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Partridge Green and Steyning and between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity. • Influence the second generation of Shoreline Management Plans and the coastal defence strategy, along the Lower Adur, Teville Stream and Ferring Rife, to improve the sustainability of flood risk management in this area. • Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Brighton and Hove, Worthing, Shoreham, and Burgess Hill). • Reduce flood risk and improve water quality by promoting and encouraging the use of SuDS in the proposed urban developments in Brighton and Hove, Worthing, Shoreham, and Burgess Hill. • Investigate the feasibility of incorporating the Teville Stream into the Floodline Warnings Direct service by installing new level gauges on the Teville stream. • Continue local authority and Environment Agency support of the Flood 1 project in relation to groundwater flooding. • Develop a flood warning system for groundwater flooding. • Continued practice and development of the Emergency Response Plan in Brighton and Hove, Worthing, Shoreham, and Burgess Hill. • Reduce surface water run-off and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices (e.g. those set out by Brighton and Hove City Council). • Support the existing flood defence measures in relation to surface water flooding, such as bunds provided by Brighton and Hove City Council. • Potential for improving the current defences, for example possible installation of demountable or temporary defences in Shoreham and Burgess Hill. • Improvements in the efficiency of channel and flood defence maintenance processes. • Effective and efficient use of developer contributions for flood risk management. • To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing runoff rates.

5.2.2 Constraints on flood risk management options Constraints limit the value of particular flood risk management options or, in some circumstances, exclude them altogether. For example, protecting conservation sites and the quality of the landscape will mean choosing flood risk management options that must be compatible with these features. Other more cost effective solutions may be unsuitable as a result.

Although constraints, by their very nature, may restrict or prevent certain actions, there may be situations where habitat will be lost and difficult choices have to be made. Replacing habitat or landscapes with an alternative either in other places, or by more valuable replacement, can be considered in some circumstances.

Constraints have also been identified through the understanding of catchment processes and recognition of the importance of certain features and issues. These are:

• Government and international legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East

Environment Agency 110 River Adur Catchment Flood Management Plan (September 2008)

Plan and compliance with the Habitats Directive. • Existing urban development may prevent reinstatement of natural river processes. • Individual homes and properties are currently at risk of flooding. • Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance. • Historic development and some heritage designations in Steyning, Bramber, and Upper Beeding present permanent physical obstructions. • Presence of protected species with specific water level, water quality, and habitat requirements, for example in the Adur Estuary SSSI. • Location of electricity pylons adjacent to the Lower River Adur (currently protected by existing defences). • No degradation of existing fish passage and habitat. • Visual impact of flood risk management activities within the proposed National Park or Areas of Outstanding Natural Beauty. • Steep catchments of the South Downs result in rapid run-off and quick responses to rainfall events. • Transport links in the catchment are a vital part of the communication network regionally, nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032. • A suitable level of productivity from agricultural land needs to be retained. • Changes to flood risk management can affect the landscape, its character and value as an amenity. • CFMP objectives and policies must complement those of the Shoreline Management Plan (SMP) that affects the CFMP area. • Available funding for the initial set up of new flood risk management schemes. • Older flood defence structures are likely to be costly to maintain. • Limited available information on surface water and groundwater flood damages.

It is important to identify the broad environmental, social and economic opportunities and constraints that may affect flood risk management when developing the catchment objectives and implementing sustainable policies that are effective in managing both current and future flood risk. Table 5.1, in the following section, identifies the opportunities and constraints that relate to the objectives for the River Adur CFMP.

5.3 CFMP objectives

During the scoping stage of developing the CFMP, we identified the areas, properties and habitats that could be affected by flooding in the CFMP area. We looked for opportunities to reduce flood risk and constraints that could limit our actions. We also reviewed legislation and other policies, plans and strategies that affect the CFMP area. This helped us develop a set of draft catchment objectives that were detailed within the scoping stage report.

These objectives are focussed on addressing the key issues in the River Adur CFMP area related to:

• people, society and communities (social); • property, assets and infrastructures (economic); • environment (environmental).

Environment Agency 111 River Adur Catchment Flood Management Plan (September 2008)

As a result of the three month consultation stage that followed the publication of the scoping report we received a few comments from consultees, which have been incorporated into the catchment objectives within the main stage. We have now agreed a final set of catchment objectives.

These catchment objectives are as follows:

Environmental

• Restore rivers and floodplains to a naturally functioning state where feasible. • Protect and enhance nationally and internationally important species and habitats.

Social

• Ensure the impact of flooding on people and property does not significantly increase in the future (for example due to climate change). • Ensure the disruption caused by flooding to transport and critical infrastructure does not significantly increase in the future (for example due to climate change). • Reduce the impact of muddy flooding.

Economic

• Ensure flood damages do not significantly increase in the future (for example due to climate change). • Ensure that river channel and flood defence maintenance expenditure is appropriate to the economic damage of flooding.

Table 5.1 identifies how the opportunities and constraints identified in section 5.2 relate to these catchment objectives for the River Adur CFMP.

Environment Agency 112 River Adur Catchment Flood Management Plan (September 2008)

Table 5.1 - Catchment objectives, opportunities and constraints Catchment objectives and the relevant opportunities and constraints in the River Adur CFMP Catchment objective Opportunities Constraints Environmental • Government and international legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive. • Enhance the character of the landscape and increase amenity • Some environmentally designated habitats are opportunities for recreation, tourism and leisure activities. susceptible to changes in flood frequency, floodwater • Move toward more natural rivers and drainage networks, as chemistry, groundwater levels and drainage system outlined within PPS25, will mean we can achieve more efficient maintenance. and sustainable water management, whilst enhancing • Existing urban development may prevent reinstatement landscape character. of natural river processes. Restore rivers and • Investigate removal of Environment Agency owned and • Individual homes and properties are currently at risk of floodplains to a maintained existing raised defences to reinstate the floodplain flooding. naturally functioning between Partridge Green and Steyning and between Steyning • Presence of protected species with specific water level, state where feasible. and Shoreham to a naturally functioning state, to provide flood water quality and habitat requirements, for example in storage and enhance conservation value and biodiversity. the Adur Estuary SSSI. • Influence the second generation of Shoreline Management • Changes to flood risk management can affect the Plans and the coastal defence strategy, along the Lower Adur, landscape, its character and value as an amenity. Teville Stream and Ferring Rife, to improve the sustainability of • Historic development and some heritage designations flood risk management in the this area. in Steyning, Bramber and Upper Beeding present • Help meet national biodiversity action plan (BAP) targets. permanent physical obstructions. • Location of electricity pylons adjacent to the Lower River Adur (currently protected by existing defences). • No degradation of existing fish passage and habitat. • CFMP objectives and policies must complement those of the Shoreline Management Plan (SMP) that affects the CFMP area. Protect and enhance • Help meet national biodiversity action plan (BAP) targets. • Some environmentally designated habitats are nationally and • Work with the High Weald AONB Joint Advisory Committee to susceptible to changes in flood frequency, floodwater internationally achieve the targets set in the High Weald AONB Management chemistry, groundwater levels and drainage system important species and Plan to maximise the opportunities for natural processes to maintenance. Environment Agency 113 River Adur Catchment Flood Management Plan (September 2008)

Catchment objectives and the relevant opportunities and constraints in the River Adur CFMP Catchment objective Opportunities Constraints habitats. reduce flooding through the adoption of river restoration • Changes to flood risk management can affect the policies, whilst enhancing landscape character. landscape, its character and value as an amenity. • Investigate removal of Environment Agency owned and • CFMP objectives and policies must complement those maintained existing raised defences to reinstate the floodplain of the Shoreline Management Plan (SMP) that affects between Partridge Green and Steyning and between Steyning the CFMP area. and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity. Social • Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Brighton and Hove, Worthing, Shoreham and Burgess Hill). • Reduce flood risk and improve water quality by promoting and encouraging the use of SuDS in the proposed urban developments in Brighton and Hove, Worthing, Shoreham and Burgess Hill. • Government and international legislation, environmental • Investigate the feasibility of incorporating the Teville Stream into management policies, plans and strategies for the the Floodline Warnings Direct service by installing new level catchment must be complied with, such as Ensure the impact of gauges on the Teville stream. accommodating new housing within the catchment as flooding on people and • Continue local authority and Environment Agency support of the detailed by the South East Plan and compliance with property does not Flood 1 project in relation to groundwater flooding. the Habitats Directive. significantly increase • Develop a flood warning system for groundwater flooding. • Visual impact of flood risk management activities within in the future (for • the proposed National Park or Areas of Outstanding example due to Continued practice and development of the Emergency Natural Beauty. climate change). Response Plan in Brighton and Hove, Worthing, Shoreham, and Burgess Hill. • CFMP objectives and policies must complement those • Investigate removal of Environment Agency owned and of the Shoreline Management Plan (SMP) that affects maintained existing raised defences to reinstate the floodplain the CFMP area. between Partridge Green and Steyning and between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity. • Influence the second generation of Shoreline Management Plans and the coastal defence strategy, along the Lower Adur, Teville Stream and Ferring Rife, to improve the sustainability of flood risk management in the this area. Environment Agency 114 River Adur Catchment Flood Management Plan (September 2008)

Catchment objectives and the relevant opportunities and constraints in the River Adur CFMP Catchment objective Opportunities Constraints • Reduce surface water run-off and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices (e.g. those set out by Brighton and Hove City Council). • Support the existing flood defence measures in relation to • Steep catchments of the South Downs result in rapid surface water flooding, such as bunds provided by Brighton and run-off and quick responses to rainfall events. Hove City Council. • Transport links in the catchment are a vital part of the • Provide development control advice to ensure no increase in Ensure the disruption communication network regionally, nationally and run-off from the new development proposed in the South East caused by flooding to internationally, in particular the railways connecting Plan (e.g. Brighton and Hove, Worthing, Shoreham and transport and critical London to the south coast and connecting the coastal Burgess Hill). infrastructure does not towns and cities, the A23, A24, A27, A259, A283 and • Potential for improving the current defences, for example significantly increase A2032. possible installation of demountable or temporary defences in in the future (for • Visual impact of flood risk management activities within Shoreham and Burgess Hill. example due to the proposed National Park or Areas of Outstanding • Investigate removal of Environment Agency owned and climate change). Natural Beauty. maintained existing raised defences to reinstate the floodplain • CFMP objectives and policies must complement those between Partridge Green and Steyning and between Steyning of the Shoreline Management Plan (SMP) that affects and Shoreham to a naturally functioning state, to provide flood the CFMP area. storage and enhance conservation value and biodiversity. • Continue local authority and Environment Agency support of the Flood 1 project in relation to groundwater flooding. • Develop a flood warning system for groundwater flooding.

• Reduce surface water run-off and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices (e.g. those set out • Steep catchments of the South Downs result in rapid by Brighton and Hove City Council). run-off and quick responses to rainfall events. • Support the existing flood defence measures in relation to • A suitable level of productivity from agricultural land Reduce the impact of surface water flooding, such as bunds provided by Brighton and needs to be retained. muddy flooding. Hove City Council. • Visual impact of flood risk management activities within • To work with Defra and farmers to produce soil management the proposed National Park or Areas of Outstanding plans which have a benefit to flood risk through reducing the Natural Beauty. run-off rate.

Environment Agency 115 River Adur Catchment Flood Management Plan (September 2008)

Catchment objectives and the relevant opportunities and constraints in the River Adur CFMP Catchment objective Opportunities Constraints Economic • Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Brighton and Hove, Worthing, Shoreham and • Government and international legislation, environmental Burgess Hill). management policies, plans and strategies for the • Reduce flood risk and improve water quality by promoting and catchment must be complied with, such as encouraging the use of SuDS in the proposed urban Ensure flood damages accommodating new housing within the catchment as developments in Brighton and Hove, Worthing, Shoreham and do not significantly detailed by the South East Plan and compliance with Burgess Hill. increase in the future the Habitats Directive. • Investigate removal of Environment Agency owned and (for example due to • Steep catchments of the South Downs result in rapid maintained existing raised defences to reinstate the floodplain climate change). run-off and quick responses to rainfall events. between Partridge Green and Steyning and between Steyning • CFMP objectives and policies must complement those and Shoreham to a naturally functioning state, to provide flood of the Shoreline Management Plan (SMP) that affects storage and enhance conservation value and biodiversity. the CFMP area. • Potential for improving the current defences, for example possible installation of demountable or temporary defences in Shoreham and Burgess Hill. Ensure that river • Improvements in the efficiency of channel and flood defence • Available funding for the initial set up of new flood risk channel and flood maintenance processes. management schemes. defence maintenance • Effective and efficient use of developer contributions for flood • Older flood defence structures are likely to be more expenditure is risk management. costly to maintain. appropriate to the • To work with Defra and farmers to produce soil management • Limited available information on surface water and economic damage of plans which have a benefit to flood risk through reducing the groundwater flood damages. flooding. run-off rate.

Environment Agency 116 River Adur Catchment Flood Management Plan (September 2008)

Not only do these objectives set the direction and vision of flood risk management for the future, they also provide us with a way of selecting the best policies to apply in different parts of the catchment. To do this we have to refine these catchment objectives into a set of more specific objectives against which we can measure future change. These objectives, known as ‘policy appraisal objectives’ play an important part in selecting the most appropriate policy for different parts of the catchment known as ‘policy units’.

To use the policy appraisal objectives, we have given each objective a specific ‘target’ that we can measure. These targets translate each policy appraisal objective into a more specific and measurable target. It is it important that the targets have some form of indicator, so that when choosing the best policy we can change the indicator under different policy options. When we revise the CFMP, we will be able to check to see how successful the policy we have selected is by looking at the indicators and seeing if they have met the policy appraisal targets.

Table 5.2 shows how the River Adur catchment objectives have been developed into policy appraisal objectives and the relevant targets and indicators.

We describe the policy appraisal process in section 6.

Environment Agency 117 River Adur Catchment Flood Management Plan (September 2008) Table 5.2 - Policy appraisal objectives, targets and indicators Catchment objective Policy appraisal objective Targets Indicators Environmental Increase the length of naturally Restore parts of the River Adur and functioning river and area of naturally floodplain to a naturally functioning active floodplain along the River Adur; state where feasible: and where feasible, providing suitable • Length of naturally functioning Restore rivers and floodplains quality habitat: river (km). to a naturally functioning state • upstream of Steyning and Upper • where feasible. Area of naturally functioning Beeding. • upstream of Steyning and Upper floodplain (km2). • downstream of Steyning and Beeding Upper Beeding. • downstream of Steyning and Upper Beeding • Protect and enhance the Adur • Protect and enhance the Adur Estuary SSSI. Estuary SSSI. • Protect and enhance the River • Protect and enhance the River Adur Adur Water Meadows and Water Meadows and Wyckham Wyckham Wood Site of Nature Wood Site of Nature Conservation • Habitat quality and species Conservation Importance. Protect and enhance nationally Importance. diversity. • Protect and enhance the Ferring and internationally important • Protect and enhance the Ferring Rife • Landscape character Rife and Meadows Site of Nature species and habitats. and Meadows Site of Nature assessment of the AONB, ESA Conservation Importance. Conservation Importance. and proposed National Park. • Increase the landscape character • Increase the landscape character value of the High Weald and value of the High Weald and Sussex Sussex Downs AONBs and Downs AONBs and South Downs South Downs ESA and proposed ESA and proposed National Park. National Park.

Environment Agency 118 River Adur Catchment Flood Management Plan (September 2008)

Catchment objective Policy appraisal objective Targets Indicators Social No significant increase in the number of • Ensure the impact of flooding on people or properties affected by the 1% Number of people and people and property does not annual probability fluvial flood event or properties affected by the 1% annual probability fluvial flood Ensure the impact of flooding significantly increase in the future in: surface water flooding in the future in: event. on people and property does • The estimated number of not significantly increase in the • Burgess Hill and Hassocks • Burgess Hill and Hassocks properties affected by surface future (for example due to • Steyning and Upper Beeding • Steyning and Upper water and groundwater flooding climate change). • Worthing • Worthing (based on historical records). • Shoreham • Shoreham • Coverage of flood warning • Brighton and Hove. • Brighton and Hove service

No increase in flooding of A roads and railway line or increase in extent of critical infrastructure flooded, from a 1% annual probability fluvial flood event or • surface water flooding in: Length of A road and railway line (km) affected by the 1% annual

Ensure the disruption caused by probability fluvial flood event. • Burgess Hill and Hassocks flooding to transport and critical • Number of critical infrastructure • Steyning and Upper Beeding Ensure the disruption caused infrastructure does not increase in sites affected by the 1% annual • Worthing by flooding to transport and the future in: probability fluvial flood event. • Shoreham critical infrastructure does not • Number and period of recorded

increase in the future (for • Burgess Hill and Hassocks A road and railway closures due No increase in the number and period of example due to climate • Steyning and Upper Beeding to surface water and A roads and railway closures due to change). • Worthing groundwater flooding. surface water flooding in Brighton and • Shoreham • Number of critical infrastructure Hove and surrounding areas. • Brighton and Hove sites recorded as being affected

by surface water and No increase in the number of critical groundwater flooding. infrastructure sites affected by surface water and groundwater flooding in Brighton and Hove and surrounding areas. Reduce the impact of muddy • Reduce the impact of muddy • Reduction in the number of • The estimated number of flooding. flooding in: properties affected by muddy properties affected by Downland Environment Agency 119 River Adur Catchment Flood Management Plan (September 2008) Catchment objective Policy appraisal objective Targets Indicators • northern parts of Worthing, flooding in: ‘muddy’ surface water flooding. including Findon. • northern parts of Worthing, including • northern parts of Brighton and Findon. Hove, Rottingdean, • northern parts of Brighton and Hove, Woodingdean, Ovingdean and Rottingdean, Woodingdean, Bevendean. Ovingdean and Bevendean. Economic No significant increase in damages from fluvial, surface water and urban drainage flooding due to future changes (urban development and climate change) in:

Ensure flood damages do not • Burgess Hill and Hassocks significantly increase due to future • Steyning and Upper Beeding change (urban development and • Shoreham climate change) in: No significant increase in damages in • Burgess Hill and Hassocks Worthing from fluvial, surface water • Total annual average damages Ensure flood damages do not • Steyning and Upper Beeding (including urban drainage flooding) and (to properties and agriculture) significantly increase in the • Worthing groundwater due to future changes from fluvial flooding (£AAD). future (for example due to • Shoreham (urban development and climate • Estimated damages resulting climate change). • Brighton and Hove change). from surface water and groundwater flooding (£). No significant increase in damages in Ensure flood damages do not Brighton and Hove from surface water significantly increase along the Lower (including urban drainage flooding) and Adur corridor. groundwater due to future changes (urban development and climate change).

No significant increase in damages along the Lower Adur corridor due to future changes (climate change). Ensure that river channel and • Ensure that river channel and • Maintain a suitable balance of • Balance of annual river channel flood defence maintenance flood defence maintenance annual river channel and flood and flood defence maintenance expenditure is appropriate to expenditure is appropriate to the defence maintenance expenditure expenditure (£) to annual the economic damage of agricultural economic damage in (£) to annual average damages from average damages from fluvial Environment Agency 120 River Adur Catchment Flood Management Plan (September 2008) Catchment objective Policy appraisal objective Targets Indicators flooding. rural areas from flooding. fluvial flooding to agriculture (£). flooding to agriculture (£). • Ensure that river channel and • Maintain a suitable balance of • Balance of annual river channel flood defence maintenance annual river channel and flood and flood defence maintenance expenditure is appropriate to the defence maintenance expenditure expenditure (£) to annual property economic damage in (£) to annual average damages from average damages from fluvial urban areas from flooding. fluvial flooding to property (£). flooding to property (£). • Ensure that expenditure on • Maintain a suitable level of • Balance of emergency works emergency surface water and emergency works expenditure when expenditure to estimated groundwater flooding works is compared to estimated damages damages resulting from surface appropriate to the estimated resulting from surface water and water and groundwater flooding damages resulting from surface groundwater flooding (£). (£). water and groundwater flooding.

Environment Agency 121 River Adur Catchment Flood Management Plan (September 2008) 6 Policy appraisal The aim of this section is to assess the impact of flood risk management policies and to assign preferred policies to various parts of the catchment.

6.1 Introduction

Until now, we have considered the CFMP area in hydrological sub-catchments and key communities in the River Adur area. We now need to consider the CFMP area in a slightly different way, bringing all the relevant information we have gained through the study together. We have divided the CFMP area into similar areas, not based on simply hydrology, but also including:

• current level of flood risk; • hydraulic characteristics and flood mechanisms; • topography, geology and drainage characteristics; • land use; • links to other plans; • opportunities for future flood risk management.

