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Summary Report December 2009

Parrett Catchment Flood Management Plan

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December 2009

Environment Agency Parrett Catchment Flood Management Plan 1

Introduction

I am pleased to introduce our summary of the Parrett Catchment

Flood Management Plan (CFMP). This CFMP gives an overview of

the flood risk in the Parrett catchment and sets out our preferred

plan for sustainable flood risk management over the next 50 to 100

years.

The Parrett CFMP is one of 77 CFMPs for England andWales. Through the CFMPs, we have assessed inlandflood risk across all of England and Wales for the firsttime. The CFMP considers all types of inland flooding,from rivers, ground water, surface water and tidalflooding, but not flooding directly from the sea (coastalflooding), which is covered by Shoreline ManagementPlans (SMPs). Our coverage of surface and groundwater is however limited due to a lack of availableinformation.

The role of CFMPs is to establish flood risk managementpolicies which will deliver sustainable flood riskmanagement for the long term. This is essential if weare to make the right investment decisions for thefuture and to help prepare ourselves effectively for theimpact of climate change. We will use CFMPs to help ustarget our limited resources where the risks aregreatest.

This CFMP identifies flood risk management policies toassist all key decision makers in the catchment. It wasproduced through a wide consultation and appraisalprocess, however it is only the first step towards anintegrated approach to Flood Risk Management. As weall work together to achieve our objectives, we mustmonitor and listen to each others progress, discusswhat has been achieved and consider where we mayneed to review parts of the CFMP.

The Parrett catchment has a history of flood risk. Overthe last 70 years numerous engineering schemes havebeen implemented to reduce flood risk in thecatchment. At present 3,300 properties are at risk in thecatchment in a 1% annual probability flood event. Thistakes account of flood defences already in place. This isexpected to increase to over 6,600 properties in thefuture.

We cannot reduce flood risk on our own, we willtherefore work closely with all our partners to improvethe co-ordination of flood risk activities and agree themost effective way to manage flood risk in the future.We have worked with others including: SouthSomerset, Taunton Deane and Sedgemoor DistrictCouncils, Natural England, Wessex Water and theNational Farmers Union to develop this plan.

This is a summary of the main CFMP document, if youneed to see the full document an electronic version canbe obtained by emailing [email protected] or alternativelypaper copies can be viewed at any of our offices inSouth West Region.

Richard CresswellSouth West Regional Director

2 Environment Agency Parrett Catchment Flood Management Plan

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 Upper Yeo and Cary sub-area 12

2 Yeovil sub-area 13

3 Upper and NW Parrett and Upper Isle sub-area 14

4 Upper Tone sub-area 15

5 Taunton sub-area 16

6 Somerset Levels and Moors sub-area 18

7 Bridgwater sub-area 20

8 Shoreline sub-area 22

Map of CFMP policies 23

Contents


The purpose of a CFMP in managing flood risk

CFMPs help us to understand thescale and extent of flooding now andin the future, and set policies formanaging flood risk within thecatchment. CFMPs should be used toinform planning and decisionmaking by key stakeholders such as:

• the Environment Agency, who willuse the plan to guide decisionson investment in further plans,projects or actions;

• Regional Assemblies and localauthorities who can use the planto inform spatial planningactivities and emergencyplanning;

• Internal Drainage Boards (IDB),water companies and otherutilities to help plan theiractivities in the wider context ofthe catchment;

• transportation planners;

• land owners, farmers and landmanagers that manage andoperate land for agriculture,conservation and amenitypurposes;

• the public and businesses toenhance their understanding offlood risk and how it will bemanaged.

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

CFMPs aim to promote moresustainable approaches tomanaging flood risk. The policiesidentified in the CFMP will bedelivered through a combination ofdifferent approaches. Together withour partners, we will implementthese approaches through a rangeof delivery plans, projects andactions.

The relationship between the CFMP,delivery plans, strategies, projectsand actions is shown in Figure 1.

Policy planning• CFMPs and Shoreline Management Plans.

• Action plans define requirement for deliveryplans, projects and actions.

Note: Some plans may not be led by us – we may identify theneed and encourage their development.

Policy delivery plans (see note)• Influence spatial planning to reduce risk and

restore floodplains.

