Wealden District Council Strategic Flood Risk Assessment Level 1: Final Report
March 2009
Prepared for:
Wealden District Council Level 1 SFRA: Final Report
Revision Schedule
Wealden District Council Strategic Flood Risk Assessment
Rev Date Details Prepared by Reviewed by Approved by
01 01/08/08 WDC Draft Helen Judd Stephen Riley Peter Mansell Level 1 SFRA Assistant Hydrologist Senior Consultant Associate Engineer
02 06/03/09 Following review Helen Judd Jon Robinson Jon Robinson by EA and WDC Assistant Hydrologist Associate Director Associate Director
Scott Wilson Ltd Scott House This document has been prepared for the titled project or named Alençon Link part thereof and should not be relied upon or used for any other project without an independent check being carried out as to its Basingstoke suitability and prior written authority of Scott Wilson being obtained. Hampshire Scott Wilson accepts no responsibility or liability for the RG21 7PP consequence of this document being used for a purpose other than the purposes for which it was commissioned. Any person using or relying on the document for such other purpose agrees, and will by Tel. 01256 310200 such use or reliance be taken to confirm his agreement to Fax. 01256 310201 indemnify Scott Wilson for all loss or damage resulting there from. Scott Wilson accepts no responsibility or liability for this document to any party other than the person by whom it was commissioned. www.scottwilson.com
ERRATA
The Wealden District Council Level 1 Strategic Flood Risk Assessment (SFRA) contains a reference to the circumstances when a Flood Risk Assessment is required, which exceed the guidance contained in Planning Policy Statement 25: Development and Flood Risk. Wealden District Council therefore amend the text of the SFRA as follows:
Paragraph 3.3.2 (page 19)
3. Flood Risk Assessments are required for all development proposals of 1 hectare or greater in Flood Zone 1.
27th March 2009
Wealden District Council Level 1 SFRA: Final Report
Table of Contents
Abbreviations...... 1
Glossary ...... 2
1 Introduction...... 4 1.1 Wealden District Council SFRA...... 4 1.2 The Aim of the WDC SFRA...... 4 1.3 Wealden District Council Level 1 SFRA Objectives ...... 5 1.4 Wealden District Council SFRA Structure ...... 5
2 Wealden District Council SFRA Study Area...... 8 2.1 Wealden District Study Area Characteristics...... 8 2.2 Flood Sources ...... 9
3 Policy Context ...... 14 3.1 Role and Responsibilities ...... 14 3.2 European Policies ...... 17 3.3 National Policies...... 17 3.4 Regional Policies...... 19 3.5 Local Policies ...... 22 3.6 Environment Agency Policies...... 24 3.7 Other Relevant Policies...... 30 3.8 Forthcoming Policies ...... 34
4 Data Collection and Review ...... 36 4.1 Overview ...... 36 4.2 Environment Agency Flood Zone Maps ...... 37 4.3 Fluvial Data ...... 37 4.4 Hydraulic Modelling ...... 38 4.5 Historical Flooding Events...... 42 4.6 Overland Flow ...... 47 4.7 Groundwater...... 47 4.8 Drainage/Sewer Flooding...... 50 4.9 Artificial Sources...... 50 4.10 Current Flood Risk Management Practices...... 51
D118200 March 2009
i Wealden District Council Level 1 SFRA: Final Report
5 Assessing Flood Risk from all Sources ...... 56 5.1 Requirements of PPS25ii ...... 56 5.2 Fluvial Flooding ...... 57 5.3 Drainage/Sewer Flooding...... 60 5.4 Overland Flow ...... 61 5.5 Groundwater Flooding...... 61 5.6 Artificial Sources (large-raised reservoirs)...... 62 5.7 Artificial Sources (other) ...... 63
6 Guidance on Applying the PPS25 Sequential Test ...... 66 6.1 What is the Sequential Test? ...... 66 6.2 How should the SFRA be used to apply the Sequential Test?...... 68 6.3 Additional Guidance ...... 70
7 Guidance on Applying the PPS25 Exception Test ...... 72 7.1 What is the Exception Test?...... 72 7.2 Why is there an Exception Test?...... 72 7.3 What is Required to Pass the Exception Test? ...... 72
8 Site Specific Flood Risk Assessment Guidance...... 75 8.1 When are Flood Risk Assessments Required?...... 76 8.2 FRA Requirements...... 76 8.3 Flood Risk Assessment Guidance Table ...... 78
9 Drainage of Development Sites...... 87 9.1 Background ...... 87 9.2 What are SuDS? ...... 87 9.3 Achieving SuDS in Developments...... 88 9.4 Drainage Strategy Requirements ...... 88 9.5 SuDS Techniques ...... 89 9.6 SuDS Design...... 91 9.7 Where can SuDS be utilised? ...... 91 9.8 SuDS Policies...... 94
10 Future Flood Risk Management Practices ...... 98 10.1 Strategic Flood Defences ...... 98 10.2 Flood Warning ...... 98
D118200 March 2009
ii Wealden District Council Level 1 SFRA: Final Report
10.3 Flood Alleviation Schemes ...... 99 10.4 Flood Mitigation on site ...... 99
11 Policy Recommendations...... 102 11.1 Flood Risk ...... 102 11.2 Flood Risk Management ...... 103 11.3 Drainage Systems ...... 104 11.4 Flood Risk & Environment...... 105
12 Emergency Planning ...... 107 12.1 Developing an Emergency Flood Plan ...... 107
13 Conclusions and Recommendations...... 110 13.1 Conclusions...... 110 13.2 Recommendations ...... 110 13.3 Further Work ...... 111 13.4 How and when the SFRA should be updated? ...... 112 13.5 Level 2 SFRA ...... 112
Appendices...... 114
Appendix A : Figures ...... 115
Appendix B: Data/Document Registers...... 117
Appendix C - Meeting Minutes ...... 119
Appendix E : Sustainability Checklists ...... 130 Appendix F SuDS Suitability based on Geology and Soils in the SFRA Study Area ...... 137
D118200 March 2009
iii Wealden District Council Level 1 SFRA: Final Report
Abbreviations
ACRONYM DEFINITION BREEAM2 BRE Environmental Assessment Method 2 CFMP Catchment Flood Management Plan DPD Development Plan Documents FRA Flood Risk Assessment GIS Geographic Information Systems IDB Internal Drainage Board LDDs Local Development Documents LDF Local Development Framework LDS Local Development Scheme LiDAR Light Detection and Ranging LPA Local Planning Authority ODPM Office of the Deputy Prime Minister PPS25 Planning Policy Statement 25: Development and Flood Risk RFRA Regional Flood Risk Assessment RPG Regional Planning Guidance SA Sustainability Assessment SAR Synthetic Aperture Radar SFRA Strategic Flood Risk Assessment SSSI Site of Special Scientific Interest SuDS Sustainable Drainage Systems WDC Wealden District Council
D118200 March 2009
1 Wealden District Council Level 1 SFRA: Final Report
Glossary
TERM DEFINITION A source of groundwater comprising water-bearing rock, sand or gravel capable Aquifer of yielding significant quantities of water. Catchment A high-level planning strategy through which the Environment Agency works with Flood their key decision makers within a river catchment to identify and agree policies to Management secure the long-term sustainable management of flood risk. Plan Both natural and human actions causing long term variations in global Climate Change temperature and weather patterns. Culvert A channel or pipe that carries water below the level of the ground. The enclosed area of land surrounding a dwelling. It is distinct from the dwelling Curtilage by virtue of lacking a roof, but distinct from the area outside the enclosure in that it is enclosed within a wall or barrier of some sort. Infrastructure used to protect an area against floods as floodwalls and Flood defence embankments; they are designed to a specific standard of protection (design standard). Flood plain Area adjacent to river, coast or estuary that is naturally susceptible to flooding. Flood storage A temporary area that stores excess runoff or river flow often ponds or reservoirs. Fluvial flooding Flooding by a river or a watercourse. Water that is in the ground, this is usually referring to water in the saturated zone Groundwater below the water table. Indicative flood A map that delineates the areas that have been predicted to be at risk of being plain map flooded during an event of specified probability. Internal Independent bodies with responsibility of ordinary watercourses within a specified Drainage Board district. Inundation Flooding. The core of the updated planning system (introduced by the Planning and Local Compulsory Purchase Act 2004). The LDF comprises the Local Development Development Documents, including the development plan documents that expand on policies Framework and provide greater detail. The development plan includes a Core Strategy, Site (LDF) Allocations Development Plan Document and a Proposals Map. Local Planning Body that is responsible for controlling planning and development through the Authority planning system. A stream or river, usually of significance that is administered by the EA and Main Rivers shown on their main rivers map. Mitigation An element of development design which may be used to manage flood risk or measure avoid an increase in flood risk elsewhere. Every river, stream, ditch, drain, cut, dyke, sluice, sewer (other than a public Ordinary sewer) and passage through which water flows and which does not form part of a watercourse main river. Risk The probability multiplied by the consequence of an event occurring A risk based approach in to assessing flood risk, which gives priority in ascending Sequential Test order of flood risk, i.e. lowest risk first. Flooding caused by a blockage or overflowing in a sewer or urban drainage Sewer flooding system. Stakeholder A person or organisation that has an interest in, or affected by the decisions made
D118200 March 2009
2 Wealden District Council Level 1 SFRA: Final Report
TERM DEFINITION within a site. A process used to identify if policies, strategies or plans promote sustainable Sustainability development and further used for improving policies. It is a requirement for Appraisal Regional Spatial Strategies and Development Plan Documents under the Planning and Compulsory Purchase Act 2004. Methods of management practices and control structures that are designed to Sustainable drain surface water in a more sustainable manner than some conventional drainage system techniques. Sustainable Development that meets the needs of the present without compromising the development ability of future generations meeting their own needs. 1 in 100 year Event that on average will occur once every 100 years. Also expressed as an event event, which has a 1% probability of occurring in any one year. Flood defence that is designed for an event, which has an annual probability of 1 in 100 year 1%. In events more severe than this the defence would be expected to fail or to design standard allow flooding.
The following table shows return periods defined as annual probability events. Return Annual period (1 in Probability x years) 1 100.0% 2 50.0% 5 20.0% 10 10.0% 20 5.0% 25 4.0% 30 3.3% 50 2.0% 75 1.3% 100 1.0% 200 0.5% 500 0.2% 1000 0.1%
D118200 March 2009
3 Wealden District Council Level 1 SFRA: Final Report
1 Introduction
The Planning and Compulsory Purchase Act 2004 (PCPA 2004)i requires Local Planning Authorities (LPAs) to produce Local Development Frameworks (LDFs) to replace the system of Local, Structure and Unitary Development Plans. LDFs are a portfolio of documents (Local Development Documents (LDDs) that collectively deliver the spatial planning strategy for the authority area. The PCPA 2004i requires LDDs to undergo a Sustainability Appraisal (SA) which assists LPAs in ensuring their policies fulfil the principles of sustainability. Strategic Flood Risk Assessments (SFRAs) are one of the documents to be used as an evidence base for planning decisions. They are also a component of the SA process and should be used in the review of LDDs or in their production.
The release of Planning Policy Statement 25ii: Development and Flood Risk in December 2006 (PPS25) emphasises the responsibility that LPAs have to ensure that flood risk is understood and managed effectively using a risk-based approach as an integral part of the strategic planning process. PPS25ii encourages LPAs to undertake SFRAs and to use their findings and those of other studies to inform strategic land use planning.
To assist LPAs in their strategic land use planning, SFRAs should present sufficient information to enable LPAs to apply the Sequential Test (described further in Section 6) to their proposed development sites/areas. The Sequential Test seeks to guide development to areas of low flood risk or, where necessary, to ensure development vulnerability is appropriate to the flooding probability of an area. To achieve this, the SFRA should have regard to river catchment wide flood issues and also involve a process which allows the LPA to determine the variations in flood risk across their administrative area as the basis for preparing appropriate policies for flood risk management for these areas.
In addition where development sites cannot be located in accordance with the Sequential Test as set out in PPS25ii (i.e. to steer development to low risk sites) the scope of the SFRA should be increased to provide the information necessary for the application of the Exception Test.
1.1 Wealden District Council SFRA
The Non Statutory Wealden Local Planiii identifies several growth areas in the area administered by Wealden District Council (WDC). The growth areas, relevant to the geographical parameters of this SFRA, are principally focused on the towns of Uckfield, Crowborough, Maresfield and Isfield.
The spatial planning of these growth areas must consider the current and future risk of flooding from a number of sources, including fluvial, drainage/sewer, overland flow, groundwater and artificial sources (reservoirs). It is therefore vitally important that flood risk is considered at a strategic scale to inform land allocations and future developments proposed by the emerging LDF.
1.2 The Aim of the WDC SFRA
WDC are currently preparing their Core Strategy and require a SFRA to inform policies and realistic approaches to managing risk of flooding. The overall aim of this study is to prepare a SFRA for WDC in accordance with PPS25ii which identifies local flooding constraints, sufficient to assist WDC in the formulation of planning policies, and
D118200 March 2009
4 Wealden District Council Level 1 SFRA: Final Report
the variation in flood risk across their administrative area for current climatic conditions and accounting for the predicted effects of climate change.
1.3 Wealden District Council Level 1 SFRA Objectives
To achieve the aim of the SFRA the following objectives for the WDC Level 1 SFRA have been met: 1. Collect, collate and review available information on flood risk for the study area;
2. Provide information on the probability of flooding, talking into account all sources of flooding and the impacts of climate change;
3. Present an assessment of the impact of all potential sources of flooding in accordance with PPS25ii, including an assessment of any future impacts associated with climate change;
4. Provide information for applying the PPS25ii Sequential Test, on the basis of the flood zones identified in PPS25ii. This will identify where sites cannot be located in Flood Zone 1 and therefore require further investigation through a Level 2 SFRA;
5. Present information enable WDC to apply the Exception Test (Level 2 SFRA) to identified growth areas;
6. Advise WDC on suitable polices to address flood risk issues in keeping with collected evidence, national, regional and local policies;
7. Advise WDC on the requirements of site specific flood risk assessments based on local flooding issues and policy recommendations;
8. Advise WDC on the applicability of Sustainable Drainage Systems (SuDS) in the study area;
9. Present sufficient information to inform WDC of the flood considerations necessary in emergency planning; and,
10. Collate and present all the data collected and generated during the production of the SFRA on an external hard drive which will be returned to WDC at the end of the project.
1.4 Wealden District Council SFRA Structure
Since this study was commissioned, the Department of Communities and Local Government has released a “Living Draft” of the Practice Guide Companioniv to accompany PPS25ii. The Practice Guide Companion to PPS25iv recommends SFRA’s are completed in two consecutive stages. This provides local planning authorities with tools throughout the LDF and SFRA process sufficient to inform decisions regarding development sites. The two stages are:
• Level 1 SFRA – Study Area Flood Source Review & Data Review; and, • Level 2 SFRA – Main SFRA and development sites assessments.
D118200 March 2009
5 Wealden District Council Level 1 SFRA: Final Report
The results of the Level 1 SFRA will enable a prompt start to the commencement of Level 2 (where required).
1.4.1 Level 1 - Area Flood Source Review & Sequential Test
This Level 1 SFRA draws on past data and presents sufficient information to enable WDC to apply the Sequential Test to potential development sites and to assist in identifying if application of the Exception Test will be necessary. The Level 1 SFRA also provides background information and a review of local policies and the potential for application of Sustainable Drainage Systems (SuDS). The review of polices is allied to guidance on the requirements for site-specific flood risk assessments. One of the objectives of the Level 1 SFRA is to collate and review available information on flood risk for the study area. The information to complete this report has been sourced from a variety of stakeholders that have included the Environment Agency, Wealden District Council, East Sussex Fire and Rescue Service, the Highways Agency and Southern Water. The information presented in this Level 1 report should not be considered as an exhaustive list of all available flood related data for the study area. The Level 1 report is a presentation of the data collected following consultation with and input from the Local Authorities and agencies within the timeframe available. This Level 1 SFRA has broadly been separated into the following topic areas: • Responsibility; • Data; • Flood Risk Guidance (including Sequential and Exception Test); and, • Emergency Planning. The deliverables from the Level 1 SFRA should be used by WDC to identify the most suitable locations for development (in line with PPS25ii and other planning drivers). Where sites cannot be located in line with the principles of PPS25ii further investigation may be required through a Level 2 SFRA.
1.4.2 Level 2 - Development Site Assessments for Exception Testing
The aim of a Level 2 SFRA is to use information obtained in Level 1, where suitable and additional works where necessary, to reduce uncertainty regarding flood risk to those developments/development sites that could not be located in a lower flood risk zone through the Sequential Test (therefore requiring application of the Exception test).
WDC has already identified that some development may be proposed in the area of Uckfield. Given a history of local flooding in Uckfield a Level 2 SFRA has been commissioned to run concurrently with this Level 1 SFRA. The Level 2 SFRA will be reported separately and will present site specific information based on development areas/sites according to the requirements of WDC.
i Edwards, M., Harwood, R., Thornton, J. & Tromans,S. (2004) ‘Planning and Compulsory Purchase Act’, HMSO ii Department for Communities and Local Government (December 2006) ‘Planning Policy Statement 25: Development and Flood Risk’ 2006, The Stationary Office: Norwich
D118200 March 2009
6 Wealden District Council Level 1 SFRA: Final Report
iii Wealden District Council (2005) ‘Non Statutory Wealden Local Plan’, Wealden District Council: Crowborough. iv Communities and Local Government (2007) ‘Development and Flood Risk: A Practice Guide Companion to PPS25 ‘Living Draft’’, Department for Communities and Local Government: London.
D118200 March 2009
7 Wealden District Council Level 1 SFRA: Final Report
2 Wealden District Council SFRA Study Area
This SFRA study area encompasses the north part of the area administered by Wealden District Council. It is bordered by the districts of Tunbridge Wells Borough, Sevenoaks District, Tendridge District, Lewes District, Rother District and Eastbourne Borough. It includes reaches of the River Teise, River Ouse, River Medway, River Rother and River Uck. This results in a study area of 513km².
Please note that this SFRA only covers the northern areas of Wealden District Council. A SFRA for the southern area of Wealden District Council has been carried out as a combined study with Eastbourne Borough Council by Scott Wilson, 2008v.
2.1 Wealden District Study Area Characteristics
The SFRA study area extends from Firle Beacon in the south to Holtye Common in the north and Weir Wood Reservoir in the west to Wadhurst in the east. The study area is predominantly rural over a varying landscape that includes both the High and Low Weald. The Low Weald; in the south is characterised by gently sloping clay vales with small greensand ridges. In contrast, the High Weald, in the north of the study area is characterised by steeper slopes that are in places heavily wooded but include areas of open heathland. Ashdown Forest covers a large part of the north of the study area and is comprised of predominantly oak-birch woodland with some open heathland ridges.
There are a number of environmentally sensitive areas that enhance the character of the district and are also important considerations in the planning process. The High Weald is classified as an Area of Outstanding Natural Beauty, There are a number of Local Nature Reserves including Old Nutley Wood, Chailey Common and Weirwood Reservoir. Buxted Park is classified as a Site of Special Scientific Interest.
The study area includes the urban centres of Forest Row, Crowborough, Uckfield and Isfield. Under the Draft South East Planvi WDC is required to provide 8000 dwellings between 2006 and 2026, which equates to an average 400 dwellings per year1.
2.1.1 Topography
The topography of the Wealden District varies from the steeper terrain of the High Weald in the north to the undulating hills of the Low Weald and South Downs in the south of the study area. The River Medway, Rother and Teise all have their sources in the High Weald and drain the north half of the study area. The valleys of these river systems are typically deeply incised in comparison to the valleys of the River Uck and Ouse whose sources are in the Low Weald. The River Ouse cuts through the South Downs that characterise the topography of the very south of the study area. The South Downs are chalk downland that is characterised broad valleys and gently rolling hills.
2.1.2 Geology and Soils
A review of the geology of the study area was undertaken using Geological maps 303 (Tunbridge Wells)vii and 319 (Lewes)viii. The geology of the study area is varied and a more detailed review of the
1 The Secretary of State's Proposed Changes to the South East Plan (published July 2008) proposes an increase in the required dwelling numbers from 8,000 to 11,000 dwellings between 2006 to 2026 (see Annex 2).
D118200 March 2009
8 Wealden District Council Level 1 SFRA: Final Report
geology and soils is presented in Appendix G. Generally the north of the study area, surrounding Ashdown Forest, is founded on Ashdown Beds. Ashdown Beds are fine grained sandstones and siltstones which can be variably permeable. The south of the study area is largely founded on the Upper Tunbridge Wells Sand formation, which comprise of a complex mix of silt and sandstones that also can be variably permeable. There are, however, smaller pockets of either Wadhurst or Grinstead Clay as well as Alluvium fringing most of the river systems.
A review of the soils of the study area was undertaken using Sheet 6 of the soil maps of England and Walesix. The soils of the Wealden SFRA study area also vary and more detail can be found in Appendix G. Generally much of the north of the study area over the Ashdown Beds is covered by the Poundgate soil association; these are naturally acid silty soils. Much of the south of the study area over the Upper Tunbridge Wells Formation is covered by the Curtisden soil association; these are silty soils.
2.1.3 Hydrogeology
According to the groundwater vulnerability map for the study areax there are no major aquifers located within the boundary. The Ashdown Formation, Wadhurst Clay Formation and Tunbridge Wells Sands Formation, that comprise the High and Low Weald, are classified as minor aquifers by the Environment Agency. These are formations that have a variable permeability that can comprise of fractured rocks. It is unlikely that they will produce large quantities of water for abstraction but can be important for local supplies and/or supplying baseflow to rivers. Guidance on SuDS can be found in Section 9 and more information on site-specific FRAs can be found in Section 8.
2.2 Flood Sources
2.2.1 Flooding History
It is known that the Wealden District has experienced past flooding problems from a number of flood sources. This has been demonstrated on both a large scale causing major disruptions and on a local scale causing temporary inconvenience. For example, the River Uck has caused fluvial flooding on many occasions in the past including incidents in 1960, 1968, 1974 and 1987. The most recent, in 2000, resulted in many people being rescued including 20 people that were trapped in a supermarket in Uckfield. The damage was mainly to commercial properties in the town centre although some residential dwellings situated in the floodplain of Olives Meadow were also affected. This same incident also caused flooding in the surrounding towns upstream and downstream including Buxted. It is thought that the high velocities in this upper catchment exacerbated the damage as well as overflowing of culverts and drainsxi In addition to fluvial flooding the District is subject to flooding of surcharged drainage systems. An example includes the surcharging of the sewer under the High Street in Crowborough, which frequently flooding shops. Since these incidents of flooding a new sewer system has been installed by Southern Water, which is designed to protect this area of Crowborough of flooding from the sewer system.
Annex C of PPS25ii identifies six different sources of flooding. Of these all but tidal sources are present within the study area. The following section outlines the nature of the various flood sources present in the study area.
D118200 March 2009
9 Wealden District Council Level 1 SFRA: Final Report
2.2.2 Fluvial
The main river catchments within the study area are:
• River Uck; • River Ouse; • River Medway; • River Teise; and, • River Rother.
The locations of the watercourses and their river catchments are illustrated in Figure 2.
River Uck
The River Uck rises from tributaries surrounding Huggets Furnace in the centre of the study area (TQ 534259). From here it flows south west and is joined by the High Hurstwood Stream (enmained) north of Potter’s Green (TQ501245). The River Uck is also joined by two tributaries from the northwest and east before flowing through Uckfield; an unnamed stream from the northwest and the Tickerage Stream (TQ488224) (enmained) from the east. The River Uck flows through Uckfield where it is joined by the Framfield Stream from the south (TQ479209). It then flows south alongside a dismantled railway before turning west. A series of weirs at TQ451181 are located where it branches into the Isfield Mill Stream (enmained) before both watercourses exit the study area.
The River Uck, to where it exits the study area, has an approximate catchment area of 86 km² of which approximately 95% is within the study area. This catchment includes the larger urban area of Uckfield and the smaller urban areas of Buxted and Hadlow Down.
River Ouse (Upper Reaches)
The River Ouse rises in the Mid Sussex District (TQ261279), and flows in a south east direction forming the western boundary of the WDC SFRA study area. It flows through the study area for approximately 2.7 km near Fletching and then flows south along the study boundary. It is joined at Sharpesbridge (TQ443206) by the Shortbridge Stream (enmained). Its confluence with the River Uck and the Isfield Mill Stream is located on the study boundary, north of Isfield (TQ443179). It exits the study area approximately 500 m south of its confluence with the River Uck (TQ445173).
The River Ouse catchment area is approximately 294 km² an estimated 35% is within the study boundary. The catchment includes the urban areas of Nutley, Danehill, Maresfield and Isfield.
River Medway
The River Medway flows from the Sevenoaks District along the northern boundary of the WDC SFRA study area for approximately 4 km. It flows west and enters the study area near Groombridge (TQ511375) where it is joined by an unnamed tributary from the south. The Medway flows along the Sussex Border path and passes the village of Hartfield to the south. It continues west and flows through the centre of Forest Row and out of the WDC SFRA study area (TQ409356).
The River Medway catchment area is approximately 491 km² an estimated 40% is within the WDC SFRA study area. The River Medway catchment includes the urban areas of Forest Row, Rotherfield Groombridge and Hartfield.
D118200 March 2009
10 Wealden District Council Level 1 SFRA: Final Report
The Weir Wood Reservoir (TQ406353) provides online attenuation but is noted in the Medway CFMPxii to not have a significant impact on flood flows. There has been significant historic flooding along the River Medway; notably in 1960, 1968 and 2000.
River Teise
The River Teise flows from the Tunbridge Wells District to the northeast of the Wealden District. It flows along the north-eastern boundary near Bayham Lake for approximately 1 km. Even though the main River Teise does not flow through the District a large area of its catchment’s and headwaters are located within the Wealden District. The River Teise total catchment area is 189 km² of which an estimated 30% is within the Wealden District. The catchment includes the urban area of Wadhurst and a number of smaller rural settlements.
River Rother
The River Rother rises near Mayfield in the east of the Wealden District (TQ567268). It flows in an easterly direction for approximately 5 km before flowing into the Rother District (TQ634261). The River Rother has a catchment area of 383 km² with an estimated 30% within the Wealden District. The catchment of the River Rother includes the urban area of Mayfield and a number of smaller rural settlements.
Other Watercourses
The rivers described above are classified as ‘main rivers’ defining the Environment Agency as the responsible authority. Main rivers can be defined as rivers or streams or watercourses of any size which are marked on the DEFRA’s main rivers map. Other Main rivers within the WDC SFRA study area include: Framfield Stream; Tickeridge Stream; High Hurstwood Stream; Ridgewood Stream; Shortbridge Stream; and, Batts Bridge Stream.
There are a number of other watercourses within the study area that can be a source of flooding. Watercourses other than main rivers are known as ‘ordinary watercourses’ and are either administered by the Local Authority or the IDB. Figure 2 presents the watercourses within the WDC SFRA study area and their administering authority.
2.2.3 Drainage/Sewers
Drainage/sewer systems are typical to all the urban centres in the study area. There are three main types of sewer systems, namely: - • ‘surface water sewers’ that convey surface water runoff from roads, roofs and pavements etc.; • ‘foul water sewers’ that convey wastewater from residential buildings, commercial buildings and industrial units etc; and, • ‘combined sewers’ that convey both wastewater and surface water together.
Sewers are known to give rise to flooding within the district. Flooding from sewers is caused when the sewer either becomes blocked or collapses or the storm generates rainfall/runoff at a rate grater than can be accommodated by the sewers design.
D118200 March 2009
11 Wealden District Council Level 1 SFRA: Final Report
Presently, sewers are designed in accordance with the guidelines presented in “Sewers for Adoption”xiii, the latest version of which was implemented by all water companies in May, 2006. These sewers are designed to accommodate a 3.3% annual probability (1 in 30 year) storm event and therefore it is likely that the majority of adequately maintained sewer systems will surcharge during storm events with a return period greater than 3.3% annual probability. For example, they should be expected to surcharge in a storm event that has a 1% annual probability (1 in 100 years). Older sewer systems are most often designed to an unknown size, condition and capacity and therefore should be expected to surcharge in storms with lower return periods.
Drainage ditches are typically constructed to drain surface water runoff from rural/agricultural areas. They require maintenance to ensure they do not become choked with vegetation or silt which can prevent/impede the passage of water. Responsibility for maintaining ditches primarily lies with the riparian owner, but may in some cases have been passed to a different authority. Figure 2 identifies the responsibility of known watercourses in the study area.
In addition, as towns and villages expand to accommodate growth the original sewer/drainage systems are rarely upgraded; eventually becoming overloaded and reducing their efficiency. Compounding this problem are the effects of climate change. Climate change is forecasted to result in milder wetter winters and more thunderstorms in summer months. This combination will increase the pressure on existing sewer systems, effectively reducing their capacity, leading to more frequent flooding.
2.2.4 Groundwater
Groundwater flooding can occur when groundwater levels rise above ground level. This typically can occur in historical watercourses (dry valleys), when there is already a strong connectivity to the groundwater regime. Incidents of groundwater flooding are recorded by the Environment Agency and WDC, when reported by residents. The local Catchment Abstraction Management (CAMS) plans review the status of the groundwater and can often provide locations that have experienced past flooding. They also provide an indication into the future trends in groundwater for example if the groundwater is in decreasing or increasing supply.
The River Medway Catchment Abstraction Management Strategy (CAMS)xiv indicates that for the Medway catchment area within the study area currently has a groundwater status of ‘no water available’. The River Adur and Ouse CAMSxv indicates that for the Ouse catchment area within the study area currently has a groundwater status of ‘over licensed’ and a proposed groundwater status of ‘no water available’.
2.2.5 Overland Flow
Overland flow can occur on any slope that is or has become impermeable. This can occur either once the top layers of soil or ground have become fully saturated or if the ground surface is of an impermeable nature such as tarmac. Overland flow is most likely to occur at the base of an escarpment but can also occur across relatively gently inclines in urbanised areas. Incidents of overland flow are recorded by the Environment Agency and WDC, when reported by residents.
D118200 March 2009
12 Wealden District Council Level 1 SFRA: Final Report
2.2.6 Artificial Sources
Artificial sources include any water bodies not covered by the previous categories. This typically includes canals, lakes, water mains and reservoirs etc. All of these artificial features can give rise to flooding if a breach (failure in containment) occurs. Incidents of flooding from artificial sources are recorded by the Environment Agency and WDC, when reported by residents.