Using these criteria, we have divided the River Adur CFMP area into nine separate policy units, shown on figure 6.1. This information is presented within Appendix B of this document, where it is used to support policy appraisal. We have revised and refined these policy unit outlines following extensive consultation and discussion. These policy units, in keeping with the high level nature of CFMPs, are defined using a broad-brush approach. They do not follow any particular contour or attempt to capture individual features, the policy units simply define an area where a particular high level policy will generally apply.

Environment Agency 122 River Adur Catchment Flood Management Plan (September 2008)

Figure 6.1 - Location of policy units

Now that we are considering the catchment in terms of ‘policy units’, we need to collate the key information presented in section 3 and 4 of this report and re-assess the issue associated with each policy unit. This has been carried out and is detailed within Appendix B of this document and is summarised here in section 6.2.

Each policy unit has then been assessed to decide which policy will provide the most appropriate level and direction of flood risk management for both now and in the future. One of the six standard flood risk management policies, listed in table 6.1 has been applied to each policy unit. We have agreed these policies nationally and are applying them to CFMPs in a standard way across England and Wales.

Environment Agency 123 River Adur Catchment Flood Management Plan (September 2008) Table 6.1 - Flood risk management policies Standard flood risk management policies Policy Policy option No active intervention (including flood warning and maintenance). Continue to monitor and 1 advise. Reduce existing flood risk management actions (accepting that flood risk will increase over 2 time). Continue with existing or alternative actions to manage flood risk at the current level 3 (accepting that flood risk will increase over time from this baseline). Take further action to sustain current scale of flood risk into the future (responding to the 4 potential increases in flood risk from urban development, land use change, and climate change). 5 Take further action to reduce flood risk (now and/or in the future). Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, 6 which may constitute an overall flood risk reduction (for example for habitat inundation).

The policy appraisal process is based on Strategic Environmental Assessment (SEA) principles (i.e. objective led) using the objectives discussed in section 5. These objectives have been allocated to each of the policy units and assigned indicators and targets so that we can decide how well each of the six policy options would achieve the objectives. We did this for each policy unit using the policy appraisal forms presented within Appendix B. Table 6.2 outlines the information contained in these forms.

Table 6.2 - Policy appraisal forms Appendix B – policy appraisal forms Form Contents B1 Purpose of the CFMP B2 Legal requirements B3a Summary of flood risk – including an explanation of model results from ‘drivers’ Source-pathway-receptor table with objectives and suggested flood risk management B3b responses B4 CFMP policy options B5 Summary of current and future levels of and responses to flood risk B6 Appraisal of policy options against policy unit objectives B7 Summary of losses and gains B8 Summary of preferred policy B9 Requirements for further policy development and appraisal B10 Indicators for monitoring, review and evaluation

Although there are no legal obligations to undertake a separate SEA for CFMPs, we recognise that environmental issues are integral to the CFMP process and that the implications of the CFMP are fully and transparently considered before final decisions are taken and action plans are implemented. The policy appraisal process integrates the requirements of an SEA and the SEA process is described in more detail in Appendix B, and sets out the important elements of the procedure.

Although it is not possible at this stage to say how each policy would deal with flood risk in terms of future schemes or measures, we have been able to determine the most likely approach to flood risk management under the policy options. We considered each of these Environment Agency 124 River Adur Catchment Flood Management Plan (September 2008) different approaches, or ‘generic responses’, in relation to each policy unit. These generic responses are listed in table 6.3, showing what they are and how they are implemented in each policy unit. Where we have been able to model the generic response using our broadscale model, we have used the results to assess how well that policy would meet out specific policy appraisal objectives. The results from this analysis can be found in Appendix B.

Table 6.3 - Generic responses Flood risk management generic responses Generic response Policy Unit Policy Option Generic response Modelled No generic response except monitoring. Stop other Flood Risk Management activities

Implications: Attenuation/retention (storage) Policy Unit 1 – Policy Option 1 - No active • No maintenance

Upper Adur intervention • Flood Warning Service Reducing the height of withdrawn raised defences • Raised embankment height reduces over time increasing flood storage

Influence and inform but reduce other Flood Risk Management activities.

Implications: Attenuation/retention Policy Option 2 - Reduce (storage) • Reduced maintenance existing flood risk • Raised embankment height management Reducing the height of reduces over time increasing raised defences flood storage • Flood warning & evacuation

Current Flood Risk Management continues through increasing conveyance and influencing and informing. Policy Option 3 - Continue with existing or alternative Implications: No actions to manage flood risk at • River maintenance (weed & the current level grass cutting, also removal of blockages in channel & on floodplain) • Flood warning & evacuation

Flood Risk Management increases into the future through increasing conveyance and influencing and informing.

Policy Option 4 - Take further Implications: action to sustain current scale • River maintenance (weed & No of flood risk into the future grass cutting, also removal of blockages in channel & on floodplain) • Flood warning & evacuation • Flood awareness

Environment Agency 125 River Adur Catchment Flood Management Plan (September 2008) Flood Risk Management increases through increasing conveyance and influencing and informing.

Implications: Policy Option 5 - Take further • River maintenance (weed & action to reduce flood risk grass cutting, also removal No (now and/or in the future). of blockages in channel & on floodplain) • Flood warning & evacuation • Flood awareness • Fluvial Defences Encourage rural land use change, increase attenuation and complete studies. Attenuation/retention Implications: (storage) Policy Option 6 - Take action • Afforestation to increase the frequency of • Sensitive farming Reducing the height of flooding to deliver benefits practices/set aside raised defences locally or elsewhere • On-line storage (existing/new) Rural land use – • Floodplain storage/wetland farming/forestry creation/river restoration • Pre-feasibility • Strategy plans No generic response except monitoring. Stop other Flood Risk Management activities

Policy Unit 2 – Policy Option 1 - No active Implications: No Burgess Hill intervention • No maintenance of channel, surface water systems or urban drainage networks • Flood Warning Service withdrawn Influence and inform but reduce other Flood Risk Management activities.

Implications: Policy Option 2 - Reduce • Reduced maintenance of existing flood risk No channel, surface water management systems or urban drainage networks • Flood warning & evacuation

Current Flood Risk Management continues through increasing conveyance and influencing and informing. Policy Option 3 - Continue with existing or alternative Implications: No actions to manage flood risk at • River maintenance (weed & the current level grass cutting, also removal of blockages in channel & on floodplain) • Flood warning & evacuation

Environment Agency 126 River Adur Catchment Flood Management Plan (September 2008) Flood Risk Management increases into the future through: • Attenuation/retention • increasing conveyance • influencing and informing • Monitoring/Advise/Survey • Studies

Implications: • SUDS - new/retrospective • River maintenance (weed &

Policy Option 4 - Take further grass cutting, also removal Increased conveyance action to sustain current scale of blockages in channel & on (removal of channel of flood risk into the future floodplain) obstructions) • Fluvial Defences • Flood awareness • Flood warning & evacuation • Emergency & disaster planning/response • Planning policy/Development control • Hydrometric network • SAMPs • Urban drainage plans

Flood Risk Management increases through: • Attenuation/retention • increasing conveyance • influencing and informing • Monitoring/Advise/Survey

Implications: • SUDS - new/retrospective Policy Option 5 - Take further • River maintenance (weed & Increased conveyance action to reduce flood risk grass cutting, also removal (removal of channel (now and/or in the future). of blockages in channel & on obstructions) floodplain) • Fluvial Defences • Flood awareness • Flood warning & evacuation • Emergency & disaster planning/response • Hydrometric network

Policy Option 6 - Take action to increase the frequency of Not Applicable Not Applicable flooding to deliver benefits locally or elsewhere No generic response except monitoring. Stop other Flood Risk Management activities

Policy Unit 3 – Implications: Attenuation/retention Steyning and Policy Option 1 - No active • No maintenance (floodplain storage or Upper intervention • Flood Warning Service wetland creation) Beeding withdrawn • Raised embankment height reduces over time increasing flood storage

Environment Agency 127 River Adur Catchment Flood Management Plan (September 2008) Influence and inform but reduce other Flood Risk Management activities.

Implications: Policy Option 2 - Reduce Attenuation/retention • Reduced maintenance existing flood risk (floodplain storage or • Raised embankment height management wetland creation) reduces over time increasing flood storage • Flood warning & evacuation

Current Flood Risk Management continues through: • Attenuation/retention • increasing conveyance • influencing and informing.

Implications: Policy Option 3 - Continue • SUDS - new/retrospective with existing or alternative • River maintenance (weed & No actions to manage flood risk at grass cutting, also removal the current level of blockages in channel & on floodplain) • Fluvial Defences maintained • Flood awareness • Flood warning & evacuation • Planning policy/Development control

Flood Risk Management increases into the future through: • Attenuation/retention • increasing conveyance • influencing and informing • Monitoring/Advise/Survey

Implications: • SUDS - new/retrospective • River maintenance (weed & Policy Option 4 - Take further Increase current flood grass cutting, also removal action to sustain current scale risk management of blockages in channel & on of flood risk into the future (defences) floodplain) • River engineering • Fluvial Defences improved • Flood awareness • Flood warning & evacuation • Emergency & disaster planning/response • Planning policy/Development control

Environment Agency 128 River Adur Catchment Flood Management Plan (September 2008) Flood Risk Management increases through: • Attenuation/retention • increasing conveyance • influencing and informing • Monitoring/Advise/Survey

Implications: • SUDS - new/retrospective Policy Option 5 - Take further • River maintenance (weed & Increase current flood action to reduce flood risk grass cutting, also removal risk management (now and/or in the future). of blockages in channel & on (defences) floodplain) • Fluvial Defences improved • Flood awareness • Flood warning & evacuation • Emergency & disaster planning/response • Planning policy/Development control

Policy Option 6 - Take action to increase the frequency of Not Applicable Not Applicable flooding to deliver benefits locally or elsewhere No generic response except monitoring. Stop other Flood Risk Management activities Policy Unit 4 – Policy Option 1 - No active Adur South Implications: No intervention Downs (West) • No maintenance • Potential for reduced retention

Influence and inform but reduce other Flood Risk Management activities.

Policy Option 2 - Reduce Implications: existing flood risk No • Reduced maintenance management • Potential for reduced retention

Current Flood Risk Management continues through: • increasing conveyance Policy Option 3 - Continue

with existing or alternative Implications: No actions to manage flood risk at • the current level River maintenance (weed & grass cutting, also removal of blockages in channel & on floodplain)

Environment Agency 129 River Adur Catchment Flood Management Plan (September 2008) Flood Risk Management increases into the future through: • Rural land use change • Attenuation/retention • increasing conveyance

Policy Option 4 - Take further Implications: Rural land use – action to sustain current scale • Sensitive farming farming/forestry of flood risk into the future practices/set aside • Off-line storage (existing/new) • River maintenance (weed & grass cutting, also removal of blockages in channel & on floodplain) Flood Risk Management increases through: • Rural land use change • Attenuation/retention • increasing conveyance

Policy Option 5 - Take further Implications: Rural land use – action to reduce flood risk • Sensitive farming farming/forestry (now and/or in the future). practices/set aside • Off-line storage (existing/new) • River maintenance (weed & grass cutting, also removal of blockages in channel & on floodplain) Encourage rural land use change, increase retention and complete studies. Policy Option 6 - Take action to increase the frequency of Implications: Rural land use – flooding to deliver benefits • Sensitive farming farming/forestry locally or elsewhere practices/set aside • Off-line storage (existing/new)

No generic response except monitoring. Stop other Flood Risk Attenuation/retention Management activities (floodplain storage or wetland creation) Policy Unit 5 – Policy Option 1 - No active Implications: Worthing intervention • No maintenance of channel, Rural land use – surface water systems or farming/forestry urban drainage networks • Flood Warning Service Decreased conveyance withdrawn Influence and inform but reduce other Flood Risk Management activities.

Implications: Policy Option 2 - Reduce • Reduced maintenance of existing flood risk No channel, surface water management systems or urban drainage networks • Flood warning & evacuation

Environment Agency 130 River Adur Catchment Flood Management Plan (September 2008) Current Flood Risk Management continues through: • Attenuation/retention • increasing conveyance • influencing and informing • studies

Implications: • SUDS - new/retrospective Policy Option 3 - Continue • River maintenance (weed & with existing or alternative grass cutting, also removal No actions to manage flood risk at of blockages in channel & on the current level floodplain) • Flood awareness • Flood warning & evacuation • Emergency & disaster planning/response • Planning policy/Development control • Flood Risk Mapping • Urban drainage plans

Flood Risk Management increases into the future through: • Attenuation/retention • increasing conveyance • influencing and informing • studies

Implications: • SUDS - new/retrospective • Infrastructure storage - STW check Policy Option 4 - Take further • River maintenance (weed & action to sustain current scale grass cutting, also removal No of flood risk into the future of blockages in channel & on floodplain) • Fluvial Defences • Flood awareness • Flood warning & evacuation • Emergency & disaster planning/response • Planning policy/Development control • Flood Risk Mapping • Urban drainage plans

Environment Agency 131 River Adur Catchment Flood Management Plan (September 2008) Flood Risk Management increases through: • Attenuation/retention • increasing conveyance • influencing and informing • studies

Implications: • SUDS - new/retrospective • River maintenance (weed & grass cutting, also removal of blockages in channel & on Policy Option 5 - Take further floodplain) action to reduce flood risk • River engineering i.e. No (now and/or in the future). channelisation • Infrastructure storage - STW check • Fluvial Defences • Flood awareness • Flood warning & evacuation • Emergency & disaster planning/response • Planning policy/Development control • Flood Risk Study • Urban drainage plans

Encourage rural land use change, increase retention and complete Attenuation/retention studies. (floodplain storage or Policy Option 6 - Take action wetland creation) to increase the frequency of Implications: flooding to deliver benefits • Sensitive farming Rural land use – locally or elsewhere practices/set aside farming/forestry • Off-line storage (existing/new) Decreased conveyance

No generic response except monitoring. Stop other Flood Risk Management activities Policy Unit 6 – Policy Option 1 - No active Brighton and Implications: No intervention Hove • No maintenance of surface water systems or urban drainage networks

Influence and inform but reduce other Flood Risk Management activities.

Implications: Policy Option 2 - Reduce • Reduced maintenance of existing flood risk No surface water systems or management urban drainage networks • Emergency & disaster planning/response

Environment Agency 132 River Adur Catchment Flood Management Plan (September 2008) Current Flood Risk Management continues through: • Rural land use change • Attenuation/retention • increasing conveyance • influencing and informing • studies Policy Option 3 - Continue with existing or alternative Implications: No actions to manage flood risk at • Sensitive farming the current level practices/set aside • SUDS - new/retrospective • Emergency & disaster planning/response • Planning policy/Development control • Data & information • Urban drainage plans Flood Risk Management increases into the future through: • Rural land use change • Attenuation/retention • increasing conveyance • Monitoring/Advise/Survey • influencing and informing • studies

Implications: Policy Option 4 - Take further • Sensitive farming action to sustain current scale No practices/set aside of flood risk into the future • SUDS - new/retrospective • Maintenance • Defences • Flood warning & evacuation • Emergency & disaster planning/response • Planning policy/Development control • Hydrometric network • Urban drainage plans

Environment Agency 133 River Adur Catchment Flood Management Plan (September 2008) Flood Risk Management increases through: • Rural land use change • Attenuation/retention • increasing conveyance • Monitoring/Advise/Survey • influencing and informing • studies

Implications: • Sensitive farming Policy Option 5 - Take further practices/set aside action to reduce flood risk • SUDS - new/retrospective No (now and/or in the future). • Infrastructure storage - STW check • Maintenance • Defences • Flood awareness • Flood warning & evacuation • Emergency & disaster planning/response • Planning policy/Development control • Hydrometric network • Urban drainage plans Policy Option 6 - Take action to increase the frequency of Not Applicable Not Applicable flooding to deliver benefits locally or elsewhere No generic response except monitoring. Stop other Flood Risk Management activities

Implications: • No maintenance of channel, Policy Unit 7 – Policy Option 1 - No active surface water systems or Shoreham and No intervention urban drainage networks Adur Estuary • Flood Warning Service withdrawn • Raised embankment height reduces over time increasing flood storage

Influence and inform but reduce other Flood Risk Management activities.

Implications: • Reduced maintenance of Policy Option 2 - Reduce channel, surface water existing flood risk systems or urban drainage No management networks • Raised embankment height reduces over time increasing flood storage • Flood warning & evacuation

Environment Agency 134 River Adur Catchment Flood Management Plan (September 2008) Current Flood Risk Management continues through: • increasing conveyance • influencing and informing

Policy Option 3 - Continue Implications: with existing or alternative • River maintenance (weed & No actions to manage flood risk at grass cutting, also removal the current level of blockages in channel & on floodplain) • Flood warning & evacuation • Emergency & disaster planning/response

Flood Risk Management increases into the future through: • Attenuation/retention • increasing conveyance • influencing and informing • Studies

Implications: • SUDS - new/retrospective Policy Option 4 - Take further • River maintenance (weed & Increase current flood action to sustain current scale grass cutting, also removal risk management of flood risk into the future of blockages in channel & on (defences) floodplain) • Flood awareness • Flood warning & evacuation • Emergency & disaster planning/response • Planning policy/Development control • Pre-feasibility • Urban drainage plans Flood Risk Management increases through: • increasing conveyance • influencing and informing • Studies Policy Option 5 - Take further Increase current flood

action to reduce flood risk risk management Implications: (now and/or in the future). (defences) • Flood Defence (Barrier) • Infrastructure storage - STW check • Pre-feasibility • Urban drainage plans Policy Option 6 - Take action to increase the frequency of Not Applicable Not Applicable flooding to deliver benefits locally or elsewhere No generic response except monitoring. Stop other Flood Risk Management activities

Policy Unit 8 – Implications: Attenuation/retention Adur Valley Policy Option 1 - No active • No maintenance (floodplain storage or (north of A27 intervention • Flood Warning Service wetland creation) to south withdrawn Steyning) • Raised embankment height reduces over time increasing flood storage

Environment Agency 135 River Adur Catchment Flood Management Plan (September 2008) Influence and inform but reduce other Flood Risk Management activities.

Implications: Attenuation/retention Policy Option 2 - Reduce • Reduced maintenance (floodplain storage or existing flood risk • Raised embankment height wetland creation) management reduces over time increasing flood storage • Flood warning & evacuation

Current Flood Risk Management continues through: • increasing conveyance • influencing and informing

Policy Option 3 - Continue Implications: with existing or alternative • River maintenance (weed & No actions to manage flood risk at grass cutting, also removal the current level of blockages in channel & on floodplain) • Flood awareness • Flood warning & evacuation • Strategy Plan

Flood Risk Management increases into the future through: • Attenuation/retention • increasing conveyance • influencing and informing • Studies

Policy Option 4 - Take further Implications: Increase current flood action to sustain current scale • River maintenance (weed & risk management of flood risk into the future grass cutting, also removal (defences) of blockages in channel & on floodplain) • Flood Defences • Flood awareness • Flood warning & evacuation • Strategy Plan

Flood Risk Management increases through: • increasing conveyance • influencing and informing Policy Option 5 - Take further Increase current flood • Studies action to reduce flood risk risk management

(now and/or in the future). (defences) Implications: • Flood Defence (Barrier) • Strategy Plan

Encourage rural land use change, increase attenuation and complete studies.

Policy Option 6 - Take action Implications: Attenuation/retention to increase the frequency of (floodplain storage or • Floodplain storage/wetland flooding to deliver benefits wetland creation) creation/river restoration locally or elsewhere • Sensitive farming practices/set aside • Pre-feasibility • Strategy plans

Environment Agency 136 River Adur Catchment Flood Management Plan (September 2008) No generic response except monitoring. Stop other Flood Risk Management activities

Policy Option 1 - No active Implications: No intervention • No maintenance • Potential for reduced retention

Influence and inform but reduce other Flood Risk Management activities.

