North and Mid Catchment Flood Management Plan Summary Report June 2012 managing flood risk We are the Environment Agency. It’s our job to look after your environment and make it a better place – for you, and for future generations. Your environment is the air you breathe, the water you drink and the ground you walk on. Working with business, Government and society as a whole, we are making your environment cleaner and healthier. The Environment Agency. Out there, making your environment a better place.

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All rights reserved. This document may be reproduced with prior permission of the Environment Agency. June 2012 Introduction

I am pleased to introduce our summary of the North and Mid Somerset Catchment Flood Management Plan (CFMP). This CFMP gives an overview of the flood risk in the North and Mid Somerset catchment and sets out our preferred plan for sustainable flood risk management over the next 50 to 100 years.

The North and Mid Somerset CFMP is one of 77 CFMPs The North and Mid Somerset catchment has a history of for and Wales. Through the CFMPs, we have flood risk. Over the last 50 years numerous engineering assessed inland flood risk across all of England and schemes have been implemented to reduce flood risk Wales for the first time. The CFMP considers all types of in the catchment. At present 2,300 properties are at risk inland flooding, from rivers, ground water, surface in the catchment in a 1% event (taking into account water and tidal flooding, but not flooding directly from flood defences). This will increase to over 4,200 the sea (coastal flooding), which is covered by properties in the future. Shoreline Management Plans (SMPs). Our coverage of We cannot reduce flood risk on our own, we will surface and ground water is however limited due to a therefore work closely with all our partners to improve lack of available information. the co-ordination of flood risk activities and agree the The role of CFMPs is to establish flood risk management most effective way to manage flood risk in the future. policies which will deliver sustainable flood risk We have worked with others including: Somerset management for the long term. This is essential if we County Council, , Wessex Water and the are to make the right investment decisions for the National Farmers Union to develop this plan. future and to help prepare ourselves effectively for the This is a summary of the main CFMP document, if you impact of climate change. We will use CFMPs to help us need to see the full document an electronic version can target our limited resources where the risks are be obtained by emailing greatest. [email protected] This CFMP identifies flood risk management policies to or alternatively paper copies can be viewed at any of assist all key decision makers in the catchment. It was our offices in South West Region. produced through a wide consultation and appraisal process; however it is only the first step towards an integrated approach to Flood Risk Management. As we all work together to achieve our objectives, we must monitor and listen to each others progress, discuss what has been achieved and consider where we may Richard Cresswell need to review parts of the CFMP. South West Regional Director

Environment Agency North and Mid Somerset Catchment Flood Management Plan 1 Contents

The purpose of a CFMP in managing flood risk 3

Catchment overview 4

Current and future flood risk 6

Future direction for flood risk management 10

Sub-areas

1 Portbury sub-area 12

2 and sub-area 14

3 Weston-super-Mare sub-area 15

4 and sub-area 16

5 Coastal Towns sub-area 17

6 Moors sub-area 18

7 Levels and Moors Towns sub-area 20

8 Levels and Moors sub-area 22

9 Uplands sub-area 24

Map of CFMP policies 25

2 Environment Agency North and Mid Somerset Catchment Flood Management Plan The purpose of a CFMP in managing flood risk

CFMPs help us to understand the • Internal Drainage Boards (IDB), CFMPs aim to promote more scale and extent of flooding now and water companies and other sustainable approaches to in the future, and set policies for utilities to help plan their managing flood risk. The policies managing flood risk within the activities in the wider context of identified in the CFMP will be catchment. CFMPs should be used to the catchment; delivered through a combination of inform planning and decision different approaches. Together with • transportation planners; making by key stakeholders such as: our partners, we will implement • land owners, farmers and land these approaches through a range • the Environment Agency, who will managers that manage and of delivery plans, projects and use the plan to guide decisions operate land for agriculture, actions. on investment in further plans, conservation and amenity projects or actions; The relationship between the CFMP, purposes; delivery plans, strategies, projects • Regional Assemblies and local • the public and businesses to and actions is shown in Figure 1. authorities who can use the plan enhance their understanding of to inform spatial planning flood risk and how it will be activities and emergency managed. planning;

Figure 1. The relationship between CFMPs, delivery plans, projects and actions

Policy planning • CFMPs and Shoreline Management Plans. • Action plans define requirement for delivery plans, projects and actions.

Policy delivery plans (see note) Projects and actions • Influence spatial planning to reduce risk and • Make sure our spending delivers the best restore floodplains. possible outcomes. • Prepare for and manage floods (including local • Focus on risk based targets, for example numbers Flood Warning plans). of households at risk. • Managing assets. • Water level management plans. • Land management and creation. Note: Some plans may not be led by us – we may identify the • Surface water management plans. need and encourage their development.