Within the Wealden District there are a number of ‘hammer ponds’ that have their origin in the iron industry that are rich in biodiversity but can present a flooding source.
v Scott Wilson (2008) ‘Eastbourne Borough Council and Wealden District Council Level 1 Strategic Flood Risk Assessment’, Scott Wilson: Basingstoke. vi South East England Regional Assembly (2006) ‘Draft South East Plan’, vii Ordnance Survey (1971) ‘Geological Survey of Great Britain (England and Wales): Tunbridge Wells’. Sheet 303, Ordnance Survey: Southampton. viii Ordnance Survey (1979) ‘Geological Survey of Great Britain (England and Wales): Lewes’, Sheet 319, Ordnance Survey: Southampton. ix Ordnance Survey (1983) ‘The Soil Survey of England and Wales: Sheet 6’, Ordnance Survey: Southampton. x NRA (1986) ‘Groundwater Vulnerability of East Sussex: Sheet 46’, HMSO: London. xi Risk Management Solutions (2000) ‘UK Floods, October 13 – 14, 2000: Examination of UK Flood Damage during increased rainfall in October 2000’, RMS Ltd: London. xii Babtie Brown & Root (2004) ‘The Medway Catchment Flood Management Plan’, Environment Agency: Worthing. xiii WRc (2006) ‘Sewers for Adoption’, WRc Ltd: Swindon. xiv Environment Agency (2005) ‘Medway Catchment Abstraction Management Strategy’, Environment Agency: Bristol. xv Environment Agency (2005) Adur and Ouse Catchment Abstraction Management Plan’, Environment Agency: Bristol.
D118200 March 2009
13 Wealden District Council Level 1 SFRA: Final Report
3 Policy Context
This section provides an overview of the planning policy framework relevant to the SFRA for WDC. Information contained in the SFRA on flooding and flood risk will enable the preparation of sustainable policies for flood risk management. The SFRA should be used to inform the Sustainability Appraisal of LDDs and will facilitate informed decision-making relating to land use and development allocation within the DPDs.
Under the Draft South East Planvi WDC must accommodate 8000 new homes by 20261. In satisfying these growth targets WDC must consider a raft of planning policies (of which flooding is one) to ensure developments are sustainable. In consideration of these polices the councils must decide on the ‘weight’ to attribute to each policy in determining the suitability of development in their areas.
3.1 Role and Responsibilities
3.1.1 Environment Agency
The Environment Agency is a governmental organisation whose overarching objective is to protect and enhance the environment in England and Wales. The Environment Agency has permissive and statutory duties to:
• Maintain or improve any watercourses which are designed as Main Rivers; • Maintain or improve an sea or tidal defences; • Install and operate flood warning equipment; • Control actions by riparian owners and occupiers which might interfere with the free flow of watercourses; and, • Supervise internal drainage boards.
Additionally, following the amendment to the Town and Country Planning Act in October 2006xvi, the Environment Agency became a statutory consultee for the LPA for all planning applications within areas of flood risk (except minor developments). The Environment Agency’s Standing Advicexvii sets out when the Environment Agency should be consulted on planning applications (consultation matrix), it includes the following planning application scenarios:
• Householder development and alterations within 20 m of the top of a bank of a Main River and/or includes culverting or control of flow of any river or stream; • Non-residential extensions with a footprint of less than 250 m² that is within 20 m of the top of bank of a Main River and/or includes culverting or control of any river or stream; • Change of use FROM ‘water-compatible’ TO ‘less vulnerable’ development within 20 m of the top of bank of a Main River AND if the site falls within Flood Zone 3; • Change of use RESULTING IN ‘highly vulnerable’ development within 20 m of the top of bank of a Main River AND if the site falls within Flood Zone 2 or 3; and, • Operational development of 1 hectare or greater if the development includes culverting or control of flow of any river or stream and/or the development is within Flood Zone 2 or 3.
D118200 March 2009
14 Wealden District Council Level 1 SFRA: Final Report
Section 8 and the Environment Agency’s standing advicexvii provides further information on when the Environment Agency should be consulted in the planning application process.
The study area falls entirely in the Environment Agency’s Southern Region but is split between the Sussex and Kent areas.
3.1.2 Local Planning Authority
The local authority has responsibility to ensure that all watercourses for which the Environment Agency or the Internal Drainage Board (IDB) is not the responsible authority are appropriately managed by the riparian landowner.
For some planning applications it is the responsibility of WDC to consult the Environment Agency. There are three guidelines as to when the LPA should consult the Environment Agency that have been summarised in Table 3-1 below.
Table 3-1: Table to show the circumstances in which the LPA has the responsibility to consult the Environment Agency
ii xvi Environment Agency Standing PPS25 Town and Country Planning xvii Advice On all planning applications in On all planning applications in Householder development and areas of flood risk areas of flood risk alterations within 20 m of the top of a bank of a Main River and/or includes culverting or control of flow of any river or stream;
On all planning applications On all planning applications that Non-residential extensions with a that are in areas where there are in areas where there are footprint of less than 250 m² that are critical drainage problems, critical drainage problems, other is within 20 m of the top of bank other than minor than minor developments3 of a Main River and/or includes developments2 culverting or control of any river or stream;
For all developments of sites For all developments of sites of Change of use FROM ‘water- of more than 1 hectare more than 1 hectare elsewhere compatible’ TO ‘less vulnerable’ elsewhere development within 20 m of the top of bank of a Main River AND if the site falls within Flood Zone 3
2 “minor development” means – i) development of an existing dwelling-house, or development within the curtilage of such a dwelling house, for any purpose incidental to the enjoyment of the dwelling-house as such; ii) the extension of the existing building used for non-domestic purposes where the floorspace created by the development does not exceed 250 square metres; and, iii) the alteration of an existing building where the alteration does not increase the size of the building 3 “minor development” means – i) development of an existing dwelling-house, or development within the curtilage of such a dwelling house, for any purpose incidental to the enjoyment of the dwelling-house as such; ii) the extension of the existing building used for non-domestic purposes where the floorspace created by the development does not exceed 250 square metres; and, iii) the alteration of an existing building where the alteration does not increase the size of the building
D118200 March 2009
15 Wealden District Council Level 1 SFRA: Final Report
Environment Agency Standing PPS25ii Town and Country Planningxvi Advicexvii Change of use RESULTING IN ‘highly vulnerable’ development - - within 20 m of the top of bank of a Main River AND if the site falls within Flood Zone 2 or 3 Operational development of 1 hectare or greater if the development includes culverting - - or control of flow of any river or stream and/or the development is within Flood Zone 2 or 3
3.1.3 Internal Drainage Board
Internal Drainage Boards (IDB) main responsibility is to maintain the watercourses appointed to them and to prevent flooding within the board’s district. IDBs are normally formed by a consortium of riparian owners for whom the IDB coordinates maintenance. They have permissive powers to undertake flood defence work on watercourses other than those that are ‘Main’. Permissive powers means that the IDB are permitted to undertake works on ordinary watercourses but the responsibility remains with the riparian owner as the IDB are not obligated.
The River Medway IDB is the only IDB that operates within the study area. Figure 2 identifies the watercourses for which they are the responsible authority.
3.1.4 Sewerage Undertakers
Sewerage undertakers are responsible for surface water and foul drainage from developments, where this is adopted via adopted sewers. Under the Water Industry Act 2003xviii sewerage undertakers are legally obliged to take on both surface and foul water from new developments. Additionally, they have a role of providing information to LPA’s so that an SFRA takes into account any areas of critical drainage problems. Southern Water is the only sewerage undertaker within the study area.
3.1.5 Highways Agency
The Highways Agency is responsible for maintaining major roads throughout England, this includes the upkeep of the stormwater drainage infrastructure associated with the road network.
3.1.6 Landowner
Landowners are responsible for safeguarding their land and other property against natural hazards, such as flooding. It is also the responsibility of landowners to manage the drainage of their land in such a way to prevent, as far as practicable, adverse impacts on neighbouring properties.
D118200 March 2009
16 Wealden District Council Level 1 SFRA: Final Report
3.2 European Policies
3.2.1 European Union Water Framework Directive
The European Union (EU) Water Framework Directive (WFD) was adopted into UK law in 2003 and followed a review of EU water policy. It seeks to restore and improve water quality in rivers, coastal water and groundwater in an integrated manner. It seeks to achieve good ecological status of water bodies through integrated river basin management. This is a method of ensuring all requirements and pressures on the water environment are taken into account within a river basin. River Basin Management Plans are required to be undertaken for each river basin district. These plans are required to include information on both surface waters and groundwater.
3.2.2 European Union Floods Directivexix
The European Directive on the Assessment and Management of Flood Risks came into force on the 26th November 2007. The Directive requires Member States and the community to consider the potential impacts that domestic policies may have on flood risk and the management of flood risk on neighbouring member states. It recognises that objectives regarding management of flood risk should be determined by the Member States themselves and should be based on local and regional circumstances. Member States have two years to transpose the Directive into domestic law and a further six years to satisfy its requirements. The Directive requires Member States to designate competent authorities to implement the Directive; for England, this will be the Environment Agency. The Directive requires the following elements to be undertaken: • preliminary flood risk assessments to identify areas that are at potentially significant flood risk, to be completed by 20 December 2011; • flood hazard maps (showing the likelihood and flow of the potential flooding) and flood risk maps (showing the impact), to be completed by 20 December 2013; • flood risk management plans (showing measures to decrease the likelihood or impact of flooding), to be completed by 22 December 2015; and • updates every 6 years thereafter that take into account the impact of climate change. The Environment Agency hope to achieve the requirements of the Directive through the use of existing published information. This may include reference or use of SFRA, CFMP and/or Strategic Flood Risk mapping projects. In some cases the assessments may require new information to be generated to inform the stages of assessment required by the Directive.
3.3 National Policies
3.3.1 Making Space for Waterxx
DEFRA published ‘Making Space for Water’ after consultation in March 2005. Its intention is to inform the development of a new strategy on the management of issues surrounding flood risk and coastal erosion for the next 20 years. It does not state specific policies but presents the Government's objectives on:
D118200 March 2009
17 Wealden District Council Level 1 SFRA: Final Report
1. Land use planning – strongly encourages Flood Risk Assessments to be prepared at all levels of the planning process; 2. Rural Issues – promote the environmental pillar of sustainable development through the use of wetlands and washlands, and managed realignment of coasts and rivers; 3. Integrated urban drainage management – committed to ensuring that SuDS techniques are incorporated in new developments; 4. Coastal issues – seeks to develop a more strategic and integrated approach to managing coastal flooding and erosion risks; and, 5. Living with flood risk – identified that there is a need to raise awareness and preparation in local communities for the changing flood and erosion risks resulting from climate change.
3.3.2 Planning Policy Statements (PPSs) and Guidance Notes
The Government publishes a suite of documents that provide further guidance on various planning subjects. This guidance is a material consideration when determining planning applications.
The PPSs of most relevant to development and flood risk for WDC are:
• PPS1xxi: Delivering Sustainable Development; • PPSxxii: Planning and Climate Change –a supplement to PPS1; • PPS3xxiii: Housing; • PPS12xxiv: Local Spatial Planning; and, • PPS25ii Development and Flood Risk
PPS1xxi sets out the overarching planning policies on the delivery of sustainable development through the planning system. PPS1xxi states that in preparing development plans local authorities should take into account ‘the potential impact of the environment on proposed developments by avoiding new development in areas at risk of flooding and sea-level rise’.
PPS: Planning and Climate Changexxii sets out how planning, in providing for the new homes, jobs and infrastructure needed by communities, should help shape places with lower carbon emissions and resilient to climate change. In particular paragraph 44 states that ‘in their consideration of the environmental performance of proposed development, taking particular account of the climate the development is likely to experience over its expected lifetime, planning authorities should expect new development to… provide public and private open space as appropriate so that it offers accessible choice of shade and shelter, recognising the opportunities for flood storage, wildlife and people provided by multifunctional greenspaces’.
PPS3xxiii underpins the delivery of the Government's strategic housing policy objectives and their goal to ensure that everyone has the opportunity to live in a decent home, which they can afford in a community where they want to live. With regard to the location of new housing development it states that ‘any physical, environmental … and flood risk should be taken into account’ (paragraph 38).
D118200 March 2009
18 Wealden District Council Level 1 SFRA: Final Report
PPS 12xxiv sets the principles under which the LDF should be developed and places emphasis on a strong evidence base, this includes SFRA.
PPS25ii requires that local councils must when preparing the LDF:-
1. Allocate all sites in accordance with the Sequential Test to reduce the flood risk and ensure that the vulnerability classification of the proposed development is appropriate to the flood zone classification; 2. Ensure Flood Risk Assessments (FRAs) are undertaken for all developments within Flood Zones 2 and 3 and sites with identified flood sources to assess the risk of flooding to the development and identify options to mitigate the flood risk to the development, site users and surrounding area; 3. Ensure FRAs are prepared for all major developments in Flood Zone 1. These are residential developments consisting of sites greater than 0.5 ha or greater than 10 dwellings and commercial developments that are greater than 1 ha. 4. Ensure flood risk to developments should be assessed for all forms of flooding; and,
3.4 Regional Policies
3.4.1 Regional Spatial Strategies (RSS)
Each of the English regions outside of London has a Regional Assembly. The assemblies are responsible for developing and co-ordinating a strategic vision for improving the quality of life in a region. The assembly is responsible for setting priorities and preparing certain regional strategies, including the Regional Spatial Strategy.
3.4.1.1 Regional Spatial Strategy formerly Regional Planning Guidance for the South East (RSS9)xxv
Policy INF1
Development should be guided away from areas at risk or likely to be at risk in future from flooding, or where it would increase the risk of flooding damage elsewhere. Existing flood defences should be protected where they continue to be relevant.
(a) Development plans should: i. include policies to protect flood plains and to protect land liable to tidal or coastal flooding from development, based on Environment Agency’s indicative maps, supplemented where necessary by historical and modelled flood data and indications as to other areas that could be at risk in the future; ii. provide criteria for redevelopment proposals in river flood plains, in order to minimise their cumulative adverse impact and secure enhancements of the flood water storage and ecological role of flood plains; iii. take account of emerging thinking on the need for ‘managed retreat’ from selected coastal defence; and iv. encourage the adoption of sustainable urban drainage practices
D118200 March 2009
19 Wealden District Council Level 1 SFRA: Final Report
(b) In addition: i. the Environment Agency plays an important role in identifying the nature and extent of flood risk and in determining priorities for food studies and the need for flood management measures. Measures may be identified in Local Environment Agency Plans (LEAPs); and ii. collaboration between a range of organisations in the preparation and implementation of Biodiversity Actions Plans (BAPs) can also make a contribution, for example, in enhancing the role of rivers and flood plains as important wetland habitats for wildlife.
Policy INF2
New development should be located and its implementation planned in such a way as to allow for sustainable provision of water services and enable timely investment in sewage treatment and discharge systems to maintain the appropriate standard of water quality. Techniques which improve water efficiency and minimise adverse impacts on water resources, on the quality, regime, and ecology of rivers, and on groundwater, should be encouraged. Redevelopment should identify and make provision for rectification of any legacy of contamination and drainage problems.
(a) Development plans should: i. take water related issues into account from an early stage in the process of identifying land for development and redevelopment, to encourage the use of sites where past problems can be solved and seek to avoid sites where water supply and/or drainage provision is likely to be unsustainable; ii. co-ordinate the timing of new development with the provision of sustainable water supplies, sewage treatment and discharge systems in accordance with advice in PPG12 (Development Plans); and iii. promote the introduction of water conservation measures and sustainable urban drainage solutions. Detailed supplementary planning guidance or site specific development briefs can help to facilitate the adoption of these measures.
(b) In addition: i. local authorities should establish or maintain ongoing liaisons with the Environment Agency, water companies and sewage statutory undertakers in order to ensure timely and sustainable provision of infrastructure for the supply of water and sewage treatment and discharge systems, particularly in connection with major new development; and ii. all relevant agencies and developers should encourage the incorporation of water conservation measures in new development, and promote public awareness of the need to reduce consumption.
3.4.2 Draft South East Planvi
The South East Plan is due to be adopted as the Regional Spatial Strategy in early 2009.
POLICY NRM 1: SUSTAINABLE WATER RESOURCES, GROUNDWATER AND RIVER QUALITY MANAGEMENT
Water supply, ground water and river water quality will be maintained and enhanced through avoiding adverse effects of development on the water environment. A twin-track approach of demand management and water resource development will be pursued, together with development of sewerage and waste water treatment infrastructure.
D118200 March 2009
20 Wealden District Council Level 1 SFRA: Final Report
In preparing Local Development Documents, and determining planning applications, local authorities should:
I. Ensure compatibility with River Basin Management Plans and take account of other plans and strategies including water and sewerage company asset management plans, the Environment Agency’s Regional Water Resources Strategy, Catchment Abstraction Management Strategies, groundwater vulnerability maps and groundwater source protection zone maps
II. Ensure that the rate and location of development does not lead to unacceptable deterioration of water quality and is in step with current and planned provision of adequate water supply, sewerage and waste water treatment infrastructure capacity
III. Require development that would use significant quantities of water to incorporate measures to achieve high levels of water efficiency, and reflect current best practice including BREEAM2 (BRE Environmental Assessment Method 2) “very good” and increasingly “excellent” standards and, where appropriate, sustainable drainage solutions where these are consistent with protection of groundwater quality
IV. Work with water and sewerage companies and the Environment Agency to identify infrastructure needs, allocate areas and safeguard these for infrastructure development
V. Encourage winter water storage reservoirs and other sustainable farming practices which reduce summer abstraction, diffuse pollution and runoff, increase flood storage capacity and benefit wildlife and recreation
VI. Not permit development that presents a risk of pollution or where satisfactory pollution prevention measures are not provided in areas of high groundwater vulnerability (in consultation with the Environment Agency).
POLICY NRM 3: SUSTAINABLE FLOOD RISK MANAGAMENT
The sequential approach to development in flood risk areas set out in PPS25 will be followed. Inappropriate development should not be allocated or permitted in zones 2 and 3 of the floodplain or areas with a history of groundwater flooding, or where it would increase flood risk elsewhere, unless there is over-riding need and absence of suitable alternatives.
Where development is proposed for parts of zones 2 and 3, local authorities (in the case of plan allocations) should undertake a Strategic Flood Risk Assessment (SFRA) and developers (in the case of specific proposals) should undertake a Flood Risk Assessment (FRA) with advice from the Environment Agency to provide a comprehensive understanding of the flood risk and options for managing that risk in a cost effective manner. These should have regard to climate change and identify appropriate types of development and suitable mitigation and adaptation measures in scheme design and layout. Existing flood defences will be protected from development. Where development is permitted in appropriately defended floodplains it must be designed to be resilient to flooding (to minimise potential damage) and to allow for the future maintenance, realignment or management of the defences to be undertaken.
In the preparation of Local Development Documents and considering planning applications, local authorities in conjunction with the Environment Agency, should also:
D118200 March 2009
21 Wealden District Council Level 1 SFRA: Final Report
I. Take account of River Basin Management Plans, Catchment Flood Management Plans and Shoreline Management Plans in developing Local Development Documents and other strategies. Where locationally specific flood risk and land management options such as flood storage, managed realignment and set back from coastal defences are identified, land should be safeguarded for these purposes and appropriate land management practices should be encouraged.
II. Require incorporation and management of Sustainable Drainage Systems (SuDS), other water retention and flood storage measures to minimise direct surface run–off, unless there are practical or environmental reasons for not doing so.
III. Take account of increased sewage effluent flows on fluvial flood risk.
3.4.3 Regional Flood Risk Appraisal (RFRA)
3.4.3.1 Regional Flood Risk Appraisal for the South East Plan 2006xxvi
The RFRA identifies areas within the South East where predicted high growth coincides with flood risk, and demonstrates how the South East Plan has considered these risks.
Only broad assessments of flood risk to growth areas have been undertaken with a view to SFRA’s providing more detailed information on the risks.
3.5 Local Policies
3.5.1 Local Plans
Wealden District Council is empowered by law to exercise planning functions. This includes the preparation of strategic planning documents that set out the planning vision for the administrative area, with due regard to national and regional policies. Currently WDC is involved in the process of preparing their Local Development Framework, this is comprised of: • Development Plan Documents (which form part of the statutory development plan); • Supplementary Planning Documents; • the Statement of Community Involvement; • the Local Development Scheme; and, • the Annual Monitoring Report
Until such a time as the LDF is adopted the existing Local Plan remains the statutory planning document for the WDC administrative area.
3.5.1.1 Wealden Local Planxxvii
The Wealden Local Plan was adopted in 1998 covering the period up to 2004. The Non-Statutory Wealden Local Plan Interim Guide for Development Control was approved by the Council in December 2005 to provide the planning policy framework up to 2011.. The following polices from the Non Statutory Wealden Local Plan are relevant to this SFRA:
D118200 March 2009
22 Wealden District Council Level 1 SFRA: Final Report
Policy NE1 – Water Resources
Development will not be permitted if it would cause an unacceptable risk to: (a) the quality of groundwater, surface water or coastal water; or (b) the potential yield of groundwater or surface water resources.
Policy CS2 – Water Resources
New development will only be permitted where adequate water resources are available and where it would not present an unacceptable risk to such resources.
Policy CS3 – Flood Risk
Development within areas at risk of flooding will not be permitted unless mitigation and/or alleviation measures incorporated and constructed prior to development commencing. This is subject to there being:
(a) No increased flood risk elsewhere; (b) No risk to life in the event of a breach or overtopping of a flood defence; (c) No requirement for new artificial flood defence in undeveloped high risk areas solely to protect the new development; (d) No detriment to the conservation and recreation value of the natural environment, including river corridors and wetlands.
Proposals for the long-term management of any flood alleviation/mitigation works must be included in any scheme submitted
Policy CS4 – Integrity of defences
Development will not be permitted where it would be detrimental to the integrity of flood defences or watercourse channels, or would impede access to and along these for future maintenance and improvement work.
Policy CS5 – Surface Water
Development will only be permitted where the following criteria are met: (a) adequate means of surface water drainage, including all appropriate alleviation and mitigation works, have been investigated, designed, and will be constructed by the developer prior to the commencement of development; (b) adequate proposals for the long-term management, of such works are included in any scheme submitted; and (c) flood risk will not be exacerbated elsewhere.
3.5.2 Local Development Framework (LDF)
The production of the LDF for the Wealden District is underway and is made up of Local Development Documents (LDDS). This SFRA forms part of the evidence base to support the emerging LDDs in particular the Core Strategy Development Plan Document.
D118200 March 2009
23 Wealden District Council Level 1 SFRA: Final Report
3.5.3 East Sussex County Council Transport and Environment Services Plan 2007 – 2008
The Transport and Environment Services Plan 2007 – 2008 provided by the Highways Agency includes policies that cover topics including environment, highway services, passenger transport, planning, traffic safety, waste management and resources. The following policies from the plan relate to either flood risk or drainage:
Policy E2.23 Appoint an officer to support the County Council and wider Cuckmere Estuary Partnership with a view to promoting a sustainable approach to coastal and flood risk management, and seeking funding to implement it;
Policy HS3.9 Work with partners to establish strategies and operational programmes to improve drainage and reduce the incidence of ponding of water on the highway; and,
Policy HS 3.10 To enhance the gulley emptying operations we will set up a programme of pipework cleaning and jetting with a view to producing an annual routine maintenance programme.
3.6 Environment Agency Policies
3.6.1 Catchment Flood Management Plans (CFMP)
CFMPs are primary Environment Agency documents. They are not classed as policy documents but are becoming increasingly influential in planning policy as they inform River Basin Management Plans and SFRAs. The aim of CFMPs is to ‘provide a useable, policy-level document that summarises all major catchment wide fluvial flood management issues concerns, opportunities and constraints’. It seeks to influence the flood risk management policies of the catchment for the next one hundred years.
3.6.1.1 Draft River Ouse CFMPxxviii
The River Ouse CFMP is currently being developed by the Environment Agency. A draft River Ouse CFMP (April 2008), published for consultation purposes, was available in time for this study. The River Ouse CFMP includes the catchment of the River Uck and acknowledges the flooding that has occurred in Uckfield.
The Environment Agency, and the partners working on this CFMP, designated policy units that set out the direction for flood risk management within the catchment in the future. Within the WDC SFRA study area two policy units have been defined that are summarised in Table 3-2 and Table 3-3. Policy Unit 5 covers Uckfield and Maresfield and Policy Unit 6 covers the area Between Uckfield and Crowborough as well as to the western boundary of the Wealden District.
D118200 March 2009
24 Wealden District Council Level 1 SFRA: Final Report
Table 3-2: Policy Unit from the Draft Ouse CFMP relevant to the WDC SFRA study area Policy unit 5 Ouse Low Weald (West) Physical characteristics: - Gently undulating countryside. - The north of the unit is underlain by greensand and gault changing to weald clay in the south, with bands of sandstone crossing the greensand and gault in the west of the unit. - The soils are seasonally wet loam to clayey over shale to the north and seasonally deep wet clay in the south over the weald clay. - This policy unit contains mostly managed grassland and arable land with isolated properties and small settlements. - Agricultural land classified as grade 3 with areas of low grade 4 to the north and grade 2 to the south. - The policy unit borders the South Downs AONB. ESA and proposed national park boundaries. - This unit includes Chailey Common SSSI, which is not located in the floodplain areas. Flood mechanism: - A low risk of localised fluvial flooding. - Localised surface water flooding in Wivlesfield and Plumpton Green. Receptor: Problem/risk - Isolated properties. - Low grade agricultural land (mainly Grade 3 or 4). - Small number of properties in Wivlesfield Green and Plumpton Green. 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 average damages (approx.) £0 Future Flood risk: - There is a low flood risk from fluvial flooding from the Bevern Stream and Longford Stream, tributaries of the River Ouse, which is not expected to increase in the future. - There is a low flood risk from surface water flooding in Wivlesfield Green and Plumpton Green. 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 average damages (approx.) £0 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. 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: Justification - The current level of flood risk is low and it is not expected to increase in the future. - The current flood risk management activities carried out for the surface water 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 increase. Catchment • Enhance landscape character and protect culturally important and heritage sites, objectives including scheduled and designated sites and features.
D118200 March 2009
25 Wealden District Council Level 1 SFRA: Final Report
Policy unit 5 Ouse Low Weald (West) • Ensure the impact of flooding on people, property and infrastructure does not increase (for example due to climate change). Catchment-wide There are opportunities to support the local schemes and studies already in place to reduce opportunities the surface water flooding problems in Wivlesfield Green. and constraints Policy 1 – do nothing. This policy option would not address the localised surface water flooding problems, which would increase if the ‘do nothing’ option were chosen.
Policy 2 – reduce the current level of flood risk management. As with policy 1, the localised surface water flooding problems would not be addressed if the current flood risk management actions were reduced.
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 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 limited opportunities within this policy unit for this policy. Uncertainties We have estimated the future increase in flood risk within this policy unit on the best available and prediction we have of climate change, frequency and size of storms, flood events and sea dependencies level rise in the future.
Table 3-3: Policy Unit from the Draft Ouse CFMP relevant to the WDC SFRA study area Policy unit 6 Lewes Physical characteristics: - The River Ouse flows through the town of Lewes. - This policy unit is mainly urbanised. - The town is located between two chalk escarpments of the South Downs. - The soils are seasonally wet deep clay. Problem/risk - The agricultural land is classed as grade 4 (poor) throughout the policy unit. - There are six SSSIs that fully or partly lie in the policy unit (including Lewes Brooks and Offham Marshes). - Lewes town is classed as an archaeologically sensitive area with at least ten Scheduled Monuments located in the policy unit. Flood mechanism: - Overtopping of raised river embankments along the River Ouse. - Combination of groundwater flooding, surface water run-off, under capacity urban drainage systems causing flooding. Receptor: - People, properties and infrastructure in Lewes. - Small sections of the Offham Marshes and Lewes Brooks SSSIs. Current Flood Risk Summary Number of properties at risk of flooding (1% annual probability flood event) 376 Total damages (approx.) (1% annual probability flood event) £8.95 million Annual average damages (approx.) £0.5 million
D118200 March 2009
26 Wealden District Council Level 1 SFRA: Final Report
Policy unit 6 Lewes Future Flood risk: - There is a high flood risk in this policy unit from fluvial flooding; the assessment remains high in the future. - Flood risk from surface water, groundwater and urban drainage problems is currently assessed as high; the assessment remains high in the future. - There is risk to life from flooding now and in the future. - Currently there are approximately 380 properties, one electricity sub station and the Lewes fire station at risk of flooding from the River Ouse from the 1% annual probability flood event in Lewes. - In the future the number of properties at risk of flooding is expected to increase to nearly 500 from a 1% annual probability flood event in this policy unit. Future Flood Risk Summary (in 100 years time) Number of properties at risk of flooding (1% annual probability flood event) 490 Total damages (approx.) (1% annual probability flood event) £15.0 million Annual average damages (approx.) £1.1 million Policy selected Policy 5 – Take further action to reduce flood risk (now and/or in the future). Although there are opportunities to reduce flooding in Lewes by increasing flood storage on the floodplain upstream in other policy units, the current level of risk in this policy unit has meant we have selected policy 5. This policy applies to this policy unit for the following reasons: - The current level of flood risk is considered unacceptable, with approximately 380 properties at risk of flooding from the River Ouse from a 1% annual probability flood event. This number is expected to increase with the groundwater and surface water Justification flooding problems experienced in Lewes, to approximately 800. - Future levels of flood risk in this policy unit are high, due to climate change and sea level rise. - Flood damages are expected to increase by £6.1 million for the 1% annual probability flood event, 100 years in the future. - Supports Defra’s recent Integrated Urban Drainage Strategy currently being piloted in Lewes. - The selected policy would achieve the social and economic catchment objectives. • Protect and enhance nationally and internationally important biodiversity species and habitats. • Reduce the number of properties affected by flooding. • Reduce disruption to regionally and locally important transport routes (road and rail). Catchment • Reduce disruption to emergency and educational establishments. objectives • Ensure that emergency arrangements, including flood warning and information, are kept up to date and exercised regularly. • Reduce the cost of flood damages in Lewes and surrounding areas. • Support the implementation of sustainable planning policies taking due regard of flood risk in line with PPS25. There is an opportunity to work with the new Integrated Urban Drainage pilot project In Lewes to help achieve its aims to assess solutions to actual and potential flooding problems in a cost effective, sustainable and integrated way, irrespective of asset ownership.
Catchment-wide Early investigations of flooding mechanisms have shown that there may be an opportunity to opportunities reduce flood risk in this policy unit by adopting policy 6 in the catchments upstream (policy and constraints units 1 and 4).
There are opportunities in this catchment to maintain the current flood defences where economically, technically and environmentally justified.
D118200 March 2009
27 Wealden District Council Level 1 SFRA: Final Report
Policy unit 6 Lewes There is future urban growth proposed in Lewes over the next 20 years. There are opportunities to reduce flood risk and improve the existing water quality by promoting and encouraging the use of Sustainable Drainage Systems (SuDS) within the new housing developments. Policy 1 – do nothing. This policy would not recognise the need to reduce flood risk. Currently there is a risk to human life from flooding and this policy option would increase this risk significantly therefore making this policy choice not an option.
Policy 2 – reduce current level of flood risk management. As with policy 1, this policy would not recognise the need to reduce flood risk, considered unacceptable now and with even more concerns for the future. Alternative policies Policy 3 - maintain current level of flood risk management. As with policy 1, this would not considered recognise the need to reduce the current flood risk.