Policy Option 2 - Reduce Implications: existing flood risk No • Reduced maintenance management • Potential for reduced retention

Current Flood Risk Management continues through: • increasing conveyance Policy Option 3 - Continue • Monitoring/Advise/Survey with existing or alternative No actions to manage flood risk at Implications: the current level • Storage areas and bunds maintained (weed & grass cutting) • Asset inspection Flood Risk Management increases into the future through: • increasing conveyance • Monitoring/Advise/Survey Policy Unit 9 –

Adur South Policy Option 4 - Take further Implications: Downs (East) action to sustain current scale No • Storage areas and bunds of flood risk into the future maintained (weed & grass cutting) • Asset inspection • Flood Defences

Flood Risk Management increases through: • Rural land use change • increasing conveyance • Monitoring/Advise/Survey

Policy Option 5 - Take further Implications: action to reduce flood risk • Sensitive farming No (now and/or in the future). practices/set aside • Storage areas and bunds maintained (weed & grass cutting) • Asset inspection • Flood Defences

Encourage rural land use change, increase retention and complete studies. Policy Option 6 - Take action to increase the frequency of Implications: No flooding to deliver benefits • Sensitive farming locally or elsewhere practices/set aside • Off-line storage (existing/new)

Environment Agency 137 River Adur Catchment Flood Management Plan (September 2008) 6.2 Policies for the River Adur catchment

Having reviewed large amounts of information and data relating to the catchment, individual policy units, and how policy units would interact with each other, and considered the comments and feedback from extensive consultation, we have allocated policies to the policy units as shown in figure 6.2.

In table 6.4 we provide a summary of the main factors we considered when selecting the most appropriate policy option for each of the policy units. We outline the flood risk in each area, any existing flood risk management problems or likely future ones that should be addressed.

We selected the most appropriate policy by assessing how well it would meet catchment objectives and the likely consequences of implementing each policy, but we deal this in more detail in the next section.

Figure 6.2 - Policy units and selected policies

Environment Agency 138 River Adur Catchment Flood Management Plan (September 2008) Table 6.4 - Policy unit justification Policy unit 1 - Upper Adur

Physical characteristics: - Largely rural landscape in the north of the CFMP area, of moderate agricultural quality with a few villages and isolated properties. - Weald Clay Formation geology set predominantly in the Low Weald Landscape Character Area, with poorly draining clay soils, which may result in rapid run-off from the land. - The north-east section (High Weald AONB) has varied topography, and this region and the southern boundary of the unit overlie sandstone geology. - The East and West Adur confluence lies west of Henfield village amongst gently sloping land, which results in slow run-off from the land. - The Adur West Branch headwaters emerge north of Coolham. - The northern section of the proposed South Downs National Park designation is present in the far south of the unit. - Flood defences extend to Bines Green on the Adur West Branch and Shermanbury on the Adur East Branch. -

Flood mechanism: - Low fluvial flood risk (some localised areas of fluvial flooding). - Adur West Branch slower response to run-off rates than the Adur East Branch. -

Receptor: Problem/risk - Mainly moderate grade Agricultural Land (Grades 3 and 4) at risk of localised fluvial flooding. - Limited environmental and landscape designations – only High Weald AONB (which is outside of floodplain) and the proposed South Downs National Park. - Significant areas of existing wet woodland, which would benefit or be increased in area through increased flooding. - Small number of isolated properties within the River Adur floodplain. - Currently approximately 5 properties at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event. - In 100 years approximately 6 properties at risk of flooding in the policy unit. - Current Flood Risk Summary Number of properties at risk of flooding (1% annual probability flood event) 5 Total damages (approx.) (1% annual probability flood event) £0.333 million Annual average damages (approx.) £38,000

Future Flood risk: - An increase in the severity of flooding does not significantly increase the risk of flooding or significantly increase the economic damages. - Flood risk is currently assessed as low, assessment remains low in the future. - Future Flood Risk Summary (in 100 years time) Number of properties at risk of flooding (1% annual probability flood event) 6 Total damages (approx.) (1% annual probability flood event) £0.424 million Annual average damages (approx.) £49,000

Policy Policy 6 - Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, selected which may constitute an overall flood risk reduction (for example for habitat inundation).

Environment Agency 139 River Adur Catchment Flood Management Plan (September 2008) This policy can deliver benefits for people and the environment locally or in other policy units. By increasing flooding locally in this unit or at least keeping water in the catchment for longer, flooding downstream can be reduced, and in many instances, increasing flooding can improve wetland biodiversity, as flooding is an essential part of floodplain ecosystems. Current management and maintenance activities include maintaining defences, grass and weed cutting, debris removal cutting back overhanging branches. Policy 6 sets a framework that actively supports increased flooding, or keeping water on the land for longer. This applies to this policy unit for the following reasons: - An increase in flooding or retaining flood water for longer in this unit, reduces flood risk to properties in Steyning, Upper Beeding and Shoreham 100 years in the future. - An increase in flooding or retaining flood water for longer in this unit, reduces economic damages, Justification from a 1% annual probability fluvial flood event 100 years in the future in Steyning and Upper Beeding, by approximately 6%. - An increase in flooding or retaining flood water for longer in this unit, also reduces economic damages, from a 1% annual probability fluvial flood event 100 years in the future locally in this policy unit, by approximately 3%. - An increase in flooding could result in an increase of approximately 1300 hectares of wetland around the River Adur Water Meadow and Wyckham Wood SNCI. This will improve local biodiversity and help meet biodiversity action plan targets. - There are relatively few constraints in this policy unit, such as environmental or landscape designations which would restrict options to increase flooding locally. - Ensure that river channel and flood defence maintenance expenditure is appropriate to the agricultural economic damage in rural areas from flooding. - Restore parts of the River Adur and floodplain to a naturally functioning state where feasible Catchment upstream of Steyning and Upper Beeding. objectives - Protect and enhance the River Adur Water Meadows and Wyckham Wood Site of Nature Conservation Importance. - Increase the landscape character value of the High Weald AONB and proposed South Downs National Park. Opportunities: - Improvements in the efficiency of channel and flood defence maintenance processes. - To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing the run-off rate. - Enhance the character of the landscape and increase amenity opportunities for recreation, tourism and leisure activities. - Move towards more natural rivers and drainage networks, as outlined within PPS25, will mean we can achieve more efficient and sustainable water management, whilst enhancing landscape character. - Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Partridge Green and Steyning to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity. - Help meet national biodiversity action plan (BAP) targets. - Work with the High Weald AONB Joint Advisory Committee to achieve the targets set in the High Weald AONB Management Plan to maximise the opportunities for natural processes to reduce flooding through the adoption of river restoration policies, whilst enhancing landscape character. Catchment-

wide Constraints: opportunities - Available funding for the initial set up of new flood risk management schemes. and - Older flood defence structures are likely to be more costly to maintain. constraints - Limited available information on surface water and groundwater flood damages. - Government and international legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive. - Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance. - Existing urban development may prevent reinstatement of natural river processes. - Individual homes and properties are currently at risk of flooding. - Presence of protected species with specific water level, water quality and habitat requirements. - Changes to flood risk management can affect the landscape, its character and value as an amenity. - Historic development and some heritage designations in Steyning, Bramber and Upper Beeding present permanent physical obstructions. - Location of electricity pylons adjacent to the Lower River Adur (currently protected by existing defences). - No degradation of existing fish passage and habitat.

Environment Agency 140 River Adur Catchment Flood Management Plan (September 2008) Policy 1 - do nothing. Although this could be considered as a possible policy option, and would have a similar long-term result as policy 6, the effects would happen in an unmanaged and unpredictable way, and local flood risk may increase.

Policy 2 - reduce current level of flood risk management. This could also be considered a possible policy option for this area, and it could allow increased floodplain inundation whilst controlling the changes that would happen in time. This policy would not provide the benefits of reducing flood risk downstream or the benefits of increasing biodiversity that would occur through a managed approach to increasing flooding through policy 6.

Alternative Policy 3 - maintain current level of flood risk management. This option results in the least favourable policies result, with moderate increases in damages locally of approximately 30% but with none of the benefits considered that would come from a managed approach of potentially increasing areas of wetland and therefore improving local biodiversity and help meet biodiversity action plan targets.

Policy 4 - maintain the current level of flood risk into the future. This policy could apply to this policy unit, but it implies a need for increased flood risk management in the future and does not consider the opportunity for large potential reduction in flood risk elsewhere. Although there is a 30% increase in flood risk in the future the assessment of flood risk remains low, with approximately 6 properties at risk under future scenarios.

Policy 5 - reduce the level of flood risk, both now and in the future. As the current and future flood risk in this unit is low, there is no justification for investing in flood defences to reduce flood risk. There is currently some uncertainty about how effective land management and vegetation cover is in altering run-off at the catchment scale. It is known to work locally, but we do not yet know its effect on the catchment as a whole. Uncertainties

and The broadscale modelling has shown that lowering or removing flood defences can help reduce flood dependencies risk in this area. We will need more detailed studies to find out if it is practical to do this and improve the environment at the same time.

Environment Agency 141 River Adur Catchment Flood Management Plan (September 2008)

Policy unit 2 – Burgess Hill Physical characteristics: - Largely comprising the urban areas Burgess Hill and Hassocks. - Policy unit is split between the High and Low Weald Landscape Character Areas. - The extreme north and extreme south of the unit area overlie sandstone (Cuckfield Member), and Weald Clays predominate throughout the central section. - The source of the Adur East Branch emerges amongst undulating topography east of Burgess Hill. - Ditchling Common SSSI grassland habitat requires a wide variation in drainage conditions. - Flood risk in Burgess Hill may increase due to pressure for urban expansion and development. Flood mechanism: - Relatively rapid runoff from steep slopes in the High Weald. - A combination of surface water flooding, urban drainage problems and under capacity of local streams causing localised areas of fluvial flooding and urban flooding. Receptor: Problem/risk - People, properties and infrastructure in Burgess Hill and Hassocks. - Local minor roads. - Currently approximately 13 properties at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event, which is expected to increase to 250 due to climate change. Current Flood Risk Summary Number of properties at risk of flooding (1% annual probability flood event) 13 Total damages (approx.) (1% annual probability flood event) £0.110 million Annual averages damages (approx.) £4,000 Future Flood risk: - Flood risk from fluvial flooding is currently assessed as low, assessment increases to medium in the future. - Flood risk from surface water flooding and urban drainage problems is currently assessed as low to medium, assessment becomes medium in the future. Future Flood Risk Summary (in 100 years time) Number of properties at risk of flooding (1% annual probability flood event) 250 Total damages (approx.) (1% annual probability flood event) £2 million Annual averages damages (approx.) £77,000 Policy 4 - Take further action to sustain current scale of flood risk into the future (responding Policy selected to the potential increases in flood risk from urban development, land use change, and climate change). Policy 4 sets a framework which prevents the level of flood risk increasing in the future as a result of climate change or increased urban growth. It does not, however, support extensive effort in reducing flood risk from its current level either now or in the future. Current maintenance activities include grass and weed cutting, debris removal cutting back overhanging branches. This may have to increase in the future under a policy 4 option. This policy is appropriate for this policy unit for the following reasons: Justification - The current level of flood risk is low. - Climate change and urban development could increase future levels of flood risk from localised flooding. - This policy would achieve the economic and social objectives of making sure that flood risk does not increase in the future as a result of climate change and/or urban development. - Ensure flood damages do not increase in Burgess Hill and Hassocks due to future change (urban development and climate change). - Ensure that river channel and flood defence maintenance expenditure is appropriate to Catchment the property economic damage in urban areas from flooding. objectives - Ensure the impact of flooding on people and property does not significantly increase in Burgess Hill and Hassocks in the future. - Ensure the disruption caused by flooding to transport and critical infrastructure does not increase in Burgess Hill and Hassocks in the future.

Environment Agency 142 River Adur Catchment Flood Management Plan (September 2008) Opportunities: - Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Burgess Hill). - Reduce flood risk and improve water quality by promoting and encouraging the use of SuDS in the proposed urban developments in Burgess Hill. - Potential for improving the current defences, for example possible installation of demountable or temporary defences in Shoreham and Burgess Hill. - Continued practice and development of the Emergency Response Plan in Brighton and Hove, Worthing, Shoreham, and Burgess Hill. - Improvements in the efficiency of channel and flood defence maintenance processes. - Effective and efficient use of developer contributions for flood risk management.

Catchment-wide Constraints: opportunities - Government and international legislation, environmental management policies, plans and and constraints strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive. - Steep catchments of the South Downs result in rapid run-off and quick responses to rainfall events. - Available funding for the initial set up of new flood risk management schemes. - Older flood defence structures are likely to be more costly to maintain. - Limited available information on surface water and groundwater flood damages. - Transport links in the catchment are a vital part of the communication network regionally, nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032. Policy 1 - do nothing. The urban areas of Burgess Hill and Hassocks currently have a low risk of flooding. However, the risk of flooding from surface water and rivers may increase with climate change and urban development. Without continued maintenance the damages and losses would increase. The number of people at risk from river flooding would increase to more than 750. Do nothing is, therefore, not an appropriate policy.

Policy 2 - reduce current level of flood risk management. As with policy option 1, the potential damages and losses would become unacceptable in the future under a ‘do less’ policy. The number of people at risk from river flooding would increase to more than 625. Alternative

policies Policy 3 - maintain the current level of flood risk management. Although the current level of considered flood risk is considered acceptable, it has been shown that flood risk will increase in the future due to a combination of fluvial, surface water and urban drainage flooding. This policy is therefore not acceptable.

Policy 5 - reduce the level of flood risk, both now and in the future. The current level of risk is considered tolerable and therefore this policy is not justified.

Policy 6 - increase flooding to reduce flooding elsewhere. There are no opportunities within this policy unit for this policy. We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change, frequency and size of storms and flood events in the future. Due to limitations in the modelling the properties at risk in the future have been Uncertainties adjusted based on Flood Zones and as such the future AAD has been estimated. and

dependencies Delivering this policy will partly depend on developing and implementing an effective urban drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties.

Environment Agency 143 River Adur Catchment Flood Management Plan (September 2008)

Policy unit 3 – Steyning and Upper Beeding Physical characteristics: - Urban area of Steyning and Upper Beeding villages, which are separated laterally by the Lower River Adur. - The unit overlies weald clay to the north and chalk to the south, and has very subdued topography. - Lies at the northern base of the South Downs escarpment and the majority of the unit lies within the proposed South Downs National Park designated area. Flood mechanism: - Land behind the defences becomes seasonally waterlogged, resulting in flashy responses to rainfall. - Combination of surface water run-off, urban drainage and under capacity of local streams causing localised fluvial flooding and urban flooding. - Overtopping of raised river embankments along the River Adur – will generally not overtop due to fluvial flooding on its own, requires significant tidal influence. Receptor: - People, properties and infrastructure in Steyning and Upper Beeding. - A small number of listed buildings and heritage sites (salterns) lie in the floodplain. Problem/risk - Currently 91 properties are at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event. - The flood risk increases slightly over the next 100 years. - Surface water flooding is likely to increase more significantly than fluvial flooding. Current Flood Risk Summary Number of properties at risk of flooding (1% annual probability flood event) 91 Total damages (approx.) (1% annual probability flood event) £2.951 million Annual averages damages (approx.) £80,000 Future Flood risk: - Flood risk from surface water flooding and urban drainage problems is currently assessed as low, assessment changes to low to medium in the future. - Flood risk from fluvial flooding is currently assessed as low, assessment changes to medium in the future. Future Flood Risk Summary (in 100 years time) Number of properties at risk of flooding (1% annual probability flood event) 112 Total damages (approx.) (1% annual probability flood event) £3.711 million Annual averages damages (approx.) £206,000 Policy 3 - Continue with existing or alternative actions to manage flood risk at the current Policy selected level (accepting that flood risk with increase over time from this baseline). This policy is appropriate where the current level of flood risk management is considered acceptable. Current management and maintenance activities include maintaining defences, grass and weed cutting, debris removal cutting back overhanging branches. It is recognised that flood risk will change in the future, and management actions may change in time to gain efficiencies or improve effectiveness. This policy is appropriate for this policy unit for the following reasons: - The current level of flood risk is low and it is not expected to increase greatly in the Justification future. - The consequences of flooding are relatively low. - The current flood risk management activities, carried out for the localised fluvial and surface water and urban drainage flooding problems, are considered appropriate and acceptable for the level of risk. - The selected policy would help achieve the catchment objectives to ensure the impact of flooding does not significantly increase. - This policy unit will also benefit from the policy 6 option adopted for policy unit 1. - Ensure flood damages do not significantly increase in Steyning and Upper Beeding due to future change (urban development and climate change). - Ensure that river channel and flood defence maintenance expenditure is appropriate to the property economic damage in urban areas from flooding. Catchment - Ensure the impact of flooding on people and property does not significantly increase in objectives Steyning and Upper Beeding in the future. - Ensure the disruption caused by flooding to transport and critical infrastructure does not increase in Steyning and Upper Beeding in the future. - Protect and enhance the River Adur Water Meadows and Wyckham Wood Site of Nature Conservation Importance.

Environment Agency 144 River Adur Catchment Flood Management Plan (September 2008) Opportunities: - Provide development control advice to ensure no increase in run-off from new development. - Reduce flood risk and improve water quality by promoting and encouraging the use of SuDS in proposed developments. - Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Partridge Green and Steyning and between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity. - Improvements in the efficiency of channel and flood defence maintenance processes. - Effective and efficient use of developer contributions for flood risk management. - Help meet national biodiversity action plan (BAP) targets.

Constraints: - Government and international legislation, environmental management policies, plans and Catchment-wide strategies for the catchment must be complied with, such as accommodating new opportunities housing within the catchment as detailed by the South East Plan and compliance with and constraints the Habitats Directive. - Steep catchments of the South Downs result in rapid run-off and quick responses to rainfall events. - Available funding for the initial set up of new flood risk management schemes. - Older flood defence structures are likely to be more costly to maintain. - Limited available information on surface water and groundwater flood damages. - Visual impact of flood risk management activities within the proposed National Park or Areas of Outstanding Natural Beauty. - Transport links in the catchment are a vital part of the communication network regionally, nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032. - Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance. - Changes to flood risk management can affect the landscape, its character and value as an amenity. Policy 1 - do nothing. The urban areas of Steyning, Upper Beeding and Bramber currently have a low level of risk of flooding. However the risk of flooding from surface water and rivers may increase with climate change. Without continued maintenance the average annual damages would increase to more than £500,000. Do nothing is, therefore, not an appropriate policy.

Policy 2 - reduce current level of flood risk management. As with policy option 1, the potential damages and losses would become unacceptable in the future under a ‘do less’ Alternative policy. The average annual damages would increase to more than £330,000. policies considered Policy 4 – maintain the current level of flood risk into the future. This policy could also apply, however, it implies increasing flood risk management costs to more than £60,000 p.a. in the future. The need for this has not been identified or considered justifiable.

Policy 5 - reduce the level of flood risk, both now and in the future. The current level of risk is adequately managed and therefore this policy is not justified.

Policy 6 - increase flooding to reduce flooding elsewhere. There are no opportunities within this policy unit for this policy. We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change (at the time of the assessment), frequency and size of storms and flood events in the future.

Uncertainties The broadscale modelling has shown that by increasing the flooding in policy units upstream and there is a small reduction in flood risk in this policy unit (approximately 5%). We will need dependencies more detailed studies to find out if it is practical to do this.

Delivering this policy will partly depend on developing and implementing an effective urban drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties.

Environment Agency 145 River Adur Catchment Flood Management Plan (September 2008)

Policy unit 4 – South Downs (West) Physical characteristics: - Steep scarp slopes of the chalk downland hills extend the entire width of the CFMP area. - Environmentally Sensitive Area and Area of Outstanding Natural Beauty. - Spring line on the southern slopes forms the headwaters of the Teville Stream and Ferring Rife. - Shallow silty soils are well drained and the chalk is an important local aquifer for water supply. - Proposed National Park with high amenity value and landscape character. - Contains a significant proportion of Scheduled Monuments and SSSIs in the CFMP area. Flood mechanism: - No fluvial flooding within the policy unit. - Land management affects runoff rates with certain types of management causing muddy floods in adjacent urban areas. Receptor: Problem/risk - None within the policy unit. - Adjacent urban areas (particularly in Policy Unit 5 (Worthing)) are receptors of flooding generated due to land management in this unit. Current Flood Risk Summary Number of properties at risk of flooding (1% annual probability flood event) 0 Total damages (approx.) (1% annual probability flood event) £455 Less than Annual averages damages (approx.) £100 Future Flood risk: - Flood risk is currently assessed as low, and it is not expected to increase under future scenarios. Future Flood Risk Summary (in 100 years time) Number of properties at risk of flooding (1% annual probability flood event) 0 Total damages (approx.) (1% annual probability flood event) £965 Less than Annual averages damages (approx.) £150 Policy 6 - Take action to increase the frequency of flooding to deliver benefits locally or Policy selected elsewhere, which may constitute an overall flood risk reduction (for example for habitat inundation). This policy can deliver benefits for people and the environment locally or in other policy units. By increasing flooding and infiltration of rainwater locally in this unit, flooding downstream can be reduced. The changes in land management can also benefit biodiversity. Current maintenance activities include grass and weed cutting. Policy 6 sets a framework that actively supports increased flooding and infiltration of rainwater and is appropriate to this policy unit for the following reasons: - Although flood risk is assessed as low within the policy unit, there is the opportunity to reduce flood risk in adjoining units. - Large rural policy unit presents opportunities for changing land use and developing possible flood storage mechanisms to reduce rapid run-off generated from land use Justification activities and the steep slopes. - Action in this unit will help reduce risk of muddy floods in places such as Findon. - There are some opportunities for reducing downstream flooding by improving or creating new habitats, which increase water retention. - Soil erosion problems can best be tackled through more sensitive land management land use change and changes in farming practices. - Increased storminess due to climate change may increase soil erosion and localised flash flooding in neighbouring catchments. - This policy would help meet the environmental and landscape objectives by working with landowners and the Government. - Ensure that river channel and flood defence maintenance expenditure is appropriate to Catchment the agricultural economic damage in rural areas from flooding. objectives - Increase the landscape character value of the Sussex Downs AONB and South Downs ESA and proposed National Park.