Environment Agency North and Mid Somerset Catchment Flood Management Plan 3 Catchment overview

The catchment of the rivers in the located on the coastal plain, include The underlying rock has a significant North and Mid Somerset CFMP are Weston-super-Mare, Burnham-on- influence on the catchment’s located in the south west of England. Sea and Highbridge, Portishead and response to rainfall, with high run-off They drain from the Mendips, flowing , , Congresbury, from the impermeable uplands in the via various channels through the Cheddar, and and south east and water-logging of the low-lying coastal plain to the Severn Street. clay lowlands. Permeable uplands in Estuary. the north east results in many rivers’ The rivers and streams flow from headwaters being limestone springs. Map 1 shows the location and extent their source in the Mendips in the of the North and Mid Somerset CFMP east of the catchment; they flow in a The catchment contains a number of area. It includes the rivers Brue, Axe, westerly direction through low-lying designated sites of national and , , coastal plain, before flowing out into international importance. A and Portbury Ditch. The downstream the through tidal significant part of the low-lying limits of the CFMP area meet with the exclusion sluices. Somerset Moors are designated upstream boundary of the North Special Protection Areas (SPA) and a The rivers Brue and Axe flow through Devon and Somerset Shoreline , which depend upon the and Moors, Management Plan (SMP) boundary at flooding. The area is also rich in where they are embanked and in tidal sluices on the Brue and Axe, archaeological sites that depend on some places perched above the and with the Severn Estuary SMP at waterlogged conditions for their surrounding floodplain. In the tidal sluices on the rest. preservation. Somerset Levels and Moors, flooding North Devon and Somerset and is caused by long duration storms or Important environmental sites in the Severn Estuary SMPs deal with a series of storms. The high-level catchment include two Areas of coastal flood management, while the embanked channels overflow and Outstanding Natural Beauty, three CFMP considers the flood risk from floodwater is stored in the moors Special Areas of Conservation, two tide-locking. before it can reach the estuary. The Ramsar and two SPA (including the capacity of these channels can be Severn Estuary), 74 Sites of Special The overall catchment area is about significantly reduced by high tidal Scientific Interest, nine National 1,100 square kilometres, and has a conditions. Internal Drainage Boards Nature Reserves and over 300 population of around 275,000. It’s a have an important role in managing Schedule Monuments. rural catchment, with urban areas land drainage within these low-lying making up only five per cent of the moors. total. Its main urban areas, mainly

4 Environment Agency North and Mid Somerset Catchment Flood Management Plan Map 1. Location and extent of the North and Mid-Somerset CFMP area

Legend Portishead North and Mid Somerset CFMP Nailsea Clevedon Urban areas Main rivers

Weston- Railway super-Mare Motorway Bath

Brean Cheddar

Burnham Wells Shepton N Mallet

Bridgwater Glastonbury Street Bruton

Somerton 0 3 6 9 12 Kilometres

© Crown Copyright. Environment Agency 100026380.

➜ Minor works undertaken on the River Brue near Glastonbury

Environment Agency North and Mid Somerset Catchment Flood Management Plan 5 Current and future flood risk

Overview of the current flood risk What is at risk?

Flood risk has two components: the Currently the main sources of flood At present there are around 7,000 chance (probability) of a particular risk for people, property, people and 3,000 commercial and flood and the impact (or infrastructure and the land are: residential properties at risk in the consequence) that the flood would whole catchment from a 1% annual • river flooding from the River Brue, have if it happened. The probability probability river flood, taking into Axe, , Congresbury of a flood relates to the likelihood of account current flood defences. Yeo particularly in Bruton, a flood of that size occurring within a Cheddar and Congresbury; This means that 2.5% of the total one year period. It is expressed as a population living in the catchment percentage. For example, a 1% flood • Tide lock flooding from the Blind are currently at risk from flooding. has a 1% chance or 0.01 probability Yeo in Clevedon, and the Uphill of occurring in any one year, and a Great Rhyne in Uphill; It is difficult to assess the current 0.5% flood has a 0.5% chance or impact of flooding to environmental • breaching/failure of 0,005 probability of occurring in any features. Many designated sites at embankments, which could be a one year. The flood risks quoted in risk would not actually be damaged problem along the Brue and Axe this report are those that take by the inundation. account of flood defences already in system across the levels and place. moors of the catchment; Three Scheduled Monuments are at risk of flooding, but again, the actual • surface water drainage flooding, This catchment has a long history of risk of damage from flooding is which has occurred in Shepton flooding, with the most significant limited. event in recent years having Mallet and Cheddar. Other towns occurred in in May have the potential to be at risk 2008 when for the second time in from surface water flooding. 18 months 30 properties were affected by surface water and river flooding after periods of heavy rainfall.

6 Environment Agency North and Mid Somerset Catchment Flood Management Plan Map 2. Flood risk to property in a 1% annual probability river flood, taking into account current flood defences

Legend

Properties with a 1% chance of flooding 20 - 30 31 - 50 51 - 100

101 - 1,000

Weston-super-Mare 1,001 - 2,000

Cheddar North and Mid Somerset CFMP Main rivers

N

Shepton Mallet

Bruton

0 4 8 12 16 Kilometres

© Crown Copyright. Environment Agency 100026380.

Table 1. Locations of towns and villages with 25 or more properties at risk in a 1% annual probability river flood

Number of properties at risk Locations

>1,000 Weston-super-Mare

500 to 1,000 Levels and Moors

100 to 500 None

50 to 100 None

25 to 50 Bruton, Shepton Mallet, Congresbury

Table 2. Critical infrastructure at risk:

20 electricity substations, 2 police stations, 1 water treatment works, 3 waste management sites, 6 care homes, 12km of main roads, 2km of motorway, 8km of mainline railway, and 6 schools.