Policy 4 – maintain the current level of flood risk into the future. As with policy 1, this would not recognise the need to reduce the current flood risk.
Policy 6 – increase flooding to reduce flood risk elsewhere. There are limited opportunities within this policy unit, due to the high density of urban development and essential infrastructure, to take this approach. 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, flood events and sea level rise in the future. Uncertainties
and The broadscale model has not included the surface water run-off, groundwater flooding and dependencies urban drainage problems. 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.
3.6.1.2 River Medway CFMPxxix
The Medway CFMP includes the catchments of the River Medway, River Tiese, River Beult, River Boune and River Eden covering much of the Wealden District SFRA study area. As a result of the technical assessments carried out in the CFMP, the Environment Agency has determined its preferred flood risk management policies to specific areas within the catchment. However, there are no policies specific to area within the Wealden District.
3.6.1.3 Draft Rother and Romney CFMPxxx
The Draft Rother and Romney CFMP identifies policy units and preferred options for the catchment. All of the Wealden study area that is covered by the Rother and Romney CFMP falls within Policy Unit 6: Rural Rother.
The policy aims to reduce the flood risk by transferring the risk to other locations where the consequences of flooding are positive. It is stressed that this would be carried out in a managed way, to localised areas, following consultation with landowners. A strategy should be developed where this is investigated in more detail.
D118200 March 2009
28 Wealden District Council Level 1 SFRA: Final Report
RURAL ROTHER
This policy unit covers areas of the Rother and Romney CFMP that are not The policy unit covered by the other policy units. In the past there has been little or no risk of flooding from rivers, surface water Problem/risk or foul water flooding. 3 to 4 properties have been known to flood from the Marsham Sewer at the base of Chick Hill, near Cliff End 6 – Take action to increase the frequency of flooding to deliver benefits locally Policy or elsewhere. In the past there has been little or no risk of flooding from rivers, surface water or foul water flooding. Areas of agricultural land are enclosed behind flood embankments which could be removed without threatening people or property. Reasons why There are opportunities to remove flood embankments in selected locations in order to attenuate flood flows, and reduce impacts elsewhere in the catchment. Agreements would need to be reached with landowners over any for any (sic) inundation of their land with support to take part in Agri-Environment schemes. Opportunities Opportunity to create a more natural river corridor through the removal of flood embankments. Providing flood storage opportunities elsewhere in the catchment will enable us Catchment-wide to reduce the impact of flooding at higher risk locations. opportunities and Potential for the introduction of more sustainable farming practices to reduce constraints storm runoff. Constraints Ensuring that any action taken does not increase the risk of flooding to people or infrastructure, and communicating this effectively to stakeholders. Support the development and recommendations of the Rye Harbour and Pett Level SSSI Water Level Management Plans (WLMP). Support the development of the WLMP for the new Dungeness, Romney Marsh and Rye Bay SSSI. Develop a System Asset Management Plan (SAMP). This plan should aim to Actions increase the frequency of flooding to deliver benefits elsewhere. For example, identify areas where creation of wetland habitat can help to reduce flooding. (Link with the Regional Habitat Creation Programme) Investigate opportunities to work with landowners to create wetland habitat (Link with the Regional Habitat Creation Programme) Risks, Climate change is predicted to cause more intense storms. uncertainties and dependencies
D118200 March 2009
29 Wealden District Council Level 1 SFRA: Final Report
3.7 Other Relevant Policies
3.7.1 Upper Medway Internal Drainage Board Bye-laws
Under the Land Drainage Act 1991, the Upper Medway IDB make the following bye-laws governing the watercourses they are responsible for. The Land Drainage Act (1991) states that: ‘these are considered necessary for securing the efficient working of the drainage system in their district’. Control of Introduction of Water and Increase of Flow or Volume of Water No person shall, without the previous consent of the Board, for any purpose, by means of any channel, siphon, pipeline, or sluice or by any other means whatsoever, introduce any water to the District or, whether directly or indirectly, increase the flow or volume of water in any watercourse in the District. Control of Sluices etc Any person having control of any sluice, slacker, floodgate, lock, weir, dam, pump, pumping machinery or other structure or appliance for introducing water into any watercourse in the District or for controlling or regulating or affecting the flow of water in, into or out of any watercourse shall use and maintain such sluice, slacker, floodgate, lock, weir, dam, pump, pumping machinery, structure or appliance in accordance with such reasonable directions as may from time to time be given by the Board with a view to the prevention of flooding or any shortage in the flow or supply of water and to the efficient working of the drainage system in the District. Diversion or Stopping up of Watercourses No person shall, without the previous consent of the Board, take any action, or knowingly permit or aid or abet any person to take any action to stop up any watercourse or divert or impede or alter the level of or direction of the flow of water in, into or out of any watercourse. Detrimental Substances not to be put into Watercourses No person shall, so as directly, or indirectly to obstruct, impede or interfere with the flow of water in, into or out of any watercourse or so as to damage the bank:- (a) discharge or put or cause or permit to be discharged or put or negligently or wilfully cause or permit to fall into any watercourse any object or matter of any kind whatsoever whether solid or liquid; (b) allow any such object or matter as is referred to in sub-paragraph (a) of this Byelaw to remain in proximity to any watercourse in such manner as to render the same liable to drift or fall or be carried into any watercourse. Provided that nothing in this Byelaw shall be deemed to render unlawful the growing or harvesting of crops in accordance with normal agricultural practice. No Obstructions within 8 Metres of the Edge of the Watercourse No person without the previous consent of the Board shall erect any building or structure, whether temporary or permanent, or plant any tree, shrub, willow or other similar growth within 8 metres of the landward toe of the bank where there is an embankment or wall or within 8 metres of the top of the batter where there is no embankment or wall, or where the watercourse -is enclosed within 8 metres of the enclosing structure. Not to Dredge or Raise Gravel. Sand etc No person shall without the previous consent of the Board dredge or raise or take or cause or permit to be dredged or raised or taken any gravel, sand, ballast, clay or other material from the bed or bank of any watercourse.
D118200 March 2009
30 Wealden District Council Level 1 SFRA: Final Report
Interference with Sluices No person shall without lawful authority interfere with any sluice, slacker, floodgate, lock, weir, dam, pump, pumping machinery or any other structure or appliance for controlling or regulating the flow of water in, into or out of a watercourse. Damage to Property of the Board No person shall interfere with or damage any bank, bridge, building, structure, appliance or other property of or under the control of the Board.
3.7.2 British Waterways
British Waterways are responsible for the maintenance of some inland waterways. However they are not responsible for any in the Wealden SFRA study area.
3.7.3 Water Utility Policies
Southern Water is responsible for the management of foul water in the WDC SFRA Study area. One of their objectives is to achieve sustainable development through the following policy:
Sustainable Development Policy Sustainable development at Southern Water means an increasing focus on the balanced consideration of economic, social and environmental aspects in making business decisions. Within and beyond the regulatory framework of the water industry, Southern Water believes adopting Sustainable Development principles will:
• Ensure the continued supply of quality drinking water and the provision of wastewater services in line with European standards; • Safeguard water supplies and enable the effective management of water resources; • Ensure the safe recycling of wastewater and sludge to the environment; • Improve services by providing them in a sustainable and cost-effective way; and, • Involve our communities and influence our business partners in working towards more sustainable futures.
3.7.4 Building Regulationsxxxi
Building Regulations set out the minimum standards required for buildings. Their aim is to ensure the health, safety and welfare of the people inside or around a building. They were first published in 1984 but significantly updated in 2002. Building Regulations are required in the construction of a new or an extension of a dwelling as well as in most cases where there is a change of use to a dwelling.
Within the regulations there is a specific section related to the rainwater drainage (Building Regulations Part H) systems that are installed into new builds.
3.7.4.1 Policy H3 Rainwater Drainage
• Adequate provision shall be made for rainwater to be carried from the roof of the building; • Paved areas around the building shall be so constructed as to be adequately drained; and,
D118200 March 2009
31 Wealden District Council Level 1 SFRA: Final Report
• Rainwater from a system provided pursuant to sub-paragraphs 1) or 2) shall discharge to one of the following, listed in order of priority:- o an adequate soakaway or some other adequate infiltration system; or, where that is not reasonably practicable; o a watercourse; or, where that is not reasonably practicable; and, o a sewer.
3.7.5 Code for Sustainable Homesxxxii
The Code for Sustainable Homes has been implemented since 1st May 2008. All new developments are required to demonstrate whether the ratings prescribed under the Code have been achieved. The Code has been developed to introduce a step-change in sustainable home building practise using a rating system that demonstrates the sustainability performance of a new home. However, it is not yet compulsory to meet any of Code levels.
It is designed so that it has benefits to the environment that include reduced greenhouse gas emissions, better adaptation to climate change and a reduced impact on the overall environment. This is in parallel with benefits to the home builder that include a mark of quality, regulatory certainty and flexibility.
As part of this therefore it will become mandatory for surface water drainage and water efficiency measures to be assessed in all new developments. To achieve the surface water mandatory credit, developments are required to ensure that run-off rates and annual volumes of run-off post development will be no greater than the previous site conditions.
The Code has created a six level rating system to reflect the degree to which sustainable measures have been introduced into a development. Further information on how SuDS can be used as a technique to achieve a higher rating can be found in Section 9.
Table 3-4: Planning document policies by subject area ISK
R
ESOURCES ESOURCES POLICY DOCUMENT POLICY ISK R R NVIRONMENT ATER E RAINAGE USTAINABLE LOOD LOOD F F MANAGEMENT S D W & Regional Planning INF1 –a1 Guidance for the South INF1 –a2 East RPG9 INF1 –a3 INF1 –a4 INF1 –b1 INF1 –b2 INF2 – a1 INF2 – a2 INF2 – a3
D118200 March 2009
32 Wealden District Council Level 1 SFRA: Final Report ISK
R
ESOURCES ESOURCES POLICY DOCUMENT POLICY ISK R R NVIRONMENT ATER E RAINAGE USTAINABLE LOOD LOOD F F MANAGEMENT S D W & INF2 – b1 INF2 – b2 South East Plan Policy NRM1 Policy NRM2 Policy NRM3 Wealden Local Plan Policy CS2 Policy CS3 Policy CS4 Objective G (Table 5.2)
Draft River Ouse CFMP Policy Unit 5
Draft River Ouse CFMP Policy Unit 6
River Medway CFMP
Draft Rother and Romney CFMP
ESCC Transport and E 2.23 Environment Services Plan
ESCC Transport and H 3.9 Environment Services Plan
ESCC Transport and H 3.10 Environment Services Plan
Upper Medway IDB
Southern Water
D118200 March 2009
33 Wealden District Council Level 1 SFRA: Final Report ISK
R
ESOURCES ESOURCES POLICY DOCUMENT POLICY ISK R R NVIRONMENT ATER E RAINAGE USTAINABLE LOOD LOOD F F MANAGEMENT S D W & Building Regulations 2008 Policy H3
Code for Sustainable Homes
3.8 Forthcoming Policies
3.8.1 Ofwat’s 2009 Price Review (PR09)
Ofwat is responsible for setting the price limits for water and sewerage companies in England and Wales. It reviews its pricing strategy on a regular bases and is currently preparing for the Price Review 2009. In The Pitt Reviewxxxiii an interim conclusion was that “as part of the forthcoming water industry pricing review, the water companies, in conjunction with local authorities and other partners, should develop proposals for investment in the existing drainage network to deal with increasing flood risk.”
xvi Department for Communities and Local Government (2006) ‘The Town and Country Planning (flooding) (England) Direction 2007’, DCLG: London. xvii Environment Agency (2007) ‘Environment Agency Standing Advice Development and Flood Risk – England’, available at http://www.pipernetworking.com/floodrisk/ accessed on 16.06.2008. xviii Office of the Public Sector Information (1991) ‘Water Industry Act 1991 c.56’, OPSI. xix European Union (2007) ‘Directive 2007/60EC of the European Parliament and of the Council of 23 October 2007on the assessment and management of flood risks’, in Official Journal of European Union. xx DEFRA (2005) ‘Making Space for Water’, DEFRA: London. xxi Communities and Local Government (2005) ‘Planning Policy Statement 1: Delivering Sustainable Development’, DCLG: London. xxii Communities and Local Government (2006) ‘Consultation - Planning Policy Statement: Planning and Climate Change – Supplement to Planning Policy Statement 1’, DCLG: London. xxiii Communities and Local Government (2007) ‘Planning Policy Statement 3: Housing – Equality Impact Assessment’, DCLG: London. xxiv Communities and Local Government (2008) ‘Planning Policy Statement 12: Local Spatial Planning’, DCLG: London. xxv Communities and Local Government (2001) ‘Regional Planning Guidance for the South East’, DCLG: London. xxvi South East England Regional Assembly (2006) ‘Regional Flood Risk Appraisal for South East Plan’, South East England Regional Assembly. xxviiWealden District Council (2005) ‘Non Statutory Wealden Local Plan’, WDC: Crowborough.
D118200 March 2009
34 Wealden District Council Level 1 SFRA: Final Report
xxviii Environment Agency (2008) ‘River Ouse Catchment Flood Management Plan: Draft Main Stage’, Environment Agency: Worthing. xxix Environment Agency (2004) The Medway Catchment Flood Management Plan’, Environment Agency: Worthing. xxx Environment Agency (2007) ‘Rother and Romney Catchment Flood Management Plan’, Environment Agency: Worthing. xxxi Office of the Deputy Prime Minister (2008) ‘Approved UK Building Regulations 2008’, TSO: London. xxxii Communities and Local Government (2006) ‘Code for Sustainable Homes: A step-change in sustainable home building practice’, DCLG: London. xxxiii Pitt, M. (2007) ‘Learning the lessons from the 2007 foods: The Pitt Review’, COI Communications: London.
D118200 March 2009
35 Wealden District Council Level 1 SFRA: Final Report
4 Data Collection and Review
One of the objectives was to ‘collect, collate and review available information on flood risk for the study area’. This section describes the data collection process, presents the available data and discusses its benefits and limitations. A comprehensive record of all the data collected through the production of the Level 1 SFRA is presented in a document register in Appendix B.
4.1 Overview
As outlined in Section 1.3 the objective of the Level 1 SFRA is to collect, collate and review the information available relating to flooding in the study area. This information is then presented in a format to enable WDC to apply the Sequential Test to their area to determine suitability of sites for development and identify sites that may need to be justified through successful application of the Exception Test.
The sequence of tasks undertaken in the preparation of the Level 1 SFRA was, in order:
• Inception meeting with Wealden District Council on 11th January, 2008 (Appendix D), which established the local stakeholders; • letters issued to stakeholders requesting data/information; • Data requests followed up; • Data collated and reviewed and data register populated; • Data reviewed against the SFRA objectives; and • Presentation of available salient information on flood sources and flood risk.
All tasks were completed between January 2008 and the end of May 2008.
4.1.1 Stakeholder Consultation
The stakeholders that were contacted to provide data/information for the SFRA include:
• East Sussex Fire and Rescue; • Environment Agency; • Highways Agency; • River Medway Internal Drainage Board; • Southern Water; and, • Wealden District Council.
4.1.2 Topographic Data
Light Detecting and Ranging (LiDAR) data was provided for the study area by the Environment Agency. LiDAR data is an airbourne survey technique that uses a laser to measure the distance between an aircraft and the ground surface. The LiDAR technique records an elevation accurate to ±0.3m every 2m. The technique records elevations from the majority of surfaces and includes features such as buildings, trees and cars. The raw data is processed to remove these features to give values for the ground surface. The LiDAR data can then be merged to create a Digital Terrain Model (DTM) of the ground surface. The available LiDAR data covers approximately 30% of the study area (Figure 4).
D118200 March 2009
36 Wealden District Council Level 1 SFRA: Final Report
Channel survey details as part of the Ouse, Barkham and Uck survey have been supplied Geographical Information System(GIS) layers and AutoCAD drawing (dwg) format. These include cross-sectional details of the River Uck through Isfield, Uckfield and Buxted. This will be a useful addition to the Level 2 SFRA.
4.2 Environment Agency Flood Zone Maps
The Environment Agency has provided an extract of their Flood Map for the study area (Figure 5). The Flood Map shows the estimated extent of the PPS25 Flood Zones 2 and 3 (ignoring the presence of flood defences) for all watercourses with a catchment area of 3km² or greater and watercourses with identified critical drainage problems. The Flood Map gives a good indication of the areas at risk of flooding in England and Wales, however it does not provide detail on individual properties or cover all watercourses in the study area. The definitions of the flood zones according to PPS25ii is presented in Table 4-1. It should be noted that the Environment Agency mapping does not delineate Flood Zone 3a and 3b. Without this distinction all Flood Zone 3 should be classified as 3b in accordance with PPS25ii. Table 4-1: PPS25iiFlood Zone classifications
PROBABILITY OF FLOOD ZONE DEFINITION FLOODING At risk from flood event greater than the 0.1% (1 in 1000 Flood Zone 1 Low Probability year) annual probability storm event At risk from flood event between the 1% (1 in 100 year) Flood Zone 2 Medium Probability and 0.1% (1 in 1000 year) annual probability storm event At risk from a flood event less than or equal to the 1% Flood Zone 3a High Probability annual probability (1 in 100 year) storm event At risk from a flood event less than or equal to the 5% Flood Zone 3b Functional Floodplain annual probability (1 in 20 year) storm event
The Environment Agency’s Flood Map has been developed using a combination of detailed information from appropriate hydraulic models (where available) and outputs from the Environment Agency’s National Generalised Model (JFLOW). Hydraulic models use detailed topographic data and rigorously derived flow estimates to derive flood extents. The National Generalised Model outputs are derived from less accurate topographic data (SAR/LiDAR data) and national data for river flows. The flood maps are reviewed every 3 months are where there has been additional hydraulic modelling the flood extents are incorporated into Flood Zones 2 and 3. At this stage the modelling of the River Medway (described below) has been incorporated into the Environment Agencies flood mapping but the modelling of the Uck and Ouse has not. The Flood Map does not provide information on flood depth, speed or volume of flow. It also does not show flooding from other sources, such as groundwater, direct runoff from fields, overflowing sewers or the effect of climate change on these sources.
4.3 Fluvial Data
GIS layers were provided by the Environment Agency and the Upper Medway IDB to show the locations of their Main rivers and watercourses respectively. The other water features in the study area were identified through a GIS query of the Ordnance Survey mastermap data provided by WDC. This
D118200 March 2009
37 Wealden District Council Level 1 SFRA: Final Report
used the attributes that are associated with the mapping to identify those that have been classified as ‘water’. In some cases watercourses may have been missed as they have been classified as another field type.
4.4 Hydraulic Modelling
Hydraulic models enable the delineation of flood plains and flood depths based on detailed topographic data of river channels including structures (bridges, culverts etc) and flood defences. Detailed hydrological analysis provides a range of flow estimates for use in the models enabling the estimation of flood extents for a range of flood return periods. Hydraulic models have been developed for a number of watercourses within the WDC SFRA study area. Hydraulic modelling outputs were requested from and provided by the Environment Agency. Figure 6 shows the watercourses for which hydraulic model results are available.
4.4.1 River Ouse (upper reaches)
The hydraulic model of the River Ouse (upper reaches) has been constructed using ISIS by Atkins (2002/2003). The model has been run for the 20% (1 in 5 year), 10% (1 in 10 year), 4% (1 in 25 year), 2% (1 in 50 year), 1.3% (1 in 75 year), 1% (1 in 100 year) and 1% (1 in 100 year) plus climate change flood events. The hydraulic model has not been made available for the Level 1 SFRA, however flood outlines from this model have been provided. This modelling does not take into account the effect of flood defences. We were made aware that there has been some additional modelling of the Upper and Middle Ouse undertaken. At the time of writing this modelling was being verified and should be included in future updates of this SFRA.
4.4.2 River Uck
The hydraulic model of the River Uck has been constructed using ISIS by Atkins (2002/2003). The model has been run for the 20% (1 in 5 year), 10% (1 in 10 year), 4% (1 in 25 year), 2% (1 in 50 year), 1.3% (1 in 75 year), 1% (1 in100 year) and 1% (1 in 100 year) plus climate change flood events. The model does not cover the whole of the River Uck within the SFRA study boundary, but does include the settlements of Uckfield and Buxted. The River Uck model also includes sections of the Framfield Stream and Tickeridge Stream. The hydraulic model and the flood outlines have been made available for the Level 1 SFRA. This modelling does not take into account flood defences.
4.4.3 River Medway
The hydraulic model of the River Medway has been constructed using ISIS by Mott MacDonald (2003/2004). The model has been run for the 20% (1 in 5 year), 10% (1 in 10 year), 4% (1 in 25 year), 2% (1 in 50 year), 1.3% (1 in 75 year) and 1% (1 in 100 year) flood events. Additional model runs have been completed that modelled the 5% annual probability (1 in 20 year) plus climate change and 1% (1 in 100 year) plus climate change. The hydraulic model has been not been made available for the Level 1 SFRA, however flood plain outlines from this model have been provided. This modelling does take into account the presence flood defences.
D118200 March 2009
38 Wealden District Council Level 1 SFRA: Final Report
4.4.4 Other Watercourses
There are a number of other watercourses within the study area that have flood zones defined. Some of these are main rivers and therefore can be named in the hydraulic modelling Table 4-2. Some however are ordinary watercourses and no names can be given.
D118200 March 2009
39 Wealden District Council Level 1 SFRA: Final Report
FRAMFIELD TICKERIDGE RIVER OUSE UCK MEDWAY RIVER ROTHER RIVER TEISE STREAM STREAM Modelled Yes Yes Yes Yes Yes Yes Yes Coverage of 100% 100% 80% 100% 100% 100% 100% model Modelled By Atkins Atkins Mott MacDonald EA EA EA and Atkins EA and Atkins Modelling ISIS ISIS ISIS JFLOW JFLOW ISIS and JFLOW ISIS and JFLOW software 0.1%, 1% (EA); 0.1%, 1% (EA); 20%, 10%, 20%, 10%, 5% + Model Runs 20%, 10%, 4%, 20%, 10%, 4%, 20%, 10%, 4%, 4%, 2%, cc, 4%, 2%, 0.1% and (annual 2%, 1.3%, 1% 0.1% and 1% 2%, 1.3%, 1% 2%, 1.3%, 1% 1.3%, 1% and 1.3%, 1% and 1% probabilities) and 1% plus cc and 1% plus cc and 1% plus cc 1% plus cc 1% + cc. (Atkins) (Atkins) Including No No Yes No No No No Defences Excluding Yes Yes No Yes Yes Yes Yes Defences All return periods All return periods All return All return All return All return All return Flood Outlines that cover the that cover the periods periods periods periods periods Atkins model Atkins model All return periods All return periods All return All return All return Flood Levels No No that cover the that cover the periods periods periods Atkins model Atkins model Table 4-2: Summary table showing the fluvial model data available for the WDC SFRA study area
D118200 March 2009
40 Wealden District Council Level 1 SFRA: Final Report
HIGH HURSTWOOD LITTLE HORSTED RIDGEWOOD SHORTBRIDE ISFIELD MILL BATTS BRIDGE RIVER STREAM STREAM STREAM STREAM STREAM STREAM Modelled Yes Yes Yes Yes Yes Yes Coverage of 50% 100% 100% 100% 100% 100% model Modelled By EA EA and Atkins EA and Atkins EA and Atkins Atkins EA Modelling software ISIS and JFLOW ISIS and JFLOW ISIS and JFLOW ISIS and JFLOW ISIS JFLOW 0.1%, 1% (EA); 0.1%, 1% (EA); 0.1%, 1% (EA); 0.1%, 1% (EA); Model Runs 20%, 10%, 4%, 20%, 10%, 4%, 20%, 10%, 4%, 20%, 10%, 4%, 20%, 10%, 4%, (annual 2%, 1.3%, 1% and 2%, 1.3%, 1% and 2%, 1.3%, 1% and 2%, 1.3%, 1% and 2%, 1.3%, 1% and 0.1% and 1% probabilities) 1% plus cc 1% plus cc 1% plus cc 1% plus cc 1% plus cc (Atkins) (Atkins) (Atkins) (Atkins) Including No No No No No No Defences Excluding Yes Yes Yes Yes Yes Yes Defences All return periods All return periods All return periods All return periods Flood Outlines that cover the that cover the that cover the that cover the All return periods Atkins model Atkins model Atkins model Atkins model All return periods All return periods All return periods All return periods Flood Levels that cover the that cover the that cover the that cover the All return periods Atkins model Atkins model Atkins model Atkins model
D118200 March 2009
41 Wealden District Council Level 1 SFRA: Final Report
4.5 Historical Flooding Events
4.5.1 Environment Agency Data
Historical flood extents have been provided by the Environment Agency as a GIS layer and have been mapped in Appendix A. Table 4-3 provides a summary of the historical flood extents and description provided by the Environment Agency. No point data has been provided by the Environment Agency. Table 4-3 : Summary of Historical Flood Extents
LOCATION/SOURCE DATE APPROXIMATE EXTENT/DESCRIPTION All reaches that (sic) including Forest Row, channel River Medway 1960 exceeded capacity. River Medway 1968 As above channel exceeded capacity Discrepancy in data some information states and (sic) overtopping of defences from Crowhurst Bridge to River Rother 1985 Scotsfoot Bridge some states an exceedence in channel capacity. River Uck 1974 Limited to Uckfield River Ouse Middle Oct 2000 Channel capacity was exceeded (no raised defences) Reaches and River Uck
4.5.2 Wealden District Council Data
WDC has provided detailed information of flooding incidents from 1990-2007 that has been collected by WDC and compiled in a database. The data provided states the date of the flooding incident; the location (including grid references in most cases); details of the problem; and the status of the incident. It should be noted that some of the incidents were unable to be plotted as they contained no postcodes or grid references. The database records flooding from all sources and therefore it was interrogated to provide data on the location of the various sources of flooding. The data has been reviewed a flooding source assigned to each record, where possible. The flooding incidents were classified into the following flooding sources:
• Drainage – This type of flooding has been described in Section.2.2.3. For example this category includes flooding incidents that have occurred when a sewer or highway drain has surcharged. This category also includes flooding that has occurred as a result of a drainage ditch becoming blocked; • Overland Flow – This type of flooding has been described in Section.2.2.5. Records in the database often associate overland flow flooding with a failure in highway drainage, however for the purpose of this assessment the incidents have been separated where possible; • Artificial – This type of flooding has been described in Section 2.2.6; • Groundwater – This type of flooding has been described in Section 2.2.4; • Fluvial - This type of flooding has been described in Section 2.2.2; • Unknown Source – Mitigation – This category was formed as there were a number of entries in the database that simply stated that sandbags were needed to prevent
D118200 March 2009
42 Wealden District Council Level 1 SFRA: Final Report
flooding. Therefore there was insufficient data to be able to ascertain the source of the flooding; and, • No Discernable Flood Source – This category was formed as there were a number of entries in the database where there was insufficient information to place it into another category.
An example of each of these categories extracted from the database is displayed in Table 4-4 below. Table 4-4: Historical Flooding from the Wealden Database
EVENT LOCATION DETAILS FLOODING STATUS DATE SOURCE June Fire Brigade, Chillies Lane, Sandbags. Unknown Passed to another 2000 Buxted authority Jan Ivy Hole Cottage, Chillies Lane, Watercourse Fluvial Advised and completed 2001 Buxted bank slippage in wet conditions, Suggested that the outlet pipes should be extended to prevent. Aug Clease Road Ltd, High Street, Flooding to Drainage/sewer Passed to another 1997 Buxted shop premises authority defective outflow from highway drainage system ESCC to investigate. Jan Perrymans Lane, Buxted Surcharging Drainage/sewer Current 1994, stream in Jul garden ESCC 1994 working on and adjacent road Jun drainage. 2000 Councils opinion taken. Surcharging stream, ESCC do not accept responsibility for highway culvert capacity. Aug Little Forge, Perrymans Lane, Surface run-off Overland flow Passed to another 1997 Buxted from highway, authority passed to ESCC.
The data is displayed in Chart 1 and in the figures in Appendix A.
D118200 March 2009
43 Wealden District Council Level 1 SFRA: Final Report
Chart 1: Types of Flooding Incidents in the Wealden District extracted from the WDC database
Types of Flooding Incidents from Wealden Database
No Discernable Flood Source Drainage 18% 24%
Fluvial 5%
Artificial 1%
Unknow n Groundw ater Source - 1% Mitigation Overland Flow 40% 11%
The WDC database shows that: -
• The majority of the entries in the WDC database record incidents when sandbags have been employed/issued but in most cases do not state the flood source they were issued to defend against; • 5% of the incidents recorded were a result of fluvial flooding. After a review of the comments the majority of these incidents were caused by a culvert in a watercourse becoming blocked or having insufficient capacity; and, • 18% of the recorded entries had no discernable flood source. In many cases these entries were statements of repair work that had taken place or complaints that had been received.
D118200 March 2009
44 Wealden District Council Level 1 SFRA: Final Report
4.5.3 CFMP Data
The Medway Catchment Flood Management Planxxxiv (CFMP) includes some of the study area and presents some points that have experienced significant flooding between 1846 and 2001. A summary of this information is presented in Table 4-5. Table 4-5: Historical Flood Events in the Wealden SFRA study area extracted from The Medway CFMPxiv
LOCATION NUMBER OF FLOOD EVENTS BETWEEN 1846 AND 2001 Forest Row 6 - 10 Hartfield 6 - 10 Groombridge 6 - 10 Eridge Station 6 - 10 Bells Yew Green 6 - 10
Causes of these flooding incidents are not presented in the CFMP. However, it does state a number of general causes to be: an insufficient channel capacity; constrictions at structures; blockages from debris within a channel; and/or inappropriate development in areas that are vulnerable to the aforementioned reasons.
The Draft River Ouse CFMPxv refers to past flooding incidents in Uckfield. These are summarised in Table 4-6 below. Table 4-6: Historic Flooding Incidents from the Draft Ouse CFMPxv Date Details 1852 Serious floods in Uckfield 1865 Serious floods in Uckfield (26th October) 1875 Serious floods in Uckfield. Highest flood since 1852. 1916 Major flooding in Uckfield.
1943 Major flooding in Uckfield (14th January). Less than 100 properties affected. 1952 Flooding in Uckfield (28th February). Less than 100 properties affected. 1974 Major flooding in Uckfield. Less than 100 properties affected. 1979 Major flooding in Uckfield (28th December). More than 100 properties affected. 1993 Major flooding in Uckfield. December 30 – 31, (peak flow 80 cumecs). 30 properties flooding in Uckfield. Flooding also in Buxted. 2000 Autumn 2000; major flooding across the south east. Uckfield severely affected. 1st – 12th October 2000 (peak flow 132 cumecs). Uckfield was cut-off as all major routes were flooded. In Uckfield up to 100 businesses and domestic properties affected. Barcombe, Isfield and Buxted also suffered flooding. Estimated as the 0.66% (1 in 150 year) annual probability storm event in Uckfield.