Environment Agency 146 River Adur Catchment Flood Management Plan (September 2008) Opportunities: - Improvements in the efficiency of channel and flood defence maintenance processes. - To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing the run-off rate. - Help meet national biodiversity action plan (BAP) targets. Catchment-wide opportunities Constraints: and constraints - Available funding for the initial set up of new flood risk management schemes. - Limited available information on surface water and groundwater flood damages. - Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance. - Changes to flood risk management can affect the landscape, its character and value as an amenity. Policy 1 - do nothing. Although this could be considered as a possible policy option, and would have a similar long-term result as policy 6, it would limit the opportunities to reduce soil erosion and surface water run-off that affect neighbouring policy units.

Policy 2 - reduce current level of flood risk management. There is already minimal flood risk management within this policy unit. It is not possible to reduce it further.

Alternative Policy 3 - maintain current level of flood risk management. This policy could also apply as policies maintaining the current level of flood risk management is the same as ‘do nothing’ in this considered case. But it does imply that a certain level of flood risk management is being carried out which is not correct.

Policy 4 - maintain the current level of flood risk into the future. As with policy 3, this policy could apply, but it implies a level of activity that is not happening.

Policy 5 - reduce the level of flood risk, both now and in the future. This policy is not justified by the level of flood risk within the policy unit. There is uncertainty about how effectively changes in land management and vegetation cover will alter run-off at the catchment scale. It is known to work locally, but we do not yet know its effect on the catchment as a whole. Uncertainties

and Changes in land management will depend on the agreement of landowners. dependencies

The understanding of the impact of climate change on groundwater is still in its infancy, and there is still a lot of uncertainly surrounding the impact on groundwater flooding events.

Environment Agency 147 River Adur Catchment Flood Management Plan (September 2008)

Policy unit 5 - Worthing Physical characteristics: - Largely an urban unit, including Worthing, Lancing and parts of Littlehampton. - Urban centres are separated by the Ferring Rife and Teville Stream floodplains. - Geology mainly comprises Chalk formation, which is dissected by Lambeth Group clays through the centre of the policy unit. - Small pockets of high grade agricultural land (grades 1 and 2) lie just north of Worthing and in Sompting, at the foot of the South Downs. - Low-lying topography across the whole coastal plain region. Flood mechanism - Combination of groundwater, surface water run-off and fluvial flooding from the Ferring Rife. Receptor: - People, properties and infrastructure in the urban areas. The A27, a main transport route, is susceptible to groundwater and surface water flooding. - Currently approximately 52 properties at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event in the Ferring Rife area. - In 100 years approximately 60 properties at risk of flooding in the Ferring Rife area. - There are many more properties at risk from fluvial, surface water and groundwater Problem/risk flooding in Sompting – the exact number is unknown. Current Flood Risk Summary Number of properties at risk of flooding (1% annual probability flood event) 52 Total damages (approx.) (1% annual probability flood event) £1.6 million Annual averages damages (approx.) £70,000 Future Flood risk: - Flood risk in the Ferring Rife area is currently assessed as low to medium, assessment remains unchanged as a result of future scenarios. - We are uncertain of the exact impact of flooding in the Teville Stream area, but it is predicted that a combination of groundwater flooding, surface water run-off and/or fluvial flooding could result in a flood event flooding the low-lying areas of Sompting. It is also predicted that future scenarios will increase this risk, however, the extent to which this increase affects the people, property and environment in the Teville Stream area is unknown. Future Flood Risk Summary (in 100 years time) Number of properties at risk of flooding (1% annual probability flood event) 60 Total damages (approx.) (1% annual probability flood event) £1.835 million Annual averages damages (approx.) £108,000 Policy 3 - Continue with existing or alternative actions to manage flood risk at the current Policy selected level (accepting that flood risk with increase over time from this baseline). This policy is appropriate where the current level of flood risk management is considered appropriate. Current management and maintenance activities include maintaining defences, grass and weed cutting, debris removal and inspections. It is recognised that flood risk will change in the future, and management actions may change in time to gain efficiencies or improve effectiveness. This policy is appropriate for this policy unit for the following reasons: - The current level of flood risk is low to medium and it is not expected to significantly Justification increase in the future. - The current flood risk management activities, carried out for the localised fluvial and surface water and urban drainage flooding problems, are considered appropriate and acceptable for the level of risk. - The selected policy would help achieve the catchment objectives to ensure the impact of flooding does not significantly increase. - Ensure flood damages do not significantly increase in Worthing due to future change (urban development and climate change). - Ensure that river channel and flood defence maintenance expenditure is appropriate to the property economic damage in urban areas from flooding. - Ensure the impact of flooding on people and property does not significantly increase in Catchment Worthing in the future. objectives - Ensure the disruption caused by flooding to transport and critical infrastructure does not increase in Worthing in the future. - Reduce the impact of muddy flooding in northern parts of Worthing, including Findon. - Protect and enhance the Ferring Rife and Meadows Site of Nature Conservation Importance.

Environment Agency 148 River Adur Catchment Flood Management Plan (September 2008) Opportunities: - Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Worthing). - Reduce flood risk and improve water quality by promoting and encouraging the use of SuDS in the proposed urban developments in Worthing. - Improvements in the efficiency of channel and flood defence maintenance processes. - Effective and efficient use of developer contributions for flood risk management. - To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing the run-off rate. - Investigate the feasibility of incorporating the Teville Stream into the Floodline Warnings Direct service by installing new level gauges on the Teville stream. - Continued practice and development of the Emergency Response Plan in Brighton and Hove, Worthing, Shoreham, and Burgess Hill. - Influence the second generation of Shoreline Management Plans and the coastal defence strategy, along the Lower Adur, Teville Stream and Ferring Rife, to improve the sustainability of flood risk management in the this area. - Reduce surface water run-off and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices. - Support the existing flood defence measures in relation to surface water flooding. - Help meet national biodiversity action plan (BAP) targets.

Catchment-wide Constraints: opportunities - Government and international legislation, environmental management policies, plans and and constraints strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive. - Steep catchments of the South Downs result in rapid run-off and quick responses to rainfall events. - Available funding for the initial set up of new flood risk management schemes. - Older flood defence structures are likely to be more costly to maintain. - Limited available information on surface water and groundwater flood damages. - Visual impact of flood risk management activities within the proposed National Park or Areas of Outstanding Natural Beauty. - CFMP objectives and policies must complement those of the Shoreline Management Plan (SMP) that affects the CFMP area. - Transport links in the catchment are a vital part of the communication network regionally, nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032. - A suitable level of productivity from agricultural land needs to be retained. - Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance. - Changes to flood risk management can affect the landscape, its character and value as an amenity. Policy 1 - do nothing. The urban areas of Worthing currently have a low level of risk of fluvial flooding and the risk of flooding from surface water and rivers may increase with climate change. Without continued maintenance the annual average damages would increase to more than £180,000. Do nothing is, therefore, not an appropriate policy.

Policy 2 - reduce current level of flood risk management. As with policy option 1, the annual average damages would increase to more than £145,000 and would become unacceptable in the future under a ‘do less’ policy. Alternative

policies Policy 4 – maintain the current level of flood risk into the future. This policy unit could also considered apply, however, it implies considerable increased flood risk management in the future. The need for this has not been identified or considered justifiable.

Policy 5 - reduce the level of flood risk, both now and in the future. The current level of risk is considered tolerable and therefore this policy is not justified.

Policy 6 - increase flooding to reduce flooding elsewhere. There are no opportunities within this policy unit for this policy.

Environment Agency 149 River Adur Catchment Flood Management Plan (September 2008) We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change (prior to the Defra October 2006 guidance), frequency and size of storms and flood events in the future.

The understanding of the impact of climate change on groundwater is still in its infancy, and there is still a lot of uncertainly surrounding the impact on groundwater flooding events. Uncertainties and Delivering this policy will partly depend on developing and implementing an effective urban dependencies drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties.

The extent of fluvial flooding and the potential consequences are uncertain for the Teville Stream. Although broad conclusions may be drawn, the lack of sufficient data to model the watercourse limits the analysis that can be completed in the CFMP. The figures presented in this table for fluvial flooding relate to the Ferring Rife.

Environment Agency 150 River Adur Catchment Flood Management Plan (September 2008)

Policy unit 6 – Brighton and Hove Physical characteristics: - Most densely populated policy unit, comprising Brighton and Hove, extending east to Rottingdean. Area of regional importance to the economy. - Chalk geology predominates with small pockets of Lambeth Group clays beneath Brighton. - There are no watercourses in this policy unit; there are however, several dry river valleys present. Flood mechanism: - Flashy response to surface water run-off. - Groundwater, urban drainage, and surface water flooding. Receptor: - People, properties and infrastructure in Brighton and Hove. - Main transport routes of A23, A27 (Lewes Road) and Brighton to London train line Problem/risk susceptible to groundwater and surface water flooding. Current Flood Risk Summary Number of properties estimated to be at risk of flooding 50 Estimated damages (based on 2000/01 event) £1.4 million Annual averages damages (approx.) - Future Flood risk: - Flood risk from groundwater and surface water flooding is currently assessed at low to medium; assessment remains low to medium in the future. - Anecdotal reports of rapid flooding to over 1m deep in some instances. Future Flood Risk Summary (in 100 years time) Number of properties at risk of flooding (1% annual probability flood event) 50 to 200 More than £1.4 Estimated damages (based on 2000/01 event) million Annual averages damages (approx.) - Policy 3 - Continue with existing or alternative actions to manage flood risk at the current Policy selected level (accepting that flood risk with increase over time from this baseline). This policy is appropriate where the current level of flood risk management is considered acceptable. Maintenance is minimal however assets are inspected. It is recognised that flood risk will change in the future, and management actions may change in time to gain efficiencies or improve effectiveness. This policy is appropriate for this policy unit for the following reasons: - The current level of flood risk is low to medium and it is not certain how this will increase in the future. Justification - The current flood risk management activities, carried out for the surface water, urban drainage and groundwater flooding problems, are considered appropriate and acceptable for the level of risk. - The selected policy would help achieve the catchment objectives to ensure the impact of flooding does not significantly increase. - A policy 6 option for policy unit 9 will also provide benefit to Brighton and Hove in the future. - Ensure flood damages do not significantly increase in Brighton and Hove due to future change (urban development and climate change). - Ensure that expenditure on emergency surface water flooding works is appropriate to the estimated damages resulting from surface water flooding. Catchment - Ensure the impact of surface water and groundwater flooding on properties does not objectives significantly increase in Brighton and Hove in the future. - Ensure the disruption caused by flooding to transport and critical infrastructure does not increase in Brighton and Hove in the future. - Reduce the impact of muddy flooding in northern parts of Brighton and Hove, Rottingdean, Woodingdean, Ovingdean and Bevendean.

Environment Agency 151 River Adur Catchment Flood Management Plan (September 2008) Opportunities: - Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Brighton and Hove). - Reduce flood risk and improve water quality by promoting and encouraging the use of SuDS in the proposed urban developments in Brighton and Hove. - Improvements in the efficiency of channel and flood defence maintenance processes. - Effective and efficient use of developer contributions for flood risk management. - To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing the run-off rate. - Continue local authority and Environment Agency support of the Flood 1 project in relation to groundwater flooding. - Develop a flood warning system for groundwater flooding. - Continued practice and development of the Emergency Response Plan in Brighton and Hove, Worthing, Shoreham, and Burgess Hill. - Influence the second generation of Shoreline Management Plans and the coastal defence strategy, along the Lower Adur, Teville Stream and Ferring Rife, to improve the sustainability of flood risk management in the this area. - Reduce surface water run-off and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices (e.g. those set out by Brighton and Hove City Council). Catchment-wide - Support the existing flood defence measures in relation to surface water flooding, such opportunities as bunds provided by Brighton and Hove City Council. and constraints

Constraints: - Government and international legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive. - Steep catchments of the South Downs result in rapid run-off and quick responses to rainfall events. - CFMP objectives and policies must complement those of the Shoreline Management Plan (SMP) that affects the CFMP area. - Available funding for the initial set up of new flood risk management schemes. - Older flood defence structures are likely to be more costly to maintain. - Limited available information on surface water and groundwater flood damages. - Transport links in the catchment are a vital part of the communication network regionally, nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032. - A suitable level of productivity from agricultural land needs to be retained. - Visual impact of flood risk management activities within the proposed National Park or Areas of Outstanding Natural Beauty. Policy 1 - do nothing. This policy would not recognise the need to manage existing levels of flood risk.

Policy 2 - reduce current level of flood risk management. As with policy 1, this policy would not recognise the need to manage existing levels of flood risk.

Alternative Policy 4 – maintain the current level of flood risk into the future. This policy unit could also policies apply, however, it implies considerable increased flood risk management in the future. The considered need for this has not currently been identified or considered justifiable.

Policy 5 - reduce the level of flood risk, both now and in the future. The current level of risk is considered tolerable and therefore this policy is not justified.

Policy 6 - increase flooding to reduce flood risk elsewhere. Because of the large groundwater element of the flooding, there are no opportunities within this policy unit for this approach.

Environment Agency 152 River Adur Catchment Flood Management Plan (September 2008) Flood risk from the sea is also a significant consideration in this policy unit. Therefore, flood risk management options must fit with shoreline management plan policy and actions.

We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change (prior to the Defra October 2006 guidance). Our Uncertainties current ability to accurately predict the impact of this, particularly the impact climate change and will have on groundwater flooding, is limited. dependencies There is currently insufficient understanding of future flood risk from surface water and groundwater in this policy unit. The estimates made are indicative based on an assumption of increase runoff due to climate change and historic incidents of flooding. Further study into future flood risk and the cost of potential mitigation measures would facilitate more informed decision making and enable more confidence to be placed in the selected policy.

Environment Agency 153 River Adur Catchment Flood Management Plan (September 2008)

Policy unit 7 - Shoreham and Adur Estuary Physical characteristics: - This unit is predominantly urban including Shoreham and Lancing. - Includes part of River Adur corridor from the coast to the A27. - The A27 trunk road and chalk downland landscape forms the northern policy unit boundary. - Shoreham airport lies entirely within this unit. - Mainly chalk geology with flat low-lying ground. Flood mechanism: - Heavily tidally influenced. - Overtopping of embankments – will not generally overtop due to fluvial flooding on its own and will require significant tidal influence. - Surface water flooding through Shoreham airport generated from run-off from the steep slopes of the South Downs – can takes weeks for the flood water to subside. Receptor: - People, properties and infrastructure of the urban areas, including A259, A27, and Shoreham Airport. - Most of the Adur Estuary SSSI lies within this policy unit, although only a minor extent that is not channel lies within the 1% annual probability flood outline. - Currently approximately 11 properties are at risk of fluvial flooding in the policy unit Problem/risk from the 1% annual probability fluvial flood event. As a result of climate change the number of properties at risk of fluvial flood alone is not expected to increase significantly. However, if a fluvial event should be combined with a significant tidal influence, it is expected that a large number of properties (around 1750) will be at risk in the future with a potential of up to £15 million damages (AAD). Current Flood Risk Summary Number of properties at risk of flooding (1% annual probability flood event) 11 Total damages (approx.) (1% annual probability flood event) £0.4 million Annual averages damages (approx.) £80,000 Future Flood risk: - Flood risk from fluvial flooding is currently assessed as low, assessment changes to high in the future due to the increased influence from the tide resulting from sea level rise. - Flood risk from surface water flooding is currently assessed as low to medium, assessment remains low to medium in the future. Future Flood Risk Summary (in 100 years time) Number of properties at risk of flooding (1% annual probability flood event) 1757 Total damages (approx.) (1% annual probability flood event) £78 million Annual averages damages (approx.) £15 million Policy 4 - Take further action to sustain current scale of flood risk into the future (responding Policy selected to the potential increases in flood risk from urban development, land use change, and climate change). Although there are opportunities to reduce flooding in this unit by increasing storage on the floodplain upstream in other policy units, the level of potential flood risk in the unit is predicted to increase significantly (up to £15 million in damages AAD) in the future. Therefore we have selected policy 4 for this policy unit. Current management and maintenance activities include grass and weed cutting, cutting back overhanging branches, channel desilting and debris removal. This policy applies to this policy unit for the following reasons: - The current level of fluvial flood risk alone is low, however a combination of a high tide and high river flows does increase the level of flood risk. Justification - The level of flood risk in Shoreham needs to be addressed – local defences will need to be maintained and improved over time to mitigate the affects of climate change, and this is recognised in the Rivers Arun to Adur Coastal Defence strategy study. - The selected policy would help achieve the economic, and social objectives by maintaining the current level of flood risk within the policy unit in the future, by carrying out appropriate works to the river wall defences through the unit. - Protection to historic landfill area from flooding. - Supports the regeneration proposals for Shoreham (Shoreham Renaissance, Shoreham Marine North, Shoreham Airport and Shoreham Hospital).

Environment Agency 154 River Adur Catchment Flood Management Plan (September 2008) - Ensure flood damages do not significantly increase in Shoreham due to future change (urban development and climate change). - Ensure that river channel and flood defence maintenance expenditure is appropriate to the property economic damage in urban areas from flooding. Catchment - Ensure the impact of flooding on people and property does not significantly increase in objectives Shoreham in the future. - Ensure the disruption caused by flooding to transport and critical infrastructure does not increase in Shoreham in the future. - Protect and enhance the Adur Estuary SSSI. - Increase the landscape character value of the Sussex Downs. Opportunities: - Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Shoreham). - Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments in Shoreham. - Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity. - Potential for improving the current defences, for example possible installation of demountable or temporary defences in Shoreham and Burgess Hill. - Improvements in the efficiency of channel and flood defence maintenance processes. - Effective and efficient use of developer contributions for flood risk management. - To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing the run-off rate. - Continued practice and development of the Emergency Response Plan in Brighton and Hove, Worthing, Shoreham, and Burgess Hill. - Influence the second generation of Shoreline Management Plans and the coastal defence strategy, along the Lower Adur, Teville Stream and Ferring Rife, to improve the sustainability of flood risk management in the this area. - Reduce surface water run-off and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices. Catchment-wide - Support the existing flood defence measures in relation to surface water flooding. opportunities - Help meet national biodiversity action plan (BAP) targets. and constraints Constraints: - Government and international legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive. - Steep catchments of the South Downs result in rapid run-off and quick responses to rainfall events. - CFMP objectives and policies must complement those of the Shoreline Management Plan (SMP) that affects the CFMP area. - Available funding for the initial set up of new flood risk management schemes. - Older flood defence structures are likely to be more costly to maintain. - Limited available information on surface water and groundwater flood damages. - Visual impact of flood risk management activities within the proposed National Park or Areas of Outstanding Natural Beauty. - Transport links in the catchment are a vital part of the communication network regionally, nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032. - Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance. - Changes to flood risk management can affect the landscape, its character and value as an amenity.

Environment Agency 155 River Adur Catchment Flood Management Plan (September 2008) Policy 1 – do nothing. If defences were permitted to fall into disrepair the annual average damages could increase to more than £20 million and significantly more than 4200 people would be at risk. This policy, therefore, could not be considered as an alternative.

Policy 2 – reduce current level of flood risk management. If the current flood risk management was reduced the annual average damages could increase to more than £17 million and substantially more than 4200 people would be at risk. This is considered unacceptable. Alternative policies Policy 3 – maintain current level of flood risk management. As with policy 1, this policy would considered not recognise the need to maintain flood risk from heavily influenced tidal flood events in the future, which is considered unacceptable.