Environment Agency North and Mid Somerset Catchment Flood Management Plan 7 Where is the risk? How we currently manage the risk

More than half of the people and The catchment has a history of flood Activities that reduce the probability properties that are at risk within the risk, generally due to the high of flooding include: catchment from a 1% annual rainfall that can lead to extensive • maintaining and improving probability river flood are located in flooding of the river valleys. Over the existing flood defences and Weston-super-Mare. last 70 years, numerous engineering structures, especially raised schemes have been implemented to The distribution of properties at risk banks of the Rivers Brue, Axe and reduce flood risk in the catchment, from a 1% annual probability river Congresbury Yeo, tidal sluices on including: flood, is illustrated in Map 2. Table 1 all river outfalls, and pumping summarises where there is flood risk • Improving flood banks of the stations for evacuation of to more than 25 properties. We Congresbury Yeo through floodplain storage; recognise that there is also a Congresbury to provide a 2% to • maintaining river channels; potential risk from surface water and 1% protection; maintenance of drainage groundwater flooding. However, • Construction of a detention networks by Internal Drainage further studies following on from the reservoir upstream of Bruton to Boards (IDBs) and landowners; CFMP are needed by us and our provide a 2% to 1% protection on • maintenance of road drainage partners to quantify this potential the Brue through Bruton. and sewers. risk. These measures have all reduced Activities that reduce the flood risk. consequences of flooding include: In addition to these engineering • understanding where flooding is schemes, other flood risk likely by using flood risk mapping; management activities are carried • providing flood forecasting and out in the catchment. These include warning services; activities which help to reduce the • promoting awareness of flooding probability of flooding and those so that organisations, that address the consequences of communities and individuals are flooding. aware of the risk and are prepared in case they need to take action in time of flood; • promoting resilience and resistance measures for those properties already in the floodplain. • working with local authorities to influence the location, layout and design of new and redeveloped property and ensuring that only appropriate development is allowed on the floodplain through the application of Planning Policy Statement 25 (PPS25).

➜ Large tracts of low-lying land see extensive flooding during the winter months

8 Environment Agency North and Mid Somerset Catchment Flood Management Plan The impact of climate change and future flood risk

In the future, flooding will be Using river models we estimate that Figure 2 shows the difference influenced by climate change, by 2100, around 9,500 people and between current and future flood changes in land use (for example 4,200 properties across the risks from a 1% annual probability urban development) and rural land catchment may be at risk from a 1% river flood at key locations in the management. In the North and Mid annual probability flood. Flood risk catchment. Following on from the Somerset catchment, climate change from rivers increases mainly in CFMP, organisations need to work will have the greatest impact on Congresbury, Wells and Weston- together to investigate flood risk flood risk. The following future super-Mare. from other sources (e.g. surface scenario for climate change was water and ground water flooding) in The sensitivity testing undertaken used in the CFMP: more detail. showed that river flooding in the • 20% increase in peak flow in all CFMP area is sensitive to climate In general, it is unlikely that the watercourses. This will increase change, as flood depths and extents impact of flooding on environmental the probability of large-scale flood increased over a wide area. The area sites will change significantly in the events; is moderately sensitive to land use future. • a total sea level rise of 500 mm by change over a wide area which leads the year 2100. This will increase to an increase in damages for both the length of time watercourses property and agricultural land. There will be tide locked on the lower is a limited pressure for development reaches of the Brue at Burnham- within the CFMP area, with the area on-Sea, Highbridge and , most under pressure being the the Uphill Great Rhyne at Uphill, coastal strip. Development at the the Land Yeo at Clevedon and the coast does not affect flooding on a Portbury Ditch at Portishead, and catchment-wide scale. the length of time moors will have to store floodwater before evacuation.

Figure 2. Current and future (2100) flood risk to property from a 1% annual probability river flood, taking into account current flood defences

3000

2500

2000

1500

1000

500 Number of Properties at Flood Risk at Properties Number of 0 Bruton Burnham-on-Sea Cheddar Clevedon Congresbury Glastonbury Portishead Shepton Mallet Wells Weston-super-Mare

Current Future

Environment Agency North and Mid Somerset Catchment Flood Management Plan 9 Future direction for flood risk management

Approaches in each sub-area

We have divided the North and Mid Somerset catchment into nine distinct sub-areas which have similar physical characteristics, sources of flooding and level of risk. We have identified the most appropriate approach to managing flood risk for each of the sub-areas and allocated one of six generic flood risk management policies, shown in Table 3.

To select the most appropriate policy, the plan has considered how social, economic and environmental objectives are affected by flood risk management activities under each policy option.

➜ Church Bridge at Bruton Map 3. North and Mid Somerset sub-areas

Portishead Yate Legend

Pill North and Mid Somerset CFMP Bristol Sub-area

Nailsea 1 Portbury (Policy 4) 2 Congresbury and Bruton (Policy 4) 3 Yatton Weston-super-Mare (Policy 5) Bath 4 River Axe and River Brue (Policy 2) 5 Weston Coastal Towns (Policy 4) -super-Mare 6 North Somerset Moors (Policy 3) 7 Levels and Moors Towns (Policy 4) 8 Levels and Moors (Policy 3) Brean Cheddar 9 Uplands (Policy 1)

Wells N Shepton Mallet

Bridgwater Bruton

Somerton 0 4 8 12 16 Wincanton Kilometres © CrownTt Copyright. Environment Agency 100026380.