D118200 March 2009
45 Wealden District Council Level 1 SFRA: Final Report
The Draft Ouse CFMPxv also identifies other notable flood sources. The CFMP identifies that hammer ponds in the catchment are a flood risk especially as the control structures are now aging. However, these are often located in rural areas and therefore the impact of a structure failing would be small. The CFMP also identifies that Buxted is at risk of overland flow flooding as a culvert under a road crossing is under capacity and this has been causing water to back up. Uckfield is also identified as being at risk of flooding from overland flow from urban areas. The CFMP has assessed the risk of groundwater flooding to be low within the catchment as there are few urban areas where there are high groundwater levels.
The Draft Rother and Romney Marsh CFMPxxxv covers 80.9 km² of the Wealden SFRA study area. It does not mention any flood incidents that have occurred on the River Rother within the Wealden SFRA study area.
4.5.4 Environment Agency Flood Reports
It is widely known that Forest Row has experienced flooding frequently in the past. The most recent flooding occurred on the 20th July 2007 after which the Environment Agency completed a report investigating the incidentxxxvi.
The main rivers in Forest Row are the River Medway and the Kidbrooke Stream. Other ordinary watercourses feed into the River Medway are Shalesbrook and Pippingford Brook there are also a number of other sewers, pipes and culverts linking the river system together.
Flooding occurred after a high intensity rainfall event caused a high volume of surface water being directed to the rivers and drains. There was no flood warning disseminated to local residents prior to the flooding occurring. Kidbrooke Stream, Shalesbrook and Pippingford Brook were unable to cope with the volume of water they received. The drainage system within the town had also insufficient capacity to channel the water to the River Medway causing flood water to back up and propagate surrounding low-lying land.
As part of the investigation a questionnaire was distributed to local residents that provides valuable anecdotal evidence of the nature of the flooding. It can be concluded from the responses included in the report that the flooding was exacerbated by:- • either a build up of debris in culverts and streams; • increased development in the area has increased surface runoff; • an inadequate drainage system; and/or, • Poor design of structures. For example, a culvert at Freshfield Bank allows the passage of more water that the stream can accommodate.
As a result of the investigation some maintenance has been carried out on the Kidbrooke Stream and debris has been cleared. A feasibility study of increasing the storage area of Kidbrooke Stream that is due to be completed early 2008. Other stakeholders that include WDC, ESCC, Forest Row Parish Council and the Upper Medway IDB have been involved in remedial measures since the flooding. The causes that have been concluded in this report are the same as the causes of flooding found in The Medway CFMP which reiterates the requirement for specific policies relating to this aspect of flood risk management.
D118200 March 2009
46 Wealden District Council Level 1 SFRA: Final Report
4.5.5 Fire Service Records
The East Sussex Fire Service was initially identified as stakeholder that could provide information. As, it is known that the fire service maintains a comprehensive list of the incidents it attends to in some cases these are flooding incidents. Information was requested from the East Sussex Fire Service including the date, location and the number of times the fire service has attended that location. However, in correspondence with a contact at the East Sussex Fire Service it was established that all of the records the East Sussex Fire Service hold have been passed on to the Environment Agency.
4.6 Overland Flow
Overland flow data has not been recorded on a regimented basis and no data has been made available from the Environment Agency on any flooding incidents occurring due to overland flow. The WDC Flooding Database recorded 77 flooding incidents as a result of overland flow, that is 11% of the flooding that has been recorded was a result of overland flow.
However, although it was not clearly stated it is likely that the overland flow would have occurred as a result of an inadequate drainage system. As, in most of the incidents recorded the overland flow floodwaters occurred from highways where it is likely that the drainage system is either not adequate or not maintained. There have been some incidents of overland flow flooding where the sources have been new developments A few examples of the data contained in WDC Flooding Database are presented in Table 4-7 the entire dataset is shown in Figure 8. Table 4-7: Examples of Overland Flow Flooding Incidents extracted from WDC Flooding Database (please refer to GIS layers or Figure 8 for all incidents)
Date Location Description of Incident Jun 2000 Western Road, Jarvis Surface water flooding indoors heavy rainfall Brook Jul 1996 Sparrows Green, Flooding from highway, sandbags employed Wadhurst Oct 2000 Highcross Fields, Surface water off new development from raised Crowborough ground
4.7 Groundwater
Borehole records were provided by the Environment Agency that contain daily records of groundwater levels at 24 boreholes across the study area. This data has been queried to establish trends in the groundwater levels at each location and assigned a ‘rising’ or ‘falling’ classification. Figure 9 presents the groundwater trends for each groundwater monitoring location within the study area alongside the groundwater flooding incidents. Table 4-8 : Summary Table of Groundwater Borehole Data Borehole National Grid Length of Record Average Dip Trend Location Reference (years) (m) Mar 1973 – Jan Rising 3.79 2 Strawberry Hill X 556940 Y 137450 2008 (25)
D118200 March 2009
47 Wealden District Council Level 1 SFRA: Final Report
Borehole National Grid Length of Record Average Dip Trend Location Reference (years) (m) Jul 1997 – Jan Falling 3.22 Bartley Mill BH X 563220 Y 135680 2008 (11) Dec 1977 – Jan Falling 4.0 Brook Farm X 556450 Y 127160 2008 (31) Oct 1978 – Jan Falling 3.5 Forest Row A X 545702 Y 135510 2008 (30) Oct 1978 – Jan Falling 3.27 Forest Row B X 545720 Y 135520 2008 (30) Oct 1978 - Jan Rising 26.86 Kingstanding A X 547250 Y 129880 2008 (30) Jul 1978 – Jan Rising 28.33 Kingstanding B X 547250 Y 129910 2008 (30) Little Quarry Oct 1977 – Aug Falling 7.41 X 554180 Y 136980 Farm 2007 (30) Meres Farm Jan 1981 – Jan Falling 5.38 X 558040 Y 125350 STW 2008 (27) Mar 1973 – Jan Falling 1.5 Neylands Farm X 538050 Y 134080 2008 (35) Mar 1973 – Feb Rising 5.17 Northdown X 559130 Y 121840 2008 (35) Park House Mar 1973 – Jan Rising 3.46 X 551370 Y 133930 Park Grove 2005 (32) Mar 1973 – Jan Falling 4.69 Prowdes X 552230 Y 137050 2008 (35) Mar 1973 – Jan Rising 4.35 Stitches Farm X 555270 Y 133220 2008 (35) Jul 1979 – Jan Falling 25.2 The Birches X 544440 Y 133240 2001 (22) Ticehurst Oct 1978 – Feb Rising 17.31 X 561990 Y 122820 Grange 2008 (20) Oct 1977 – Jan Falling 10.14 Toad Hall X 556520 Y 131370 2008 (31) Mar 1973 – Jan Rising 17.82 Upper Old Mill X 558540 Y 123800 2008 (35) Mar 1973 – Jan Falling 2.55 Yewlands X 544310 Y 128820 2008 (35) Mar 1989 – Jan Rising 40.75 Fairwarp X 546635 Y 127156 2008 (19) Halland Godfrey Apr 1964 – Jan Falling 3.89 X 551254 Y 116146 Cottage 2008 (44) Mar 1987 – Jan Falling 30.65 Sheffield Forest X 542271 Y 126888 2008 (21) Mar 1987 – Jan Falling 4.58 Stumblewood A X 540123 Y 130835 2008 (21) Mar 1987 – Jan Falling 5.31 Stumblewood B X 540122 Y 130853 2008 (21)
D118200 March 2009
48 Wealden District Council Level 1 SFRA: Final Report
Of the flood incidents recorded on the WDC Flooding Database 1% are as a result of groundwater rising above the ground surface. The 7 incidents that have been recorded are summarised in Table 4-9 below and are displayed in the figures in Appendix A. There are no boreholes within the immediate vicinity of the flooding incidents although there is a monitoring borehole within 6 km² of a flooding incident. To establish whether the data can be used to make an assessment of risk the boreholes closest to the flooding incidents were reviewed around the time the incident was recorded. This found that for all of the flooding incidents the groundwater in the nearest borehole was rising. Table 4-9: Summary of Groundwater Flooding Incidents extracted from WDC Flooding Database Nearest Borehole Reading Date Location Description of Incident at Time of Flood 1st Nov Fairview Lane, Flooding from spring The nearest borehole is Park 1994 Crowborough House (2.4 km²). In Sep 1994 dip of 5.33 m and Jan 1995 dip of 1.46 m. A rising trend overall. 1st Feb High Street, Increased flow to basement The nearest borehole is 1996 Hartfield found the adjacent well to be Forest Row A (2 km²). In Jan high 1996 a dip of 3.73 m and in Apr dip of 3.62 m. A falling trend overall. Dec 1997 Forge Rise, Flood of garden possibly from The nearest borehole is Uckfield spring, advised to not and Halland Godfrey Cottage (6 drain km²). In Nov 2007 a dip of 5.61 m, in Dec 2007 a dip of 4.67 m and in Jan 2008 a dip of 2.68 m. A falling trend overall. 10th Apr Viewswood Path, Water running from adjacent The nearest borehole is 2001 Uckfield play area into front garden of Fairwarp (5 km²). In Mar 2001 property. Appears to be a a dip of 39.49 m and in Apr spring. Once a pond at this 2001 a dip of 39.2 m. A rising location before development. trend overall. Advised owner of possible land drainage and contractors. 1st Apr Senlac Green, Water comes up from same The nearest borehole is 2004 Uckfield spot in rear garden when Fairwarp (5.4 km²). In Mar raining - no drains shown on 2004 a dip of 40.02 m and in plan - suggest takes trial hole May a dip of 39.88 m. A rising to investigate trend overall. 1st Mar Hempstead Lane, Concerned re ground water The nearest borehole is 2003 Uckfield coming through retaining wall Fairwarp (6 km²). In Feb 2003 and impact of impending a dip of 38.67 m and in Mar Kings Court development- 2003 a dip of 38.43 m. A drainage details yet to be rising trend overall. submitted will be checked to ensure no adverse effect
D118200 March 2009
49 Wealden District Council Level 1 SFRA: Final Report
Nearest Borehole Reading Date Location Description of Incident at Time of Flood 1st Oct Herne Down, Spring water in front garden The nearest borehole is Park 2007 Crowborough flows over onto road, worse House (4.5 km²). In Sep 1997 since building work at no. 19. a dip of 3.88 m in Oct 2007 a dip of 3.32 m. A rising trend overall.
4.8 Drainage/Sewer Flooding
Southern Water has provided details from their DG5 sewer flooding database. The database records the locations of the most recent sewer flooding incidents that have occurred over the last 10 years. The historical records indicate that there have been 30 locations with recorded incidents of flooding from sewers in WDC due to hydraulic problems. The majority of the problems were from a foul or combined sewer and one resulted in internal flooding to a property.
The data provides historical point source data however it does not indicate where a flooding incident is a recurring problem, or what level of flooding occurred. As a consequence a return period and severity cannot be assigned to each incident.
The Southern Water data has been used in conjunction with the WDC Flooding Database, which in some instances identifies the source of flooding as a drain or sewer. This has enabled a map (and a GIS layer) to be produced presenting the Southern Water data alongside the data extracted from the WDC Flooding database. This type of flooding is the second most commonly recorded flooded incident from the WDC Flooding Database. In the majority of cases this was a result of a blocked/broken pipe causing surcharge or a ditch that had not been adequately maintained.
4.9 Artificial Sources
The Environment Agency are the Statutory Body for Reservoir Safety under the Reservoirs Act 1975 as amended by the Water Act 2003xxxviii. They hold a ‘Register of Reservoirs’ which shows data for the ‘large raised reservoirs’ located within the study boundary. For the purposes of the Reservoirs Act 1975, reservoirs are defined as an impounded body of water of a volume greater than 25,000 cubic metres. From information provided by the Environment Agency and a review of ordnance Survey 1:50,000 mapping the following reservoirs have been identified within the study area: • Buckhurst Park Lake, near Crowborough; • Searle’s Lake, near Uckfied; • Upper Woman’s Way Pond, near Maresfield; • Wadhurst Park Lake; and, • Weirwood Reservoir, near Forest Row.
The Environment Agency’s records also detail the reservoir volume; surface area; year built; dam type; capacity; owner; and the undertaker. It is known that the Environment Agency assign the reservoirs a risk category according to guidance compiled by the Institute of Civil Engineersxxxvii. Reservoir Inspection reports were also requested but were not supplied.
D118200 March 2009
50 Wealden District Council Level 1 SFRA: Final Report
The Water Act 2003xxxviiialso introduced the requirement for large raised reservoirs to introduce flood plans, so that emergency services can respond effectively. This is likely to become a legal requirement in Spring 2009 for large-raised reservoirs where the failure could have significant consequences for downstream areas. Guidance on the production of these plans is currently being developed by DEFRA and is due to be circulated for consultation in Summer 2008. However, it should be noted that as well as the artificial sources listed above, the CFMP identifies hammer ponds within the study area as posing a potential flood risk. The Weald is noted for having a number of ‘hammer ponds’ that are a remnant of the iron industry where they were used to create power for furnaces. They are mostly located in woodland areas and were created by damming a stream. They can vary in size but are often have a surface area of 1 hectare or more.
Water main pipes can also be classified as an artificial source of flooding should they break or develop leaks. The WDC Flooding Database has recorded that 1% of the flooding incidents occurred as a result of artificial sources. These did not occur from large raised reservoirs that are listed by the Environment Agency, but smaller lakes, ponds or water main failures. A summary of the flooding incidents recorded in the WDC Flooding Database are presented in Table 4-10. Table 4-10: Summary of Flooding Incidents from Artificial Sources extracted from WDC Flooding Database
Date Location Description of Incident Oct 1994 Coopers Wood, Broken water main (now fixed) disrupted stream. Crowborough May 1994 Crowborough Hill, Flooding of property due to a broken water main Crowborough under chapel Jun 1992 Crowborough Hill, Flooding of cellar. "One-off" incident due to water Crowborough main break. Jul 1997 Clapwater, Fletching Concerned re levels of Searles Lake - governed by Reservoir Act therefore refered to ESCC Jan 2000 Forest Springs Fish Surcharging lakes - complaint to planning Farm, Hartfield Nov 1993 Belmont Road, Pond overflowing on to path due to part blocked Uckfield outlet. ESCC to clear under Bell Lane. Feb 2007 Coopers Wood, SW flow into rear garden- traced to pond Crowborough overflowing at Cas Mia, Coopers lane - overflow level has been set too high- letter sent to owner
Artificial Sources along with the flooding incidents from Artificial Sources are presented in Figure 11.
4.10 Current Flood Risk Management Practices
Flood management measures are those measures put in place to reduce the risk to people and property from the hazard of flooding. These management measures can be divided in to six types:-
• Flood Defences; • Flood Risk Management; • Flood Warning; • Flood Alleviation Techniques;
D118200 March 2009
51 Wealden District Council Level 1 SFRA: Final Report
• Flood Risk Management Strategies; and, • Emergency Plans.
4.10.1 Flood Defences
Flood defences are typically engineered structures designed to limit the impact of flooding. Flood defences take several forms including bunds/embankments, canalised channels, culverts and flood storage areas among others. Flood defences are typically designed and constructed to protect people and property from a given magnitude of flood. This is referred to as the standard of protection (SOP) and may vary depending on the age of the structure, the value attributed to the people and property it is designed to serve and the scale/cost of works necessary to construct the defence. For new defences, these issues and others are balanced through a cost benefit analysis to determine if investment in defence schemes can be justified. Information on defence structures within the study areas has been provided by the Environment Agency from their National Flood and Coastal Defence Database (NFCDD). The NFCDD is used as a repository for information relating to flood defences including their location, type, condition and design standard. The NFCDD is still being populated and constantly updated, as a result some fields remain blank or contain default values. Consequently, the information provided for this SFRA does not have a full set of descriptions in the majority of cases. From a review of the information presented in the NFCDD it is clear there are several defences in the study area (shown in Figure 12). The NFCDD has recorded defences along the River Medway; River Uck; Framfield Stream; Little Horstead Stream; and, Ridgewood Stream. The entire reach of the River Medway through the Wealden District has a form of flood defence. From the headwaters (west of Forest Row) to Lower Parrock (east of Forest Row) the NFCDD has described the flood defences to be “channel section”. From Lower Parrock to where the River Medway exits Wealden District in the east the NFCDD describes the flood defence as a ‘natural bank’. The Environment Agency have confirmed that along this length there are no formal defences and these are maintained banks. The River Uck through Uckfield is described by the NFCDD as a ‘maintained channel’ and ‘river bank’. There are also a number of structures along this reach that have been identified as outfalls and pipes. Framfield Stream, Little Horstead Stream and Ridgewood Stream have been identified as ‘maintained channels’ and ‘river banks’.
4.10.2 Flood Warning
Ensuring people in areas of flood risk are aware of potential flooding is key to ensuring they are prepared, facilitating the protection of property and evacuation where necessary.
The Environment Agency operates a flood warning service in all areas at risk of flooding. It consists of four flood warning codes from ‘All Clear’ to ‘Severe Flood Warning’ that indicate the level of danger. The flood warnings are disseminated through a variety of mediums that include TV, radio, an automated voice messaging service direct to a phone/fax/pager, the Internet and/or loudhailer. There is also an emergency Floodline number (0845 988 1188) and a quick dial number for individual rivers. The Flood Warning areas present within the study boundary are displayed in, these are the:
• River Medway between Forest Row and Penshurst;
D118200 March 2009
52 Wealden District Council Level 1 SFRA: Final Report
• River Uck from Hempstead Lane to the A22 at Uckfield, including Mill Lane, River Way, High Street and the Bellbrook Industrial Estate; • River Uck at Buxted between Parsonage Wood and the High Street including the Old Mill area; • River Uck and confluence with the River Ouse including Isfield Mill and White Bridge; and, • River Ouse from Freshfield Bridge to Sharpesbridge including Sheffield Park Station and Fletching Mill.
Flood warning areas are only provided for flooding from fluvial and tidal sources, they do not include warnings of flooding from other flood sources. For example no flood warnings are issued when drains are surcharged or for flooding from overland flow.
4.10.3 Flood Alleviation Schemes
A list of the flood alleviation schemes within the WDC SFRA study area and River Ouse catchment has been provided by the Environment Agency. The only flood alleviation scheme within the study area is the Uckfield Flood Relief Scheme that was constructed between 1978 and 1981. This scheme increased the capacity of the River Uck between Hempstead Mill and Isfield gauging station; including the installation of a twin box culvert beneath Uckfield Mill. In the urban areas the improvement scheme offers a standard of protection of 2% annual probability (1 in 50 year) and a 10% annual probability (1 in 10 year) in the rural areas.
4.10.4 Flood Risk Management
In addition to the flood defences and warning services provided by the Environment Agency, the Environment Agency is also involved in an ongoing programme of maintenance and management of water levels and watercourses throughout the study area. The Environment Agency maintenance and operations department carry out channel clearances, maintain defences and structures and ensure that water levels are maintained. The Local Authorities and the Internal Drainage Boards may also undertake work on smaller, ordinary watercourses from time to time to ensure that culverts are clear of debris.
These activities form an important part of the overall flood risk management of the area and ensure that flood defences and flood warning assets operate as designed. No information was available from the Environment Agency or the Local Authority of the maintenance programmes in the study area.
The Upper Medway IDB confirmed that no formal maintenance regime is followed, but maintenance is undertaken on an as needed basis. However, ordinary watercourses in Forest Row are maintained on average once every ten years, due to the fast flowing nature of these systems. They are also regularly checked following heavy rainfall events or when blockages are reported. The ordinary watercourses of Withyham and Ashurst are within large agricultural areas and the landowners prefer to have the banks of the streams flail mowed once a year following the harvest.
4.10.5 Flood Risk Management Strategies
Flood Risk Management Strategies are documents that outline how the Environment Agency intend to management flood risk in the future. This could be through the widespread incorporation of SuDS or engineered solutions such as flood alleviation schemes. There are presently no Flood Risk
D118200 March 2009
53 Wealden District Council Level 1 SFRA: Final Report
Management Strategies, ongoing or imminent in the WDC SFRA study area at the time of writing besides the Flood Alleviation Scheme described in Section 4.10.3.
4.10.6 Flood Mitigation on Site
40 dwellings or business in Uckfield have been chosen for a pilot flood resilience scheme through funding from DEFRA. This scheme targets those areas that have suffered from flooding recently and may include methods that prevent flood water entering buildings or techniques that minimise the damage to the properties. No further information on this pilot scheme was available for this study, however more information on flood mitigation for individual sites/developments is presented in Section 10.
4.10.7 Emergency Plans
More detail on Emergency Planning is presented in Section 12. Wealden District Council has an Emergency Planning Department that is already involved in emergency planning in times of flood. The Wealden District Council Emergency Incident Resource Packxxxixhas been made available for this Level 1 SFRA. It covers incidents such as evacuation, severe weather, pandemic, animal diseases, pollution and flooding.
The aim of the districts flood plan is to:-
“co-ordinate the council’s service response to offer temporary shelter and assistance to persons who are threatened by or are experiencing an actual flooding incident occasioned by flooding”.
The flood plan identifies the flood warning areas within the district and provides their corresponding quickdial numbers for the Environment Agency’s ‘Floodline’ service. The plan identifies the roles and responsibilities of persons within the District as well as the individuals who will receive the flood warning from the Environment Agency. The plan has a separate ‘Sandbags Policy’ for times of flood, within this policy sandbags are to be given freely during emergencies.
It is recommended that the flood plan should be used in conjunction with the ‘Generic Emergency Plan’ and other site-specific flood plans such as the ‘Uckfield Flood Plan’. The Generic Emergency Plan lists facilities and resources that will be used in an emergency such as rest centres, emergency transport, incident manager and utilities along with a list of contact names and numbers. The Generic Emergency Plan has considered the requirement for transport and lists coaches and minibuses with their capacities in the plan. It has considered the requirement of emergency food and a number of supermarkets have agreed to supply emergency food if necessary.
The Uckfield Flood Planxl was updated in 2005 and sets out a framework to coordinate a response to flooding or the threat of flooding in the Uckfield area. It details the adequate responses to each of the flood warning codes that are disseminated by the Environment Agency. It identifies an incident control post that is outside a fluvial flood risk zone as well as rest centres. Uckfield has been split into four sectors with routes of evacuation outlined to land outside Flood Zone 2 from each. The flood plan recognises that the most vulnerable institutions will need to be targeted first in an evacuation situation and Millington Court (residential care home) has a specific flood plan. Further information on before and after the flooding has been included in the flood plan that considers the safety of buildings; disposal of damaged goods; emotional support; health; power loss implication; practical support; and, high profile responders.
D118200 March 2009
54 Wealden District Council Level 1 SFRA: Final Report
xxxiv Babtie, Brown & Root (2004) The Medway Catchment Flood Management Plan’, Environment Agency: Worthing. xxxv Environment Agency (2007) ‘Draft Rother and Romney Marsh Catchment Flood Management Plan’, xxxvi Environment Agency (2007) ‘Forest Row Flood Report’, Environment Agency: Bristol. xxxvii The Institute of Civil Engineers (1978) ‘Floods and Reservoir Safety’, David Green (Printers) Ltd: Kettering, Northamptonshire, UK. xxxviii Office of Public Sector Information (2003) ‘Water Act’, OPSI. xxxix Wealden District Council (2007) ‘Wealden District Council Emergency Incident Resource Pack’, WDC: Crowborough. xl Uckfield Flood Planning Group (2005) ‘Uckfield Flood Plan’, East Sussex County Council: Lewes.
D118200 March 2009
55 Wealden District Council Level 1 SFRA: Final Report
5 Assessing Flood Risk from all Sources
Two of the objectives of this Level 1 SFRA are to ‘provide information on the probability of flooding, taking into account all sources of flooding and the impacts of climate change’ and ‘present an assessment of the impact of all potential sources of flooding in accordance with PPS25ii, including an assessment of any future impacts associated with climate change’.
This section describes the data used in the production of the mapping to be used by WDC in the application of the Sequential Test. To facilitate production of the maps and GIS layers, some of the data received from the stakeholders has been standardised and/or combined
5.1 Requirements of PPS25ii
PPS25ii and its accompanying Practice Guideiv requires a SFRA to present sufficient information on all flood sources to enable LPAs to apply the Sequential Test within the administrative area. In order to apply the Sequential Test information is required on the probability associated with flooding from the different flood sources. In addition, the assessment of probability should also account for the effects of climate change on a flood source for the lifetime of any development that would be approved through the emerging LDF. For all but fluvial flood sources the current paucity of data makes definition of robust classifications of probability unreliable. For example to define high, medium and low probabilities for groundwater flooding within the study area based on one reported incident (with no corresponding record of the severity of that flood) is not robust. Consequently for all flood sources other than fluvial sources, where only anecdotal evidence of flooding is available subjective assessments of probability have been made where the data allows. The sources of flooding should also be investigated through a site specific assessment of flood risk submitted as part of a planning application. Details of the requirements for flood risk assessments are presented in Section 8. The follow section explains how the available data has been used to achieve the requirements of PPS25ii and the Practice Guideiv.
D118200 March 2009
56 Wealden District Council Level 1 SFRA: Final Report
5.2 Fluvial Flooding
5.2.1 Requirements
PPS25ii requires definition of the following fluvial flood zones as in Table 4-1. In accordance with paragraph 3.17 of the PPS25 Practice Guideiv, all areas within Flood Zone 3 should be considered as Flood Zone 3b unless, or until, assessment shows to the satisfaction of the Environment Agency that the area falls within Flood Zone 3a. Therefore in areas where the functional floodplain has not been defined and no suitable surrogate data is available the functional floodplain (Flood Zone 3b) has been defined as the extent of Flood Zone 3a. Section 4.3 identifies the sources of data used to map the fluvial flood zones required by PPS25ii. The mapping has been produced through the use of flood outlines generated by hydraulic models or use of the Environment Agency’s Flood Map. In the Wealden District the correct return period is not available for all of the watercourses, this applies in particular in climate change scenarios. Where the appropriate flood zone has not been available a surrogate flood zone has been mapped. The suitability of surrogates for use in Flood Zone mapping has been based on a review of peak flood flows (where available) or subjectively based on the available data. This approach has been agreed with the Environment Agency.
This approach has been in the following situations:
1. where the extent of Flood Zone 3b (5% annual probability) in 2008 is required but not available the preferred surrogate of a 4% (1 in 25 year) annual probability flood outline has been used. Where this is not available Flood Zone 3 in 2008 has been assumed to be Flood Zone 3b; 2. where the extent of Flood Zone 2 (0.1% annual probability) in 2115 is required but not available (all situations) a 50m buffer has been generated around the 2008 Flood Zone 2 to account for climate change increases in flood level; 3. where the extent of Flood Zone 3a (1% annual probability) in 2115 is required but not available a 50m buffer has been generated around the 2008 Flood Zone 3 to account for climate change increases in flood level; and, 4. where the extent of Flood Zone 3b (5% annual probability) in 2115 is required but not available the preferred surrogate of a 2% (1 in 50 year) annual probability flood outline has been used to account for climate change increases in flood level. Where this is not available a 50m buffer has been generated around the 2008 Flood Zone 3.
5.2.2 Climate Change
Climate change is predicted to increase peak river flow by 20% up to 2115 and as a result increase floodplain volume and area, which will present a risk to an increased number of properties. Modelled climate change scenarios have only been modelled for the River Uck and Ouse.
D118200 March 2009
57 Wealden District Council Level 1 SFRA: Final Report
Table 5-1 : Fluvial Flood Zone Mapping Data Sources
Current Flood Zones (2008) Climate Change Flood Zones (2115) Watercourse Flood Zone 2 Flood Zone 3a Flood Zone 3b Flood Zone 2 Flood Zone 3a Flood Zone 3b 2008 Flood Zone Modelled 1% Flood Zone 2 Modelled 1% Modelled 4% 2 from EA Flood annual probability Modelled 2% annual River Ouse from EA Flood annual probability annual probability Map plus 50 m storm event plus probability storm event Map storm event storm event buffer climate change Modelled 1% Modelled 4% annual probability Modelled 2% annual Modelled 1% annual probability 2008 Flood Zone storm event plus probability storm event Flood Zone 2 annual probability storm event and 2 from EA Flood climate change/ and 2008 Flood Zone 3 River Uck4 from EA Flood storm event and Flood Zone 3 from Map plus 50m and 2008 Flood from EA Flood Map plus Map Flood Zone 3 from EA Flood Map buffer Zone 3 from EA 50 m buffer (assumed to EA Flood Map (assumed to be Flood Map plus 50 be Flood Zone 3b) Flood Zone 3b) m buffer 2008 Flood Zone Modelled 1% Flood Zone 2 Modelled 4% River Flood Zone 3 from 2 from EA Flood annual probability Modelled 2% annual from EA Flood annual probability Medway5 EA Flood Map Map plus 50m storm event plus probability storm event Map storm event buffer climate change Flood Zone 3 from 2008 Flood Zone 2008 Flood Zone 3 from Flood Zone 2 2008 Flood Zone 3 Flood Zone 3 from EA Flood Map 2 from EA Flood EA Flood Map plus 50 River Rother from EA Flood from EA Flood Map EA Flood Map (assumed to be Map plus 50m m buffer (assumed to be Map plus 50 m buffer Flood Zone 3b buffer flood zone 3b) Flood Zone 3 from 2008 Flood Zone 2008 Flood Zone 3 from Flood Zone 2 2008 Flood Zone 3 Flood Zone 3 from EA Flood Map 2 from EA Flood EA Flood Map plus 50 River Teise from EA Flood from EA Flood Map EA Flood Map (assumed to be Map plus 50m m buffer (assumed to be Map plus 50 m buffer Flood Zone 3b) buffer flood zone 3b)
4 Please note that the River Uck model does not cover the River Ucks entire extent within the Wealden District. Furthermore the model does however incorporate sections of its tributaries Framfield Stream and Tickeridge Stream. For the hydraulic model extent please refer to Error! Reference source not found. 5 Please note that the flood extents from the River Medway have already been incorporated into the Environment Agency flood mapping
D118200 March 2009
58 Wealden District Council Level 1 SFRA: Final Report
Current Flood Zones (2008) Climate Change Flood Zones (2115) Watercourse Flood Zone 2 Flood Zone 3a Flood Zone 3b Flood Zone 2 Flood Zone 3a Flood Zone 3b Modelled 4% annual Modelled 1% Modelled 2% annual Modelled 1% probability storm annual probability 2008 Flood Zone probability storm event Flood Zone 2 annual probability event and Flood storm event plus Tickeridge 2 from EA Flood and 2008 Flood Zone 3 from EA Flood storm event and Zone 3 from EA climate change and Stream Map plus 50m from EA Flood Map plus Map Flood Zone 3 from Flood Map 2008 Flood Zone 3 buffer 50 m buffer (assumed to EA Flood Map (assumed to be from EA Flood Map be flood zone 3b) Flood Zone 3b) plus 50 m buffer Modelled 4% annual Modelled 1% Modelled 2% annual Modelled 1% probability storm annual probability 2008 Flood Zone probability storm event High Flood Zone 2 annual probability event and Flood storm event plus 2 from EA Flood and 2008 Flood Zone 3 Hurstwood from EA Flood storm event and Zone 3 from EA climate change/ and Map plus 50m from EA Flood Map plus Stream Map Flood Zone 3 from Flood Map 2008 flood zone 3 buffer 50 m buffer (assumed to EA Flood Map (assumed to be from EA Flood Map be flood zone 3b) Flood Zone 3b) plus 50 m buffer Modelled 4% annual Modelled 1% Modelled 2% annual Modelled 1% probability storm annual probability 2008 Flood Zone probability storm event Flood Zone 2 annual probability event and Flood storm event plus Ridgewood 2 from EA Flood and 2008 Flood Zone 3 from EA Flood storm event and Zone 3 from EA climate change/ and Stream Map plus 50m from EA Flood Map plus Map Flood Zone 3 from Flood Map 2008 flood zone 3 buffer 50 m buffer (assumed to EA Flood Map (assumed to be from EA Flood Map be flood zone 3b) Flood Zone 3b) plus 50 m buffer Modelled 4% annual Modelled 1% Modelled 2% annual Modelled 1% probability storm annual probability 2008 Flood Zone probability storm event Flood Zone 2 annual probability event and Flood storm event plus Shortbridge 2 from EA Flood and 2008 Flood Zone 3 from EA Flood storm event and Zone 3 from EA climate change/ and Stream Map plus 50m from EA Flood Map plus Map Flood Zone 3 from Flood Map 2008 flood zone 3 buffer 50 m buffer (assumed to EA Flood Map (assumed to be from EA Flood Map be Flood Zone 3b) Flood Zone 3b) plus 50 m buffer Flood Zone 3 from 2008 Flood Zone 2008 flood zone 3 from Flood Zone 2 2008 Flood Zone 3 Batts Bridge Flood Zone 3 from EA Flood Map 2 from EA Flood EA Flood Map plus 50 m from EA Flood from EA Flood Map Stream EA Flood Map (assumed to be Map plus 50m buffer (assumed to be Map plus 50 m buffer Flood Zone 3b) buffer Flood Zone 3b)
D118200 March 2009
59 Wealden District Council Level 1 SFRA: Final Report
5.3 Drainage/Sewer Flooding
5.3.1 Requirements and Data
Areas at risk from sewer flooding have been determined through review of the records from the DG5 registers provided by Southern Water, WDC Flooding Database and the Highways Agency. The DG5 register records flooding incidents as a result of temporary works as well as ongoing hydraulic capacity problems. The WDC Flooding Database records all flooding incidents that have been reported. There is also no information provided with the sewer flooding records of mitigation works that have been undertaken to prevent further flooding at locations. As per fluvial flooding, areas with high, medium and low probability should be defined based on the available data. The definition of functional floodplain is not required for flooding from sewers. Due to the lack of resolution of the data and the relatively short period for which the records are available (≤10 years), definition of flooding probability cannot currently follow the same approach as that used for fluvial flooding. Therefore based on the available data the following criteria have been used to define flood zones in 2008: • High Probability - Greater than 5 properties affected within a radius of 200 metres;
• Medium Probability – Between 2 and 5 properties affected within a radius of 200 metres; and,
• Low Probability - Less than 2 properties affected within a radius of 200 metres.