Policy 5 - reduce the level of flood risk, both now and in the future. The current level of risk is managed adequately and therefore this policy is not justified.

Policy 6 – increase flooding to reduce flood risk elsewhere. There are limited opportunities within this policy unit, due to the high density of development and essential infrastructure, to take this approach. Flood risk from the sea is a significant consideration in this policy unit. Therefore, fluvial flood risk management options must fit with the shoreline management plan policy and actions.

We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change (prior to the Defra October 2006 guidance), frequency and size of storms and flood events in the future. Although the Defra 2006 guidance suggests greater levels of sea rise in the future, than used in the broadscale modelling, this would not change the policy selected for this policy unit. Uncertainties

and The broadscale model has not included the drainage network through the Shoreham Airport dependencies site. This area is at risk from overtopping of the Adur and also from groundwater and surface water run-off. There is, therefore, some uncertainty in the resulting flood extent and severity – particularly in the long-term. We have taken this uncertainty into account when selecting the most appropriate policy, but we must look at this again at the next CFMP review.

Delivering this policy will partly depend on developing and implementing an effective urban drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties.

Environment Agency 156 River Adur Catchment Flood Management Plan (September 2008)

Policy unit 8 – Adur Valley (north of A27 to south of Steyning) Physical characteristics: - Unit consists of the rural landscape immediately adjacent to the river corridor and contains a few isolated properties. - River Adur corridor, including a small part of the Adur Estuary SSSI. - Relatively flat low-lying ground in a valley between the South Downs Chalk block. Flood mechanism: - Heavily influenced tidal flooding. - Overtopping of embankments – will not generally overtop due to fluvial flooding on its own and will require significant tidal influence. Receptor: - Infrastructure (roads and rail), isolated properties and agricultural land. - Sussex Downs AONB, South Downs ESA and Proposed National Park. - Includes part of the Adur Estuary SSSI and part of the Beeding Hill and Newtimber Hill SSSI. No extent of these SSSIs are located within the 1% annual probability flood outline within this policy unit. Problem/risk - The majority of the River Adur Meadows, Shoreham-by-Sea, the Mill Hill, Shoreham-by-Sea and the Old Erringham Farm valley and road cutting SNCIs. No extent of these SNCIs are located within the 1% annual probability flood outline. - Currently no properties are at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event. Current Flood Risk Summary Number of properties at risk of flooding (1% annual probability flood event) 0 Total damages (approx.) (1% annual probability flood event) £27,000 Annual averages damages (approx.) £450 Future Flood risk: - Flood risk is currently assessed as low, and it is not expected to increase under future scenarios. Future Flood Risk Summary (in 100 years time) Number of properties at risk of flooding (1% annual probability flood event) Less than 5 Total damages (approx.) (1% annual probability flood event) £65,000 Annual averages damages (approx.) £1,000 Policy 6 - Take action to increase the frequency of flooding to deliver benefits locally or Policy selected elsewhere, which may constitute an overall flood risk reduction (for example for habitat inundation). This policy can deliver benefits for people and the environment locally or in other policy units. By increasing flooding locally in this unit, flooding downstream can be reduced, and in many instances, increasing flooding can improve wetland biodiversity, as flooding is a natural part of floodplain ecosystems. Current management and maintenance activities include grass and weed cutting, cutting back overhanging branches, channel desilting and debris removal. Policy 6 sets a framework that actively supports increased flooding, or at least keeps water on the land for longer. This applies to this policy unit for the following reasons: - With a low flood risk within this policy unit, there is no need for a significant flood risk reduction policy. - Applying policy 6 here may help reduce flood risk downstream in policy unit 7. Justification - An increase in flooding could result in an increase of approximately 140 hectares of wetland around the River Adur Meadows, Shoreham-by-Sea and the Mill Hill, Shoreham- by-Sea SNCIs. This will improve local biodiversity and help meet biodiversity action plan targets. - This policy would help meet the catchment objectives, having a positive effect on biodiversity in this area, leading to an eventual increase in extent, quality and diversity of wetland habitats, with opportunities for recreation and landscape. Emphasis would be placed on helping the public and landowners to understand the risk of flooding and climate change better; encourage close partnership with local communities and rural development authorities; and build policy objectives into planning documents. - Ensure flood damages do not significantly increase along the Lower Adur corridor. - Restore parts of the River Adur and floodplain to a naturally functioning state where Catchment feasible downstream of Steyning and Upper Beeding. objectives - Increase the landscape character value of the Sussex Downs AONB and South Downs ESA and proposed National Park.

Environment Agency 157 River Adur Catchment Flood Management Plan (September 2008) Opportunities: - Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan - Reduce flood risk and improve water quality by promoting and encouraging the use of SuDS in the proposed urban developments. - Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity. - Enhance the character of the landscape and increase amenity opportunities for recreation, tourism and leisure activities. - Move toward more natural rivers and drainage networks, as outlined within PPS25, will mean we can achieve more efficient and sustainable water management, whilst enhancing landscape character. - Help meet national biodiversity action plan (BAP) targets.

Catchment-wide Constraints: opportunities - Government and international legislation, environmental management policies, plans and and constraints strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive. - Steep catchments of the South Downs result in rapid run-off and quick responses to rainfall events. - Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance. - Individual homes and properties are currently at risk of flooding. - Presence of protected species with specific water level, water quality and habitat requirements, for example in the Adur Estuary SSSI. - Changes to flood risk management can affect the landscape, its character and value as an amenity. - Historic development and some heritage designations in Steyning, Bramber and Upper Beeding present permanent physical obstructions. - Location of electricity pylons adjacent to the Lower River Adur (currently protected by existing defences). - No degradation of existing fish passage and habitat. Policy 1 - do nothing. Although this could be considered as a possible policy option, and would have a similar long-term result as policy 6, the effects would happen in an unmanaged and unpredictable way, and local flood risk may increase.

Policy 2 - reduce current level of flood risk management. This could also be considered a possible policy option for this area, and it could allow increased floodplain inundation whilst controlling the changes that would happen in time. However, this policy does not reflect the scale of the likely changes and it does not ensure the level of investment and commitment to meet the catchment objectives.

Alternative Policy 3 - maintain current level of flood risk management. This option results in the least policies favourable result, with increases in damages locally of approximately 68% but with none of considered the benefits that would come from a managed approach of potentially increasing areas of wetland and therefore improving local biodiversity and help meet biodiversity action plan targets.

Policy 4 - maintain the current level of flood risk into the future. This policy could apply to this policy unit, but it implies a need for increased flood risk management in the future and does not consider the opportunity for potential reduction in flood risk in policy unit 7.

Policy 5 - reduce the level of flood risk, both now and in the future. This policy is not justified by the current and future level of flood risk within the policy unit, and would require an unsustainable level of investment in flood defences to meet future changes.

Environment Agency 158 River Adur Catchment Flood Management Plan (September 2008) Flood risk from the sea should also be a consideration in this policy unit due to the effect of sea level rise. Therefore, fluvial flood risk management options must consider the effects of shoreline management plan policy and actions.

We have estimated the future increase in flood risk within this policy unit on the best available Uncertainties prediction we have of climate change (prior to the Defra October 2006 guidance), frequency and and size of storms and flood events in the future. Although the Defra 2006 guidance suggests dependencies greater levels of sea rise in the future, than used in the broadscale modelling, this would not change the policy selected for this policy unit.

The broadscale modelling has shown that lowering or removing flood defences can help reduce flood risk in neighbouring policy units. We will need more detailed studies to find out if it is practical to do this and improve the environment at the same time.

Environment Agency 159 River Adur Catchment Flood Management Plan (September 2008)

Policy unit 9 – South Downs (East) Physical characteristics: - Steep scarp slopes of the chalk downland hills extend the entire width of the CFMP area. - Environmentally Sensitive Area and Area of Outstanding Natural Beauty. - Shallow silty soils are well drained and the chalk is an important local aquifer for water supply. - Proposed National Park with high amenity value and landscape character. - Contains a large proportion of Scheduled Monuments and a significant proportion of SSSIs in the CFMP area. Flood mechanism: - No fluvial flooding within the policy unit. - Land management affects runoff rates with certain types of management causing muddy floods in adjacent urban areas. Receptor: Problem/risk - None within the policy unit. - Adjacent urban areas (particularly in Policy Unit 6 - Brighton and Hove) are receptors of flooding generated due to land management in this unit. Current Flood Risk Summary Number of properties at risk of flooding (1% annual probability flood event) 0 Total damages (approx.) (1% annual probability flood event) £0 Annual averages damages (approx.) Negligible Future Flood risk: - Flood risk is currently assessed as low, and it is not expected to increase under future scenarios. Future Flood Risk Summary (in 100 years time) Number of properties at risk of flooding (1% annual probability flood event) 0 Total damages (approx.) (1% annual probability flood event) £0 Annual averages damages (approx.) Negligible Policy 6 - Take action to increase the frequency of flooding to deliver benefits locally or Policy selected elsewhere, which may constitute an overall flood risk reduction (for example for habitat inundation). This policy can deliver benefits for people and the environment locally or in other policy units. By increasing flooding and infiltration of rainwater locally in this unit, flooding downstream can be reduced. Current maintenance activities include grass and weed cutting. The changes in land management can also benefit biodiversity. Policy 6 sets a framework that actively supports increased flooding and infiltration of rainwater and is appropriate to this policy unit for the following reasons: - Although flood risk is assessed as low within the policy unit, there is the opportunity to reduce flood risk in adjoining units. - Large rural policy unit which presents opportunities for changing land use and developing possible flood storage mechanisms to reduce rapid run-off generated from Justification land use activities and the steep slopes. - Action in this unit will help reduce risk of muddy floods in the suburbs of Brighton. - There are some opportunities for reducing downstream flooding by improving or creating new habitats, which increase water retention. - Soil erosion problems can best be tackled through more sensitive land management, land use change, and changes in farming practices. - Increased storminess due to climate change may increase soil erosion and localised flash flooding in neighbouring catchments. - This policy would help meet the environmental and landscape objectives by working with landowners and the Government. - Ensure that flood defence maintenance expenditure is appropriate to the agricultural Catchment economic damage in rural areas from flooding. objectives - Increase the landscape character value of the Sussex Downs AONB and South Downs proposed National Park.

Environment Agency 160 River Adur Catchment Flood Management Plan (September 2008) Opportunities: - Improvements in the efficiency of flood defence maintenance processes. - To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing the run-off rate. - Help meet national biodiversity action plan (BAP) targets. - Continue local authority and Environment Agency support of the Flood 1 project in relation to groundwater flooding. - Develop a flood warning system for groundwater flooding.

Constraints: Catchment-wide - Available funding for the initial set up of new flood risk management schemes. opportunities - Older flood defence structures are likely to be more costly to maintain. and constraints - Limited available information on surface water and groundwater flood damages. - Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance. - Changes to flood risk management can affect the landscape, its character and value as an amenity. - Visual impact of flood risk management activities within the proposed National Park or Areas of Outstanding Natural Beauty. - Government and international legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive. Policy 1 - do nothing. Although this could be considered as a possible policy option, and would have a similar long-term result as policy 6, it would limit the opportunities to reduce soil erosion and surface water run-off that affect neighbouring policy units.

Policy 2 - reduce current level of flood risk management. There is already minimal flood risk management within this policy unit. It is not possible to reduce it further.

Alternative Policy 3 - maintain current level of flood risk management. This policy could also apply as policies maintaining the current level of flood risk management is the same as ‘do nothing’ in this considered case. But it does imply that a certain level of flood risk management is being carried out which is not correct.

Policy 4 - maintain the current level of flood risk into the future. As with policy 3, this policy could apply, but it implies a level of activity that is not happening.

Policy 5 - reduce the level of flood risk, both now and in the future. This policy is not justified by the level of flood risk within the policy unit. There is uncertainty about how effective changes in land management and vegetation cover will alter run-off at the catchment scale. It is known to work locally, but we do not yet know its effect on the catchment as a whole. Uncertainties

and Changes in land management will depend on the agreement of landowners. dependencies

The understanding of the impact of climate change on groundwater is still in its infancy, and there is still a lot of uncertainly surrounding the impact on groundwater flooding events.

Environment Agency 161 River Adur Catchment Flood Management Plan (September 2008) 7 Delivering the CFMP The aim of this section is to outline what we need to do next. We have prepared an action plan which sets out what we will do to deliver the selected policy in each policy unit. We have also said what we think the consequences of these policies will be in the future, so that we can tell whether we are achieving the goals we have set.

7.1 Action Plan

We have identified a number of actions, which to some extent are part of the routine work carried out by the organisation involved in flood risk management, and apply to all of the policy units. These are:

• support and influence the System Asset Management Plans (SAMPs) we are preparing. These plans provide information on all flood defence structures (including assets owned by private companies). They provide guidance on how the structures work and whether repairs or improvements will be needed in the future. Plans will include reasons for the chosen approach. • We are working to improve our flood warning service. Floodline Warnings Direct is the UK's first integrated multi-channel warning system, providing flood warning and information to the public, professional partners and the media. • A National Flood Forecasting System is being developed and this should help us to forecast flooding better in the River Adur CFMP area. • We will work to support the development of Strategic Flood Risk Assessments by local planning authorities. • We will continue to improve floodplain mapping.

We have agreed a set of actions to carry out the policies. We will need to take some actions in the short term. Other long-term actions will be necessary throughout the lifetime of the plan. Some actions depend on others being completed and, therefore, will not happen straight away. This is shown in table 7.1.

Environment Agency 162 River Adur Catchment Flood Management Plan (September 2008) Table 7.1 - Summary table of action plan Policy Unit 1 – Upper Adur Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Policy 6 – Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, which may constitute an overall flood risk reduction. Restore parts of the River Adur Length of naturally functioning and floodplain to a naturally river (km). functioning state where feasible

upstream of Steyning and Upper Area of naturally active floodplain Beeding. 2 (km ).

Balance of annual river channel and flood defence maintenance expenditure (£) to annual average Identification of damages from fluvial flooding to opportunities for the agriculture (£). creation of attenuation Ensure that river channel and and wetland within the flood defence maintenance Flood damages downstream in Adur Tidal Strategy (for Adur Tidal Strategy. expenditure is appropriate to the policy unit 3 (Steyning and entire tidal reach) to agricultural economic damage in Upper Beeding) (£AAD). include investigation of Identification in rural areas from flooding. locations for large-scale Environment Agency 2009 to 2014 Medium completed Adur Tidal Number of people affected by flood attenuation and Strategy study of the 1% annual probability flood wetland creation on the opportunities for efficient event downstream in policy unit River Adur. channel and defence 3 (Steyning and Upper maintenance and Beeding). reduction of flood risk in downstream policy units. Protect and enhance the River Adur Water Meadows and Habitat quality and species Wyckham Wood Site of Nature diversity (area SNCI, km2). Conservation Importance.

Increase the landscape character Landscape character assessment value of the High Weald AONB of the AONB and proposed and proposed South Downs National Park. National Park.

Environment Agency 163 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 1 – Upper Adur Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s)

Environment Agency Increase the landscape character Landscape character assessment value of the High Weald AONB National Farmers of the AONB and proposed Set up working groups to and proposed South Downs Union National Park. explore the use of Agri- National Park.

Environment and Mid Sussex District Woodland Schemes Agri-Environment and Council grants to help fund the Woodland Scheme 2008 to 2013 Low Flood damages downstream in

change of land use and grants established. Restore parts of the River Adur policy unit 3 (Steyning and Horsham District land use management to and floodplain to a naturally Upper Beeding) (£AAD). Council increase the water functioning state where feasible

retention in the catchment. upstream of Steyning and Upper Number of people affected by the Natural England Beeding. 1% annual probability flood event downstream in policy unit 3 Defra (Steyning and Upper Beeding).

SAMP which Flood damages downstream in compliments CFMP policy unit 3 (Steyning and Restore parts of the River Adur Develop the SAMP with policy option to Take Upper Beeding) (£AAD). and floodplain to a naturally consideration and action to increase the functioning state where feasible inclusion of measures that frequency of flooding to Environment Agency 2008 to 2013 Medium Number of people affected by upstream of Steyning and Upper will reduce existing effort deliver benefits locally or the 1% annual probability flood Beeding. in this policy unit. elsewhere, which may event downstream in policy unit

constitute an overall 3 (Steyning and Upper flood risk reduction. Beeding). Environment Agency Flood damages downstream in policy unit 3 (Steyning and National Farmers Restore parts of the River Adur Upper Beeding) (£AAD). Union and floodplain to a naturally Encourage and influence functioning state where feasible Number of people affected by the uptake of Whole Farm Mid Sussex District upstream of Steyning and Upper the 1% annual probability flood Plans in the Upper Adur Whole Farm Plans set Council Beeding. event downstream in policy unit catchment to provide up in the Upper Adur 2008 to 2013 Low 3 (Steyning and Upper advice on better land use catchment. Horsham District Beeding). practice with respect to Council run-off generation. Increase the landscape character Landscape character assessment Natural England value of the High Weald AONB of the AONB and proposed and proposed South Downs National Park. Landowners National Park.

Environment Agency 164 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 1 – Upper Adur Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Balance of annual river channel and flood defence maintenance expenditure (£) to annual average damages from fluvial flooding to Ensure that river channel and agriculture (£). flood defence maintenance Pre feasibility study to expenditure is appropriate to the Flood damages downstream in investigate removal of agricultural economic damage in policy unit 3 (Steyning and Environment Agency rural areas from flooding. Upper Beeding) (£AAD). owned and maintained Environment Agency structures (flood Number of people affected by the embankments) where Natural England 1% annual probability flood event additional storage could downstream in policy unit 3 Pre feasibility study 2012 to 2022 Medium reduce flood risk to Mid Sussex District (Steyning and Upper Beeding). completed. Steyning and Upper Council Beeding, restore rivers Increase the landscape character and floodplains to a Horsham District Landscape character assessment value of the High Weald AONB naturally functioning state Council of the AONB and proposed and proposed South Downs and contribute to meeting National Park. Biodiversity Action Plan National Park. targets.

Protect and enhance the River Adur Water Meadows and Habitat quality and species Wyckham Wood Site of Nature diversity (area SNCI, km2). Conservation Importance.

Environment Agency 165 River Adur Catchment Flood Management Plan (September 2008)

Policy Unit 2 – Burgess Hill Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Policy 4 – Take further action to sustain current scale of flood risk into the future (responding to the potential increases in flood risk from urban development, land use change, and climate change). Total annual average damages Ensure flood damages do not (to properties and agriculture) increase in Burgess Hill and from fluvial flooding (£AAD). Hassocks due to future change

(urban development and climate Estimated damages resulting change). from surface water flooding (£).

Number of people and Strengthen development properties affected by the 1% control advice, annual probability fluvial flood event. including the use of Ensure the impact of flooding on

SuDS, through Local people and property does not The estimated number of Develop Framework Environment Agency significantly increase in Burgess properties affected by surface policies. In particular Hill and Hassocks in the future. water flooding. polices should ensure Appropriate policies in Horsham District

that the there is no Local Development Council Coverage of Flood Warning increase in run-off from Framework which ensure Ongoing High Service new developments and flood risks from all Mid Sussex District seek opportunities to sources are not Council Length of A road and railway reduce current run-off increased into the future. line (km) affected by the 1% rates, where possible to Lewes District annual probability fluvial flood ensure flood risk does Council event. not increase in the future, particularly in and around Number of critical infrastructure Burgess Hill. Ensure the disruption caused by sites affected by the 1% annual flooding to transport and critical probability fluvial flood event. infrastructure does not increase in Burgess Hill and Hassocks in the Number and period of recorded future. A road and railway closures due to surface water flooding.

Number of critical infrastructure sites recorded as being affected by surface water flooding.

Environment Agency 166 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 2 – Burgess Hill Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s)

Total annual average damages Ensure flood damages do not (to properties and agriculture) increase in Burgess Hill and from fluvial flooding (£AAD). Hassocks due to future change

Develop an Integrated (urban development and climate Environment Agency Estimated damages resulting Urban Drainage change). from surface water flooding (£). Strategy for Burgess Hill Water companies with a review of receiving Deliver an integrated watercourses/ urban drainage Mid Sussex District 2008 to 2013 High catchments, foul and strategy. Council surface water drainage,

and implications of Lewes District Ensure that river channel and Balance of annual river channel climate change to be Council flood defence maintenance and flood defence maintenance considered. expenditure is appropriate to the expenditure (£) to annual average property economic damage in damages from fluvial flooding to urban areas from flooding. property (£).