10 Environment Agency North and Mid Somerset Catchment Flood Management Plan Table 3. Policy options Policy 1 Areas of little or no flood risk where we will continue to monitor and advise This policy will tend to be applied in those areas where there are very few properties at risk of flooding. It reflects a commitment to work with the natural flood processes as far as possible.

Policy 2 Areas of low to moderate flood risk where we can generally reduce existing flood risk management actions This policy will tend to be applied where the overall level of risk to people and property is low to moderate. It may no longer be value for money to focus on continuing current levels of maintenance of existing defences if we can use resources to reduce risk where there are more people at higher risk. We would therefore review the flood risk management actions being taken so that they are proportionate to the level of risk.

Policy 3 Areas of low to moderate flood risk where we are generally managing existing flood risk effectively This policy will tend to be applied where the risks are currently appropriately managed and where the risk of flooding is not expected to increase significantly in the future. However, we keep our approach under review, looking for improvements and responding to new challenges or information as they emerge. We may review our approach to managing flood defences and other flood risk management actions, to ensure that we are managing efficiently and taking the best approach to managing flood risk in the longer term.

Policy 4 Areas of low, moderate or high flood risk where we are already managing the flood risk effectively but where we may need to take further actions to keep pace with climate change This policy will tend to be applied where the risks are currently deemed to be appropriately-managed, but where the risk of flooding is expected to significantly rise in the future. In this case we would need to do more in the future to contain what would otherwise be increasing risk. Taking further action to reduce risk will require further appraisal to assess whether there are socially and environmentally sustainable, technically viable and economically justified options.

Policy 5 Areas of moderate to high flood risk where we can generally take further action to reduce flood risk This policy will tend to be applied to those areas where the case for further action to reduce flood risk is most compelling, for example where there are many people at high risk, or where changes in the environment have already increased risk. Taking further action to reduce risk will require additional appraisal to assess whether there are socially and environmentally sustainable, technically viable and economically justified options.

Policy 6 Areas of low to moderate flood risk where we will take action with others to store water or manage run-off in locations that provide overall flood risk reduction or environmental benefits This policy will tend to be applied where there may be opportunities in some locations to reduce flood risk locally or more widely in a catchment by storing water or managing run-off. The policy has been applied to an area (where the potential to apply the policy exists), but would only be implemented in specific locations within the area, after more detailed appraisal and consultation.

Environment Agency North and Mid Somerset Catchment Flood Management Plan 11 Sub-area 1

Portbury

Our key partners are: tidally influenced river flood risk to The vision and localised areas in extreme preferred policy North Somerset Unitary Authority conditions. As the primary source is surface water and sewer flooding, Policy Option 4 - we are already Internal Drainage Boards flooding is shallow, relatively slow managing the flood risk effectively, moving and confined to the low- Port of Bristol Authority but we may need to take further lying land. actions to keep pace with climate Wessex Water The Royal Portbury Docks is a key change. transportation link for the South The current level of flood risk is West of England. The industrial area considered to be low and The issues in this surrounding the docks includes acceptable. Surface water flooding properties with a high probability of sub-area is considered more likely due to flooding. tide-locked urban drainage The main source of flood risk is tidal The industrial area surrounding the networks. flooding, through overtopping or a docks is currently at risk of flooding breach of the coastal flood defence Climate change and the potential from the combined 1% annual walls, embankments and outfall dock development are likely to probability river flood event. controls. Tidal flooding is addressed increase future levels of flood risk in the Severn Estuary Shoreline In the future the risk is expected to from surface water flooding to Management Plan. increase with more surface water unacceptable levels. The chosen flooding. policy sets a framework that Other risks are from surface water prevents the level of flood risk flooding as a result of tide-locked increasing in the future as a result urban drainage networks, and of climate change and/or increased urban growth and would limit further key infrastructure from becoming at risk of river or surface water flooding.

12 Environment Agency North and Mid Somerset Catchment Flood Management Plan Proposed actions to implement the preferred policy

Liaise with key stakeholders to:

• understand and review existing flood risk management activities undertaken within the unit; • develop and implement a system for monitoring, recording and sharing information on flooding from other sources (sewer/surface water) in order to establish baseline information and measure the impacts of climate change.

Using this baseline information, develop an integrated drainage plan (surface water /sewer/river flooding) for the Royal Portbury Docks which aims to maintain the same standard of protection into the future, allowing for potential increases in rainfall intensity and tide-locking due to climate change. Consider the impacts of the Shoreline Management Plan in the work.

Implement the integrated drainage plan as part of the dock development.

Whilst the integrated urban drainage plan is being developed, continue with existing flood risk management activities in the Royal Portbury Docks. This includes

• routine inspection and maintenance of river channels, flood walls/embankments and the urban sewer system; • reactive maintenance such as dredging or unblocking when required; • discouraging re-development and intensification of development in areas with a higher probability of flooding.

Encourage the use of Sustainable Drainage Systems (SuDS) on all new developments and redevelopments.

➜ The wildlife corridor within the heavily developed Portbury docks complex.