It is intended that in cases where a development site is identified, a 200m buffer is defined around the site to identify the number of sewer flooding incidents and subsequent probability classification for the development.
5.3.2 Climate Change
Climate change is predicted to result in an increase short duration high intensity rainfall and more frequent periods of long duration rainfall, with peak rainfall intensities predicted to increase by 30% by 2115. Consequently there may be a reduction in the standard of protection that sewers provide against surcharging as the 3.3% (1 in 30 years) annual probability storm event becomes more frequent. It is therefore likely that flood risk to the study area from sewer flooding will increase with climate change. Therefore based on the available data and its spatial distribution the following criteria have been used to define flood zones in 2115:
• High Probability - Greater than 5 properties affected within a radius of 300 metres;
• Medium Probability – Between 2 and 5 properties affected within a radius of 300 metres; and,
• Low Probability - Less than 2 properties affected within a radius of 300 metres.
It is intended that in cases where a development site is identified, a 150m buffer is defined around the site to identify the number of sewer flooding incidents and subsequent probability classification for the development.
D118200 March 2009
60 Wealden District Council Level 1 SFRA: Final Report
5.4 Overland Flow
5.4.1 Requirements and Data
As per fluvial flooding, areas with high, medium and low probability should be defined based on the available data. The definition of functional floodplain is not required for flooding from overland flow. Incidents of overland flow flooding has been provided within WDC Flooding Database. Therefore based on the available data and its spatial distribution the following criteria have been used to define flood zones in 2008: • High Probability - Greater than 3 properties affected within a radius of 100 metres;
• Medium Probability – 2 properties affected within a radius of 100 metres; and,
• Low Probability - Less than 2 properties affected within a radius of 100 metres.
It is intended that in cases where a development site is identified, a 100m buffer is defined around the site to identify the number of overland flow flooding incidents and subsequent probability classification for the development.
5.4.2 Climate Change
Peak rainfall intensities are currently predicted to increase by 30% by the year 2115. The UK should expect to experience an increase in short duration high intensity rainfall along with more frequent periods of long duration rainfall events. Consequently it is predicted that pluvial flooding will increase, therefore posing greater risk to the study area. Therefore based on the available data and its spatial distribution the following criteria have been used to define flood zones in 2115:
• High Probability - Greater than 3 properties affected within a radius of 150 metres;
• Medium Probability – 2 properties affected within a radius of 150 metres; and,
• Low Probability - Less than 2 properties affected within a radius of 150 metres.
It is intended that in cases where a development site is identified, a 150m buffer is defined around the site to identify the number of overland flow flooding incidents and subsequent probability classification for the development.
5.5 Groundwater Flooding
5.5.1 Requirements and Data
As per fluvial flooding, areas with high, medium and low probability should be defined based on the available data. The definition of functional floodplain is not required for flooding from groundwater sources. Data has been extracted from WDC Flooding database that was used to develop the following criteria have been used to define flood zones in 2008:-
• High Probability - Greater than 3 properties affected within a radius of 100 metres;
D118200 March 2009
61 Wealden District Council Level 1 SFRA: Final Report
• Medium Probability – 2 properties affected within a radius of 100 metres; and,
• Low Probability - Less than 2 properties affected within a radius of 100 metres.
It is intended that in cases where a development site is identified, a 100m buffer is defined around the site to identify the number of groundwater flooding incidents and subsequent probability classification for the development.
5.5.2 Climate Change
As written in Section 2.2.4 the Medway catchment area within the study area currently has a groundwater status of ‘no water available’. The Ouse catchment area within the study area currently has a groundwater status of ‘over licensed’ and a proposed groundwater status of ‘no water available’. Over the next 100 years the changing climate will change groundwater movements within the district and there is ongoing research into this area. Therefore based on the available data and its spatial distribution the following criteria have been used to define flood zones in 2115:
• High Probability - Greater than 3 properties affected within a radius of 150 metres;
• Medium Probability – 2 properties affected within a radius of 150 metres; and,
• Low Probability - Less than 2 properties affected within a radius of 150 metres.
It is intended that in cases where a development site is identified, a 150m buffer is defined around the site to identify the number of groundwater flooding incidents and subsequent probability classification for the development.
5.6 Artificial Sources (large-raised reservoirs)
5.6.1 Requirements and Data
As per fluvial and tidal flooding, areas with high, medium and low probability should be defined based on the available data. The definition of functional floodplain is not required for flooding from artificial sources. Information on the large-raised reservoirs within the study area was provided by the Environment Agency (List of Reservoirs). This contains a hazard classification based on the type of reservoir and the volume it holds. There are four categoriesxli: • A – At least 10 lives at risk and extensive property damage; • B – Fewer than 10 lives at risk but extensive property damage; • C – Negligible risk to human life but property damage; • D – No significant risk to life or property damage; and, • Unknown.
D118200 March 2009
62 Wealden District Council Level 1 SFRA: Final Report
5.6.2 Climate Change
There is no standard of defence associated with the Reservoirs within the District, consequently the effect on climate change on these sources can not be assessed effectively.
5.7 Artificial Sources (other)
5.7.1 Requirements and Data
As per fluvial and tidal flooding, areas with high, medium and low probability should be defined based on the available data. The definition of functional floodplain is not required for flooding from artificial sources. From a review of the WDC Flooding Database it was found that all of incidents of flooding from artificial sources were not from large-raised reservoirs, but from ponds and lakes or water mains. Data has been extracted from WDC Flooding database that was used to develop the following criteria have been used to define flood zones in 2008:-
• High Probability - Greater than 3 properties affected within a radius of 100 metres;
• Medium Probability – 2 properties affected within a radius of 100 metres; and,
• Low Probability - Less than 2 properties affected within a radius of 100 metres.
It is intended that in cases where a development site is identified, a 100m buffer is defined around the site to identify the number of flooding incidents from artificial sources and subsequent probability classification for the development.
5.7.2 Climate Change
Therefore based on the available data and its spatial distribution the following criteria have been used to define flood zones in 2115:
• High Probability - Greater than 3 properties affected within a radius of 150 metres;
• Medium Probability – 2 properties affected within a radius of 150 metres; and,
• Low Probability - Less than 2 properties affected within a radius of 150 metres.
It is intended that in cases where a development site is identified, a 100m buffer is defined around the site to identify the number of flooding incidents from artificial sources and subsequent probability classification for the development.
These criteria are summarised in Table 5-2 and 5-3 on the proceeding pages.
xli Institution of Civil Engineers (1996) ‘Floods and reservoir safety’, Thomas Telford Limited.
D118200 March 2009
63 Wealden District Council Level 1 SFRA: Final Report
Table 5-2: Flood Risk Classification in 2009 of all Flood Sources based on the data available to this Level 1 SFRA
Very High Risk High Risk Medium Risk Low Risk Flood Source (Flood Zone 3b) (Flood Zone 3a) (Flood Zone 2) (Flood Zone 1)
Fluvial Flood event less than or equal Flood event less than or equal Flood event between the 1% Flood event greater than the to the 5% annual probability (1 to the 1% annual probability (1 (1 in 100 year) and 0.1% (1 in 0.1% (1 in 1000 year) annual in 20 year) storm event in 100 year) storm event 1000 year) annual probability probability storm event storm event Drainage Greater than 5 properties Between 2 and 5 properties Less than 2 properties affected within the previous 10 affected within the previous 10 affected within the previous 10 N/A year period within a radius of year period within a radius of year period within a radius of 200 metres. 200 metres. 200 metres.
Overland Flow Greater than 3 properties 2 properties affected within a Less than 2 properties affected within a radius of 100 radius of 100 metres. affected within a radius of 100 N/A metres. metres.
Groundwater Greater than 3 properties 2 properties affected within a Less than 2 properties N/A affected within a radius of 100 radius of 100 metres. affected within a radius of 100 metres. metres. Artificial Sources (Large The Environment Agency’s List of Reservoirs provides a hazard classification for each of these according to their dam type and Raised volume. These are presented in the Sequential Test series of figures. Reservoirs) Artificial Greater than 3 properties 2 properties affected within a Less than 2 properties Sources (Other) affected within a radius of 100 radius of 100 metres. affected within a radius of 100 N/A metres. metres.
D118200 March 2009
64 Wealden District Council Level 1 SFRA: Final Report
Table 5-3: Flood Risk Classification in 2115 of all Flood Sources based on information available in this Level 1 SFRA
Very High Risk High Risk Medium Risk Low Risk Flood Source (Flood Zone 3b) (Flood Zone 3a) (Flood Zone 2) (Flood Zone 1)
Fluvial Flood event less than or equal Flood event less than or equal Flood event between the 1% Flood event greater than the to the 5% annual probability (1 to the 1% annual probability (1 (1 in 100 year) and 0.1% (1 in 0.1% (1 in 1000 year) annual in 20 year) storm event in 100 year) storm event 1000 year) annual probability probability storm event storm event Drainage Greater than 5 properties Between 2 and 5 properties Less than 2 properties affected affected within a radius of 300 affected within a radius of 300 within a radius of 300 metres. N/A metres. metres.
Overland Flow Greater than 3 properties 2 properties affected within a Less than 2 properties affected affected within a radius of 150 radius of 150 metres. within a radius of 150 metres. N/A metres.
Groundwater Greater than 3 properties 2 properties affected within a Less than 2 properties affected N/A affected within a radius of 150 radius of 150 metres. within a radius of 150 metres. metres. Artificial Sources (Large The Environment Agency’s List of Reservoirs provides a hazard classification for each of these according to their dam type and Raised volume. These are presented in the Sequential Test series of figures. Reservoirs) Artificial Greater than 3 properties 2 properties affected within a Less than 2 properties affected Sources (Other) affected within a radius of 150 radius of 150 metres. within a radius of 150 metres. metres.
D118200 March 2009
65 Wealden District Council Level 1 SFRA: Final Report
6 Guidance on Applying the PPS25 Sequential Test
Objective 4 of this Level 1 SFRA is to provide information for applying the PPS25ii Sequential Test, on the basis of the flood zones identified in PPS25ii. This will identify where sites cannot be located in Flood Zone 1 and therefore require further investigation through a Level 2 SFRA’.
6.1 What is the Sequential Test?
The PPS25ii Sequential Test is a risk based approach to determine the suitability of development according to flood risk from fluvial and tidal flood sources. PPS25ii requires LPAs to apply the Sequential Test at all stages of the planning process to ensure that where possible developments are removed from areas with a high probability of flooding. Through application of the Sequential Test LPAs are encouraged to guide new development towards areas of the lowest flood probability. Allied to the Sequential Test, PPS25ii also assigns different vulnerabilities to different types of development. If, when applying the Sequential Test, development in the floodplain is necessary the LPA should also bear in mind the vulnerability classification of their proposed development to assess if it is appropriate in an area of flood risk. In exceptional circumstances the LPA may be required to undertake the Exception Test to justify development (discussed further in Section 7). Table D2 of PPS25ii presents types of development according to their flood vulnerability. By using this information in tandem with the Sequential Test developments should be guided to those areas where the development vulnerability is appropriate to the flooding probability. Table 6-1 : Flood Risk Vulnerability Classification (from PPS25ii, Appendix D, Table D2ii) • Essential transport infrastructure (including mass evacuation ESSENTIAL routes), which has to cross the area at risk, and strategic utility INFRASTRUCTURE infrastructure, including electricity generating power stations and grid and primary substations. • Police stations, Ambulance stations and Fire stations and Command Centres and telecommunications installations required to be operational during flooding. HIGHLY • Emergency dispersal points. VULNERABLE • Basement dwellings. • Caravans, mobile homes and park homes intended for permanent residential use. • Installations requiring hazardous substances consent.
D118200 March 2009
66 Wealden District Council Level 1 SFRA: Final Report
• Hospitals. • Residential institutions such as residential care homes, children’s homes, social services homes, prisons and hostels. • Buildings used for: dwelling houses; student halls of residence; drinking establishments; nightclubs; and hotels. MORE • Non–residential uses for health services, nurseries and educational VULNERABLE establishments. • Landfill and sites used for waste management facilities for hazardous waste. • Sites used for holiday or short-let caravans and camping, subject to a specific warning and evacuation plan. • Buildings used for: shops; financial, professional and other services; restaurants and cafes; hot food takeaways; offices; general industry; storage and distribution; non–residential institutions not included in ‘more vulnerable’; and assembly and leisure. LESS • Land and buildings used for agriculture and forestry. VULNERABLE • Waste treatment (except landfill and hazardous waste facilities). • Minerals working and processing (except for sand and gravel working). • Water treatment plants. • Sewage treatment plants (if adequate pollution control measures are in place). • Flood control infrastructure. • Water transmission infrastructure and pumping stations. • Sewage transmission infrastructure and pumping stations. • Sand and gravel workings. • Docks, marinas and wharves. • Navigation facilities. • MOD defence installations. WATER- • Ship building, repairing and dismantling, dockside fish processing COMPATIBLE and refrigeration and compatible activities requiring a waterside DEVELOPMENT location. • Water-based recreation (excluding sleeping accommodation). • Lifeguard and coastguard stations. • Amenity open space, nature conservation and biodiversity, outdoor sports and recreation and essential facilities such as changing rooms. • Essential ancillary sleeping or residential accommodation for staff required by uses in this category, subject to a specific warning and evacuation plan.
The PPS25 Practice Guideiv notes that ‘where a land use is not specifically referred to in Table D.2 it should be allocated to the most appropriate vulnerability classification based on comparison with the characteristics of other uses in the table, informed by the consideration of the risks from flooding.’ PPS25ii acknowledges that some areas will (also) be at risk of flooding from flood sources other than fluvial and tidal systems. Consequently all sources of flooding must be considered when looking to
D118200 March 2009
67 Wealden District Council Level 1 SFRA: Final Report
locate development. Other sources of flooding requiring consideration when situating new development allocations in the WDC administrative area include: • Pluvial; • Groundwater; • Sewers; and; • Artificial Sources.
These sources of flooding are typically less understood than tidal and fluvial sources. Consequently data often only exists as point source data or through interpretation of local conditions. In addition there is no guidance on suitable return periods to associate with floods arising from these sources. High, medium and low classifications have been defined for the different flood sources where possible, however, when assessing these sources through the Sequential Test, if a location is recorded as having experienced repeated flooding from the same source this should be investigated further through a site specific flood risk assessment.
6.2 How should the SFRA be used to apply the Sequential Test?
WDC should use the information presented and mapped (Figure Sets 13 and 14) (Figure 20 and Figure 21) in this Level 1 SFRA (and accompanying GIS layers) to undertake the Sequential Test. The Sequential Test should be accurately documented to ensure that the decision processes followed for the locating of a development are consistent and transparent. The Sequential Test should be carried out on all development sites and seek to guide development to the lowest flood risk areas (Flood Zone 1). Where there are no reasonably available alternative sites in Flood Zone 1 to accommodate development, sites in Flood Zones 2 or 3 may be considered but must balance the flood probability and development vulnerability of sites. This should be based on the Flood Zone and Flood Risk Vulnerability Compatibility which is presented in Table 6-2. The Level 1 SFRA mapping provides the tools by which WDC and developers can undertake the Sequential Test to strategic allocations and land holdings. This is achieved by presenting information to identify the variation in flood risk across the local authority administrative area, allowing an area- wide comparison of future development sites with respect to flood risk. Table 6-2: Flood Risk Vulnerability and Flood Zone ‘Compatibility’ from PPS25ii, Appendix D, Table D.3.
FLOOD RISK ESSENTIAL WATER HIGHLY MORE LESS VULNERABILITY INFRASTRUCTURE COMPATIBLE VULNERABLE VULNERABLE VULNERABLE CLASSIFICATION
1
ONE Exception Z 2 Test Required
LOOD Exception F Exception Test 3A Test Required Required
D118200 March 2009
68 Wealden District Council Level 1 SFRA: Final Report
FLOOD RISK ESSENTIAL WATER HIGHLY MORE LESS VULNERABILITY INFRASTRUCTURE COMPATIBLE VULNERABLE VULNERABLE VULNERABLE CLASSIFICATION Exception Test 3B Required - Development is appropriate - Development should not be permitted
The following flow diagram (Diagram 1), taken from the Practice Guide to PPS25ii and the Flood Risk Matrix (Reference 17) illustrates how the Sequential Test should be undertaken. The full process is described fully in PPS25, A Practice Guide 2008iv. Additional guidance to assist WDC undertake the Sequential Test on a strategic basis is detailed in Section 6.3. Diagram 1: Application of the Sequential Test (from Figure 4.1 of PPS25: Practice Guideiv)
D118200 March 2009
69 Wealden District Council Level 1 SFRA: Final Report
6.3 Additional Guidance
The sequence of steps presented below in tandem with Diagram 1 is designed to provide WDC and developers additional guidance on how to apply the Sequential Test strategically. The steps are designed to ensure land allocations are allocated in line with the principles of the Sequential Test or, failing this, that the requirement for application of the Exception Test is clearly identified.
1. The strategic developments (i.e. housing, hospitals, industrial etc) that need to be accommodated in the WDC administrative area within the lifetime of the LDF should be assigned a vulnerability classification in accordance with Table D.2 “Flood Risk Vulnerability Classification” in PPS25 (Table 6 1)ii; 2. The Flood Zone classification of all development sites identified by WDC should be determined based on a review of the Sequential Test Maps (Figure Sets 13 and 14) this should consider the effects of climate change on flood zone definition for the design life of any development that the site may be suitable for, i.e.: • 60- year design life (up to 2070) for commercial / industrial developments; and, • 100 year design life (up to 2110) for residential developments
3. In the first instance the ‘highly vulnerable’ developments WDC is required to accommodate should be located in those sites it has identified as being within Flood Zone 1. If the ‘highly vulnerable developments’ cannot be located in Flood Zone 1, because the identified sites are unsuitable or there are insufficient sites in Flood Zone 1 then sites in Flood Zone 2 can be considered. If sites in Flood Zones 1 and 2 are inadequate, then to accommodate the development the LPA may have to identify additional sites in Flood Zones 1 or 2. 4. Once all ‘highly vulnerable’ developments have been allocated to a development site, WDC can consider those development types defined as ‘more vulnerable’. In the first instance ‘more vulnerable’ development should be located in any unallocated sites in Flood Zone 1. Where these sites are unsuitable or there are insufficient sites, sites in Flood Zone 2 can be considered. If there are insufficient sites in Flood Zone 1 or 2 to accommodate the ‘more vulnerable’ development types, sites in Flood Zone 3a can be considered. However, any ‘more vulnerable’ developments in Flood Zone 3a will require application of the Exception Test (described in Section 7). 5. Once all ‘more vulnerable’ developments have been allocated to a development site, the LPA can consider those development types defined as ‘less vulnerable’. In the first instance ‘less vulnerable’ development should be located in any remaining unallocated sites in Flood Zone 1, 2 or 3a (in that order). Less vulnerable development types are not appropriate in Flood Zone 3b – Functional Floodplain. 6. ‘Essential infrastructure’ developments should also be preferentially located in the lowest flood risk zone, however this type of development may be located in Flood Zones 3a and 3b, where necessary, through application of the Exception Test. 7. Finally, it is recommended that water compatible development is considered. Water compatible developments typically have the least flood risk constraints and therefore it is considered appropriate to consider them last when allocating development sites. For decisions made through steps 4 to 7 it will also be necessary to consider the risks posed to the site from other flood sources and where comparable development sites in the same flood zone may be more suitable due to:
D118200 March 2009
70 Wealden District Council Level 1 SFRA: Final Report
• flood risk management measures, • the rate of flooding, • flood water depth, or, • flood water velocity.
Appendix Table 1 (Appendix D) is provided as a suggested pro-forma for WDC to follow when undertaking the Sequential Test. The table has been prepared to assist WDC provide a transparent and structured reporting system and to assist in identifying where developments/development sites may require application of the Exception Test.
D118200 March 2009
71 Wealden District Council Level 1 SFRA: Final Report
7 Guidance on Applying the PPS25 Exception Test
7.1 What is the Exception Test?
After application of the Sequential Test, if it is has not been possible for a development to be located in a low risk flood zone, or a flood zone where the development vulnerability is appropriate then it may be necessary and appropriate to apply the Exception Test to the allocation, providing the development is consistent with the wider sustainability objectives of the area Table 6-1 provides guidance on the vulnerability of types of development and in conjunction with Table D3 where various types of development are appropriate with regards to flood risk and where it may be appropriate for the Exception Test to be applied.
7.2 Why is there an Exception Test?
The Exception Test is essential in cases where the Sequential Test is unable to deliver acceptable sites for development. In some areas of flood risk development may be required to ensure social or economic blight does not occur, thus ensuring continued sustainable development or constraints on land elsewhere (areas protected by nature conservation designations preclude the identification of additional lower risk areas).
7.3 What is Required to Pass the Exception Test?
The Exception Test consists of three parts which are detailed below. All three parts must be satisfied before development in a flood risk area can be justified.
7.3.1 Part A – Wider Sustainability to the Community
‘It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by the SFRA where one has been prepared. If the DPD has reached the ‘submission’ stage (Figure 4 of PPS12; Local Development Frameworks) the benefits of the development should contribute to the Core Strategy’s Sustainability Appraisal’ (Appendix F). For individual allocations and planning applications it is necessary to provide evidence that will allow the LPA to assess whether wider sustainability benefits will be provided that will outweigh the flood risk implications of development at the site. Consequently the following steps should be considered: • The planning application should be scored against the sustainability criteria of the Sustainability Appraisal (SA). In the absence of a SA the checklists should reflect the Government’s Sustainability Strategy; • Where a development fails to score positively against the SA the LPA could consider planning conditions or Section 106 Agreements;
The Practice Guide for PPS25iv suggests that where ‘the Sustainability Appraisal is unavailable the developer / LPA will have to provide reasoned justification detailing how the planning application provides wider sustainability benefits to the community that outweigh flood risk. LPAs may consider
D118200 March 2009
72 Wealden District Council Level 1 SFRA: Final Report
the use of a sustainability checklist for this purpose. ’For development sites to successfully apply the Exception Test it must satisfy the above criteria in addition to the criteria provided under Parts B and C (below).
7.3.2 Part B – Brownfield Land
‘The development must be on developable previously developed land or, if it is not on previously developed land, that there are no reasonable alternative sites on developable previously developed land’ii. Planning Policy Statement 3: Housingxxi defines brownfield land as: ‘Previously-developed land is that which is or was occupied by a permanent structure, including the curtilage of the developed land and any associated fixed surface infrastructure.’ The definition includes defence buildings, but excludes: • Land that is or has been occupied by agricultural or forestry buildings; • Land that has been developed for minerals extraction or waste disposal by landfill purposes where provision for restoration has been made through development control procedures; • Land in built-up areas such as parks, recreation grounds and allotments, which, although it may feature paths, pavilions and other buildings, has not been previously developed; and • Land that was previously-developed but where the remains of the permanent structure or fixed surface structure have blended into the landscape in the process of time (to the extent that it can reasonably be considered as part of the natural surroundings).
There is no presumption that land that is previously-developed is necessarily suitable for housing development nor that the whole of the curtilage should be developed. For development sites to successfully apply the Exception Test it must satisfy the above criteria in addition to the criteria provided under Parts A and C.
7.3.3 Part C – Flood Risk
‘A FRA must demonstrate that the development will be safe, without increasing food risk elsewhere, and, where possible, will reduce flood risk overall’ii The Practice Guide to PPS25iv notes that it is the responsibility of the developer to prepare a comprehensive flood risk management strategy for the site and this should cover the following points: • The design of any flood defence infrastructure; • Safe access and egress; • Operation and maintenance; • Design of development to manage and reduce flood risk wherever possible; • Resident awareness; • Flood warning; and, • Evacuation procedures and funding arrangements.
The PPS25 Practice Guideiv also provides details on the definition of ‘safe’ in Chapter 4 – The Sequential and Exception Tests. In addition the Environment Agency has defined the minimum requirement for the definition of ‘safe’ as: • Dry access for more and highly vulnerable uses;
D118200 March 2009
73 Wealden District Council Level 1 SFRA: Final Report
• Dry escape for residential dwellings should be up to the 1 in 100 year flood event taking into account climate change; and • Preferably dry for other uses such as educational establishments and less vulnerable land use classifications. However the definition of safe should be clarified and agreed between the LPA and local Environment Agency officers and may require additional considerations depending on the precise nature of the proposed development and flood risk. Further guidance on what is safe can be found in the Defra/Environment Agency research document ‘Flood Risk Assessment Guidance for New Development’ (FD2320/R2). Details of mitigation measures that can be used to alleviate flooding and contribute to making a development safe are provided in Section 8. Before any development in a floodplain is approved the Environment Agency must be consulted on the proposed mitigation measures. To ensure that Part C of the Exception Test is satisfied with regard to preventing the increase of flood risk elsewhere, the Environment Agency requires the following methods and techniques to be considered: • Floodplain compensation; • Reduction in runoff rates; • Reduction of building footprints; • Replacement of solid buildings with buildings on stilts; • Provision of community benefit for existing properties; and, • Meeting the objectives of the relevant CFMP.
It must be recognised that this list is not prescriptive and the Environment Agency should be contacted on a site by site basis to determine what measures will be necessary to suit the scale and nature of the development and flood risk. The tables in Appendix E are provided to assist WDC ensure they have robust justification against parts A and B of the Exception Test for any developments requiring application of the test. Where necessary part C of the Exception Test will be addressed in a Level 2 SFRA.
D118200 March 2009
74 Wealden District Council Level 1 SFRA: Final Report
8 Site Specific Flood Risk Assessment Guidance
Objective 7 of this Level 1 SFRA is to ‘advise WDC on the requirements of site-specific Flood Risk Assessments based on local flooding issues and policy recommendations’.
Flood risk is a fundamental consideration for any development project regardless of scale or type. Understanding the flood risk to and arising from a development is key to managing the risk to people and property, reducing the risk of injury, property damage or even death. Climate change is of particular concern to flood risk, with current predictions suggesting the UK will experience milder wetter winters and on average hotter drier summers, whilst sea levels will continue to rise. This will lead to an increase in rainfall and therefore flood events in winter months and increase the risk of large thunderstorms in the summer months, as well as increasing the unpredictability of our weather.
Evidence collected through this Level 1 SFRA demonstrates flooding in the WDC study area is not limited to just rivers. In fact flooding is proven to arise from a number of sources, each presenting their own type of risk and requiring management. In addition some areas currently defended from flooding may be at risk in the future as the effects of climate change take hold or as the condition of defences deteriorates with age or as defence strategies change or a combination of these causes.
A failure to adequately consider flood risk in development proposals can have significant implications for the planning and development processes and longer term on the residents of new or existing developments. Issues that may arise through inappropriate consideration of flood risk include:
• Failure to consider wider plans prepared by the Environment Agency or other operating authorities may result in an objection to a proposed scheme;
• Failure to identify flood risk issues early in a development project could result in failure of a development proposal, requiring redesign of the site to mitigate flood risk;
• Failure to adequately assess all flood risk sources and construct a development that is safe over its lifetime could increase the number of people at risk from flooding and/or increase the risk to existing populations;
• Failure to mitigate the risk arising from development may lead to claims against the developer if an adverse effect can be demonstrated (i.e. flooding did not occur prior to development) by neighbouring properties or residents; and,
• Properties may be uninsurable and therefore effectively unable to be sold if flood risk management is not adequately provided for the lifetime of the development.
However, development can work within the limitation posed by flood risk if the risk is accurately understood and managed. Using a sound understanding of flood risk to locate, and design developments enables flood risks to be managed through positive planning. This positive planning needs to consider the risks to a development from local flood sources but also the consequences a development may have on increasing flood risk elsewhere. Early identification of flood risk constraints can ensure developments maximise development potential whilst satisfying the principles of sustainability.