Number of people and properties affected by the 1% Review actions annual probability fluvial flood recommended in the If required, action plan event. Wivelsfield Land for managing future flood Ensure the impact of flooding on Drainage Study to ensure risk in Wivelsfield Lewes District people and property does not The estimated number of they address future flood 2008 to 2013 Medium developed to supplement Council significantly increase in Burgess properties affected by surface risk. Where actions do not Wivelsfield Land Hill and Hassocks in the future. water flooding. adequately address future Drainage Study. flood risk develop a plan to Coverage of Flood Warning rectify this. Service

Environment Agency 167 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 2 – Burgess Hill Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Ensure flood damages do not Total annual average damages increase in Burgess Hill and (to properties and agriculture) Hassocks due to future change from fluvial flooding (£AAD). (urban development and climate change). Estimated damages resulting from surface water flooding (£).

Number of people and properties affected by the 1% annual probability fluvial flood Increase the coverage of Ensure the impact of flooding on event. the Floodline Warnings people and property does not Direct service in significantly increase in Burgess The estimated number of Burgess Hill and Hill and Hassocks in the future. properties affected by surface Hassocks to ensure the Coverage of the water flooding. impact of flooding on Floodline Warnings people and property does Direct service greater Environment Agency 2008 to 2010 High Coverage of Flood Warning not increase due to future than 77% in Burgess Hill Service changes. This may and Hassocks. Length of A road and railway include creating a flood line (km) affected by the 1% warning area for the annual probability fluvial flood Burgess Hill and event. Hassocks community. Number of critical infrastructure Ensure the disruption caused by sites affected by the 1% annual flooding to transport and critical probability fluvial flood event. infrastructure does not increase in

Burgess Hill and Hassocks in the Number and period of recorded future. A road and railway closures due to surface water flooding.

Number of critical infrastructure sites recorded as being affected by surface water flooding.

Environment Agency 168 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 2 – Burgess Hill Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Number of people and properties affected by the 1% Ensure the impact of flooding on annual probability fluvial flood people and property does not event. significantly increase in Burgess Hill and Hassocks in the future. The estimated number of properties affected by surface Environment Agency water flooding.

Length of A road and railway Mid Sussex District line (km) affected by the 1% Work with others to find Council Attendance at annual probability fluvial flood innovative solutions to emergency response event. improve and develop Lewes District 2008 to 2010 High planning sessions. Emergency Response Council Number of critical infrastructure Plans Ensure the disruption caused by sites affected by the 1% annual Horsham District flooding to transport and critical probability fluvial flood event. Council infrastructure does not increase in

Burgess Hill and Hassocks in the Number and period of recorded future. A road and railway closures due to surface water flooding.

Number of critical infrastructure sites recorded as being affected by surface water flooding. Install water level gauges on the streams Water level gauges Total annual average damages within Burgess Hill and installed with earlier and Ensure flood damages do not (to properties and agriculture) Hassocks to increase the more localised flood increase in Burgess Hill and from fluvial flooding (£AAD). efficiency of the Flood warnings from Flood Environment Agency 2008 to 2010 High Hassocks due to future change Warnings Direct, to Warnings Direct for (urban development and climate Estimated damages resulting ensure the impact of Burgess Hill and change). from surface water flooding (£). flooding on people and Hassocks. property does not increase in the future.

Environment Agency 169 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 2 – Burgess Hill Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Total annual average damages Ensure flood damages do not (to properties and agriculture) increase in Burgess Hill and Assess the potential for from fluvial flooding (£AAD). Hassocks due to future change improving current (urban development and climate defences, installation of Estimated damages resulting SAMP covering the change). demountable defences from surface water flooding (£). Burgess Hill and Environment Agency Ongoing Medium and channel and flood Ensure that river channel and Hassocks area Balance of annual river channel defence management flood defence maintenance and flood defence maintenance programmes as part of expenditure is appropriate to the the SAMP. expenditure (£) to annual average property economic damage in damages from fluvial flooding to urban areas from flooding. property (£).

Environment Agency 170 River Adur Catchment Flood Management Plan (September 2008)

Policy Unit 3 – Steyning and Upper Beeding Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Policy 3 – Continue with existing or alternative actions to manage flood risk at the current level (accepting that flood risk will increase over time from this baseline).

Total annual average damages Ensure flood damages do not (to properties and agriculture) Continue to apply significantly increase in Steyning from fluvial flooding (£AAD). guidance in PPS25 and and Upper Beeding due to future

ensure that flood risk Environment Agency change (urban development and Estimated damages resulting issues identified in the Appropriate policies in climate change). from surface water flooding (£). CFMP and the Strategic Local Development Horsham District Ongoing High

Flood Risk Assessment Framework. Council are used to allocate and manage development at Steyning and Bramber. Ensure the impact of flooding on people and property does not Number of people and properties significantly increase in Steyning affected by the 1% annual and Upper Beeding in the future. probability fluvial flood event.

Continue with existing Ensure that river channel and Balance of annual river channel Environment Agency level of asset flood defence maintenance and flood defence maintenance Current level of maintenance, looking for Ongoing Medium expenditure is appropriate to the expenditure to annual average maintenance. Horsham District efficiencies and property economic damage in damages from fluvial flooding to Council improvements urban areas from flooding. property. Ensure the impact of flooding on Number of people and properties people and property does not affected by the 1% annual significantly increase in Steyning Continue to provide a probability fluvial flood event. and Upper Beeding in the future. Floodline Warnings Direct service in Steyning Maintained Floodline Total annual average damages (to properties and agriculture) and Upper Beeding to Warnings Direct Environment Agency 2008 to 2010 High Ensure flood damages do not from fluvial flooding (£AAD). ensure the impact of service in Steyning and significantly increase in Steyning flooding on people and Upper Beeding and Upper Beeding due to future Estimated damages resulting property continues to be change (urban development and from surface water flooding. managed. climate change). Coverage of Flood Warning Service

Environment Agency 171 River Adur Catchment Flood Management Plan (September 2008)

Policy Unit 4 – South Downs (West) Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Policy 6 – Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, which may constitute an overall flood risk reduction. Balance of annual river channel and flood defence maintenance expenditure (£) to annual average Environment Agency damages from fluvial flooding to Ensure that river channel agriculture (£). Set up working groups to National Farmers and flood defence explore the use of Agri- Union maintenance expenditure is Number of people affected by the Environment and appropriate to the 1% annual probability flood event Woodland Schemes Horsham District agricultural economic downstream in policy units 5 grants to help fund the Council Agri-Environment and damage in rural areas from (Worthing) and 7 (Shoreham and change of land use and Woodland Scheme Ongoing Medium flooding. Adur Estuary). land use management to Adur District Council grants established. increase the water The estimated number of properties retention in the catchment Worthing Borough affected by Downland ‘muddy’ and reduce the risk of Council surface water flooding downstream in flooding in policy unit 5 policy unit 5 (Worthing). (Worthing). Arun District Council Increase the landscape

character value of the Sussex Landscape character assessment Natural England Downs AONB and South of the AONB, ESA and proposed Downs ESA and proposed National Park National Park

Environment Agency 172 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 4 – South Downs (West) Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Balance of annual river channel and Environment Agency flood defence maintenance

expenditure (£) to annual average National Farmers damages from fluvial flooding to Union Ensure that river channel agriculture (£).

and flood defence Horsham District Encourage and influence the maintenance expenditure is Number of people affected by the Council uptake of Whole Farm appropriate to the 1% annual probability flood event

Plans in the South Downs agricultural economic downstream in policy units 5 Adur District Council (West) catchment to provide Whole Farm Plans set damage in rural areas from (Worthing) and 7 (Shoreham and 2008 to 2013 Low advice on better land use up in the South Downs flooding. Adur Estuary). Worthing Borough practice with respect to run- (West) catchment. Council off generation and reduction The estimated number of properties

of flood risk in policy unit 5 affected by Downland ‘muddy’ Arun District Council (Worthing). surface water flooding downstream in

policy unit 5 (Worthing). Natural England Increase the landscape

character value of the Sussex Landscape character assessment of Landowners Downs AONB and South the AONB, ESA and proposed

Downs ESA and proposed National Park Defra National Park Work with the South Downs South Downs Join Balance of annual river channel and Joint Committee (merger of Ensure that river channel Committee flood defence maintenance the Sussex Downs and flood defence expenditure (£) to annual average Conservation Board and the maintenance expenditure is Environment Agency damages from fluvial flooding to East Hampshire AONB Joint appropriate to the agriculture (£). Advisory Committee) to agricultural economic Horsham District achieve the targets set in the damage in rural areas from Council Flood damages downstream in policy Sussex Downs AONB Sussex Downs AONB flooding. units 5 (Worthing) and 7 (Shoreham Management Strategy to Management Strategy 2012 to 2022 Medium Adur District Council and Adur Estuary) (£). maximise the opportunities implementation.

for natural processes to Arun District Council reduce flooding through the Increase the landscape

adoption of wetland creation, character value of the Sussex Landscape character assessment of Worthing Borough whilst enhancing landscape Downs AONB and South the AONB, ESA and proposed Council character. Actions will Downs ESA and proposed National Park

reduce the risk of flooding in National Park Natural England policy unit 5 (Worthing).

Environment Agency 173 River Adur Catchment Flood Management Plan (September 2008)

Policy Unit 5 – Worthing Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Policy 3 – Continue with existing or alternative actions to manage flood risk at the current level (accepting that flood risk will increase over time from this baseline). Strengthen development Total annual average damages control advice, including Ensure flood damages do not (to properties and agriculture) the use of SuDS, through significantly increase in Worthing from fluvial flooding (£AAD). Environment Agency Local Develop Framework due to future change (urban

policies to ensure no development and climate Estimated damages resulting Worthing Borough increase in run-off from Deliver advice and change). from surface water and Council new developments and guidance to local Ongoing High groundwater flooding (£).

seek opportunities to authorities. Arun District Council reduce current run-off

rates, where possible, to Reduce the impact of muddy The estimated number of Adur District Council ensure flood risk continues flooding in northern parts of properties affected by Downland to be managed through Worthing, including Findon. ‘muddy’ surface water flooding. the planning process.

Total annual average damages Ensure flood damages do not (to properties and agriculture) significantly increase in from fluvial flooding (£AAD). Environment Agency Worthing due to future change Develop an Integrated (urban development and climate Estimated damages resulting Urban Drainage Study for Water companies change). from surface water and Worthing with a review of Integrated Urban groundwater flooding (£). receiving watercourses/ Worthing Borough Drainage study 2008 to 2013 Medium catchments, foul and Council completed. surface water drainage and implications of climate Arun District Council Protect and enhance the Ferring change to be considered. Rife and Meadows Site of Habitat quality and species Adur District Council Nature Conservation diversity. Importance.

Environment Agency 174 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 5 – Worthing Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Understanding of flood risk in this policy unit should be enhanced through a detailed flood risk study. This should concentrate on the present flood risk Environment Agency Total annual average damages associated with the Teville Ensure flood damages do not (to properties and agriculture) Stream catchment and Worthing Borough significantly increase in from fluvial flooding (£AAD). include obtaining LiDAR Flood risk study Council Worthing due to future change 2008 to 2011 High data, carrying out completed. (urban development and climate Estimated damages resulting topographical surveys, Arun District Council change). from surface water and creating models and groundwater flooding (£). undertaking a hydrological Adur District Council study. Options for restoring the channel should be considered including at Homefield and Teville Gate. Ensure that river channel and Balance of annual river channel flood defence maintenance and flood defence maintenance expenditure is appropriate to the Environment Agency expenditure (£) to annual average property economic damage in damages from fluvial flooding to urban areas from flooding. Continue with existing Worthing Borough property (£). Current level of level of maintenance, Council maintenance Ongoing Medium looking for efficiencies and maintained. improvements Arun District Council Protect and enhance the Ferring Habitat quality and species Adur District Council Rife and Meadows Site of Nature diversity. Conservation Importance.

Environment Agency 175 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 5 – Worthing Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Number of people and properties affected by the 1% annual probability fluvial flood event. Ensure the impact of flooding on

people and property does not The estimated number of significantly increase in Worthing properties affected by surface in the future. water and groundwater flooding.

Coverage of Flood Warning Service Continue to provide a Length of A road and railway Floodline Warnings Coverage of the line (km) affected by the 1% Direct service, including Floodline Warnings annual probability fluvial flood Environment Agency Ongoing High installation of a Flood Direct service greater event. Warning level gauge and than 77% service on the Teville Number of critical infrastructure Stream. Ensure the disruption caused by sites affected by the 1% annual flooding to transport and critical probability fluvial flood event. infrastructure does not increase in Worthing in the future. Number and period of recorded A road and railway closures due to surface water flooding.

Number of critical infrastructure sites recorded as being affected by surface water flooding.

Environment Agency Number of people and properties affected by the 1% Worthing Borough annual probability fluvial flood Continued practice and Ensure the impact of flooding on Attendance to Council event. development of the people and property does not emergency response Ongoing High emergency response significantly increase in Worthing planning sessions. Arun District Council The estimated number of plan. in the future. properties affected by surface Adur District Council water and groundwater flooding.

Environment Agency 176 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 5 – Worthing Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Sussex Police and Length of A road and railway other emergency line (km) affected by the 1% services. annual probability fluvial flood event.

Number of critical infrastructure Ensure the disruption caused by sites affected by the 1% annual flooding to transport and critical probability fluvial flood event. infrastructure does not increase in Worthing in the future. Number and period of recorded A road and railway closures due to surface water flooding.

Number of critical infrastructure sites recorded as being affected by surface water flooding.

Environment Agency 177 River Adur Catchment Flood Management Plan (September 2008)

Policy Unit 6 – Brighton and Hove Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Policy 3 – Continue with existing or alternative actions to manage flood risk at the current level (accepting that flood risk will increase over time from this baseline).

Ensure the impact of surface The estimated number of water and groundwater flooding properties affected by surface Strengthen development on properties does not water and groundwater flooding. control advice, significantly increase in Brighton including the use of and Hove in the future. SuDS, through Local Number and period of recorded Develop Framework Environment Agency A road and railway closures due policies to ensure no to surface water and increase in run-off from Deliver advice and Ensure the disruption caused by Brighton and Hove groundwater flooding. new developments and guidance to local Ongoing High flooding to transport and critical City Council seek opportunities to authorities. infrastructure does not increase in Number of critical infrastructure reduce current run-off Brighton and Hove in the future. Adur District Council sites recorded as being affected rates, where possible, to by surface water and groundwater ensure impact of flooding flooding. does not increase in the future due to Reduce the impact of muddy development. flooding in northern parts of The estimated number of Brighton and Hove, Rottingdean, properties affected by Downland Woodingdean, Ovingdean and ‘muddy’ surface water flooding. Bevendean. Ensure flood damages do not Develop an Integrated Estimated damages resulting Brighton and Hove significantly increase in Brighton Urban Drainage Strategy from surface water and City Council and Hove due to future change for Brighton and Hove with groundwater flooding (£). (urban development and climate a review of receiving Deliver an integrated Environment Agency change). watercourses/ catchments, urban drainage 2010 to 2015 High Reduce the impact of muddy foul and surface water strategy. The estimated number of Water companies flooding in northern parts of drainage and implications properties affected by Downland Brighton and Hove, Rottingdean, of climate change to be ‘muddy’ surface water flooding. Adur District Council Woodingdean, Ovingdean and considered. Bevendean. Undertake a study to Environment Agency Ensure the impact of surface investigate groundwater The estimated number of water and groundwater flooding flooding within the policy Brighton and Hove properties affected by surface Study completed. Ongoing Medium on properties does not unit and the possibility for City Council water and groundwater flooding. significantly increase in Brighton developing a flood and Hove in the future. warning system for Brighton University

Environment Agency 178 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 6 – Brighton and Hove Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) groundwater flooding Number and period of recorded within in the areas at risk Network Rail A road and railway closures due Ensure the disruption caused by of groundwater flooding. to surface water and flooding to transport and critical groundwater flooding. infrastructure does not increase

in Brighton and Hove in the Number of critical infrastructure future. sites recorded as being affected

by surface water and groundwater flooding. Environment Agency

Brighton and Hove Work with others to find Ensure that expenditure on Balance of emergency works City Council innovative solutions to Attendance to emergency surface water expenditure to estimated

improve and develop emergency response Ongoing High flooding works is appropriate to damages resulting from surface Adur District Council emergency response planning sessions. the estimated damages resulting water and groundwater flooding

plan. from surface water flooding. (£). Sussex Police and other emergency services.

Environment Agency 179 River Adur Catchment Flood Management Plan (September 2008)

Policy Unit 7 – Shoreham and Adur Estuary Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Policy 4 – Take further action to sustain current scale of flood risk into the future (responding to the potential increases in flood risk from urban development, land use change, and climate change). Number of people and properties affected by the 1% annual Strengthen development Ensure the impact of flooding on probability fluvial flood event. control advice, people and property does not

including the use of significantly increase in The estimated number of properties SuDS, through Local Shoreham in the future. affected by surface water and Develop Framework groundwater flooding. policies to ensure no increase in run-off from Length of A road and railway line new developments and Deliver advice and (km) affected by the 1% annual seek opportunities to guidance to local probability fluvial flood event. reduce current run-off authorities. Policies in Environment Agency rates, where possible, to Local Development Ongoing High Number of critical infrastructure ensure impact of flooding Framework include Adur District Council sites affected by the 1% annual Ensure the disruption caused by does not increase in the developer probability fluvial flood event. flooding to transport and critical future. contributions. infrastructure does not increase Number and period of recorded A Investigate how in Shoreham in the future. road and railway closures due to developer contributions surface water and groundwater can be used to help flooding. sustain the current scale of flood risk into the Number of critical infrastructure future. sites recorded as being affected by surface water and groundwater flooding. Develop an Integrated Urban Drainage Total annual average damages (to Strategy for Shoreham- Ensure flood damages do not Environment Agency properties and agriculture) from By-Sea with a review of significantly increase in Deliver an integrated fluvial flooding (£AAD). receiving watercourses/ Shoreham due to future change urban drainage Water companies 2009 to 2012 Medium catchments, foul and (urban development and climate strategy. Estimated damages resulting from surface water drainage, change). Adur District Council surface water and groundwater and implications of flooding (£). climate change to be considered.

Environment Agency 180 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 7 – Shoreham and Adur Estuary Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Total annual average damages (to Ensure flood damages do not properties and agriculture) from Undertake a study to significantly increase in fluvial flooding (£AAD). investigate the future Shoreham due to future change flood risks to Shoreham- (urban development and climate Estimated damages resulting from By-Sea as a result of change). surface water and groundwater predicted sea level rise Study completed. Environment Agency 2008 to 2012 High flooding (£). and the development of Ensure that river channel and Balance of annual river channel the Adur Tidal walls flood defence maintenance and flood defence maintenance scheme including barrier expenditure is appropriate to the expenditure (£) to annual average option. property economic damage in damages from fluvial flooding to urban areas from flooding. property (£).

Environment Agency Total annual average damages (to Work with others to find Ensure flood damages do not properties and agriculture) from innovative solutions to Attendance to significantly increase in Adur District Council fluvial flooding (£AAD). improve and develop emergency response Shoreham due to future change Ongoing High emergency response planning sessions. (urban development and climate Sussex Police and Estimated damages resulting from plan. change). other emergency surface water and groundwater

services. flooding (£). Total annual average damages (to Ensure flood damages do not properties and agriculture) from significantly increase in fluvial flooding (£AAD). Shoreham due to future change

Environment Agency (urban development and climate Estimated damages resulting from Coverage of the change). Increase the coverage of Adur District Council surface water and groundwater Floodline Warnings the Floodline Warnings Ongoing High flooding (£). Direct service Direct service Sussex Police and greater than 77% Ensure the impact of flooding on Number of people and properties other emergency services. people and property does not affected by the 1% annual significantly increase in probability fluvial flood event. Shoreham and Adur Estuary in the future. Coverage of Flood Warning Service

Environment Agency 181 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 7 – Shoreham and Adur Estuary Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Total annual average damages (to Ensure flood damages do not properties and agriculture) from increase in Shoreham due to fluvial flooding (£AAD). Assess the potential for future change (urban improving current development and climate Estimated damages resulting from defences, installation of SAMP including the change). surface water and groundwater demountable defences Shoreham and Adur Environment Agency Ongoing Medium flooding (£). and channel and flood Estuary defence management Ensure that river channel and Balance of annual river channel programmes as part of flood defence maintenance and flood defence maintenance the SAMP. expenditure is appropriate to the expenditure (£) to annual average property economic damage in damages from fluvial flooding to urban areas from flooding. property (£).