Environment Agency North and Mid Somerset Catchment Flood Management Plan 13 Sub-area 2

Congresbury and Bruton

Our key partners are: The total number of properties in Undertake a supplementary study to Congresbury and Bruton currently in the feasibility study (July 2007) to North Somerset Unitary Authority the 1% annual probability flood assess the future standard of extent is 180. This is expected to protection of the Bruton Flood increase to 310 in the future flood Alleviation Scheme, taking account extent. the potential impacts of climate Internal Drainage Boards change. Revisit the options Wessex Water appraisal in light of the aim to The vision and maintain the current standard of preferred policy protection into the future. The issues in this Prepare flood emergency plans for sub-area Policy Option 4 - we are already Congresbury and Bruton, taking managing the flood risk effectively, account of the potential impacts of There will be greater pressure on the but we may need to take further climate change and including urban drainage system and actions to keep pace with climate scenarios of overtopping and watercourse within Congresbury to change. breach of flood defence embankments. manage the increased rates and This policy would permit volumes of run-off expected due to improvements to the existing Until the above investigations are climate change. The probability of schemes to ensure that the completed, continue with existing sewer flooding is expected to consequences of flooding in the flood risk management activities in increase. There will be increased future will remain the same as the the towns, including: overtopping of embankments in the current situation. reach of main river and increased • routine inspection and probability of failure of maintenance of river channels, embankments. urban sewer system and flood Proposed actions alleviation schemes; Flood flows into Bruton are to implement the • reactive maintenance such as managed by the retention dam, unblocking of structures when which is located in rural land preferred policy required; upstream of the town. There is a • using the planning process to residual risk associated with a Undertake a feasibility study to discourage re-development, breach of the dam. Bruton has assess the current and future encourage relocation and limit experienced surface water flooding standard of protection of the intensification of development in in the past. This has primarily been Congresbury flood alleviation areas with a higher probability of caused by under capacity of the scheme, with an allowance for the flooding. land and urban drainage systems to potential impacts of climate manage direct run-off from the change. Investigate options for Encourage the use of Sustainable surrounding sleep slopes of the upgrading the scheme to maintain Drainage Systems on all new urban area. the same standard of protection developments and redevelopments. into the future.

14 Environment Agency North and Mid Somerset Catchment Flood Management Plan Sub-area 3

Weston-super-Mare

Our key partners are: one of the many camping grounds in Using this baseline information and the area. Around 2,050 properties are the findings of the pre-feasibility North Somerset Unitary Authority affected by sewer and river flooding studies of the Uphill Great Rhyne currently and this may increase to and , develop an Somerset County Council 3,375 in the next 100 years. integrated urban drainage plan (surface water /sewer/river Internal Drainage Boards The vision and flooding) for Weston-super-Mare South West Regional Development which aims to improve the current Agency preferred policy standard of protection, allowing for potential increases in rainfall Weston Vision Policy Option 5 - we can generally intensity and tide-locking due to take further action to reduce flood Wessex Water climate change. Consider the risk. impacts of the Shoreline Management Plan in the strategy. Flood risk is considered high in The issues in this Weston-super-Mare at present and Implement the strategy as part of sub-area this is expected to increase further in new development / redevelopment. the future. Additional appraisal will be required to assess whether there Until the flood management Flooding from the Severn Estuary is are socially and environmentally strategy is completed, continue with the main source of flooding in this sustainable, technically viable and existing flood risk management sub-area and this is covered in the economically justified options. activities in Weston-super-Mare, North Devon and Somerset Shoreline including: Management Plan. • routine inspection and This is the most densely populated Proposed actions maintenance of river channels, sub-area in the CFMP area and is to implement the masonry walls and under considerable pressure for embankments, and the urban development. Low lying areas of the preferred policy sewer system; sub-area are predominantly located • reactive maintenance such as on impermeable clay soil, which is Liaise with key stakeholders to: unblocking of structures when particularly susceptible to drainage • understand and review existing required; problems. The main non-tidal source flood risk management activities • using the planning process to of flooding is surface water and sewer undertaken within the sub-area; discourage re-development, flooding (including the impacts of and encourage relocation and limit tide-locking) with flooding being • develop and implement a system intensification of development in shallow, relatively slow moving and for monitoring, recording and areas with a higher probability of confined to the low-lying land. As sharing information on flooding flooding. such flooding is caused by intense from other sources rainfall there can be little warning. Encourage the use of Sustainable (sewer/surface water) in order to Drainage Systems on all new As well as permanent residents, establish baseline information developments and redevelopments. Weston-super-Mare attracts a large and measure the impacts of number of tourists each year over the climate change. summer, including those staying in

Environment Agency North and Mid Somerset Catchment Flood Management Plan 15 Sub-area 4

River Axe and River Brue

Our key partners are: the future, even with a reduction in Support implementation of water maintenance. level management plans by:

Internal Drainage Boards The East Lydford Flood Alleviation • ensuring that responsible parties Natural England Scheme is no longer active and are identified and aware of their there may be an opportunity to actions; and Land managers reduce maintenance of the scheme. • work with key stakeholders to seek improvements in the The current flood risk management efficiency of water level activities carried out for the surface management operations. The issues in this water flooding problems are sub-area considered appropriate and acceptable for the level of risk. Consider the potential changes due River flooding from the River Axe to climate change, and the outcome and Cheddar Yeo affects agricultural of the SAMPs. land, and some residential Proposed actions properties within small Whilst the SAMPs are being communities. River Flooding from to implement the developed, continue with existing the River Brue and preferred policy flood risk management activities. affects isolated properties and This includes: properties in East Lydford, Through the development of System • routine inspection and agricultural land, the A37, A371 and Asset Management Plans (SAMPs), maintenance of river channels the railway line. identify the current annual costs of and flood defence non-tidal flood risk management in Some surface water run-off and embankments, including weed- the River Axe valley compared with urban drainage problems exist. cutting; the costs of other activities (such as • operation of water level Currently in the sub-area, 43 water level management, legal over- management structures in line properties are at risk of flooding in rides and fisheries). with existing plans; the 1% annual probability flood • reactive maintenance such as Undertake a pre-feasibility study for event, and this is expected to unblocking when required. the decommissioning of the East increase to 52 properties in the • in the River Brue area, discourage Lydford Flood Allevation Scheme future event. new development in areas more and implement findings. prone to flooding, encourage Identify specific locations on the relocation to areas away from the The vision and River Axe and devise schemes floodplain and use of SuDS in all preferred policy where watercourses and floodplains new developments and can be restored by reducing redevelopments. conveyance where appropriate, Policy Option 2 - we can generally reducing incidents of tree clearance reduce existing flood risk in the river corridor (where such management actions. features do not increase the flood The current level of flood risk is low risk) and removing or altering and it is not expected to increase in obstructions and implement findings.

16 Environment Agency North and Mid Somerset Catchment Flood Management Plan Sub-area 5

Coastal Towns

Our key partners are: The vision and Liaise with key stakeholders to: preferred policy • understand and review existing North Somerset Council flood risk management activities Somerset County Council Policy Option 4 - we are already undertaken within the unit; managing the flood risk effectively, • develop and implement a system Wessex Water but we may need to take further for monitoring, recording and actions to keep pace with climate sharing information on flooding change. from other sources (sewer/surface water) in order to The issues in this The current level of flood risk from establish baseline information river flooding is considered to be sub-area and measure the impacts of low and acceptable. This sub-area climate change. This sub-area includes the towns of has a higher probability of surface Portishead, Clevedon, Burnham-on- water flooding than river flooding. Using this information, develop and Sea and Highbridge. Climate change and the potential implement an integrated drainage urban development are likely to plan (surface water /sewer/river The main source of flood risk is tidal increase future levels of flood risk flooding) for Clevedon, Portishead flooding, through overtopping or a from surface water flooding to and Burnham which aims to breach of the coastal flood defence unacceptable levels. The chosen maintain the same standard of walls, embankments and outfall policy sets a framework that protection into the future, allowing controls. Tidal flooding is addressed prevents the level of flood risk for potential increases in rainfall in the Severn Estuary and North increasing in the future as a result intensity and tide-locking due to Devon and Somerset Shoreline of climate change and/or increased climate change. Management Plans. urban growth and would limit further key infrastructure from Whilst the integrated urban Other risks are from surface water drainage plan is being developed, flooding as a result of tide-locked becoming at risk of river or surface water flooding. continue with existing flood risk urban drainage networks and tidally management activities. This influenced river flood risk to includes: localised areas in extreme conditions. Proposed actions • routine inspection and to implement the maintenance of river channels, Currently these towns have a total of flood walls/embankments and 250 properties at risk in the 1% preferred policy the urban sewer system annual probability flood extent. This • reactive maintenance such as is expected to increase to 375 Support the preparation of flood dredging or unblocking when properties in the future extent. emergency plan for caravan parks, required to manage the increased risk of • discouraging re-development and surface water flooding in the future, intensification of development in taking account of the potential areas with a higher probability of impacts of climate change. Make flooding reference to the existing Coastal Flooding Loud Hailer Route in the Encourage the use of Sustainable area. Drainage Systems on all new developments and redevelopments.

Environment Agency North and Mid Somerset Catchment Flood Management Plan 17 Sub-area 6

North Somerset Moors

Our key partners are: Currently, this sub-area has 72 continued embankment properties at risk in the 1% annual maintenance (especially of the Natural England probability flood extent. This is Congresbury Yeo) in the future is expected to increase to 133 necessary. This sub-area is rich in North Somerset Unitary Authority properties in the future extent. environmental designations. These Flood risk from tidal flooding designations are water-based. Somerset County Council through overtopping or a breach of Some moors rely on frequent flood Internal Drainage Boards the coastal flood defence walls, events for their water-based embankments and outfall controls environmental designations to Wessex Water is addressed in the Severn Estuary remain in a healthy state. Land managers Shoreline Management Plan.

The vision and The issues in this preferred policy sub-area Policy Option 3 - we are generally This sub-area includes the Gordano managing existing flood risk Valley and the communities of effectively. , Kenn, , Nailsea, Yatton and . The current flood risk management activities carried out for the flooding The main risk is from tidally problems are considered influenced river flooding during appropriate and acceptable for the tide-locked conditions and level of risk. overtopping of flood embankments on the main river channels, At the present time we cannot including risk of breach. generally justify increasing actions to address climate change or reduce Communities and isolated flood risks further. The scattered properties are at risk from surface nature of the problems makes such water run-off from the surrounding investment unlikely to be economic higher level land and as a result of or sustainable. tide-locked agricultural drainage networks. Flood flows due to breaches in embankments are considered hazardous to life and therefore

18 Environment Agency North and Mid Somerset Catchment Flood Management Plan Proposed actions to implement the preferred policy

Continue with existing flood risk management activities in Nailsea, Yatton and Wrington, including:

• Routine inspection and maintenance of river channels, flood walls/embankments, and the urban sewer system; • Reactive maintenance such as unblocking of structures when required; • Using the planning process to discourage re-development, encourage relocation and limit intensification of development in areas with a higher probability of flooding; • Encourage the use of SuDS on all new developments and redevelopments.