D118200 March 2009
75 Wealden District Council Level 1 SFRA: Final Report
This Level 1 SFRA presents sufficient information to assist WDC to apply the ‘Sequential Test’ and identify where the ‘Exception Test’ may be required. However, the scale of assessment undertaken for a Level 1 Strategic Flood Risk Assessment is typically inadequate to accurately assess the risks faced by a particular discrete development at a given location within the study area. This Level 1 SFRA has attempted to identify all sources of flood risk at the catchment and district scale using the best available information. More local and site specific sources of flooding may become apparent during a Level 2 SFRA or during the course of a site specific FRAs.
Therefore, as part of planning applications for both allocated and non-allocated sites, site specific FRAs will be required in areas at risk of flooding. The FRAs are required to assess the flood risk posed to proposed developments and to ensure that where necessary, and appropriate, suitable mitigation measures are included in the development. This section presents the recommendations for site specific FRAs, the circumstances under which they should be prepared and their requirements for submission with planning applications to WDC. The site specific FRA guidance presented in the following sections has been developed based on: • The recommendations presented in PPS25ii and its accompanying Practice Guideiv; • The Environment Agency’s standing advice to LPAs through their Piper Networkingxlii website • A review of the policies in the current WDC Local Plan, and • The information and findings gathered and developed during preparation of this Level 1 SFRA.
8.1 When are Flood Risk Assessments Required?
When informing developers of the requirements of a FRA for a development site, consideration should be given to the position of the development relative to flood sources and the nature and location of any downstream development, the vulnerability of the proposed development and its scale. In accordance with PPS25ii FRAs should always be provided with a planning application in the following situations: • Development other than minor development in Flood Zones 2 & 3; • Development in Flood Zone 1 where there are critical drainage problems; • Any development exceeding one hectare in extent; • Development within 20m of the bank top of a Main River; and, • Any culverting operation or development which controls the flow of any river or stream.
The Environment Agency are a statutory consultee for all developments in the above cases. However for flooding from other sources or a selected number of development scenarios within the study area the LPA must establish the requirements for FRAs and assess their suitability as part of the planning application. Such situations, established through a review of the information collected for this Level 1 SFRA and review of national policy and include sites at risk from sewer flooding, groundwater flooding, artificial sources or in an area identified as at risk from overland flow flooding.
8.2 FRA Requirements
In general, for all planning applications where a FRA is required by PPS25 or the GDPO, it will be necessary to prepare an FRA document to the satisfaction of the Environment Agency.
D118200 March 2009
76 Wealden District Council Level 1 SFRA: Final Report
Table 8-1 presents an indication of the requirements for FRAs meeting these criteria; however the precise requirements should be agreed and established with the Environment Agency at the outset of each project. In scenarios where the Environment Agency are not the statutory consultee, the requirements of the FRA should be based on the guidance presented in Table 8-1 and discussed with the LPA at the outset of the assessment. The Practice Guide accompanying PPS25iv advocates a staged approach to any site specific FRA with the findings from each stage informing the next and site master plans, iteratively throughout the development process. The staged approach comprises: • Level 1 FRA - Screening Study; • Level 2 FRA - Scoping Study; and, • Level 3 FRA - Detailed Study.
It will not always be necessary to prepare each of the documents, in some cases where a site is known to flood it may be appropriate to prepare a Level 2 or 3 assessment directly. Annex E of PPS25ii and section 3.78 of its accompanying Practice Guide present the minimum requirements for FRA. This includes:
• Considering the risk of flooding arising from the development in addition to the risk of flooding to the development;
• Identifying and quantifying the vulnerability of the development to flooding from different sources and identify potential flood risk reduction measures;
• Assessing of the remaining ‘residual’ risk after risk reduction measures have been taken into account and demonstrate that this is acceptable for the particular development;
• Assessing the vulnerability of those that could occupy and use the development, taking account of the Sequential and Exception Tests and the vulnerability classification, including arrangements for safe access;
• Considering how the ability of water to soak into the ground may change with development, along with how the proposed layout of development may affect drainage systems; and,
• Fully accounting for current climate change scenarios and their effect on flood zoning and risk.
The stages approach is intended to limit the level of assessment to be appropriate to the nature of the flood source and type of development. Where a particular element of the FRA cannot be achieved to the satisfaction of the Environment Agency or LPA by a screening study it will be necessary to advance to a scoping study. Similarly where information in a scoping study inadequately identifies and mitigates flood risk a detailed study will be necessary.
8.2.1 Level 1 - Screening Study
A Level 1 Screening Study is intended to identify if a development site has any flood risk issues that warrant further investigation. This should be based on existing information such as that presented in
D118200 March 2009
77 Wealden District Council Level 1 SFRA: Final Report
the Level 1 SFRA. Therefore this type of study can be undertaken by a development control officer in response to the developer query or by a developer where the Level 1 SFRA is available. Using the information presented in the Level 1 SFRA and associated GIS layers a development control officer could advise a developer of any flooding issues affecting the site. This information can then be used by the developer as a basis to further their understanding of how the flood risks could potentially affect their development.
8.2.2 Level 2 - Scoping Study
A Level 2 Scoping Study is predominately a qualitative assessment designed to further understanding of how the flood sources affect the site and the options available for mitigation. The Level 2 FRA should be based on existing information where this is available to further a developers understanding of the flood risk and how it affect their development. This type of assessment should also be used to inform master plans of the site raising a developer’s awareness of the additional elements the proposed development may need to consider in order to appropriately and effectively manage flood risk.
8.2.3 Level 3 – Detailed Study
Where the quality and/or quantity of information for any of the flood sources affecting a site is insufficient to enable a robust assessment of the flood risks, further investigation will be required. For example; it is generally considered inappropriate to base a flood risk assessment for a residential care home at risk of flooding from fluvial sources on Flood Zone maps alone. In such cases the results of hydraulic modelling are preferable to ensure details of flood flow velocity, onset of flooding and depth of flood water is fully understood and that the proposed development incorporates appropriate mitigation measures.
Further details of the elements a Level 2 and/or a Level 3 site specific flood risk assessment should consider are presented in Table 8-1.
8.3 Flood Risk Assessment Guidance Table
The FRA Guidance Table 8-1 is intended to provide guidance to developers and local authorities on the requirements of site-specific FRA for flooding from all sources present in the study area and for the common range of development scenarios.
8.3.1 FRA Guidance Table 8 – 1 Accompanying Notes
The following set of notes have been developed with the intention of being used in conjunction with Table 8 – 1. The notes below are provided to assist the LPA and developers understand the minimum requirements of flood risk assessments for development scenarios where the LPA will determine if development is appropriate against some flood risks.
Using Table 8 – 1 and information provided in the Sequential Test Maps the LPA/developer should identify the nature of the proposed development (e.g. Change of use RESULTING IN ‘highly vulnerable’ or ‘more vulnerable’ development) and location relative to the various flood sources (e.g. within a high or medium area of risk from groundwater flooding).
D118200 March 2009
78 Wealden District Council Level 1 SFRA: Final Report
Using Table 8 – 1 the LPA/Developer can them establish that the LPA should be consulted for developments in these areas and that a flood risk assessment will be required that conforms to PPS25ii and addresses the elements of Groundwater Flood Note 1.
Flood Evacuation Plan (for use when referred to by Table 8-1)
Where Flood Evacuation Plans (FEP) are required as part of a planned development, these should be prepared in conjunction with the guidance presented in PPS25ii. The strategy should define the principles for dealing with the flood risk to a specific development and include the following documents: 1. Emergency Route Plan; 2. Checklist of Do’s and Don’ts formulated taking into account the specific building design; 3. Poster design to be displayed in Communal Areas setting out the flood risks and emergency procedures for particular building.
The fundamental points of the Flood Evacuation Plan are as follows: • Education and Training - increase awareness regarding the risk of flooding. This can be achieved by ensuring that all people are familiar with the flood evacuation strategy and the emergency route plan provided for each building. • Practical Flood Advice – Checklists of flood ‘dos and don’ts’. This will make reference to the how floodwaters enter a building, the risks they pose, how to react, as well as describe other potential hazards, for example floodwaters are likely to enter the building via the front door therefore do no attempt to exit via this route. • Flood Warning Service and Flood Wardens - Each building should be linked to the Environment Agency’s Flood Warning Service, if available. This system issues warnings of flood events for areas at risk of fluvial and/or tidal flooding. If appropriate to the nature of development, a Flood Warden can be nominated to ensure an appropriate system within the building for receiving the warnings is set up and that appropriate action is taken. • Emergency Route Plan - The Health and Safety Plan for each building should include an emergency route plan showing recommended routes offsite to nominated reception centres. Alternatively, where evacuation is not possible, routes to the upper floors and possible rescue or resupply locations.
D118200 March 2009
79 Wealden District Council Level 1 SFRA: Final Report
Sewer/Drainage Flooding Note 1 (SFN 1) (for use when referred to by Table 8-1)
In addition to following the principles of PPS25ii an appropriate FRA will:
1. Review the latest DG5 register held by Southern Water and the latest WDC Flooding Database for historical flooding incidents; 2. Review asset improvement schemes; 3. If the application site or adjacent property has experienced flooding to determine the frequency and depth; and, 4. If building interiors of the site (or neighbouring) experienced flooding employ mitigation methods e.g. pressure sealing doors, strategic placement of cables (see Flood Resilient construction).
Possible mitigation may include: • Raising finished floor levels • Construct buildings with solid floors • Provide raised walkways to ensure safe access and egress during a flood event • Incorporate SuDS to limit runoff
If step 1 identifies the application site has previously flooded and the application is for a ‘major development’ (defined by PPS25ii) please also refer to Note 2 (SFN 2).
Further Information • DCLG Improving the Flood Performance of New Buildings – Flood Resilient Construction 2007 • Building Regulations 2000 Approved Document H3 Rainwater Drainage • Code for Sustainable Homes 2008
Sewer/Drainage Flooding Note 1 (SFN 2) (for use when referred to by Table 8-1) (for ‘major developments’)
In addition to following the principles of PPS25ii an appropriate FRA will, as well as SFN 1:
1. Hydraulic modelling or a capacity assessment of the receiving sewer should confirm the sewer has sufficient capacity to drain the sites surface water.
Further Information • DCLG Improving the Flood Performance of New Buildings – Flood Resilient Construction 2007 • Building Regulations 2000 Approved Document H3 Rainwater Drainage • Code for Sustainable Homes 2008
D118200 March 2009
80 Wealden District Council Level 1 SFRA: Final Report
Sewer/Drainage Flooding Note 3 (SFN 3) (for use when referred to by Table 8-1) (for ‘major developments’)
In addition to following the principles of PPS25ii an appropriate FRA will as well as SFN 1 and 2:
1. If step 1 of SFN 1 identifies the application site has previously flooded mitigation through SuDS should be provided (CIRIA 697). To determine the appropriate SuDS technique infiltration testing will need to be carried out following the methodology in BRE 365. SuDS guidance is provided in Section 9; and, 2. A Drainage Strategy should be developed incorporating SuDS to manage risk from sewer flooding.
Further Information • DCLG Improving the Flood Performance of New Buildings – Flood Resilient Construction 2007 • Building Regulations 2000 Approved Document H3 Rainwater Drainage • Code for Sustainable Homes 2008
Groundwater Flooding Note 1 (GWFN 1) (for use when referred to by Table 8-1)
In addition to following the principles of PPS25ii an appropriate FRA will:
1. Review the WDC Flooding Database for historical flooding incidents; 2. Review geology and hydrogeological mapping available from British Geological Survey; 3. Review groundwater/borehole data held by the Environment Agency for trends; 4. If the application site is within a high or medium risk area of flooding from groundwater on an aquifer with a rising groundwater trend then appropriate mitigation should be provided. It is advisable that basement dwellings are not appropriate in this situation.
Possible mitigation could include: • Raising finished floor levels – to be considered on site by site basis • Constructing buildings with solid floors • Providing raised walkways to ensure safe access and egress during a flood event.
Further Information • DCLG Improving the Flood Performance of New Buildings – Flood Resilient Construction 2007
D118200 March 2009
81 Wealden District Council Level 1 SFRA: Final Report
Groundwater Flooding Note 1 (GWFN 2) (for use when referred to by Table 8-1)
In addition to following the principles of PPS25ii an appropriate FRA will, as well as GWFN 1:
1. Carry out pre and post development groundwater monitoring with site-specific boreholes. Where the foundations of the development disturb penetrate groundwater the FRA will demonstrate that groundwater flow paths are not adversely affected.
Possible mitigation could include: • Ensure that building foundations and piling do not disrupt groundwater flow routes.
Further Information • DCLG Improving the Flood Performance of New Buildings – Flood Resilient Construction 2007
Overland Flow Flooding Note 1 (OFFN 1) (for use when referred to by Table 8-1)
In addition to following the principles of PPS25ii an appropriate FRA will:
1. Review the WDC Flooding Database for historical flooding incidents; 2. If the application site has experienced flooding assess the frequency/depth;
Possible mitigation could include: • solid flooring, • Free draining sub floor voids
If the application is for a ‘major development’ (as defined by PPS 25ii) please also refer to OFFN 2.
Further Information • DCLG Improving the Flood Performance of New Buildings – Flood Resilient Construction 2007
D118200 March 2009
82 Wealden District Council Level 1 SFRA: Final Report
Overland Flow Flooding Note 1 (OFFN 1) (for use when referred to by Table 8-1) (for ‘major developments’)
In addition to following the principles of PPS25ii an appropriate FRA will, as well as OFFN 1):
1. Runoff Assessment of contributing catchment;
Possible mitigation could include: • strategic orientation of the buildings to limit the impedance of overland flow routes and/or could be to control overland flow through the incorporation of SuDS • solid flooring, • Free draining sub floor voids
Further Information • DCLG Improving the Flood Performance of New Buildings – Flood Resilient Construction 2007
Artificial Sources Flooding Note 1 (ASFN 1) (for use when referred to by Table 8-1)
In addition to following the principles of PPS25ii an appropriate FRA will: 1. Review latest WDC Flooding Database; 2. Review Flood Plans for ‘large-raised reservoirs’; and, 3. Ensure that site occupants are aware of local Evacuation Plans.
Artificial Sources Flooding Note 2 (ASFN 2) (for use when referred to by Table 8-1)
In addition to following the principles of PPS25ii an appropriate FRA will, as well as ASFN 1:
1. Develop a Flood Evacuation Plan.
D118200 March 2009
83 Wealden District Council Level 1 SFRA: Final Report
Artificial Sources Flooding Note 3 (ASFN 3) (for use when referred to by Table 8-1)
In addition to following the principles of PPS25ii an appropriate FRA willassess Residual Risk from failure of ‘large-raised reservoirs’
Possible mitigation could include: • strategic orientation of buildings to limit impedance of overland flow routes.
Fluvial Flooding Note 1 (FFN Note 1) (for use when referred to by Table 8-1)
In addition to following the principles of PPS25ii an appropriate FRA will:
1. Ensure the developer is aware of local Evacuation Plans; 2. Advise the developer to sign up to Environment Agency Flood Warning Service; 3. Exception Test may be required depending on PPS25ii vulnerability classification; 4. If the site is considered within the undefended floodplain, any increases in building footprint may require flood compensation storage on a level for level basis; and 5. If the site is considered defended, residual risk must be identified in the FRA in the event of a failure of the defences, either through overtopping or breach (depending on the nature of the defences). Flow paths to the site should be identified to determine the level of residual flood risk to the site and potential egress/access routes.
Possible mitigation may include: • Set floor levels no lower than existing levels AND include flood proofing where appropriate, or • set floor levels 300mm above the 1% annual probability flood level including an allowance for climate change for the lifetime of the development. • Flood resilience or resistant techniques.
Fluvial Flooding Note 2 (FFN Note 2) (for use when referred to by Table 8-1)
In addition to following the principles of PPS25ii an appropriate FRA will, as well as FFN Note 1:
1. An Evacuation Plan should be developed.
D118200 March 2009
84 Wealden District Council Level 1 SFRA: Final Report
Fluvial Flooding Note 3 (FFN Note 3) (for use when referred to by Table 8-1)
In addition to following the principles of PPS25ii an appropriate FRA will, as well as FFN Note 1 and 2:
1. A Drainage Strategy should be developed.
xlii Environment Agency (2007) ‘Environment Agency Standing Advice: Development and Flood Risk’ available at http://www.pipernetworking.com/floodrisk/index.html
D118200 March 2009
85 Wealden District Council Level 1 SFRA: Final Report
Table 8-1: Flood Risk Assessment (FRA) Guidance Table
D118200 March 2009
86
Wealden District Council Level 1 Strategic Flood Risk Assessment
Table 8 – 1: Flood Risk Guidance Table (should be used in conjunction with the main Level 1 SFRA report
Sewer Flooding Groundwater Flooding Overland Flow Artificial Sources Development (including boundary walls Development Development including culverting or control of Within Flood Zone 3a (1% annual Within Flood Zone 2 (0.1% annual Within Flood Zone 1 (<0.1% annual etc.) within 20 metres of the top of a bank Within Flood Zone 3b For areas defined as at medium of For areas defined as at medium For areas defined as at medium Category flow of any river or stream. probability flood extent) probability flood extent) probability flood extent) For areas defined as at medium or high of a main river. high risk or flooding from this source of high risk or flooding from this of high risk or flooding from this risk of flooding from this source the the following issues must be source the following issues must source the following issues must following issues must be considered considered be considered be considered
Consult EA Consult EA with FRA showing design details of any culvert or Residential development including extensions to Consult Local Planning Authority with Flood Risk Consult Local Planning Authority with Flood Risk Consult Local Planning Authority Consult Local Planning Authority with Consult Local Planning Authority with Consult Local Planning Authority Consult Local Planning Authority flow control structure proposed. building footprints is not appropriate. Assessment Assessment Flood Risk Assessment Flood Risk Assessment with Flood Risk Assessment with Flood Risk Assessment
1 1 FURTHER INFORMATION Necessary to preserve existing functional floodplain and Refer to Fluvial Flood Note 1 (FFN 1) • Refer to Fluvial Flood Note 1 (FFN 1) • Refer to Sewer/Drainage Flood Note • Refer to Groundwater Flood Note • Refer to Overland Flow Flood • Refer to Artificial Sources Flood Householder development http://www.pipernetworking.com EA Flood Defence Consent required. because risks to building in these areas are too great. 1(SFN 1) 1 1(GWFN 1) 1 Note 1(OFFN 1) 1 Note 1(ASFN 1) 1 and alterations FURTHER INFORMATION FURTHER INFORMATION FURTHER INFORMATION http://www.pipernetworking.com http://www.pipernetworking.com • http://www.pipernetworking.com
Consult EA Consult EA with FRA showing design details of any culvert or Extension to non-residential developments in Flood Consult Local Planning Authority with Flood Risk Consult Local Planning Authority with Flood Risk Consult Local Planning Authority Consult Local Planning Authority with Consult Local Planning Authority with Consult Local Planning Authority Consult Local Planning Authority flow control structure proposed. Zone 3b is not appropriate. Assessment Assessment Flood Risk Assessment Flood Risk Assessment with Flood Risk Assessment with Flood Risk Assessment
1 1 Non- residential extensions FURTHER INFORMATION Necessary to preserve existing functional floodplain and • Refer to Fluvial Flood Note 1 (FFN 1) and Fluvial • Refer to Fluvial Flood Note 1 (FFN 1) and Fluvial • Refer to Sewer/Drainage Flood Note • Refer to Groundwater Flood Note • Refer to Overland Flow Flood • Refer to Artificial Sources Flood 1 1 1 1 1 1 with a footprint of less than • http://www.pipernetworking.com EA Flood Defence Consent required. because risks to building in these areas are too great. Flood Note 2 (FFN 2) Flood Note 2 (FFN 2) 1(SFN 1) and Sewer/Drainage Flood 1(GWFN 1) Note 1(OFFN 1) Note 1(ASFN 1) and Artificial 1 1 250m² Note 2(SFN 2) Sources Flood Note 2 (ASFN 2)
FURTHER INFORMATION FURTHER INFORMATION FURTHER INFORMATION • http://www.pipernetworking.com http://www.pipernetworking.com http://www.pipernetworking.com
Only Consult EA if site falls within Flood Zone 3a or 3b Consult EA under part IV, Section 109 (1) of the Water Less vulnerable uses are not permitted in Flood Zone Consult EA with FRA Consult Local Planning Authority with Flood Risk Consult Local Planning Authority Consult Local Planning Authority with Consult Local Planning Authority with Consult Local Planning Authority Consult Local Planning Authority Resources Act 1991 to gain consent when plans include 3b. Assessment Flood Risk Assessment Flood Risk Assessment with Flood Risk Assessment with Flood Risk Assessment erection of any structure in, over or under a watercourse Flood Evacuation Plan 1 required Flood Risk Assessment Required Flood Evacuation Plan 1 required for all other Refer to Fluvial Flood Note 1 (FFN 1) 1 and Fluvial • Refer to Sewer/Drainage Flood Note • Refer to Groundwater Flood Note • Refer to Overland Flow Flood • Refer to Artificial Sources Flood Change of use FROM ‘water developments Flood Note 2 (FFN 2) 1 1(SFN 1) 1 1(GWFN 1) 1 Note 1(OFFN 1) 1 Note 1(ASFN 1) 1 and Artificial 1 compatible’ TO ‘less EA Flood Defence Consent required. FURTHER INFORMATION Sources Flood Note 2 (ASFN 2) • vulnerable’ development FURTHER INFORMATION http://www.pipernetworking.com • http://www.pipernetworking.com FURTHER INFORMATION FURTHER INFORMATION • http://www.pipernetworking.com • http://www.pipernetworking.com
Only Consult EA if site falls within Flood Zone 3a or 3b Consult EA under part IV, Section 109 (1) of the Water Highly and more vulnerable uses are not permitted in Highly vulnerable uses are not permitted in Flood Consult EA with FRA Consult Local Planning Authority Consult Local Planning Authority with Consult Local Planning Authority with Consult Local Planning Authority Consult Local Planning Authority Resources Act 1991 to gain consent when plans include Flood Zone 3b. Zone 3a Flood Risk Assessment Flood Risk Assessment with Flood Risk Assessment with Flood Risk Assessment erection of any structure in, over or under a watercourse Flood Evacuation Plan 1 required 1 Change of use RESULTING Flood Risk Assessment Required Flood Evacuation Plan required for all other Consult EA with FRA • Refer to Sewer/Drainage Flood Note • Refer to Groundwater Flood Note • Refer to Overland Flow Flood • Refer to Artificial Sources Flood developments 1(SFN 1) 1 1(GWFN 1) 1 Note 1(OFFN 1) 1 Note 1(ASFN 1) 1and Artificial 1 1 IN ‘highly vulnerable’ or EA Flood Defence Consent required. Flood Evacuation Plan required FURTHER INFORMATION Sources Flood Note 2 (ASFN 2) ‘more vulnerable’ FURTHER INFORMATION • http://www.pipernetworking.com development • http://www.pipernetworking.com FURTHER INFORMATION FURTHER INFORMATION • http://www.pipernetworking.com FURTHER INFORMATION • http://www.pipernetworking.com • http://www.pipernetworking.com
Consult EA Consult EA with FRA showing design details of any culvert or Consult EA with FRA and Sequential Test evidence Consult EA with FRA and Sequential Test evidence Consult EA with FRA and Sequential Test evidence Consult Local Planning Authority with Flood Risk Consult Local Planning Authority with Consult Local Planning Authority with Consult Local Planning Authority Consult Local Planning Authority flow control structure proposed. (and where required confirm Exception Test has been (and where required confirm Exception Test has (and where required confirm Exception Test has Assessment Flood Risk Assessment Flood Risk Assessment with Flood Risk Assessment with Flood Risk Assessment applied). been applied) been applied) 1 FURTHER INFORMATION • Refer to Fluvial Flood Note 1(FFN 1) Fluvial Flood • Refer to Sewer/Drainage Flood Note • Refer to Groundwater Flood Note • Refer to Overland Flow Flood • Refer to Artificial Sources Flood • http://www.pipernetworking.com EA Flood Defence Consent required. Only water compatible uses are permitted in this flood Flood Evacuation Plan 1 required Flood Evacuation Plan 1 required Note 2 (FFN2) 1 and Fluvial Flood Note 3 (FFN3) 1 1(SFN 1) 1, Sewer/Drainage Flood Note 1(GWFN 1) 1 and Groundwater Flood Note 1(OFFN 1) 1 Note 1(ASFN 1) 1 and Artificial zone and ‘essential infrastructure’ through the process • Flood Evacuation Plan 1 required 2(SFN 2) 1 and Sewer/Drainage Flood Note 2 (GWFN 2) 1 Sources Flood Note 2 (ASFN 2) 1 Operational development of 1 1 of the Exceptions Test. • Drainage Strategy Required Note 3 (SFN 3) less than 1 hectare FURTHER INFORMATION FURTHER INFORMATION FURTHER INFORMATION • http://www.pipernetworking.com Flood Evacuation Plan 1 required • http://www.pipernetworking.com • http://www.pipernetworking.com
FURTHER INFORMATION • http://www.pipernetworking.com
Consult EA Consult EA with FRA showing design details of any culvert or Consult EA with FRA and Sequential Test evidence Consult EA with FRA and Sequential Test evidence Consult EA with FRA and Sequential Test evidence Consult EA with FRA. Consult Local Planning Authority with Consult Local Planning Authority with Consult Local Planning Authority Consult Local Planning Authority flow control structure proposed. (and where required confirm Exception Test has been (and where required confirm Exception Test has (and where required confirm Exception Test has Flood Risk Assessment Flood Risk Assessment with Flood Risk Assessment with Flood Risk Assessment applied). been applied) been applied) A FRA is required for all sites over 1ha. A FRA is required for all sites over 1ha. A Flood Risk Assessment would need to be • Refer to Sewer/Drainage Flood Note • Refer to Groundwater Flood Note • Refer to Overland Flow Flood • Refer to Artificial Sources Flood Only water compatible uses are permitted in this flood Flood Evacuation Plan 1 required Flood Evacuation Plan 1 required undertaken on all sites greater than 1ha in size in 1(SFN 1) 1, Sewer/Drainage Flood Note 1(GWFN 1) 1 and Groundwater Flood Note 1(OFFN 1) 1 Note 1(ASFN 1) 1 and Artificial EA Flood Defence Consent required. zone and ‘essential infrastructure’ through the process compliance with PPS25. 2(SFN 2) 1and Sewer/Drainage Flood Note 2 (GWFN 2) 1 Sources Flood Note 2 (ASFN 2) 1 1 Operational development of FURTHER INFORMATION of the Exceptions Test. Note 3 (SFN 3) 1ha or greater • http://www.pipernetworking.com FURTHER INFORMATION FURTHER INFORMATION 1 FURTHER INFORMATION Flood Evacuation Plan required • http://www.pipernetworking.com • http://www.pipernetworking.com FURTHER INFORMATION • http://www.pipernetworking.com • http://www.pipernetworking.com
FURTHER INFORMATION • http://www.pipernetworking.com
Key: Scenarios colour coded Green the will be assessed by the Environment Agency as they are a statutory consultee Scenarios colour coded Yellow will need to be assessed by the Local Authority
1 Contained in the main Level 1 SFRA report The green cells of the above table are repeated from those provided by the Environment Agency Standing Advice Development and Flood Risk – England found on http://www.pipernetworking.com . Any apparent inconsistencies presented for faithfulness to the original source.
Wealden District Council Level 1 SFRA: Final Report
9 Drainage of Development Sites
Objective 8 of this Level 1 SFRA is to ‘advise WDC on the applicability of Sustainable Drainage Systems (SuDS) in the study area’. In keeping with the guidance of PPS25ii, local authorities should encourage the application of Sustainable Drainage Systems (SuDS). This chapter presents a summary of a selection of the SuDS techniques available and a review of the soils and geology of the study area, enabling WDC to identify what type of SuDS techniques could be employed in development schemes within the SFRA study area.
9.1 Background
Traditionally, built developments have utilised piped drainage systems to manage storm water and convey surface water run-off away from developed areas as quickly as possible. Typically these systems connect to the public sewer system for treatment and/or discharge to local watercourses. Whilst this approach rapidly transfers storm water from developed areas, the alteration of natural drainage processes can potentially impact on downstream areas by increasing flood risk and reducing water quality. Receiving watercourses are therefore much more sensitive to rainfall intensity, volume and catchment land uses after a catchment or areas of a catchment have been developed. Due to the difficulties and inconvenience associated with up grading sewer systems it is uncommon for sewer and drainage systems to keep pace with the rate of development/re-development. As development progresses and/or urban areas expand, the drainage systems become inadequate for the volumes and rates of storm water they receive, resulting in increased flood risk and/or pollution of watercourses. Allied to this, the implications of climate change on rainfall intensities leads to flashier catchment/site responses and surcharging of piped systems. In addition, as flood risk has increased in importance within planning policy, a disparity has emerged between the design standard required of new conventional sewer systems the scenarios required by PPS25. Typically sewer systems are designed to accommodate the 3.3% annual probability storm without flooding at the ground surface in accordance with Sewers for Adoptionxiii, whilst new developments are required to mitigate against the risks up to the 1% annual probability flood. This results in drainage inadequacies for the flood return period which need to be taken into consideration when designing drainage systems. Whilst the risk of flooding from fluvial systems can be managed, an inappropriately designed site drainage system could generate a new flood risk to development and existing property. A sustainable solution to these issues is to reduce the volume and/or rate of water entering the sewer system and watercourses. The Government’s preferred method to achieve this is through the use of SuDS. PPS25ii notes that regional planning bodies and local authorities should promote the use of SuDS for the management of runoff. Whilst the PPS25 Practice Guideiv recognises the significance of SuDS in controlling the impact of development on local flood risk in step four of the ‘Flood Risk Management Hierarchy’.
9.2 What are SuDS?
SuDS are a varied collection of techniques designed to manage storm water in a sustainable manner. SuDS achieve this by seeking to manage surface water from new developments as close to its source as possible and by mimicking the surface water flow regime present on a site prior to development.
D118200 March 2009
87 Wealden District Council Level 1 SFRA: Final Report
Typically this approach involves a move away from conventional piped systems to engineering solutions inspired by natural drainage processes. For SuDS to be fully sustainable they should seek to contribute to each of the three goals of sustainability (identified below), with the favoured system contributing equally to each goal. The three goals of sustainable drainage systems are: 1. Reduce flood risk (to the site and neighbouring areas), 2. Reduce pollution, and, 3. Provide landscape and wildlife benefits. In addition, SuDS should also be designed to ensure they remain effective for storm events up to and including the 1% annual probability storm event including an increase in peak rainfall intensities to account for the predicted effects of climate change.