Environment Agency 182 River Adur Catchment Flood Management Plan (September 2008)

Policy Unit 8 – Adur Valley (north of A27 to south Steyning) Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Policy 6 – Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, which may constitute an overall flood risk reduction. Adur Tidal Strategy (for Opportunities for the Restore parts of the River Adur Length of naturally functioning entire tidal reach) to include creation of and floodplain to a naturally river (km). investigation of large-scale attenuation and Environment Agency 2008 to 2030 Medium functioning state where feasible flood attenuation and wetland identified downstream of Steyning and Area of naturally functioning wetland creation on the within the Adur Tidal 2 Upper Beeding. floodplain (km ). River Adur. Strategy. Environment Agency Increase the landscape character Landscape character assessment Set up working groups to value of the Sussex Downs National Farmers of the AONB, ESA and proposed explore the use of Agri- AONB and South Downs ESA Union National Park. Environment and and proposed National Park. Woodland Schemes Agri-Environment and Horsham District grants to help fund the Woodland Scheme Council 2008 to 2013 Low change of land use and land grants established. use management to Adur District Council Ensure flood damages do not Total annual average damages increase the water retention significantly increase along the (to properties and agriculture) in the catchment. Natural England Lower Adur corridor. from fluvial flooding (£AAD).

Defra Environment Agency

Increase the landscape character National Farmers Landscape character assessment value of the Sussex Downs Encourage and influence the Union of the AONB, ESA and proposed AONB and South Downs ESA uptake of Whole Farm National Park. and proposed National Park. Plans in the Adur Valley Whole Farm Plans set Horsham District catchment to provide advice up in the Adur Valley Council 2008 to 2013 Low on better land use practice catchment. with respect to run-off Adur District Council Ensure flood damages do not Total annual average damages generation. significantly increase along the (to properties and agriculture) Natural England Lower Adur corridor. from fluvial flooding (£AAD).

Landowners

Environment Agency 183 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 8 – Adur Valley (north of A27 to south Steyning) Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Work with the South Downs Joint Committee (merger of the Sussex Ensure flood damages do not Total annual average damages significantly increase along the Downs Conservation Board (to properties and agriculture) Lower Adur corridor. and the East Hampshire from fluvial flooding (£AAD). AONB Joint Advisory South Downs Join Committee) to achieve the Committee targets set in the Sussex Downs AONB Environment Agency Management Strategy to Sussex Downs AONB maximise the opportunities Management Strategy Horsham District 2008 to 2020 High for natural processes to implementation. Council reduce flooding through the Increase the landscape character adoption of wetland Adur District Council Landscape character assessment value of the Sussex Downs creation, whilst enhancing of the AONB, ESA and proposed AONB and South Downs ESA landscape character. Natural England National Park. and proposed National Park. Actions will reduce the risk of flooding in policy units 3 (Steyning and Upper Beeding) and 7 (Shoreham and Adur Estuary). Study to investigate the Increase the landscape character Landscape character assessment removal of Environment value of the Sussex Downs of the AONB, ESA and proposed Agency owned and Environment Agency AONB and South Downs ESA National Park. maintained structures and proposed National Park. (flood embankments) South Downs Join where additional storage Committee could reduce flood risk to Restore parts of the River Adur Steyning, Upper Beeding Study completed. Horsham District 2008 to 2020 Medium Length of naturally functioning and floodplain to a naturally and Shoreham-By-Sea, Council river (km). functioning state where feasible restore rivers and downstream of Steyning and floodplains to a naturally Adur District Council Area of naturally functioning Upper Beeding. 2 functioning state and floodplain (km ).

contribute to meeting Natural England Biodiversity Action Plan targets.

Environment Agency 184 River Adur Catchment Flood Management Plan (September 2008)

Policy Unit 9 – South Downs (East) Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Policy 6 – Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, which may constitute an overall flood risk reduction. Balance of annual river channel Environment Agency and flood defence maintenance expenditure (£) to annual average National Farmers damages from fluvial flooding to Union Set up working groups to agriculture (£). Ensure that river channel and explore the use of Agri- Mid Sussex District flood defence maintenance Environment and Flood damages downstream in Council expenditure is appropriate to the Woodland Schemes policy unit 6 (Brighton and Hove) agricultural economic damage grants to help fund the (£). Horsham District in rural areas from flooding. change of land use and Agri-Environment and Council Ongoing Medium land use management to Woodland Scheme The estimated number of

increase the water grants established. properties affected by Downland Adur District Council retention in the ‘muddy’ surface water flooding

catchment and reduce downstream in policy unit 6 Brighton and Hove the risk of flooding in (Brighton and Hove). City Council policy unit 6 (Brighton

and Hove). Increase the landscape character Lewes District Landscape character value of the Sussex Downs Council assessment of the AONB and AONB and South Downs proposed National Park. proposed National Park. Natural England

Environment Agency 185 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 9 – South Downs (East) Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s) Balance of annual river channel Environment Agency and flood defence maintenance expenditure (£) to annual average National Farmers damages from fluvial flooding to Union agriculture (£). Ensure that flood defence Horsham District Encourage and influence maintenance expenditure is Flood damages downstream in Council the uptake of Whole Farm appropriate to the agricultural policy unit 6 (Brighton and Hove)

Plans in the South Downs economic damage in rural areas (£). Mid Sussex District (East) catchment to from flooding. Whole Farm Plans set Council provide advice on better The estimated number of up in the South Downs 2008 to 2013 Low land use practice with properties affected by Downland (East) catchment. Brighton and Hove respect to run-off ‘muddy’ surface water flooding City Council generation and reduction downstream in policy unit 6

of flood risk in policy unit 6 (Brighton and Hove). Lewes District Council (Brighton and Hove).

Adur District Council Increase the landscape character Amount of disruption caused by value of the Sussex Downs Natural England soil erosion from surface water AONB and South Downs run-off. proposed National Park. Landowners

Environment Agency 186 River Adur Catchment Flood Management Plan (September 2008) Policy Unit 9 – South Downs (East) Action Success Criteria Lead Partners Timescale Priority Objective(s) Indicator(s)

Work with the South South Downs Join Downs Joint Committee Committee (merger of the Sussex

Downs Conservation Environment Agency Board and the East

Hampshire AONB Joint Ensure that river channel and Balance of annual river channel Horsham District Advisory Committee) to flood defence maintenance and flood defence maintenance Council achieve the targets set in expenditure is appropriate to the expenditure (£) to annual average 2008 to 2023 High the Sussex Downs agricultural economic damage damages from fluvial flooding to Adur District Council AONB Management Sussex Downs AONB in rural areas from flooding. agriculture (£).

Strategy to maximise the Management Strategy Mid Sussex District opportunities for natural implementation. Council processes to reduce

flooding through the Lewes District adoption of wetland Council creation, whilst

enhancing landscape Brighton and Hove character. Actions will City Council Increase the landscape character reduce the risk of Amount of disruption caused by value of the Sussex Downs flooding in policy unit 6 2008 to 2023 Medium soil erosion from surface water Natural England AONB and South Downs (Brighton and Hove). run-off. proposed National Park.

Horsham District Balance of annual river channel Council and flood defence maintenance expenditure (£) to annual Support the Adur District Council Ensure that river channel and average damages from fluvial recommendations Continue with the flood defence maintenance flooding to agriculture (£). implemented from the ‘Flood Defence Mid Sussex District expenditure is appropriate to the ‘Flood Defence Assessment of 2008 to 2013 Medium Council agricultural economic damage The estimated number of Assessment of Downland Downland Flooding’ in rural areas from flooding. properties affected by Downland Flooding’ (Binnie, Black recommendations. Lewes District Council ‘muddy’ surface water flooding and Veatch 2001). downstream in policy unit 6 Brighton and Hove (Brighton and Hove). City Council

Environment Agency 187 River Adur Catchment Flood Management Plan (September 2008) 7.2 Consequences of our policies

We selected policies for each policy unit based on a thorough understanding of the catchment and how it responds to flooding. Using this knowledge and the hydraulic models developed for this study, we have been able to determine what the future might look like.

We have modelled a set of ‘generic responses’, which represent how each policy might be implemented. The results of this modelling have given us a good indication of how the catchment will change and how flood risk may respond. Table 7.2 contains a summary of the expected consequences of the policy selected in each policy unit.

Table 7.2 - Summary of CFMP policy consequences Policy consequences Policy unit Policy Consequence of the selected policy This policy will reduce runoff from the largest part of the river Adur catchment which will help prevent increasing flood risk in Steyning and Upper Beeding. It will create more wetland habitat. It will be achieved primarily through changes to the way land is used and the river managed. Farming practices will have changed to reduce soil Policy unit 1 – Upper Adur 6 erosion and run-off. Land use changes will result in more floodplain being wet grassland of high value to wildlife. The rivers will be allowed to behave naturally with more frequent flooding of the floodplain and more natural features developing such as meanders. The additional storage of flood waters on the floodplain will reduce flood risk downstream. Implementing policy 4 will support the urban growth needed in this area. The implications of this are ultimately in the hands of the planning authorities. An important part of this policy will be working with the planning authorities to achieve sensible and sustainable Policy unit 2 – Burgess Hill 4 responses to flood risk, including the impact of surface water flooding. With the implementation of policy 4, urban growth will not cause an increase in flood risk. Flood risk in urban areas will increase due to climate change, The current flood risk management activities, carried out for the localised fluvial and surface water and urban drainage flooding problems are considered appropriate and acceptable for the level of risk. The current level of flood risk is low and is not expected to Policy unit 3 – Steyning and increase significantly. It is recognised that flood risk will change in 3 Upper Beeding the future, and management actions may change in time to gain efficiencies or improve effectiveness. The application of policy 6 to policy unit 1 will benefit policy unit 3, reducing the requirement for a significant improvements to existing flood defences and infrastructure. No impacts on environmental designations are expected. Flooding of urban areas caused by surface water run-off from agricultural land will be reduced in Findon and Worthing for example. This will be achieved by changes to land management Policy unit 4 – South Downs that will increase infiltration of rainfall on the land. More arable land 6 (West) will be converted back to grassland and less winter sown crops will be grown. In addition, schemes that increase storage of rainwater on the Downs will be implemented where necessary, such as the creation of low dams. Flood risk in urban areas will increase due to climate change. The current flood risk management activities, carried out for the localised fluvial and surface water and urban drainage flooding problems are considered appropriate and acceptable for the level Policy unit 5 – Worthing 3 of risk. The current level of flood risk is low and is not expected to increase significantly. It is recognised that flood risk will change in the future, and management actions may change in time to gain efficiencies or improve effectiveness. The application of policy 6 to policy unit 4 will benefit policy unit 5, reducing the requirement for a

Environment Agency 188 River Adur Catchment Flood Management Plan (September 2008) Policy consequences Policy unit Policy Consequence of the selected policy significant improvements to existing flood defences and infrastructure. Current studies and measures will be continued and alternative methods of management may be adopted. Due to the uncertainty regarding flood risk (particularly from groundwater) additional studies will be required to access the most effective and efficient Policy unit 6 – Brighton and Hove 3 mitigation measures. It is anticipated that there will be an increase in flood risk in Brighton and Hove. However, Brighton and Hove will benefit from changes in land management recommended in Policy Unit 9. With flood risk predicted to become a far more significant feature of this policy unit, policy 4 will support investigations to identify Policy unit 7 – Shoreham and 4 sustainable solutions to deal with increased flooding. Some Adur estuary additional investment and innovative solutions may be needed to continue to defend key areas. Policy 6 in the River Adur catchment between Steyning and Shoreham will require a more detailed study to investigate the feasibility of re-connecting the river to the floodplain and to design a Policy unit 8 – Adur valley (north system that will maximise flood reduction and improve habitats and 6 of A27 to south of Steyning) biodiversity. The consequence of this may be a very different landscape to the present one, with increased areas of wetland and some very different, but more sustainable and still valuable, habitats created. Flooding of urban areas caused by surface water run-off from the steep slopes of the downs will be reduced in Brighton and Hove. This will be achieved by changes to land management that will Policy unit 9 – South Downs increase infiltration of rainfall on the land. More arable land will be 6 (East) converted back to grassland and less winter sown crops will be grown. In addition, schemes that increase storage of rainwater on the Downs will be implemented where necessary, such as the creation of low dams.

7.3 Monitoring, review and evaluation

We will be responsible, together with others from the steering group and consultation group, for implementing this CFMP. We need to continue to review and monitor it to help us:

• manage how we implement the CFMP; • check that the CFMP is being implemented as it should; • check that the policies and actions of the CFMP are being implemented.

As CFMP sponsor, the Area Flood Risk Manager consulted with others when finalising this CFMP document to set a timetable for implementing CFMP actions. The Regional Strategic Planning Team will manage the implementation and help involve both internal and external groups. A steering group would help with this, meeting regularly (twice a year) to guide, review and act on the monitoring process and its results.

We need to record progress and performance. We will evaluate how CFMP policies are applied and will ensure that we consider them alongside SMP policies. We will update and expand CFMP data to make sure we have the most up to date information available. We will look at new planning and modelling tools, the effects of recent significant flood events, catchment development and improved understanding of climate change or changes in national policy guidance.

The CFMP will be a ‘living document’ that develops as we understand more about flood risk.

Environment Agency 189 River Adur Catchment Flood Management Plan (September 2008) We will use clear measures to monitor how the CFMP is performing and we will produce regular progress reports. Targets and indicators are set for each of the catchment objectives used for the policy appraisal, and are listed in table 5.2. These will be the main measures of how successful we are in achieving efficient and effective flood risk management within the CFMP area.

We are likely to carry out a formal review of this CFMP in approximately six years time, or if we need to reflect significant changes in flood risk, or to inform or influence other plans, such as the Water Framework Directive River Basin Management Plans. As part of the CFMP review process, we will review the modeling techniques undertaken, particularly as understanding of sea level rise and land use changes improves.

Environment Agency 190 River Adur Catchment Flood Management Plan (September 2008) Glossary of terms

— A — Agricultural Land Classification (ALC) The system used by Defra of grading farmland according to the degree to which its physical characteristics impose long-term limitations on agricultural use. It helps to enable informed choices to be made about its future use within the planning system. Land is graded from 1 (excellent) to 5 (very poor).

Annual Average Damage Costs This is a statistical value which takes into account all the flood damages that would occur over a very long period of time and expresses that damages as an average over one year. We can use this standardised measure of flood damage to assess change within a given location, or make comparisons between different areas.

Annual Average Rainfall The sum of total annual rainfall for a location averaged over the number of years of data summed.

Annual Probability Flood Event This is the statistical chance of a flood event occurring in any one year. The chance is stated as a percentage, for example, 1% annual probability flood event means that there is a 100 to 1 chance of this magnitude of flood event happening in any one year.

Appraisal Defining objectives, examining options and evaluating costs, benefits, risks, opportunities and uncertainties before a decision is made.

Area of Outstanding Natural Beauty (AONB) Areas designated under the National Parks and Access to the Countryside Act 1949 as being of high scenic quality. Development in AONBs is controlled by local planning authorities and is generally given a higher level of control than surrounding areas. AONBs also have ‘management plans’ for the purpose of enhancing natural beauty.

Environment Agency 191 River Adur Catchment Flood Management Plan (September 2008) Attenuation This is the process of holding some water back within the catchment during a flood event. This has the effect of slowing down the rate of drainage from the catchment and it also reduces peak flows downstream.

— B — Biodiversity Action Plan (BAP, UKBAP, LBAP)) An agreed plan for any habitat or species, arising from the UN Biodiversity Convention, that forms part of the UK’s commitment to biodiversity, BAPs are statutory documents. They include UK and local plans (UKBAP and LBAP respectively).

Birds Directive European Community Directive (79/409/EEC) on the conservation of wild birds, which provides for Special Protection Areas (SPAs). Statutory protection for SPAs is given under the Conservation (Natural Habitats, etc.) Regulations (1994).

— C — Capital plan The Environment Agency’s short, medium and long-term programme for capital engineering schemes over the next 3 – 10 years.

Catchment The area drained by a particular river. A surface water catchment is the area defined by the highest boundary between two catchments, whilst a groundwater catchment is the area that contributes to the groundwater part of the river flow.

Catchment Abstraction Management Strategy (CAMS) Environment Agency strategy document outlining the availability and pressures on water resources in a catchment.

Catchment Flood Management Plan (CFMP) A catchment-wide strategic planning framework for the integrated management of flood risks to people and the developed and natural environment in a sustainable way.

Catchment policies The outputs of the CFMP, which are the agreed policies for flood risk management within a defined area called a policy unit. Environment Agency 192 River Adur Catchment Flood Management Plan (September 2008)

Common Agricultural Policy (CAP) The CAP is a system of EU agricultural subsidies and programmes. The subsidies guarantee a minimum price to producers by direct payment of a subsidy for crops planted. Reforms of the system are currently underway, including a new Single Payment Scheme for direct farm payments that is being introduced into the UK.

Communication plan The plan setting out the CFMP consultation programme, as well as specific arrangements for internal (Environment Agency) and external consultation.

Conservation Areas These are areas, usually in towns and villages, where the character of buildings and other public spaces is of “special architectural or historical interest”. These areas are defined by the local planning authorities and have different development controls to open countryside and built up areas not under this definition.

Consultation group A group of people whom we consult and who have an interest in the development of the CFMP and its final policies.

Conveyance Conveyance is a measure of how well a channel or structure, such as a bridge or culvert, allows water to pass through. It depend on the physical characteristics of the channel or structure, including its size, shape, how rough its surface is, and how twisty it is.

Countryside Character Areas Non-statutory sub-divisions of England, as defined under the Countryside Agency’s Countryside Character Initiative which have a similar countryside character and specific ecological and landscape issues. There are 159 Character Areas in England.

Countryside and Rights of Way (CRoW) Act 2000 Primary legislation which came into force on 30 January 2001 and provides extra protection and management procedures for nature conservation sites and landscape designations. Also introduces provisions for access to the countryside.

Environment Agency 193 River Adur Catchment Flood Management Plan (September 2008) — D — Defra The Department for Environment, Food and Rural Affairs has responsibilities for the development of flood risk management in the UK and funding of environmental, agricultural and flood risk management programmes.

— E — English Heritage English Heritage is the Government’s statutory advisor on the historic environment. Further information can be found on English Heritage’s website: http://www.english-heritage.org.uk

Environment Agency Non-departmental public body responsible for implementing government policy relating to the environment and flood risk management in England and Wales.

Environment Impact Assessment (EIA) Identifies and assesses the likely effects and significance of a project or development on the environment. EIAs are statutory for many developments that could have an adverse effect on the environment and for any plan affecting a European designated site for conservation.

Environmentally Sensitive Areas (ESA) ESA schemes were introduced by the Ministry of Agriculture, Fisheries and Food (MAFF; predecessor to Defra) in 1987. They are governed by Defra and offer incentives to encourage farmers to adopt agricultural practices, which protect and enhance parts of the country of particularly high landscape, wildlife of historic value.

Environmental Stewardship Scheme (ESS) ESS is a new agri-environmental scheme, launched in March 2005, which provides funding to farmers and other land managers in England who manage their land in a way that benefits the environment. The scheme is intended to build on the recognised success of the ESA and Countryside Stewardship schemes.

— F — Flood Alleviation Scheme (FAS) A scheme designed to reduce the risk of flooding in a specific location.

Environment Agency 194 River Adur Catchment Flood Management Plan (September 2008) Flood damages Flood damages are worked out from the estimated flood depth and extent data obtained from hydraulic modelling. By combining information on the type and value of properties within the modelled flood outline, it is possible to calculate the overall damage flooding would cause. Flood damage figures can be given for a range of magnitudes of flood event, for example, the 1% annual probability flood event.

Flood defence A structure (or system of structures) to reduce flooding from rivers or the sea.

Flood Estimation Handbook (FEH) Flood Estimation Handbook provides the current ways of estimating flood flows for the UK.

Floodplain Any area of land over which water flows or would flow if there were no flood defences. Can also be an area where water is stored during a flood event.

Flood risk The level of flood risk is the product of the frequency or likelihood of the flood events and their consequences (such as loss, damage, harm, distress and disruption).

Flood Risk Assessment (FRA) An assessment that is undertaken for a specific area or proposed development to identify potential sources of flooding and the associated risks. A flood risk assessment is required for development proposals in accordance with PPS25.

Flood risk management Changing the frequency or consequences of flooding to an appropriate level, and monitoring to make sure that flood risk remains at this level.

Flood risk management measures Interventions that modify flooding and flood risk either by changing the frequency of flooding, or by changing the extent and consequences of flooding, or by reducing the vulnerability of these exposed to flood risks.