• Prepare for and manage floods (including localFlood Warning plans).

• Managing assets.

• Water level management plans.

• Land management and habitat creation.

• Surface water management plans.

Projects and actions• Make sure our spending delivers the best

possible outcomes.

• Focus on risk based targets, for example numbersof households at risk.


The catchment of the River Parrett islocated in the south west of England.It drains from the Quantocks,Blackdown Hills and Mendips,flowing through the low-lyingSomerset Levels and Moors to theBristol Channel at Bridgwater Bay.

Map 1 shows the location and extentof the River Parrett CFMP area. Itincludes the tributaries of the riversIsle, Tone, Yeo and Cary. BelowBridgwater, the downstream limit ofthe CFMP area overlaps with theupstream boundary of the NorthDevon and Somerset ShorelineManagement Plan (SMP) boundary.

The North Devon and Somerset SMPdeals with coastal floodmanagement, while the CFMPconsiders tidal flood risk along theRivers Parrett and Tone to the tidallimits at Oath and Newbridgerespectively.

The overall catchment area is about1,700 square kilometres, and has apopulation of around 300,000. It’s arural catchment, with urban areasmaking up only four per cent of thetotal. Its main urban areas includeTaunton, Bridgwater and Yeovil.

The rivers and streams flow fromtheir source in the hills in thesouthwest and east of the

Catchment overview

catchment. They flow in a north andwesterly direction down into anextensive lowland floodplain, beforeflowing out into the Bristol Channelthrough the Parrett Estuary. Themajor rivers start in the steepuplands, then flow through flat lowermoors, where they are embankedand in some places perched abovethe surrounding floodplain. Thelower reaches of the rivers Tone andParrett are tidal for some 30km(18.6miles) from the Severn Estuary.The steepness of the uplands,coupled with the geology and soilconditions, generates quick run-offfrom short intense rainfall. In theSomerset Levels and Moors, floodingis caused by longer duration stormsor a series of storms of low intensity.The high-level embanked channelsoverflow and floodwater is stored inthe moors before it can reach theestuary. The capacity of thesechannels can be significantlyreduced by high tidal conditionsbacking up the Parrett.

Internal Drainage Boards have animportant role in managing landdrainage within these low-lyingmoors.

The underlying rock has a significantinfluence on the catchment’sresponse to rainfall, with high run-off

from the impermeable uplands in theeast and waterlogging of thelowlands. The area does not haveany major aquifers so groundwaterflooding is not a major risk.

The catchment contains a number ofdesignated sites of national andinternational importance. Asignificant part of the low-lyingSomerset Moors are designatedSpecial Protection Areas and aRamsar site, which depend uponflooding. The area is also rich inarchaeological sites that depend onwaterlogged conditions for theirpreservation.

Important environmental sites in thecatchment include 104 squarekilometres of Areas of OutstandingNatural Beauty, 0.8 squarekilometres of Special Areas ofConservation (SAC), 43 squarekilometres of Ramsar, 72 squarekilometres of Sites of SpecialScientific Interest and 112Scheduled Monuments.


Map 1. Location and extent of the Parrett CFMP area

© Crown Copyright. Environment Agency 100026380.

Legend

Parrett CFMP

Urban areas

Main rivers

Railway

MotorwayStreet

Wells

Bridgwater

Williton

Taunton

Wellington

Chard

Langport

CastleCary

Burnham

Ilminster Yeovil

Honiton

Crewkerne Sherborne

Beaminster

0 4 8 12 16Kilometres

N

➜ Strengthening the historic Baltmoor Wall on the River Tone, one of many flood defences wemanage in the catchment


Current and future flood risk

Flood risk has two components: thechance (probability) of a particularflood and the impact (orconsequence) that the flood wouldhave if it happened. The probabilityof a flood relates to the likelihood ofa flood of that size occurring within aone year period. it is expressed as apercentage. For example, a 1%annual probability flood has a 1%chance or 0.01 probability ofoccurring in any one year, and a0.5% flood has a 0.5% chance or0.005 probability of occurring in anyone year. The flood risks quoted inthis report are those that takeaccount of flood defences already inplace.