9.3 Achieving SuDS in Developments
The application of SuDS techniques is not limited to one technique per site. Often a successful SuDS solution will utilise a number of techniques in combination, providing flood risk, pollution and landscape/wildlife benefits to the site and surrounding area. A common issue with incorporating SuDS in developments is the belief that all SuDS are ‘land hungry’ and significantly impact on the developable area of sites. However, SuDS can be designed to achieve the above goals without significantly impacting on development. In addition, SuDS can be employed on a strategic scale, for example with a number of sites contributing to large scale jointly funded and managed SuDS, however, each development site must offset its own increase in runoff; attenuation cannot be “traded” between developments. Such an approach is advocated by the Management Train, which recommends incorporating a chain of techniques throughout a development (as outlined in CIRIA C697) where each component adds to the performance of the whole system. The total SuDS system can be spread throughout a site and more readily incorporated into the sites infrastructure. The Management Train approach consists of four stages: Prevention good site design and upkeep to prevent runoff and pollution (e.g. limited paved areas, regular pavement sweeping)
Source control runoff control at/near to source (e.g. rainwater harvesting, green roofs, pervious pavements)
Site control water management from a multitude of catchments (e.g. route water from roofs, impermeable paved areas to one infiltration/holding site)
Regional control integrate runoff management from a number of sites (e.g. into a wetland).
9.4 Drainage Strategy Requirements
A drainage strategy should be designed to demonstrate to the Environment Agency/LPA that a site can be drained in a sustainable manner. It should show that through redevelopment flood risk to
D118200 March 2009
88 Wealden District Council Level 1 SFRA: Final Report
properties downstream of the site will not be exacerbated. A drainage strategy should include the following information: 1. Permitted discharge rates derived in consultation with the Environment Agency/LPA; 2. Storm water runoff calculations from parcels of land on the site including allowances for climate change for the lifetime of the development; 3. Attenuation required on each parcel of land to restrict runoff to permitted discharge rates; 4. Proposed means of attenuation; 5. Distribution of storm water attenuation across the site; 6. Design standards and parameters of the proposed storm drainage techniques; and, 7. To demonstrate control of flooding up to the 1% annual probability storm event including the effects of climate change.
This list should not be considered as exhaustive and may require additional elements depending on the nature and scale of the proposed development and mitigation required. Further Information • Code for Sustainable Homes 2008 • Building Regulations 2000 Approved Document H3 Rainwater Drainage • BRE 365 Soakaway Design • CIRIA C697 The SuDS Manual
9.5 SuDS Techniques
There are a wide range of SuDS techniques available for use throughout the 4 stages of the Management Train. Techniques available to manage the quantity of storm water typically operate in combination or solely on the basis of infiltration and attenuation. The effectiveness of techniques on achieve the goals of reducing pollution and providing amenity benefit will depend on a number of other factors such as filtration, settlement and oxidation. The SUDS manual (C697) provides a summary of SuDS techniques and their suitability to meet the three goals of sustainable drainage systems and their suitability within the stages of the Management Train.
D118200 March 2009
89 Wealden District Council Level 1 SFRA: Final Report
Table 9-1: Summary of SuDS Techniques and their Suitability to meet the three goals of sustainable drainage systems
MANAGEMENT SUDS WATER WATER AMENITY SUDS TECHNIQUE DESCRIPTION TRAIN PRINCIPLE QUANTITY QUALITY BIODIVERSITY Layer of vegetation or gravel on roof areas providing Green roofs Attenuation absorption and storage. ● ● ● Capturing and reusing rainwater for domestic or Rainwater harvesting Attenuation irrigation uses. ● ○ ○
Prevention Permeable Infiltration through the surface into underlying layer. Infiltration pavements ● ● ○ Drain filled with permeable material with a perforated Filter drains Infiltration X pipe along the base. ● ● Similar to filter drains but allows infiltration through Source Infiltration trenches Infiltration X sides and base. ● ● Soakaways Underground structure used for store and infiltration. Attenuation ● ● X Vegetated areas used for treating runoff prior to Bio-retention areas Attenuation discharge into receiving water or infiltration ● ● ● Grassed depressions, provides temporary storage, Swales Attenuation conveyance, treatment and possibly infiltration. ● ● ○ Provides treatment by filtering runoff through a filter Sand filters Infiltration X media consisting of sand. ● ● Dry depressions outside of storm periods, provides Basins temporary attenuation, treatment and possibly Attenuation ● ● ○
Site infiltration. Designed to accommodate water at all times, provides
Ponds attenuation, treatment and enhances site amenity Attenuation ● ● ● Regional Regional value. Similar to ponds, but are designed to provide Wetland Attenuation continuous flow through vegetation. ● ● ●
Key: ● – highly suitable, ○ - suitable depending on design, X – unsuitable
D118200 March 2009
90 Wealden District Council Level 1 SFRA: Final Report
9.6 SuDS Design
Detailed guidance for the design of SuDS is available in the CIRIA SuDS Manual C697, and the associated document ‘Site Handbook for the Construction of SuDS, (C698). These publications provide best practice guidance on the planning, design, construction, operation and maintenance of SuDS, to ensure effective implementation within developments. The design of SuDS measures should be undertaken as part of a drainage strategy and design for a development site. A ground investigation should form part of the SuDS assessment to determine ground conditions and the most appropriate SuDS technique(s). Hydrological analysis should be undertaken using industry approved procedures, to ensure an appropriate design is developed. This should account for the effects of climate change over the lifetime of the proposed system/development and based on an agreed permitted rate of discharge from the site. During the design process, liaison should take place with the authority responsible for the receiving water body and any organisations involved in the long term maintenance of the system. This may include liaison with WDC, the Environment Agency and Southern Water. Liaison with these organisations should focus on establishing a suitable design methodology, any restrictions and provision for the long-term maintenance of the SuDS system.
9.7 Where can SuDS be utilised?
The underlying ground conditions of a development site will often influence the type of SuDS technique suitable at an individual site. While this will need to be determined through ground investigations carried out on-site, an initial assessment of a sites suitability to the use of SuDS can be obtained from a review of the available soils/geological survey of the area. The potential suitability of infiltration or attenuation SuDS techniques for the various soils and strata throughout the study area are tabulated in Appendix F. The following maps were reviewed in the preparation of Appendix F: • The Soil Survey of England and Wales 1993 – 1:250,000 Soils Maps (Sheet 6); • The Geological Survey of Great Britain (England and Wales) 1:50,000 Series Solid and Drift Edition Sheets 319 (1979) and Sheet 303 (1971); and • The Soils Map Legend. Tables presented in Appendix E are provided as a guide alone and should not be used to accept or refuse SuDS techniques. Overall the suitability and design of a SuDS system should be determined on a site by site basis through consultation with the authority responsible for the receiving waterbody. The tables in Appendix E is provided to assist WDC develop an understanding of the types of SuDS features that could be incorporated into development sites they may bring forward through their LDF. The same approach can also be used when assessing the feasibility of SuDS systems for windfall sites. It is recommended that WDC complete Table 13-1 to assist in identifying suitable SuDS for development sites in their areas. Completion of Table 13 - 1 will assist in identifying where various types of SuDS are most suitable and enable developers to account for SuDS when developing master plans for development sites.
D118200 March 2009
91 Wealden District Council Level 1 SFRA: Final Report
9.7.1 SuDS Constraints
During the design process, in addition to considering the properties of the underlying soils and strata it is necessary to also consider the sensitivity of the receiving waterbody and any previous uses of the site.
The use of SuDS can be limited based on a number of issues, which include: • Groundwater vulnerability and potential contamination of an aquifer; • Current or aspirational water quality of a receiving watercourse; • The presence of groundwater Source Protection Zones and potential contamination of a potable water source; • Restrictions on infiltration on contaminated land to prevent the spread of contamination; and, • Restricted area on development sites where housing densities are high.
9.7.2 Groundwater Vulnerability
Groundwater resources may be vulnerable to contamination from both direct sources (e.g. into groundwater) or indirect sources (e.g. infiltration of discharges onto land). Groundwater vulnerability within the study area has been determined by the Environment Agency, based on a review of aquifer characteristics, local geology and the leachability of soils. The vulnerability of the groundwater is important when advising on the suitability of SuDS. Through examination of groundwater vulnerability maps for the study area are summarised in Table 9-2 present the aquifer classifications present in the study area and shown in Figure 15. • NRA (1986) ‘Groundwater Vulnerability of East Sussex: Sheet 46’, HMSO: London. Table 9-2: Groundwater vulnerability by area
FULL VULNERABILITY TYPICAL VULNERABILITY LOCATION CLASSIFICATION DESCRIPTION Highly Vulnerable Uckfield, (precautionary Crowborough Minor High (H) U approach due to limited soil information) River Medway corridor, Minor High (H) 1 Highly Vulnerable River Ouse corridor Maresfield, Pittdown, West of Uckfield, Minor Intermediate Moderately Forest Row, (I) 1 Vulnerable Isfield, Groombridge, Hartfield, Northern
D118200 March 2009
92 Wealden District Council Level 1 SFRA: Final Report
FULL VULNERABILITY TYPICAL VULNERABILITY LOCATION CLASSIFICATION DESCRIPTION Wadhurst, Rotherfield Ashdown Forest, Minor Low (L) Low Vulnerability West of Crowborough. Between Rotherfield, Mayfield, Burnt Non-Aquifer Low Vulnerability Oak and the eastern SFRA study boundary.
9.7.3 Source Protection Zones
In addition to groundwater vulnerability, the Environment Agency also defines groundwater Source Protection Zones around groundwater abstraction points. Source Protection Zones (SPZ) are defined to protect areas of groundwater that are used for potable supply, including public/private potable supply, (including mineral and bottled water) or for use in the production of commercial food and drinks. SPZs are defined based on the time it takes for pollutants to reach an abstraction point. Depending on the nature of the proposed development and the location of the development site with regards to the SPZs, restrictions may be placed on the types of SuDS appropriate to certain areas. Any restrictions imposed on the discharge of site generated runoff by the Environment Agency will be determined on a site by site basis using a risk based approach. The SPZ for the study area are displayed in Figure 16.
9.7.4 Water Quality
Under the Water Framework Directive all member states are required to take steps to achieve good ecological status of water bodies by 2015. To achieve this, discharges to watercourses draining development areas will require pre-treatment to remove oils and contaminants. Appropriately designed SuDS can assist developments improve water quality discharges through passive treatment, whilst additionally providing ecological benefit to a development or local area.
9.7.5 Contaminated Land
Previous site uses can leave a legacy of contamination that if inappropriately managed can cause damage to local waterbodies. During the design of SuDS it is essential to have regard to the nature of potential ground contamination. Particular restrictions may be placed on infiltration bases SuDS, forcing consideration of attenuation based systems.
D118200 March 2009
93 Wealden District Council Level 1 SFRA: Final Report
9.7.6 High development densities
Where developments are required to achieve high development densities it is essential that the requirement for SuDS and their constraints are identified early in the site master planning process. High development densities can restrict the land area available for SuDS, which if mandatory can affect the ability of a site to gain planning permission. Early consideration of SuDS enables the drainage requirements to be integrated with the design, limiting the impact they have on developable area and development densities.
9.8 SuDS Policies
In addition to the policies presented in PPS25 advocating the use of SuDS there are a number of other policies and planning documents that promote SuDS in new developments.
9.8.1 PPS25ii
In terms of identifying a requirement to consider SuDS on a development project the following general principle (set out in PPS25ii) should be followed: “The surface water drainage arrangements for any development site should be such that the volumes and peak flow rates of surface water leaving a developed site are no greater than rates prior to the proposed development, unless specific off-site arrangements are made and result in the same net effect.” This is to alleviate the pressure on sewer systems that may be old or serving a catchment area greater than their original design or designed to a standard less than the 1% annual probability event now required. If a proposed development results in an increase in surface water runoff, then the Environment Agency will generally expect to see SuDS forming part of the proposed mitigation. Where the consented discharge rates are low, retrofitting of SuDS can significantly impact development proposals. There are, at present, no legally binding obligations relating to the provision and maintenance of SuDS. However, PPS25ii states that: “where the surface water system is provided solely to serve any particular development, the construction and ongoing maintenance costs should be fully funded by the developer.” The most convenient vehicle for agreeing long-term management responsibilities is through Section 106 of the Town and Country Planning Act. Under this, agreement for SuDS maintenance can be a requirement of the planning consent..
9.8.2 Building Regulations 2002 H3 Rainwater Drainagexxxi
The Building Regulations 2002 enable the principles of PPS25ii to be enforced during construction by stipulating that: 1. Adequate provision shall be made for rainwater to be carried from the roof of the building; 2. Paved areas around the building shall be so constructed as to be adequately drained;
D118200 March 2009
94 Wealden District Council Level 1 SFRA: Final Report
3. Rainwater from a system provided pursuant to sub-paragraphs (1) or (2) shall discharge to one of the following, listed in order of priority: • an adequate soakaway or some other adequate infiltration system; or, where that is not reasonably practicable, • a watercourse; or, where that is not reasonably practicable, • a sewer. As the Environment Agency are the consenting authority for discharges to controlled waters (i.e. groundwater or watercourses), SuDS will be favoured for the removal of pollutants and attenuation of discharge rates.
9.8.3 Code for Sustainable Homesxxxii
Rating against the Code for Sustainable Homes became a mandatory requirement for all new homes in April 2008. If the Code is applied, proposed developments are assessed against a number of sustainability criteria that include ‘water use’ and ‘surface water run-off’. For each category points are awarded depending on the sustainability of the management technique proposed (i.e the more sustainable the more points are awarded). The points for each category are collated and the development is given an overall code level from 1 – 6. Under the Code ‘internal water use’ and ‘management of surface water runoff from developments’ will be assessed as mandatory elements, requiring developments to demonstrate their sustainability against these criteria. Table 9-3 and Table 9-4 summarises the measurement criteria used for both potable water consumption and surface water runoff in the Code for Sustainable Homesxxxii. Table 9-3: Summary of the measurement criteria for water use
CATEGORY 2 WATER CREDITS ISSUE MEASUREMENT CRITERIA AVAILABLE Where predicted water consumption (calculated using One of the the Code water calculator) accords with the following following point Indoor Water levels: scores Use ≤ 120 l/p/d 1 (Mandatory ≤ 110 l/p/d 2 element) ≤ 105 l/p/d 3 ≤ 90 l/p/d 4 ≤ 80 l/p/d 5 External For providing a system to collect rain water for use in 1 water use irrigation e.g.water butts.
Table 9-4: Summary of the measurement criteria for surface water runoff
CATEGORY 4 SURFACE WATER RUNOFF CREDITS ISSUE MEASUREMENT CRITERIA AVAILABLE
D118200 March 2009
95 Wealden District Council Level 1 SFRA: Final Report
CATEGORY 4 SURFACE WATER RUNOFF CREDITS ISSUE MEASUREMENT CRITERIA AVAILABLE Where rainwater holding facilities/sustainable drainage (SuD) is used to provide attenuation of water run-off to either natural watercourses or municipal systems. 0 Management Points for attenuation covering: of surface • Hard surfaces water runoff Where SuDS are used to improve water quality of from discharges or for protecting the quality of receiving developments waters by: (Mandatory Ensuring no discharge to the watercourse for rainfall 2 element) depths up to 5mm, or, Establish agreements for the ownership, long term operation and maintenance of all sustainable drainage elements.
9.8.4 Draft South East Planvi
As highlighted in Section 203.4.2 Policy NRM 3: Sustainable Flood Risk Management states that
‘In the preparation of Local Development Documents and considering planning applications, local authorities in conjunction with the Environment Agency, should also:
IV. Require incorporation and management of Sustainable Drainage Systems (SuDS), other water retention and flood storage measures to minimise direct surface run–off, unless there are practical or environmental reasons for not doing so’.
9.8.5 Environment Agency Policies
The Environment Agency (Southern Region) has stipulated that new developments should meet the following requirements: -
• The drainage system must be designed to control runoff up to a 1% annual probability (1 in 100 year) storm event (plus an allowance for climate change of 30%); • The rate at which surface water is discharged from the site may vary with the severity of the storm event but must not exceed the greenfield runoff rate for a given storm event; • Excess surface water runoff must be stored on site and released to receiving watercourses at greenfield rates; and, • Surface water discharges to watercourses must not exceed a velocity of 1 m/s.
9.8.6 Draft River Ouse Catchment Flood Management Planxv
Throughout the River Ouse CFMP the text encourages the Local Authorities to promote the use of SuDS in new developments. Policy 6 that covers the area between Uckfield and Crowborough states that as a catchment ‘there are oppportunites to reduce flood risk and improve the existing water quality by promoting and encouraging the use of SuDS within new housing developments’.
D118200 March 2009
96 Wealden District Council Level 1 SFRA: Final Report
9.8.7 Draft Rother and Romney Catchment Flood Management Planxxx
The Draft Rother and Romney CFMP does not have specific policies on SuDS. It does however recommend the CFMP policies promote the use of SuDS in new developments to enhance the water environment.
9.8.8 Other Policies
SuDS are also promoted in ‘Making Space for Water’; RPG9 (INF2).
D118200 March 2009
97 Wealden District Council Level 1 SFRA: Final Report
10 Future Flood Risk Management Practices
Current flood risk management practises within WDC SFRA study area have been described in Section 4.9. This section describes the practises that are planned for the area or can be incorporated into new developments.
10.1 Strategic Flood Defences
The relevant CFMPs set out the Environment Agency’s preferred plans for sustainable flood risk management over the next 50-100 years.
10.1.1 River Adur and Ouse CFMP Consultation Draft Planxv
One of the aims of the River Adur and Ouse CFMPxv is to challenge some of the traditional methods of flood risk management such as raised defences and control structures by introducing more sustainable methods of reducing flood risk. It encourages planners to seek opportunities to restore sections of floodplains which increase the flood storage capacity and therefore reduce the flood risk downstream. The CFMP has identified that the flood plain upstream of Uckfield may have opportunities for this type of flood risk management. This is reflected in the policies recommended for the part of the Ouse catchment within the WDC SFRA study area (see Section 11).
10.1.2 River Medway CFMPxiv
The River Medway CFMPxxix identifies no future defence schemes within the WDC SFRA study area.
10.1.3 Draft Rother and Romney CFMPxxx
As referred to in Section 3.6.1 the draft CFMP policies that affect the study area seek opportunities to create a more natural river corridor through the removal of flood embankments. This aims to provide flood storage opportunities that will reduce the impact of flooding at higher risk locations elsewhere in the catchment.
10.2 Flood Warning
Flood Warning is an essential component of the strategy to reduce flood risk. The current flood warning systems provided by the Environment Agency are described in Section 4.10.2. However, it is noted in the Ouse CFMPxv that only approximately 58% of properties that are within Flood Warning Areas have signed up to receive the automated service. In addition the flood warning system only operates for fluvial or tidal flooding; taking into consideration that the majority of flooding within the Wealden District occurs from other sources this means that most flooding incidents are likely to occur without any warning.
Sir Michael Pitt’s reviewxliii of the summer 2007 floods stresses the importance of developing a flood warning system for surface water flooding. One of the reports interim conclusions (IC3) was “the Environment Agency further develops tools and techniques for predicting and modelling river flooding,
D118200 March 2009
98 Wealden District Council Level 1 SFRA: Final Report
especially to take account of extreme multiple events; and takes forward work to develop similar tools and techniques to model surface water flooding.”
The Environment Agency is currently researching a flood warning system for surface water flooding. This will require rainfall alerts from the Met Office that are currently not widely available but are being piloted in a study in 2008. Following this pilot further testing and feasibility of a warning system will need to be carried out before a warning system could be widely used.
10.3 Flood Alleviation Schemes
The potential for flooding can be increased in areas where flood alleviation measures are not maintained regularly and/or adequately. Breaches in flood defences for example are most likely to occur where the defence has been degraded or not maintained to its design standard. Drainage infrastructure in urban areas can also frequently become blocked with debris which, if not removed, can lead to blockages in culverts and backing up of a watercourse resulting in flooding of property.
It is therefore an essential aspect of flood risk management practise that all flood alleviation schemes are regularly maintained to a specified design standard. It is the responsibility of the riparian owner to maintain the watercourses or defences to a suitable standard. The Local Authority or Environment Agency has permissive powers to act should the riparian not satisfy their maintenance requirements.
A feasibility study of increasing the storage area of Kidbrooke Stream is due to be completed early 2008.
10.4 Flood Mitigation on site
Flood mitigation measures can also be incorporated within a development and are usually more appropriate in areas of residual flood risk. The Pitt Reviewxliii recognised the importance of flood resilient and resistant techniques and came to an interim conclusion (IC11) that “no new building should be allowed in a flood risk area that is not flood-resilient, and that Government should work with organisations such as the Royal Institute of British Architects and the building industry to encourage flood-resilient building and development design.”
The Code for Sustainable Homesxxxii also offers credits for developments that consider flood risk (Table 10-1). Whilst preference is given to sites located in low flood risk zones, commensurate with policies presented in PPS25ii. One credit is made available for developments in Flood Zones 2 or 3 that are appropriately flood resilient and resistant. Table 10-1: Summary of the measurement criteria for Flood Risk
CATEGORY 4 SURFACE WATER RUNOFF CREDITS ISSUE MEASUREMENT CRITERIA AVAILABLE Where evidence is provided to demonstrate that the Flood Risk development is located Flood Zone 1 and there is a low 2 risk from all sources of flooding.
D118200 March 2009
99 Wealden District Council Level 1 SFRA: Final Report
CATEGORY 4 SURFACE WATER RUNOFF CREDITS ISSUE MEASUREMENT CRITERIA AVAILABLE Development is located in Flood Zone 2 or 3 where the habitable parts of dwelling sand access routes to ground level and the site are at least 600mm above the flood level. 1 An appropriate assessment demonstrating the development is appropriately flood resilient and resistant, including safe access and escape routes and that any residual risk can be safely managed.
Flood Risk mitigation measures that can be employed on individual sites can be split into three categories when including flood avoidance which should always be the first consideration through application of the Sequential Test:- .
10.4.1 Flood Avoidance
This is defined as:
‘Constructing a building and its surrounds (at site level) in such a way to avoid it being flooded (e.g. by raising it above the flood level, re-sitting outside flood risk area etc.)’.
These are used to restrict the pathway between the flooding source and the receptor. The preferential option is to locate the building outside a flood risk area through rearranging the site layout if possible. Alternatives within this category could include a permanent or temporary defence such as raised kerbs to contain and route flood water through a site or demountable barriers.
10.4.2 Flood Resistance
This is defined as:
‘Constructing a building in such a way to prevent floodwater entering the building and damaging its fabric’.
Floodwaters will enter buildings through the weakest points in the construction which maybe in the brickwork, party walls of terraced or semi-detached buildings, expansion joints between walls where different construction materials meet, vents, door thresholds, seepage from below ground through floors and basements and/or sanitary appliances from backflow from surcharged drainage systems.
Flood resistance techniques are employed within the fabric of the buildings. They include the use of low permeability materials in the construction of the building and are likely to only be effective for short duration flood events and of low flooding depths (less than 0.3 m). They may be used in conjunction with flood resilience techniques when the predicted flood level is between 0.3 - 0.6 m.
10.4.3 Flood Resilience/Repairable
This is defined as:-
D118200 March 2009
100 Wealden District Council Level 1 SFRA: Final Report
‘Constructing a building in such a way that although floodwater may enter the building its impact is reduced (i.e. no permanent damage is caused, structural integrity is maintained and drying and cleaning is facilitated)’.
Flood resilience techniques are also employed on buildings within the floodplain. This type of approach is often more appropriate when the predicted depth of flooding is greater than 0.3 m or flooding is expected to last for a long time. In these cases the use of more durable materials that will not be easily damaged by floodwaters as well as the use of construction materials that are more effective at draining and drying are recommended.
There is currently no guidance with the UK Building Regulations for appropriate means of construction for properties in flood risk areas. For more information on flood resistant construction please refer to DCLG (2007) ‘Improving the Flood Performance of New Buildings: Flood Resilient Construction’xliv xliii Pitt, M. (2007) ‘Learning the lessons from the 2007 foods: The Pitt Review’, COI Communications. xliv Communities and Local Government (2007) ‘Improving the Flood Performance of New Buildings: Flood Resilient Construction’, DCLG: London.
D118200 March 2009
101 Wealden District Council Level 1 SFRA: Final Report
11 Policy Recommendations
Objective 6 of this Level 1 SFRA is ‘to advise WDC on suitable policies to address flood risk issues in keeping with collected evidence, national, regional and local policies’. To meet this objective, national and local policies have been reviewed against the local flood risk issues and goals identified by the Environment Agency in the CFMP. From these policies the following catchment wide and specific area strategies have been developed under the headings Flood Risk, SuDS, Flood Mitigation and the Water Environment. Integration of these suggested policy considerations into the LDF and LDDs should ensure that the objectives and aspirations of the Environment Agency and national policy are met whilst strengthening the position of the LPA with regard to flood risk.
11.1 Flood Risk
PPS25ii aims to guide new development to those areas at lowest risk of flooding, both now and in the future (allowing for the effects of climate change) and to ensure development does not increase the risk of flooding elsewhere.
11.1.1 Study Area Wide Policy Recommendations
To achieve the aim of PPS25ii the following policy considerations are recommended:
• Have regard to the cumulative impact of development on flood risk;
• Ensure that where proposed development reduces current and future floodplain storage that compensatory storage is provided to ensure that there is no net loss in flood storage capacity; • Determine decisions for windfall development through application of the Sequential Test, where necessary. Where this is not practical WDC should assess the flood risk in accordance with the companion guide to PPS 25;
• Consider the wider sustainable benefits of addressing flood risk;
• Engage with stakeholders throughout the Local Development Framework process to investigate initiatives for the reduction of flood risk where appropriate;
• Ensure flood risk assessments prepared for developments conform to national policy and the additional elements identified in this SFRA, where considered suitable by WDC and the Environment Agency; and,
• Have regard to the role development sites could have to alleviate flood risk elsewhere.
11.1.2 Area Specific Policy Recommendations
• A small amount of groundwater flooding has been noted as occurring in the areas of Uckfield, Crowborough and Hartfield. It is therefore recommended that WDC should ensure new developments in high and medium risk areas in these settlements (identified from the
D118200 March 2009
102 Wealden District Council Level 1 SFRA: Final Report
Sequential Test Maps) undertake Flood Risk Assessments to determine the risks from groundwater flooding and incorporate mitigation measures into the design of any buildings to prevent flood damage from this source.
Through integration of these recommendations, it is considered that the emerging LDF will comply with PPS25ii and the aspirations and policies represented in following and presented in Section 3:
• Regional Planning Guidance for the South East (RPG9) Policy INF1
• The South East Plan Policy NRM3Wealden Local Plan Policy CS3
11.2 Flood Risk Management
Evidence collected through the Level 1 SFRA suggests flood risk throughout the study area is exacerbated by poor capacity of some structures (bridges, culverts etc). With the impact of climate change, flooding as a result of poor capacity of structures would be expected to increase. To mitigate for this WDC should consider the following policy recommendations.
11.2.1 Study Area Policy Recommendations
• Where directly relevant to potential development, opportunities should be sought to ‘daylight’ (deculvert) culverted rivers and watercourses, where possible, to return them to a natural state, reducing build up of water flows and under capacity where this does not exacerbate the flooding elsewhere;
• Where, as part of development, deculverting is not possible but necessary seek opportunities to facilitate the investigation and where necessary and suitable the upgrade of, bridges, culverts, drainage systems etc in line with current climate change considerations, through the LDF;
• Safeguard floodplains from development, ensuring the maximum possible capacity is available to attenuate floodwater and thereby safeguard existing property. Where development in the floodplain is unavoidable and flood plain storage is reduced, the development should provide compensatory storage to ensure that there is no net loss in flood storage capacity.
• Seek opportunities where appropriate, taking into account social, economic and environmental factors, to restore natural river forms and floodplains (through managed retreat where possible) and in so doing restore river corridors and floodplains ;
• Where appropriate flood risk from developments should be mitigated through development of flood storage schemes which may also provide amenity benefit;
• When a planning application is submitted for a change of use flood in Flood Zone 2 and 3, evacuation plans should be developed through liaison with the emergency services;
• Emergency Plans should be formulated to accompany FRAs for all ‘more and highly vulnerable’ developments as well as ‘less vulnerable’ developments with greater than 10 people working/living at the site. These Emergency Plans should be allied to those already developed by WDC and East Sussex County Council;
D118200 March 2009
103 Wealden District Council Level 1 SFRA: Final Report
Through integration of these suggestions, the emerging LDF will comply with PPS25 and the aspirations and policies represented in following documents:
• Regional Planning Guidance for the South East (RPG9) Policy INF1; and
• Wealden Local Plan Policy CS4.
11.3 Drainage Systems
Due to expansion of developed areas, the drainage systems designed to serve the original settlements can become overloaded leading to flooding. In addition the design standard of newer sewer systems is typically to accommodate the 3.3% annual probability (1 in 30 year) storm event, with events in excess of this expected to result in flooding. With the impacts of climate change the effective design standard of the sewer system is expected to decrease leading to more frequent flooding and more severe flooding within the design standard of the defence. In addition, conventional drainage systems typically discharge storm water to nearby watercourses. As urbanisation and intensification of catchments increases, storm water inputs can impact on water quality. With the incorporation of the Water Framework Directive into UK law the councils should seek opportunities to contribute to the goal of improving the quality of local watercourses. It has been demonstrated in the review of the Wealden District Council Database that 14% of flooding incidents within the study area have occurred as a result of drainage problems. In addition to this 11% of the recorded incidents have been a result of overland flow which are suggested to have occurred due to an insufficient drainage network.
11.3.1 Study Area Wide Policy Recommendations
The following study wide policies are recommended:
• Surface water flooding should be investigated in detail as part of FRAs for developments located in high and medium risk areas (identified from the Sequential Test Maps), and comprehensive surface water runoff calculations undertaken. Planning applications for developments in these areas should submit a FRA that considers flooding from the sewer system and the consequences of a failure of the drainage system through blockage;
• WDC should also seek opportunities through development to deliver schemes to alleviate flooding from surface water runoff to existing properties.
• Sustainable drainage design should consider the impacts of climate change for the lifetime of the development;
• the potential benefits an appropriately designed SuDS should be considered in terms of biodiversity improvements, amenity value, water quality and resource value of a development and/or surrounding area;
• the vulnerability and importance of local water resources should be taken into account when determining the suitability of drainage strategies/SuDS; and,
D118200 March 2009
104 Wealden District Council Level 1 SFRA: Final Report
• discharge rates from new developments should not increase following redevelopment, including allowances for climate change and preferably restrict discharge rates to greenfield runoff rates in areas known to have a history of sewer flooding.
11.3.2 Area Specific Policies
The majority of urban settlements within study area have suffered from flooding as a result of lack of capacity in the existing drainage infrastructure and/or the speed at which storm water is delivered to watercourses. This includes the settlements of Uckfield, Crowborough, Mayfield, Wadhurst, Forest Row and Hartfield. In these areas the following area specific policies are recommended: • WDC should ensure all proposed developments in these areas restrict their discharge rates to greenfield rates and that this reduction should be achieved through the use of SuDS6; and
• Any development proposals that incorporate a drainage strategy should also include a maintenance programme.