Develop System Asset Management Plans (SAMP). Where appropriate, separate flood risk management costs. In many cases the current annual costs of non-tidal flood risk management in Puxton, Kenn and Tickenham are associated with other activities (such as water level management, conservation objectives, legal over-rides and fisheries) and flood risk benefits from the activities.

Where work is carried out purely for FCRM, assess the level of this against annual average damages of flooding, including the impact of climate change and water level management activities. If appropriate, make recommendations for improving the efficiency of existing activities and implement

Continue to support the implementation of water level management plans in the Puxton, Kenn and Tickenham areas by:

• ensuring that those responsible parties are identified and aware of their actions; and

• working with key stakeholders to seek improvements in the efficiency of water level management operations.

➜ Looking across Weston Moor from Weston in Gordano

Environment Agency North and Mid Somerset Catchment Flood Management Plan 19 Sub-area 7

Levels and Moors Towns

Our key partners are: Risks also occur from surface water The vision and flooding from surrounding hill slopes preferred policy District Council and from an under capacity of the urban drainage network. Council Policy Option 4 - we are already Currently, the towns have a total of managing the flood risk effectively, Somerset County Council 225 properties at risk in the 1% but we may need to take further annual probability flood extent. This actions to keep pace with climate Emergency Services is expected to increase to 900 change. Wessex Water properties at risk in the future extent. The current level of river flood risk is Land managers Groundwater resulting from springs low. However, flood depths and emerging from the foot of permeable velocities are expected to increase. Department for Environment, Food geology slopes can cause problems As a result there is the potential for and Rural Affairs in Cheddar. hazard and risk to life to increase. The social consequences of river flooding are significant. A The issues in this significant increase in surface water sub-area flooding is also expected. Climate change (in increased flows) This sub-area includes the towns of and urban drainage surface water Cheddar, Glastonbury, Wells and incidents could significantly Shepton Mallet. increase future levels of flood risk to an unacceptable level. The main risks are from river flooding in Wells, from the Cheddar Yeo in Cheddar, the in Shepton Mallet and the Millstream in Glastonbury.

20 Environment Agency North and Mid Somerset Catchment Flood Management Plan Proposed actions to implement the preferred policy

Liaise with key stakeholders to:

• understand and review existing flood risk management activities undertaken in Wells, Shepton Mallet and Glastonbury; • develop and implement a system for monitoring, recording and sharing information on flooding from other sources (sewer/surface water) in order to establish baseline information and measure the impacts of climate change. • Develop and implement a strategy to manage the potential impacts of climate change on combined surface water, sewer and river flooding in the urban and highway drainage systems in Cheddar and Glastonbury. • revise options appraisal and recommendations for flood risk management in Cheddar paying particular attention to the 2006 and 2008 flood events and the potential impacts of climate change, in light of a policy to sustain the current scale of flood risk into the future. Implement recommendations.

Undertake a study to investigate the potential for flood warning service to be introduced in Cheddar, Shepton Mallet, Wells and surrounding villages. Consider the use of rainfall forecasting techniques in place of water level or flow gauge data for triggering flood warnings. Based on the outcomes of the study, implement a flood warning system.

Prepare a flood emergency plan for Cheddar, Wells and Shepton Mallet taking account of the potential impacts of climate change and including scenarios of sewer flooding and overtopping or a breach of sluice gates in the urban river system and include procedures for protecting the heritage sites in Wells.

Until strategy is completed, continue with existing flood risk management activities.

Encourage the use of Sustainable Drainage Systems on all new developments and redevelopments.Use the planning process to discourage re-development, encourage relocation and limit intensification of development in areas with a high risk of flooding.

➜ The Cheddar Yeo flowing through the town of Cheddar.

Environment Agency North and Mid Somerset Catchment Flood Management Plan 21 Sub-area 8

Levels and Moors

Our key partners are: remain for a considerable length of Flood flows due to breaches in time due to the flat topography and embankments are considered District Council slow drainage. Flooding also occurs hazardous to life, and this is a if the embankments along the main major focus for maintenance now Sedgemoor District Council river channels fail. This type of and in the future flooding is more hazardous to Mendip District Council Environmental designations properties close to the breach as affected are water-based and rely Somerset County Council there is less warning, and flood on frequent flood events to remain flows and velocities are higher. in a healthy state. Flooding is not Internal Drainage Boards Surface water run-off from the expected to negatively affect these sloping topography and urban Natural England sites now or in the future and in drainage surface water flooding most cases additional flooding The Royal Society for the Protection from under capacity drainage would be beneficial. of Birds networks are also issues.