Since Roman times, attempts havebeen made to evacuate floodwaterfrom the low-lying areas of theParrett catchment, where once therivers overflowed. The floodplainswould be under water for months ifleft to drain by gravity alone. In thelast 60 years, many flood defenceschemes have been built, includingthe Sowy River, taking overflow fromthe River Parrett to the King’sSedgemoor Drain, and new pumpingstations assisting the evacuation offloodwater from the Moors.

The most recent significant flood inthe Parrett catchment was theautumn/winter flooding of 2000, theworst since October 1960. Flooddefences built in Taunton andelsewhere since 1960 have reducedthe risk of flooding. Despite theseworks approximately 350 propertieswere flooded in the River Parrettcatchment and extensive flooding ofthe Somerset Levels and Moorsoccurred.

Currently the main sources of floodrisk for people, property,infrastructure and the land are:

• river flooding from the RiverParrett and its tributaries,particularly in Taunton andLangport;

• tidal flooding from the RiverParrett in Bridgwater;

• breaching/failure ofembankments, which could be aproblem along rivers across thelevels and moors of thecatchment;

• surface water drainage and sewerflooding, which has occurred inparts of Bridgwater and Taunton,and rural upland slopes. Othertowns have the potential to be atrisk from surface water flooding.

Overview of the current flood risk

At present there are around 17,000people and 4,000 commercial andresidential properties at risk in thewhole catchment from a 1% annualprobability river flood taking intoaccount current flood defences.

This means that 6% of the totalpopulation living in the catchmentare currently at risk from flooding.

It is difficult to assess the currentimpact of flooding to environmentalfeatures. Many designated sites atrisk have a positive benefit fromwinter flooding and would notactually be damaged by theinundation. 16 ScheduledMonuments are at risk of flooding,but again, the actual risk of damagefrom flooding is limited.

What is at risk?

‘The oldest man living does not

remember such great floods and so

much water. Everything beyond

Bridgwater is like a sea.’ 1809

Table 2. Critical infrastructure at risk:

1 ambulance station, 2 fire stations, 1 police station, 66 electricity substations, 3 water treatment works, 2 wastewater treatment works, 1 care home, 30km main roads, 8km motorway, 36km mainline railway, and 16 schools

Number of properties at risk Locations

>1,000 Taunton

500 to 1,000 Levels and Moors

100 to 500 Bridgwater

50 to 100 None

25 to 50 None


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

15 - 50

51 - 100

101 - 500

501 - 1,000

1,001 - 2,000

Parrett CFMP

Main rivers

Bridgwater

YeovilTaunton


N

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


How we currently manage the risk

The catchment has a history of floodrisk, generally due to the highrainfall that can lead to extensiveflooding of the river valleys. Overthe last 70 years, numerousengineering schemes have beenimplemented to reduce flood risk inthe catchment, including

• widening and deepening of riversin Taunton, and Hillfarrance;

• building a flood bypass channel;the Sowy River Parrett Reliefchannel reducing flood riskbetween Langport and Bridgwaterby bypassing flood flow direct tothe Parrett Estuary at Dunball;

• improving flood banks of the Tonethrough Ham, Creech St Michael,Ruishton and Stanmoor.

These measures have all reducedflood risk.

In addition to these engineeringschemes, other flood riskmanagement activities are carriedout in the catchment. These includeactivities which help to reduce theprobability of flooding and thosethat address the consequences offlooding.

Activities that reduce the probabilityof flooding include:

• maintaining and improvingexisting flood defences andstructures, especially tidal banksof the River Parrett;

• maintenance of drainagenetworks by Internal DrainageBoards and landowners;

• maintaining river channels; • maintenance of road drainage

and sewers; • working with local authorities to

influence the location, layout anddesign of new and redevelopedproperty and ensuring that onlyappropriate development isallowed on the floodplain throughthe application of Planning PolicyStatement 25 (PPS25).

Activities that reduce theconsequences of flooding include:

• understanding where flooding islikely by using flood risk mapping;

• providing flood forecasting andwarning services;

• promoting awareness of floodingso that organisations,communities and individuals areaware of the risk and are preparedin case they need to take action intime of flood;

• promoting resilience andresistance measures for thoseproperties already in thefloodplain.