Flood Risk Management Plans (FRMPs)

Environment Agency 195 River Adur Catchment Flood Management Plan (September 2008) The purpose of the flood risk management plans is to identify means of reducing the impacts of flooding in the study area.

Flood risk maps Maps developed by the Environment Agency for the estimated extent of the floodplain with a 1% risk of fluvial flooding and/or a 0.5% risk of tidal inundation. Defended areas are also shown. These maps are sometimes referred to as Section 105 maps, Flood Zone Maps or Indicative Flood Maps.

Flood Zone The area identified on the Environment Agency flood risk maps that could be affected by flooding, either from rivers or the sea, if there were no flood defences, for the specific annual probability event.

Fluvial The activity of rivers resulting from inflows of rainfall and surface and groundwater, and including the influence of stream gradient and sinuosity, which together control the volume and flow of water.

Freshwater Fisheries Directive Designation An EC Directive (78/659/EEC) aiming to protect and improve water quality and forming part of our water quality monitoring programme. The Directive sets standards to protect freshwater fisheries, mainly relating to the quality of the water, and requires certain designated stretches of water to meet these standards in order so that fish can live or breed.

— G — Geographical Information System (GIS) A GIS is a computer-based system for capturing, storing, checking, integrating, manipulating, analysing and displaying data that are spatially referenced.

Geomorphology The physical processes that create sediment erosion and deposition and which define the shape of a river and its floodplain.

General quality assessments

Environment Agency 196 River Adur Catchment Flood Management Plan (September 2008) The general quality assessment scheme is used to classify river quality. Biological and chemical assessment can be made of the changes in quality over time and of the varying quality at different locations in England and Wales.

Groundwater Water occurring below ground surface in natural formations (typically rocks, gravels and sands).

— H — Habitats Directive The EC Directive (92/43/EEC) establishing a system of protection for certain fauna, flora and habitats of European conservation importance. The 24 articles of the Directive include a range of measures for the conservation of features in the landscape that are important for wildlife and for the protection of species listed in the Annexes. The Directive provides for the designation and protection of Special Areas of Conservation (SACs). These SACs, with Special Protection Areas (SPAs), classified under the Birds Directive, are known as the Natura 2000 network.

Historic Environment Records (HER’s) In England, the prime sources of information on recorded historic environment assets will be the local authority Historic Environment Records (HER) or Sites and Monuments Records (SMR) and the National Monuments Records (NMR). SMRs contain information about all known archaeological remains, whilst HERs (which most local authority SMRs are changing to) aim to provide information on all known historic environment assets. A list of HERs can be found on the Heritage Gateway website: http://www.heritagegateway.org.uk/Gateway/CHR/

Historic environment Encompassing all elements of designated or un-designated archaeological sites, historic buildings and historic landscapes. It also includes sites of palaeoenvironmental interest that provide information about the nature of past landscapes, climate and environments.

Hydraulic model A computer simulation used to estimate the water level in a river or river system for a given flow.

Hydrological model

Environment Agency 197 River Adur Catchment Flood Management Plan (September 2008) A method of estimating the flow in a river or catchment arising from rainfall falling into the catchment. Models typically account for factors such as catchment area, topography, soils, geology and land use.

— I — Inception report Provides a detailed description of the work carried out during the CFMP inception phase. This includes a summary of catchment data collection and early understanding of the main issues to be considered for effective flood risk management during subsequent phases of the CFMP process.

Internal drainage boards (IDB) Independent bodies that manage land drainage in areas that need special drainage. There are some 200 boards in England, concentrated in the lowland areas of East Anglia, Somerset, Yorkshire and Lincolnshire. Each board operates within a defined area where they have power under the Land Drainage Act 1991 to carry out flood defence works on watercourses that are not designated as “main rivers”. Members of the internal drainage board include elected members that represent people occupying the land in the district and members nominated by local authorities to represent other interests.

Indicative standard of protection The range of level of protection to be considered for flood defences, based on the use of the land being protected. They do not represent any entitlement to protection or minimum level to be achieved.

— L — Land use How an area of land is used (for example, residential, agriculture, forestry, etc.). The term ‘land use’ is used in many contexts and is controlled by the town and country planning system.

Land management A scheme, plan or other project deliberately using particular practices to affect the character, quality or value of an area. Land management is subject to UK legislation and may require authorisation from a competent authority (for example Natural England) or, where it results in a change in land use, may require planning permission.

Landscape Character Areas (LCAs) Environment Agency 198 River Adur Catchment Flood Management Plan (September 2008) Landscape Character Areas are developed by the Countryside Agency under the Countryside Character Initiative, and have a strong social, historical and cultural element. The Countryside Character Initiative is a programme of information and advice on the character of the English countryside. It includes systematic descriptions of the features and characteristics that make the landscape, and guidance documents on how to carry out Landscape Character Assessments.

Listed buildings English Heritage is the national body responsible for identifying and protecting historic buildings and for compiling registers of ‘listed’ historic buildings. There are three grades of listed buildings: Grade I buildings are those of exceptional interest; Grade II* buildings are particularly important buildings of more than special interest; and Grade II buildings are of special interest, warranting every effort to preserve them. The process of listing is covered by legislation within The Town and Country Planning Act 1990 and the Planning (Listed Buildings and Conservation Areas) Act 1990. Other authorities (including us) must consider the importance of these buildings.

Local authority development plans These statutory land development plans generally cover a 10-year period from the date they are adopted however, the local authorities currently review these plans every five years. A district council and a unitary authority will produce a local plan and a county council will produce a structure plan. A structure plan guides the local plans of several district councils.

Local Biodiversity Action Plan (LBAP) A local agenda (produced by the local authority) with plans and targets to protect and enhance biodiversity and achieve sustainable development.

Local Development Framework (LDF) The new planning system that has been designed to streamline the local planning process and promote a proactive, positive approach to managing development. A Local Development Framework is a ‘folder’ of Local Development Documents that outlines how planning will be managed in the specified area.

Local Environment Agency Plan (LEAP) An Environment Agency non-statutory plan based on the river basin (or sub-catchments or groups of smaller catchments) providing environmental baseline information and

Environment Agency 199 River Adur Catchment Flood Management Plan (September 2008) actions/objectives for that river basin (these replace the National Rivers Authority’s Catchment Management Plans).

Local Nature Reserve (LNR) Local Nature Reserves are designated under the National Parks and Access to the Countryside Act 1949 by local authorities (which must have some legal control over the site) in consultation with English Nature for their locally important wildlife or geological features. They are generally intended for education and amenity as well as conservation.

Local Planning Authority (LPA) The local authority or council that is empowered by law to exercise planning functions for a particular area of the UK. The authority is often a Borough or District Council, but National Park Authorities are also considered to be local planning authorities.

— M — Main River Watercourses defined on a ‘main river map’ designated by Defra. We have powers to carry out flood defence works, maintenance and operational activities for main rivers only. Responsibility for maintenance however, rests with the riparian owner (the land owner).

Making Space for Water Defra’s strategy for flood and coastal erosion risk management, published in 2005.

Modelling and decision support framework (MDSF) A GIS based decision support tool developed specifically to help the CFMP process by automating parts of the analysis.

— N — National Nature Reserve (NNR) National Nature Reserves are designated under the National Parks and Access to the Countryside Act 1949 or the Wildlife and Countryside Act 1981 (as amended) mainly for nature conservation, but can also include sites with special geological or physical features. They were set up to protect the most important areas of wildlife habitat and geological formations in Britain, and as places for scientific research. They are usually owned or leased by English Nature, or managed in accordance with a Nature Reserve Agreement with the landowner or occupier. Environment Agency 200 River Adur Catchment Flood Management Plan (September 2008)

National Parks The National Park Authority's duties and powers are derived from a number of Acts of Parliament and statements of Government Policy, most recently the Environment Act 1995. The statutory purposes of National Parks are: 1) to conserve and enhance the natural beauty, wildlife and cultural heritage of the area and 2) to promote opportunities for the understanding and enjoyment of the area's special qualities by the public. National Park Authorities also have a duty to encourage the economic and social well being of the communities within the National Park.

Natural area profiles Natural Areas are developed by English Nature, each with specific wildlife and natural features. There are 120 Natural Areas in England and each has a unique identity due to the interaction of wildlife, landforms, geology, land use and human impact.

Natural England Formed by bringing together English Nature, the landscape, access and recreation elements of the Countryside Agency and the environmental land management functions of the Rural Development Service, Natural England works towards the delivery of four strategic outcomes, which together deliver on the purpose to conserve, enhance and manage the natural environment for the benefit of current and future generations.

Non-main river Non-main rivers are all watercourses not designated as Main Rivers (see above). The local authority or internal drainage board has permissive powers to maintain but as for Main Rivers, responsibilities to do so rest with the riparian owner.

— P — Planning and Compulsory Purchase Act (2004) Legislation promoted by the Office of the Deputy Prime Minister, which substantially reformed the town planning and compulsory purchase framework in Great Britain. It amended and recalled significant parts of the existing planning and compulsory purchase legislation and introduced reforms such as the abolition of Local Plans and Structure Plans, and their replacements with Local Development Frameworks.

Planning Policy Statement 25: Development and Flood Risk (PPS25) (replaced Planning Policy Guidance Note 25: Development and Flood Risk (PPG25)) Environment Agency 201 River Adur Catchment Flood Management Plan (September 2008) Planning Policy Guidance Notes (PPGs), and their replacements Planning Policy Statements (PPSs), have been prepared by the Government to explain statutory provisions and provide guidance to local authorities and others on planning policy and the operation of the planning system. Local authorities must take their contents into account in preparing their development plans.

Priority action Urgent work that is a priority (for example urgent repairs or stand-alone improvements that should be carried out immediately and not wait until the CFMP process has been completed).

Probability of occurrence The probability of a flood event being met or exceeded in any one year (usually expressed as a return period – for example 1% annual probability).

Project board The project board oversees the production of the CFMP, and is made up of Environment Agency staff together with staff from other operating authorities or interested groups.

— R — Ramsar Site Site identified or meeting criteria set out in The RAMSAR Convention on Wetlands of International Importance. This definition has no legal status, but such sites are designated as SSSIs under the Wildlife and Countryside Act 1981 (as amended).

Receptor The thing that is affected by (receives) flooding. Receptors can be environmental (for example SSSI), social (for example people or public transport) or economic (for example property or agricultural land).

Regional flood defence committee capital investment programme Details of proposed flood defence schemes and planned improvements within the catchment.

Regional planning guidance (RPG) Planning Guidance issued by the Government Office for the region. RPGs are to be replaced by statutory Regional Spatial Strategies.

Registered battlefields Environment Agency 202 River Adur Catchment Flood Management Plan (September 2008) English Heritage maintains a register of historic battlefields. The Register offers them protection and promotes a better understanding of their significance. Each Register entry is based on the available evidence and includes a map of the battlefield area showing the position of the armies and features that were part of the original battleground. The maps are the starting point for battlefield conservation and interpretation because they identify the most visually sensitive areas.

Registered historic parks and gardens English Heritage maintains a register of parks and gardens of special historic interest in England. The register seeks to ensure that the features and qualities that make these landscapes of national importance are safeguarded but does not give extra protection.

Risk assessment Considering the risks inherent in a project, leading to the development of actions to control, mitigate or accept the risks.

Regional Spatial Strategy (RSS) This is a strategy for how a region should look in 15 to 20 years time and possibly longer. The Regional Spatial Strategy identifies the scale and distribution of new housing in the region, indicates areas for regeneration, expansion or sub-regional planning and specifies priorities for the environment, transport, infrastructure, economic development, agriculture, minerals and waste treatment and disposal. Most former Regional Planning Guidance is now considered RSS and forms part of the development plan. Regional Spatial Strategies are prepared by Regional Planning Bodies.

Riparian Land or habitat connected with, or immediately next to, the banks of a river or stream.

River Basin Management Plans (RBMPs) A management plan required to be prepared for each River Basin District within the European Union by the Water Framework Directive to be that sets out the management for that district.

— S — Scenario A possible future situation, which can influence either catchment flood processes or flood responses. Scenarios are usually made up of the following: urban development (both in the

Environment Agency 203 River Adur Catchment Flood Management Plan (September 2008) catchment and river corridor); change in land use and land management practice (including future environmental designations); or climate change.

Scheduled monuments (SM), Scheduled ancient monuments (SAM) To protect archaeological sites for future generations, the most significant of them may be “scheduled”. Scheduling is the process through which nationally important sites and monuments are given legal protection by being placed on a list, or ‘schedule’. English Heritage identifies sites in England, which should be placed on the schedule by the Secretary of State for Culture, Media and Sport. The current legislation, the Ancient Monuments and Archaeological Areas Act 1979, supports a formal system of Scheduled Monument Consent for any work affecting a designated monument.

Section 105 The Section of the Water Resources Act under which Floodplain Mapping is carried out. Level A was the initial Section 105 modelling, whilst level B modelling has been undertaken to look at key areas in more detail.

Shoreline Management Plan (SMP) Non-statutory plans to provide sustainable coastal defence policies (to prevent erosion by the sea and flooding of low-lying coastal land), and to set objectives for managing the shoreline in the future. They are prepared by us or maritime local authorities, acting individually or as part of coastal defence groups.

Site of National Conservation Interest (SNCI) SNCIs are designated at a local level by being included in local or unitary development plans for their regional or local conservation interest. They are usually adopted by Local Authorities for planning but have no statutory protection.

Site of Special Scientific Interest (SSSI) Sites notified under the Wildlife and Countryside Act 1981 (as amended) and the Countryside and Rights of Way (CRoW) Act 2000 for their flora, fauna, geological or physical features. Notification of a SSSI includes a list of activities that may be harmful to the special interest of the site. The Wildlife and Countryside Act 1981 (as amended) provides significantly enhanced protection for SSSIs. All cSACs, SPAs and Ramsar sites are designated as SSSIs.

Environment Agency 204 River Adur Catchment Flood Management Plan (September 2008) South East England Regional Assembly (SEERA) An assembly of 112 members, including elected councillors nominated by the region's local authorities to be a representative ‘voice’ of the region.

South East Plan A new planning document submitted to the Government in March 2006 that sets out a vision for the future of the South East region to 2026, outlining how to respond to challenges facing the region such as housing, the economy, transport and protecting the environment. The aim is to ensure that the South East remains economically successful and an attractive place to live for future generations.

Special Area for Conservation (SAC) and candidate Special Area for Conservation (cSAC) An internationally important site for habitats and/or species, designated as required under the EC Habitats Directive. A cSAC is a candidate site, but has the same status as if it were a confirmed site. SACs are protected for their internationally important habitat and non-bird species. They also receive SSSI designation under The Countryside and Rights of Way (CRoW) Act 2000; and The Wildlife and Countryside Act 1981 (as amended).

Special Protection Area (SPA) A site of international importance for birds, designated as required by the EC Birds Directive. SPAs are designated for their international importance as breeding, feeding and roosting habitat for bird species. The Government must consider the conservation of SPAs in all its planning decisions. SPAs receive SSSI designation under The Countryside and Rights of Way (CRoW) Act 2000 and The Wildlife and Countryside Act 1981 (as amended).

Strategy plan A long-term (usually 50 years or more) plan for managing rivers or coasts. It includes all the work needed to meet flood and coastal defence objectives for the target area. A strategy plan is more detailed and usually covers a smaller area than a CFMP.

Strategic Environmental Assessment (SEA) Strategic Environmental Assessment systematically appraises the potential effects of high level decision-making, such as policies, plans, strategies and programmes, on the environment, before they are approved, to help promote sustainable development. The SEA Directive (2001/42/EC) is implemented in England through the Environmental Assessment of Plans and Programmes Regulation (SI 1633 2004). Under these regulations, SEA is not a statutory Environment Agency 205 River Adur Catchment Flood Management Plan (September 2008) requirement for CFMPs, however, as Environment Agency best practice and under Defra advice, we are applying SEAs when we develop CFMPs.

Structure plan A structure plan is part of the development plan, prepared by county councils or a combination of unitary authorities, containing strategic policies that cover key planning issues over the area and provide a framework for local planning, including Unitary Development Plans (UDPs). To be replaced under the new planning system with local development frameworks (which comprise all sub-regional plans).

Sub-catchment Either a smaller catchment within a larger one (that is the area drained by a tributary of the main catchment), or an area of the catchment identified for the purpose of the CFMP process.

Surface water Any water body that is not groundwater (for example rivers, estuaries, ponds, etc.) as well as temporary waters caused by flooding, urban run-off, etc.

Sustainability A broad concept which deals with man’s effect on society, the economy and the environment. It aims to achieve an efficient, effective solution to development which does not have undue costs or impacts in the present or the future. As an operational objective in planning and development it involves, inter alia, taking account of future changes. There is no comprehensive statutory definition of sustainability, although it is a duty of many Government bodies (including the Environment Agency).

Sustainable drainage systems (SuDs) A sequence of management practices and control structures designed to minimise the impact of surface water on flood risk and the environment. Techniques include the use of porous materials and soak-away systems to increase the time taken for water to enter the river network.

— T — Telemetry The means by which a data signal is transferred to a remote control centre via the telephone network.

Environment Agency 206 River Adur Catchment Flood Management Plan (September 2008) — U — Unitary Development Plan (UDP) A statutory plan produced by unitary authorities, comprising part of the Development Plan and written in two parts: Part I – a written statement which contains the authority’s general policies for their area; Part II – both a written statement and an ordnance plan, describing the policies in detail and illustrating them on a geographical basis. A UDP replaces local plans within unitary authorities.

— V — Velocity (water) The speed at which water is flowing, usually measured in metres per second.

— W — Water Framework Directive (WFD) European Community Directive (2000/60/EC) on integrated river basin management. The WFD sets out environmental objectives for water status based on: ecological and chemical parameters; common monitoring and assessment strategies; arrangements for river basin administration and planning; and a programme of measures in order to meet the objectives.

Water Level Management Plan (WLMP) A programme designed to control the level and distribution of surface and groundwater in a designated area (usually for a SSSI or other Conservation site).

Wildlife and Countryside Act 1981 (as amended) The principle mechanism for the legislative protection for wildlife in Great Britain. This legislation is the means by which the EC Habitats Directive and EC Birds Directive are implemented in Britain.

Environment Agency 207 River Adur Catchment Flood Management Plan (September 2008) List of abbreviations

— A — AAD Annual Average Damage ALC Agricultural Land Classification AOD Above Ordnance Datum AONB Area of Outstanding Natural Beauty

— B — BAP Biodiversity Action Plan

— C — CAMS Catchment Abstraction Management Strategy CAP Common Agricultural Policy CFMP Catchment Flood Management Plan COWs Critical Ordinary Watercourses

— D — Defra Department for Environment, Food and Rural Affairs

— E — EH English Heritage ESA Environmentally Sensitive Area EU European Union Environment Agency 208 River Adur Catchment Flood Management Plan (September 2008)

— F — FEH Flood Estimation Handbook FFD Freshwater Fisheries Directive FRMP Flood Risk Management Plan

— G — GQA General Quality Assessment

— I — IDB Internal Drainage Board

— L — LBAP Local Biodiversity Action Plan LCA Landscape Character Area LDF Local Development Framework LEAP Local Environment Agency Plan LNR Local Nature Reserve LPA Local Planning Authority

— M — MAFF Ministry of Agriculture, Fisheries and Food MDSF Modelling and Decision Support Framework

Environment Agency 209 River Adur Catchment Flood Management Plan (September 2008) — N — NFCDD National Flood and Coastal Defence Database NNR National Nature Reserve NRA National Rivers Authority NSRI National Soil Resources Institute

— O — ODPM Office of the Deputy Prime Minister

— P — PAG Project Appraisal Guidance PPG Planning Policy Guidance notes PPS Planning Policy Statement

— R — RE River Ecosystem RPG Regional Planning Guidance RSS Regional Spatial Strategy

— S — SAC Special Area of Conservation SEA Strategic Environmental Assessment SEERA South East England Regional Assembly Environment Agency 210 River Adur Catchment Flood Management Plan (September 2008) SFVI Social Flood Vulnerability Index SM Scheduled Monument SMP Shoreline Management Plan SNCI Site of Nature Conservation Interest SPA Special Protection Area SPARQ Spatial Pressures Analysis of River Quality SSSI Site of Special Scientific Interest SUDS Sustainable Drainage Systems

— U — UDP Unitary Development Plan UKBAP UK Biodiversity Action Plan

— W —

WFD Water Framework Directive WLMP Water Level Management Plan

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