Wessex Water Currently the sub-area has 165 properties at risk of flooding in the National Farmers Union Proposed actions to 1% annual probability flood event. Farming and Wildlife Advisory Group This is expected to increase to 215 implement the preferred properties in the future extent. policy Land managers

Department for Environment, Food Continue with existing flood risk and Rural Affairs The vision and management activities. This preferred policy includes: • Working with Local Council’s to The issues in this Policy Option 3 - we are generally undertake routine inspection, managing existing flood risk sub-area maintenance and upgrade of effectively. urban/land drainage system in and ; Numerous isolated properties, The current level of flood risk is low, • Routine inspection and major roads, including the M5, and including very few isolated maintenance of river channels, the Bristol to Exeter railway line are properties being affected and it is flood walls/embankments, and at risk from river flooding combined not expected to increase in the the urban sewer system in the with surface water flooding and future. Huntspill area; tidally influenced river flooding The current flood risk management • Reactive maintenance such as (caused by tide locking). activities carried out for the surface unblocking when required; River flooding occurs when the water flooding problems are • Encourage the use of SuDS on all capacity of the river and rhyne considered appropriate and new developments and network is exceeded after long acceptable for the level of risk. redevelopments; periods of rainfall. Flooding occurs • Continuing to promote catchment relatively slowly, at a shallow depth, sensitive farming around and over a wide area. Floodwaters Wedmore.

22 Environment Agency North and Mid Somerset Catchment Flood Management Plan • Use the planning process to Through the development of System Whilst the studies are being discourage re-development, Asset Management Plans (SAMPs), undertaken, continue with existing encourage relocation and limit identify the current annual costs of flood risk management activities in intensification of development in non-tidal flood risk management in North, South Drain and River Brue areas of high risk of flooding North, South Drain and River Brue, areas. This includes: around Huntspill; compared with the costs of other • Routine inspection and activities (such as water level Undertake an investigation to maintenance of river channels management, legal over-rides and identify opportunities to work with and rhynes, including weed- fisheries). environmental organisations to cutting; integrate day to day flood Improve the efficiency of existing • Operation of water level management with environmental flood risk management activities in management structures in line management. line with the recommendations. with existing plans, including operation of the large pumping Carry out a study to identify Support implementation of water stations at North Drain and Gold opportunities to link flood level management plans by: Corner; management with priority • ensuring that responsible parties • Routine inspection and restoration/enhancement of are identified and aware of their maintenance of flood defence Biodiversity Action Plan , actions; and embankments on the main rivers internationally/nationally • work with key stakeholders to and on small-scale private flood designated environment sites and seek improvements in the defence schemes; national nature reserves and efficiency of water level • Flood warning service on the produce 'opportunity maps'. management operations. River Brue. Work with farming related bodies to identify and promote adaptive farming techniques in floodplain areas.

➜ The River Brue near Clewer

Environment Agency North and Mid Somerset Catchment Flood Management Plan 23 Sub-area 9

Uplands

Our key partners are: topography can resist the extent of Proposed actions flood flows causing water levels to to implement the South Somerset District Council rise quickly, with little roaming. The catchments in this area are small, preferred policy Mendip District Council resulting in relatively small peak flows. No specific actions have been North Somerset Unitary Authority identified in this sub-area. We will Currently 27 properties are at risk of Bath and North East Somerset continue to monitor and advise. flooding in the 1% annual Unitary Authority probability flood extent. This is Somerset County Council likely to increase to around 30 properties in the future extent. Internal Drainage Boards

Natural England The vision and Wessex Water preferred policy National Farmers Union Policy Option 1 - we will continue to Farming and Wildlife Advisory Group monitor and advise. Land managers We do not currently undertake any flood risk management in this sub- area. We are not aware of any other The issues in this Stakeholders undertaking flood risk sub-area management in this sub-area although it is possible that very small scale activities are carried out This sub-area is essentially rural, and some areas to protect featuring forestry and all grades of individual properties from surface agricultural land. The sub-area is water flooding. Given the generally rich in environmental and permeable geology and sparse landscape designations. population, we do not expect a The main source of flooding is significant number of properties to surface water and flooding from be affected in the future. rivers which are small in nature. No critical infrastructure sites are Being of permeable geology, the expected to be affected during the percentage run-off from land in the 1% annual event probability flood, northern portion is generally low, although there may be some although steep slopes in some localised flooding of roads. areas can increase run-off rates locally. In the southern portion the less permeable geology can result in higher run-off rates and the steep

24 Environment Agency North and Mid Somerset Catchment Flood Management Plan Map of CFMP policies

Map of the policies in the North and Mid Somerset catchment Legend Portishead 1 5 North and Mid 6 Bristol Somerset CFMP Clevedon Nailsea Main rivers

Urban areas 6 Preferred approach 3 Yatton 2 Policy 1 Weston- Policy 2 super-Mare 9 Policy 3 Policy 4 Cheddar Brean Policy 5 7 Radstock 5 Policy 6 Frome Burnham 4 Wells N 8 7 7 Glastonbury 9

Bridgwater Bruton Street 2 Mere 4

0 3 6 9 12 Somerton Kilometres

© Crown Copyright. Environment Agency 100026380.

The sub-areas

1Portbury 2 Congresbury and Bruton 3 Weston-super-Mare 4 River Axe and River Brue 5. Coastal Towns 6. North Somerset Moors 7. Levels and Moors Towns 8. Levels and Moors 9. Uplands

Environment Agency North and Mid Somerset Catchment Flood Management Plan 25 Would you like to find out more about us, or about your environment?

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