Through integration of these suggestions, the emerging LDF will comply with PPS25 and the aspirations and policies represented in following and presented in Section 3:
• Regional Planning Guidance for the South East (RPG9) Policy INF2;
• Wealden Local Plan Policies: NE1, CS5, PW5; and,
• Cuckmere and Sussex Havens Catchment Flood Management Plan Objectives A, B and E in Table 5.2.
11.4 Flood Risk & Environment
As the population increases and climate change leads to hotter drier summers, the prospect of droughts will increase. New development can tackle this by incorporating water efficiency measures, such as greywater recycling, rainwater harvesting and water use minimisation technologies. In doing so, knock-on benefits could be felt by the sewer system which will receive less wastewater from properties, potentially freeing up capacity during flood events. In addition, increasing people’s awareness of the water environment around them together with its importance and its hazards, will contribute to their understanding of where floods come from and what they can do to limit the consequences of flooding and resource shortages.
11.4.1 Study Area Wide Policy Recommendations
In terms of flood risk and the environment the following is recommended:
6 The Government’s preferred method to achieve this is through the use of Sustainable Drainage Systems (SuDS). PPS25 notes that regional planning bodies and local authorities should promote the use of SuDS for the management of runoff. Whilst the PPS25 Practice Guide recognizes the significance of SuDS in controlling the impact of development on local flood risk in step four of the ‘Flood Risk Management Hierarchy’. .
D118200 March 2009
105 Wealden District Council Level 1 SFRA: Final Report
• Ensure that proposed developments can be accommodated by the existing water resource provision. Where a development cannot be met by current water resources, ensure that the phasing of development is in tandem with resource infrastructure investment;
• Seek opportunities to ‘daylight’ (de-culvert) watercourses and increase people’s interaction with watercourses ; and
• dopt a policy for all development sites, where appropriate, of the routine maintenance of all watercourses ensuring they are clear of debris that could affect flood flow conveyance and water quality.
Through integration of these suggestions, the emerging LDF will comply with PPS25 and the aspirations and policies represented in following and presented in Section 3:
• Regional Planning Guidance for the South East (RPG9);
• Wealden Local Plan Policy CS2; and,
• Cuckmere and Sussex Havens Catchment Flood Management Plan Objective D, Table 5.2.
Table 6.3 in the CFMP provides a summary of the flood risk management policies that have been set out by the Environment Agency and assigned to different zones of the study area. The strategies suggested above integrate with these aspirations and if adopted will aid to strengthen the position of WDCs flood risk management.
Adoption of policies to address the points of consideration identified above will ensure the emerging LDDs and LDF for WDC are in agreement with the policy and planning documents presented in Section 3. In addition the suggested policy recommendations will ensure several of the existing policies are strengthened to ensure flooding is a key consideration for new developments, especially in light of information specific to the study area.
D118200 March 2009
106 Wealden District Council Level 1 SFRA: Final Report
12 Emergency Planning
Objective 9 of this Level 1 SFRA is ‘to present sufficient information to inform WDC of the flood considerations necessary in emergency planning’. In Sir Michael Pitts Reviewxliii of the 2007 floods he recognises the ‘dedicated and quick response’ of emergency services which prevented the worsening of many situations. However, he also identified a number of failings and opportunities to improve our preparedness for future flood events. In particular he advises that with ‘stronger local leadership of flood risk management, clarification of roles, more effective co-operation between responsible organisations, better protection of infrastructure and wider and deeper public engagement’ the impact of flooding on communities could be significantly reduced. If many of these opportunities identified by Sir Michael Pitt are to be achieved, the role local authorities have in planning and responding to flood events must be clearly defined. To assist local authorities in understanding their role it is essential to have a technically sound emergency plan in place to provide clear procedural instructions to the organisations, companies and individuals involved and affected. The mobilisation and organisation of the emergency services and supporting agencies, for example East Sussex County Council and WDC can be integral in the coordinated rescue, treatment and transport of potentially large numbers of displaced residents or casualties. Similarly during and after a flood event the role of the local authority can include providing transport for the evacuees and safe rest centres in the event of homes being flooded. Further health and welfare issues are inevitable as a result of serious flood events, which may impact on the ability of people to return to their homes or places of business. Whilst this SFRA is not designed to fulfil that role it does contain useful information for WDC and other key organisations to assist them in understanding their risks and begin the process of developing an appropriate co-ordinated response.
12.1 Developing an Emergency Flood Plan
To assist the local authority to develop an emergency plan it is recommended that a staged approach is followed. This may consist of the following stages: 1. Understanding of how a flood might impact on the WDC area by identifying key infrastructure, buildings and organisations that may be at risk of flooding, 2. Liaise with the organisations responsible for at risk infrastructure and buildings to establish what the consequences of a flood would be on them and the individuals who rely on them and what emergency procedures they have in place for dealing with a flood, 3. Liaise with the same organisations to establish a coordinated strategy for dealing with flood events.
12.1.1 Identifying at Risk Installations
Using the maps provided as part of this Level 1 SFRA, WDC can identify (map) key installations located in flood risk areas. In achieving this WDC may find it advantageous to adopt a tiered approach to identify those installations that are at primary flood risk (i.e. at risk themselves) and those areas at risk as a consequence of an installation being un-operational as a result of a flood. For example a flooded fire station would be a primary impact of flooding, the area served by that fire station would be
D118200 March 2009
107 Wealden District Council Level 1 SFRA: Final Report
at a secondary impact of the flooding, due to the potentially limited ability of the fire service to provide adequate coverage in the area. The Uckfield Flood Plan is an example of where the vulnerable institutions have been mapped in relation to the flood zone mapping produced by the Environment Agency. The methodology used in developing this flood plan should be replicated across the study area. However, there are facilities that were not included in the Uckfield Flood Plan but which would be appropriate to include in any future flood plans. It is recommended that any flood plan should consider the following installations for mapping of primary and secondary impacts. This list is not exhaustive and it is possible that other strategic facilities may be identified during the production of a plan. • Police stations; • Ambulance stations; • Fire stations; • Hospitals • Command centres; • Telecommunications installations; • Emergency dispersal points; • Water treatment works; • Sewage Treatment Works; • Radio Stations; and, • Electricity sub stations. It is also recommended that installations that may be relied on to house displaced residents or from where vulnerable residents may need to be evacuated swiftly are also identified. These may include: • Residential institutions such as residential care homes, children’s homes, social services homes, prisons and hostels; • Student halls of residence; and, • Non-residential uses for health service, nurseries and educational establishments. • Leisure centres; • Churches; • Schools; and, • Community Centres. This list of suggested installations/institutions presented above should not be considered exhaustive. Discussions should be held within WDC and with the emergency services to establish those installations and organisations that should be mapped to assist in developing a robust emergency plan. The Uckfield Flood Plan makes reference a database called ‘CareFirst’ that holds information on locations of vulnerable residents in the district. This may be a useful source of information when mapping the vulnerable institutions and essential infrastructure.
D118200 March 2009
108 Wealden District Council Level 1 SFRA: Final Report
12.1.2 Individual Flood Responses/Mitigation Measures
Once at risk installations have been identified, WDC should liaise with the relevant organisations to establish if they are aware of their risk to flooding and if so if they are also aware of the primary and secondary impacts of their flood risk. Discussions should also be held to establish any flood event procedures they maintain and/or mitigation measures. Using this information it may be necessary to return to the mapping exercise to redefine impact areas, to either account for mitigation measures already in place (i.e transfer of fire personnel to a secondary facility suitable to maintain an adequate level of cover in the event of an emergency) or to extend secondary impact areas.
12.1.3 Coordinated Flood Emergency Planning
Using the information collected through stages two and three WDC may wish to facilitate a forum to establish the development of a coordinated flood emergency plan with the emergency services and key local stakeholders. This should build on the findings of the first two phases identifying where the emergency response of an installation/organisation may be at conflict with the procedures of another or local hazards. For example the evacuation of a school by sending pupils home, would not be suitable for those pupils whose homes are flooded, consequently an intermediary step may be required to safeguard pupils.
Similarly understanding how key infrastructure (evacuation routes, tele-communications) may be affected by a flood should be understood to ensure emergency services can access an area before flood hazards become too great.
The aim of this stage should be to identify how key organisations should respond during a flood event to ensure the smooth and effective protection of local residents and key infrastructure.
In addition the process may also identify installations and or organisations where their risks are currently too great given their vulnerability or importance wither economically or in responding to flood events. In such circumstances the information collected may be of use in justifying strategic flood alleviation measures or relocating strategic infrastructure.
D118200 March 2009
109 Wealden District Council Level 1 SFRA: Final Report
13 Conclusions and Recommendations
13.1 Conclusions
Following completion of the WDC Level 1 SFRA the following conclusions can be made: - 1. Based on the information collected and presented in this Level 1 SFRA Wealden DC have sufficient information to apply the Sequential Test to their potential development sites; 2. Using the information presented in the maps and GIS layers accompanying this Level 1 SFRA, WDC can broadly identify suitable sites for development. Through discussion with the Environment Agency WDC will be able to identify those sites where further investigation of the flood zones is required. For example, for a site located adjacent to watercourse it would be appropriate to investigate the site and watercourse to determine Flood Zone 3b where this data is not available. Where a site is located on the boundary of Flood Zone 2 and 3 the site should be investigated to establish the effect climate change may have in changing the Flood Zone for the site: 3. The collected information identifies the WDC study area as experiencing flooding from a number of flood sources; 4. Whilst flooding occurs from a number of sources, there is insufficient/inadequate data to enable robust quantified assessments of risk and/or probability for all flood sources; and 5. Despite the current paucity of data there is sufficient evidence in national research to warrant and justify the policy recommendations if the recorded flood events are not to be exacerbated due to climate change.
13.2 Recommendations
Based on the information presented and collected through this Level 1 SFRA the following recommendations are made: 1. Wealden DC should apply the Sequential Test to determine where various types of development would be appropriate in line with the principles of Planning Policy Statement 25: Development & Flood Riskii. 2. Through application of the Sequential Test, WDC should identify those sites requiring application of the Exception Test. Once these sites have been identified, WDC will be required to provide responses to parts ‘a’ and ‘b’ of the Exception Test before part ‘c’ is approached. 3. Following completion of the Sequential Test and parts ‘a’ and ‘b’ of the Exception Test a meeting should be sought with the Environment Agency to confirm their acceptance of WDCs arguments and justification for progressing with sites requiring the Exception Test. This meeting should also be used to confirm the information the Environment Agency will require to demonstrate a site is safe in line with part ‘c’ of the Exception Test. 4. Once the LPA and Environment Agency are in agreement regarding those sites for application of the Exception Test, confirmation of the works necessary to demonstrate a site is safe in line with the Exception Test is required.
D118200 March 2009
110 Wealden District Council Level 1 SFRA: Final Report
5. WDC should seek incorporate the recommended policies in Section 11 into their emerging LDDs to facilitate synergy between national and regional policy and aspirations regarding flood risk management. 6. WDC, in conjunction with East Sussex County Council and the Emergency Services should develop a district wide Emergency Plan building on the methodology used in developing the Uckfield Flood Plan. 7. To strengthen the District Emergency Plan, Flood Resilience Forums should be established within Parish areas to canvas opinion of flooding issues and collect additional information to inform and advise the continued development and improvement of emergency plans. 8. The WDC Flooding Database is an important and unique asset when reviewing flood risk issues in the district. Through developing this Level 1 SFRA it has been noticed that the database has the potential to provide considerable added value through relatively simple adjustments. These are: - • When entering data ensure that a full address (including postcode) as well as a grid reference is entered. This could be achieved by not allowing the entry to be finished until all the fields are completed; • Create an additional field that lists the source of flooding (limited to a look up list). It is appreciated that in all cases it may not be possible, in these instances an ‘unknown source’ could be flagged; • Integrate the database with GIS to aid data entry and presentation/querying, • Aim to ensure that the database is as comprehensive as possible by including the flooding incidents that have been logged by the Environment Agency and the Fire Service (possible through emergency planning or flood resilience forum meetings). 9. In our opinion the data received from Southern Water could be improved. The details of improvement schemes that have been undertaken since the incidents of sewer flooding listed have not been recorded in a manner that can be easily transferable to other interested parties. It is recommended that WDC liaise with Southern Water to establish how more transparent reporting of flooding incidents can be shared to improve the assessment of flood risk and where investment may be required to alleviate flooding issues. 10. Through the development of this Level 1 SFRA it has been noted that there are numerous ‘hammer ponds’ located in the district. Although there have been no recorded incidents of flooding from this artificial source, with the increase in development planned for the district and the predicted effects of climate change the potential risk they present should be considered. It is recommended that WDC map the locations of the hammer ponds and carry out an initial quality/safety screening to identify if the ponds present a real risk to existing or planned development.
13.3 Further Work
As populations grow and the effects of climate change make our weather more unpredictable, flooding will be just one of a number of water related issues that local authorities will need to consider in the future. As well as increasing pressure on flood plains, the projected growth in housing stocks and population will have an impact on the availability of water resources, this could be especially significant in areas of low yield (such as the south east of England) and during the drier summers forecasted due to the effects of climate change. Several key pieces of legislation and planning policy,
D118200 March 2009
111 Wealden District Council Level 1 SFRA: Final Report
currently integrated or due to be integrated with UK law will have an impact on the management of the water environment now and in the future. For example: • The Water Framework Directive; • The Groundwater Daughter Directive; • The EU Flooding Directive; • Planning Policy Statement 25: Development & Flood Risk; • Planning Policy Statement 23 Planning and Pollution Control; • Planning Policy Statement: Planning and Climate Change - Supplement to Planning Policy Statement 1; and, • BREEAM Guidelines on the Code for Sustainable Homes.
13.4 How and when the SFRA should be updated?
The SFRA should be a living document. New sources of data will become available on a regular basis and as such WDC should liaise with the Environment Agency to determine a rolling programme for updates that is acceptable to all parties.
The SFRA should also be updated when any new elements arise such as:
• New climate change updates, • Modelling result updates • Issue of new guidance documentation (such as the final version of the PPS25 Practice Guide Companion).
The preparation or finalisation of Preliminary Risk Assessments, required by the EU Flooding Directive, may form a useful point in time to review the SFRA and assess its contribution to the Flooding Directives requirements or where an update to the SFRA may benefit from new data generated as part of assessments prepared to meet the requirements of the Flooding Directive.
13.5 Level 2 SFRA
From a wider review of the available data, and based on Scott Wilson’s experience in producing flood risk assessments and SFRAs, we consider it unlikely that the available data will be sufficient to satisfy part ‘c’ of the Exception Test. To satisfy part ‘c’ of the Exception Test the Practice Guideiv companion to PPS25ii requires the following minimum data to be derived for each development site: • Flood probability; • Flood water depth; • Flood water velocity, and, • Rate of onset of flooding.
D118200 March 2009
112 Wealden District Council Level 1 SFRA: Final Report
This data can only be determined through hydraulic modelling. The current paucity of suitable data from the existing hydraulic models and/or a lack of models for several of the watercourses in the study area will prevent this from being achieved using the existing data set. Therefore the Level 2 SFRA may require hydraulic modelling for any sites identified as requiring the Exception Test and potentially adjacent to watercourses where there is insufficient data to define all the PPS25ii flood zones including the effects of climate change.
D118200 March 2009
113 Wealden District Council Level 1 SFRA: Final Report
Appendices
D118200 March 2009
114 Wealden District Council Level 1 SFRA: Final Report
Appendix A : Figures
Figure 1: SFRA Study Area Figure 2: Watercourse Responsibility and Catchment Areas Figure 3: Administrative Areas Figure 4: Topographic Data (LiDAR) Figure 5: Environment Agency Flood Zones 2 & 3 Figure 6: Hydraulic Model Extents Figure 7: Historical Fluvial Flooding Data Figure 8: Historical Overland Flow Flooding Points Figure 9: Historical Groundwater Flooding Points and Groundwater Monitoring Trends Figure 10: Historical Drainage/Sewer Flooding Figure 11: Artificial Sources and Historical Flooding Points from Artificial Sources Figure 12: Flood Defences and Flood Warning Areas Figure 13: Sequential Test Map Set 2008 Figure 14: Sequential Test Map Set 2115 Figure 15 : Groundwater Vulnerability Zones Figure 16: Source Protection Zones
D118200 March 2009
115 Wealden District Council Level 1 SFRA: Final Report
D118200 March 2009
116 Wealden District Council Level 1 SFRA: Final Report
Appendix B: Data/Document Registers
D118200 March 2009
117 Wealden District Council Level 1 SFRA: Final Report
D118200 March 2009
118 Wealden District Council Level 1 SFRA: Final Report
Appendix C - Meeting Minutes
D118200 March 2009
119 Wealden District Council Level 1 SFRA: Final Report
D118200 March 2009
120 Wealden District Council Level 1 SFRA: Final Report
D118200 March 2009
121 Wealden District Council Level 1 SFRA: Final Report
D118200 March 2009
122 Wealden District Council Level 1 SFRA: Final Report
D118200 March 2009
123 Wealden District Council Level 1 SFRA: Final Report
D118200 March 2009
124 Wealden District Council Level 1 SFRA: Final Report
D118200 March 2009
125 Wealden District Council Level 1 SFRA: Final Report
Appendix D : Tables
D118200 March 2009
126 Wealden District Council Level 1 SFRA: Final Report
Table 0-1: Sequential Test Table
DEVELOPMENT EXCEPTION TEST FLUVIAL FLOOD ZONE TIDAL FLOOD ZONE GROUNDWATER DRAINAGE PLUVIAL VULNERABILITY CANDIDATE (Y/N)
SITE EASTING NORTHING Essential Infrastructure / Compare Flood Zone 1 2 3a 3b 1 2 3a 3b (Y/N) (Y/N) (Y/N) Water Compatible and Development / Highly / More / Less Vulnerability within Exampl ###### ###### Residential - More Exception Test e Vulnerable
D118200 March 2009
127 Wealden District Council Level 1 SFRA: Final Report
Those sites considered necessary for application of the Exception test should be presented in Table 0 -2. The table should be completed to include the LPAs justification under parts ‘a’ and ‘b’ of the Exception Test for discussion and review with the Environment Agency before commencing with the Level 2 SFRA. Table 0-2: Sites for Application of the Exception Test (copy as necessary)
EXCEPTION TEST DEVELOPMENT VULNERABILITY PART A PART B PART C SITE FLOOD ZONE Essential Infrastructure / To be addressed in the Level Water Compatible Wider Sustainability Brownfield Land (Y/N) 2 SFRA / Highly / More / Less Example Flood Zone More Vulnerable • Close proximity to Development of brownfield 3a transport infrastructure site assists LPA to satisfy • Gentrification government targets • Intensification to reduce pressure for Green belt review
D118200 March 2009
128 Wealden District Council Level 1 SFRA: Final Report
Table 13-1:Sustainable Drainage Systems Summary for Allocation Sites
GENERAL SITE GENERAL AQUIFER GROUNDWATER SITE NOTES DRAINAGE APPROPRIATE SUDS FRA REQUIREMENTS NAME GEOLOGY TYPE VULNERABILITY AREA ASSESSMENT
D118200 March 2009
129 Wealden District Council Level 1 SFRA: Final Report Appendix E : Sustainability Checklists
D118200 March 2009
130 Wealden District Council Level 1 SFRA: Final Report
Wealden District Council’s Sustainability Checklist
OBJECTIVE TARGET INDICATOR
SOCIAL Ensure that everyone has the opportunity to Meet the housing targets in the draft South Number of housing completions live in a good quality, sustainably constructed East Plan To provide affordable housing Number of affordable housing completions and affordable home within the district to meet housing needs. House price to income ratio Number of official homeless acceptances Households on housing register Improve the health and well being of the Over the long term, reduce death rates from Age standardised mortality rate per 1000 by cause population these diseases Improve life expectancy. (cancer all ages) Age standardised mortality rate per 1000 by cause Reduce distance of travel to (circulatory diseases under age 75) health provision Age standardised mortality rate per 1000 by cause (all causes) Life expectancy % of all new residential development within 30 minutes public transport time of a GP Promote social inclusion and create/ sustain Improve Index of Multiple Deprivation (IMD) Households with no earner as a percentage of all vibrant communities ranking for more deprived areas. households Change in rank of most deprived areas (IMD) Reduce the percentage of households with Income deprivation – percentage of people in the no earner area % of people who say they are satisfied with their local areas as a place to live
D118200 March 2009
131 Wealden District Council Level 1 SFRA: Final Report
To ensure a safe environment including Reduce the risk of danger through careful Total recorded crime rates per 1000 population reducing crime and the fear of crime preventative design measures Domestic burglaries per 1000 population Violent offences per 1000 population Reduce crime by 12.5% by 2007 – 2008 Residents who say that they feel fairly safe or very safe after dark Reduce incidence of speeding and traffic Residents who say that they feel fairly safe or very speeds generally safe outside during the day Installations of sprinklers in new buildings % of major housing developments designed on home zone principles/ incorporating traffic management and speed reduction measures To provide accessible and high quality public New development to be accessible by Population within 20 minutes travel time of a range services and facilities regular public transport, walking and cycling of 3 different sports facility types Additional facilities to be provided in Public libraries that provide access to ICT conjunction with new development if Percentage of new residential development within required 30 minutes public transport time of a GP, hospital, primary and secondary school, employment and a major retail centre. Distance of developments to leisure facilities
ENVIRONMENTAL To reduce the risk of flooding and the Minimise the number of properties at risk of Number of properties at risk of flooding consequential damage to property and public flooding % of new development with Sustainable well being Drainage systems installed (SUDS)
D118200 March 2009
132 Wealden District Council Level 1 SFRA: Final Report
Make the most efficient use of land by 60% of all new dwellings on previously Percentage of residential development completed prioritising Brownfield sites for development, developed land Promoting the remediation on brownfield land the re-use of existing buildings and promoting of contaminated land Average density of new residential development higher development densities % of all new housing completions at less than 30 dph Percentage of large scale employment development completed on brownfield land the number of sites of potential concern with respect to land contamination the number of sites for which there is sufficient detailed information to decide whether remediation of the land is necessary expressed as a % of all sites of potential concern for that year Number of redevelopment proposals resulting in clean –up of contaminated sites Reduce air pollution and ensure local air To maintain current level – no air Number of air quality action plans quality continues to improve quality action plans Levels of NO2; PM10 and SO2 Days when air pollution is moderate or high Reduce emissions of greenhouse gases and Further reductions in CO2 emissions CO2 emissions resulting detriment to the environment and public well being Conserve and enhance the biodiversity of the No further loss of ancient woodland Area and percentage of SSSI’s favourable or District Reverse the long term decline in unfavourable recovering populations of farmland and woodland birds Population of wild birds ( (SE England data to be obtained from the British Trust for Ornithology) 95% of SSSI’s in favourable condition by Area of ancient woodland Area of Lowland Heath; 2010 Calcareous Grassland; Ancient Woodland; and Reed Beds Number of breeding ponds for Great Increase the area of land that qualifies as Crested Newts; and the number of nesting Barn SSSI Owl pairs
Provision of biodiversity, woodland areas and wildlife corridors in new developments
D118200 March 2009
133 Wealden District Council Level 1 SFRA: Final Report
Conserve, enhance and make accessible for Reduce the number of Listed buildings at Number of Listed buildings enjoyment, the District’s countryside (in risk Number of Conservation Areas particular protecting the best and most versatile Number of Listed buildings at risk agricultural land), landscape, historic and built Increase satisfaction with parks and open Access to open space (forthcoming open space environment space audit) Residents satisfied with Local Authority parks and open space Reduce the need to travel by car and promote Increase the number of people travelling by Distance travelled alternative methods of transport sustainable methods Mode of travel for all journeys Number of cars per household Reduce road congestion Resident satisfaction with local bus services Freight carried by road Minimise waste, maximise the re-use of By 2010 reduce the biodegradable Household waste collected per capita materials, recycling and composting municipal waste landfilled to 75% of that Household waste recycled produced in 1995 Percentage of waste arising: composted and going to landfill Minimise the amount of household and commercial waste produced
By 2010 provide kerbside recycling of at least two waste materials to all households
Reduce total volume of waste Maintain and where appropriate improve To exceed the Environment Agency Rivers of very good, good or fair chemical and quality of groundwater and surface waters in guidelines at Pevensey Bay and Birling Gap biological water quality the District and promote water efficiency Grey/green water recycling measures in new Maximise recycling of water development Daily domestic water use per capita consumption Reduce per capita consumption of water
All inland and coastal waters to reach “good” status by 2015
D118200 March 2009
134 Wealden District Council Level 1 SFRA: Final Report
Promote energy efficiency measures and Reduce energy usage Increase in number Energy usage (gas and electricity) encourage the use of renewable energy of new build homes meeting Percentage of new build and retrofit homes meeting EcoHomes very good standard (Building Eco-Homes very good standard Research Establishment) Increase in number of commercial buildings Percentage of commercial buildings meeting meeting BREEAM very good standard BREEAM very good standard (current data gap) % electricity output from renewable sources Increase energy supplies from renewable sources Reduce the global, social and environmental Maximise the use of local Use of local resources impact of consumption of resources by using resources (e.g. wood) Percentage of new build and retrofit homes sustainably produced and local products meeting EcoHomes very good standard (current data gap) Percentage of commercial buildings meeting BREEAM very good standard (current data gap) % of wood used in Wealden from a Wealden source
ECONOMIC Maintain and enhance the prosperity of the Increase GDP GDP £ per head or Gross Value Added District and increase the vitality of villages and (GVA) per capita the rural economy Increase in number of businesses Rural VAT based enterprises and shops in rural areas, and Delivery of agreed targets under Service retention of existing ones. Level Agreement with Action in Rural Sussex Change of use of commercial sites in villages Increase the number of community information points Promote sustainable tourism Influence and support the work of Percentage of jobs in the tourism sector key partner agencies Delivery of specific projects such as 1066 Goes Green and Tourism without Traffic % view that trend in demand in Wealden is increasing Number of planning applications approved for hotels, Bed and Breakfast and visitor attractions
D118200 March 2009
135 Wealden District Council Level 1 SFRA: Final Report
Ensure high and stable levels of employment Increase weekly earnings in line Jobseekers allowance claimants and provide support for small firms and local with South East Average Average gross weekly earnings by residence businesses Unemployed economically active Increase business start up figures Business start up and closure figures Amount of land developed for employment by type Develop and maintain a skilled workforce to Influence and support the work of People of working age with no qualifications support long term competitiveness key partners such as the Wealden Professional occupations amongst the employed Education Business Partnership workforce Percentage employed in elementary occupations Increase the number of people of % of 16-19 population in full or part time education working age with qualifications % of the population with an achieved Level 2 Educational attainment levels qualification Stimulate regeneration of town centres Develop and foster Town Centre Amount of retail and employment land developed in Partnerships town centres (large scale) Ranking of town centres in Index of Multiple Deprivation (IMD) Delivery of agreed targets under the Eastbourne and District Enterprise Agency Service Level Agreement Maximise SEEDA Small Rural Towns funding Improvements (identified through Health Checks) completed Develop a dynamic, diverse, and knowledge Increase number of people with Business start up and closures based economy NVQ Level 4 and above People of working age with NVQ Level 4 and above Employment sector by type
D118200 March 2009
136 Wealden District Council Level 1 SFRA: Final Report
Appendix F SuDS Suitability based on Geologyxlv and Soilsxlvi in the SFRA Study Area
LOCATION (AT APPROPRIATE SUDS GEOLOGY PERMEABILITY THICKNESS SURFACE) TECHNIQUES Grinstead Clay Low Up to 26.6 m - Small pocket northwest Attenuation known of Uckfield; - Small pockets around the Uck; Upper Tunbridge Wells Sand Variably Up to - Park Corner; Infiltration and Combined approximately Infiltration/Attenuation 100 m - Between Stonelands Farm and Hendal Farm; - Sheffiekl Park; - Danehurst; - Uckfield New Town; - Fletching; and, - Fringes of the north of Newick. Tunbridge Wells Sand, Variably - From Buxted to Hadlow Infiltration and Combined undivided Down to Five Ashes; Infiltration/Attenuation - Hazelhurst - Jews Wood; - Woods Green; - Northern areas of Wadhurst; and, - Crowhurst and surrounding areas.;
Lower Tunbridge Wells Sand Variably Up to 33 m - Maresfield; Infiltration and Combined Infiltration/Attenuation - Budletts Common; - Bird-in-Eye - Parts of Ridgewood; and, - Uckfield. Ashdown Beds Variably Up to 210 m - Ashdown Forest and Infiltration and Combined surrounding areas Infiltration/Attenuation including Crowborough; Nutley; Danehill; Hartfield; Forest Row; and Groombridge. - Etchingwood; - Waldron Down; and; - Framfield.
D118200 March 2009
137 Wealden District Council Level 1 SFRA: Final Report
LOCATION (AT APPROPRIATE SUDS GEOLOGY PERMEABILITY THICKNESS SURFACE) TECHNIQUES Head Low - Fringing the River Uck; Attenuation parts of the River Medway; and, parts of the River Ouse. Alluvium Low - Fringing the River Uck; Attenuation parts of the River Medway; and, parts of the River Ouse. Wadhurst Clay Low Up to 78 m - Framfield; Attenuation - West of Ridgewood to Hawkhurst Common; - East of Uckfield; - Wadhurst Park and surrounding areas east and west; - North of Crowborough; - West of Upper Hartfield; - Southern areas of Wadhurst; - Mark Cross; and, - Rotherfield;
APPROPRIATE SUDS SOIL ASSOCIATION PERMEABILITY LOCATION TECHNIQUES Poundgate Slowly Permeable - Ashdown Forest Infiltration and Combined Infiltration/Attenuation Curtisden Slowly Permeable - Most of study area Infiltration and Combined including:- Infiltration/Attenuation - Hartfield; - Nutley; - Fletching; - Buxted; - Hadlow; - Forest Row; - Groombridge; - Mayfield; - Northern Wadhurst; and, - Framfield.
D118200 March 2009
138 Wealden District Council Level 1 SFRA: Final Report
APPROPRIATE SUDS SOIL ASSOCIATION PERMEABILITY LOCATION TECHNIQUES Wickham 1 Slowly Permeable - East of Erridge; Infiltration and Combined Infiltration/Attenuation - An area south and east of Crowborough that includes Marck Cross, Rotherhurst and southern parts of Wadhurst. Waterstock Permeable - Fringes the River Ouse; Infiltration and, the River Uck; and; - Parts of Islfield. South Petherton Highly permeable - East of Withyham. Infiltration Fladbury 3 Low permeabilty - Fringes River Medway; Attenuation River Ouse; and, the River Uck.
xlv Ordnance Survey (1979) ‘Geological Survey of Great Britain (England and Wales): Lewes’, Sheet 319, Ordnance Survey: Southampton. Ordnance Survey (1971) ‘Geological Survey of Great Britain (England and Wales): Tunbridge Wells’. Sheet 303, Ordnance Survey: Southampton. xlvi Ordnance Survey (1983) ‘The Soil Survey of England and Wales: Sheet 6’, Ordnance Survey: Southampton.
D118200 March 2009
139