Almost half of the people andproperties that are at risk within thecatchment from a 1% annualprobability river flood, are located inTaunton. A further 4% are located inBridgwater.

The distribution of properties at riskfrom a 1% annual probability riverflood, is illustrated in Map 2. Table 1summarises where there is flood riskto more than 25 properties. Werecognise that there is also apotential risk from surface water andgroundwater flooding. However,further studies identified in theCFMP are required to be taken by usand our partners to quantify thispotential risk.

Where is the risk?

➜View from Burrow Mump of floods atBurrowbridge in January 2001


The impact of climate change and future flood risk

In the future, flooding will beinfluenced by climate change,changes in land use (for exampleurban development) and rural landmanagement. In the West Somersetcatchment, climate change will havethe greatest impact on flood risk. Thefollowing future scenario for climatechange was used in the CFMP:

• 20% increase in peak flow in allwatercourses. This will increasethe probability of large-scale floodevents;

• a total sea level rise of 500 mm bythe year 2100. This will increasethe risk of flooding at Minehead,Porlock and Watchet.

Using river models we estimate thatby 2100, around 3,500 people and2,040 properties across thecatchment may be at risk from a 1%annual probability flood. Flood riskfrom rivers increases mainly inMinehead, Watchet and Dunster.

The sensitivity testing undertakenshowed that river flooding in thecatchment is not sensitive to changesto the predicted urban development,but is very sensitive to climatechange, as flood depths and extentsincreased. Land use changes wasalso found to have a widespreadaffect on the CFMP area.

0

2000

4000

6000

8000

10000

12000

Taunton Bridgwater Yeovil

Num

ber o

f Pro

pert

ies

at F

lood

Ris

k

Current Future

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

Figure 2 shows the differencebetween current and future floodrisks from a 1% annual probabilityriver flood at key locations in thecatchment. Following on from theCFMP, organisations need to worktogether to investigate flood risk fromother sources (e.g. surface water andground water flooding) in more detail.

In general, it is unlikely that theimpact of flooding on environmentalsites will change significantly in thefuture.


Approaches in each sub-area

We have divided the Parrett catchment into eightdistinct sub-areas which have similar physicalcharacteristics, sources of flooding and level of risk. Wehave identified the most appropriate approach tomanaging flood risk for each of the sub-areas andallocated one of six generic flood risk managementpolicies, shown in Table 3.

To select the most appropriate policy, the plan hasconsidered how social, economic and environmentalobjectives are affected by flood risk managementactivities under each policy option.

Map 3. Parrett sub-areas

Wells

Brean

Chard

Yeovil

Bruton

Seaton

Martock

Cheddar

Honiton

Taunton

SomertonLangport

Minehead

Williton

Bridport

Tiverton

Axminster

Crewkerne

Wincanton

Ilminster

Sherborne

West Hill

Beaminster

Wellington

Lyme Regis

Bridgwater

D h

Cullompton

Charminster

Milbourne Port

Shepton Mallet

South Petherton

Radstock

Ottery St Mary



LegendParrett CFMP

Sub-area

Upper Yeo and Cary (Policy 3)

Yeovil (Policy 4)

Upper and North West Parrett, and Upper Isle (Policy 3)

Upper Tone (Policy 3)

Taunton (Policy 5)

Somerset Levels and Moors (Policy 6)

Bridgwater (Policy 4)

Shoreline (Policy 3)

1

2

3

4

5

6

7

8

9

N

Future direction for flood risk management

➜ Bishops Lydeard, Somerset


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 defencesif we can use resources to reduce risk where there are more people at higher risk. We would therefore reviewthe 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 offlooding 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 reviewour approach to managing flood defences and other flood risk management actions, to ensure that we aremanaging 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 wemay 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, butwhere the risk of flooding is expected to significantly rise in the future. In this case we would need to do morein the future to contain what would otherwise be increasing risk. Taking further action to reduce risk will requirefurther appraisal to assess whether there are socially and environmentally sustainable, technically viable andeconomically 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 mostcompelling, for example where there are many people at high risk, or where changes in the environment havealready increased risk. Taking further action to reduce risk will require additional appraisal to assess whetherthere 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 inlocations 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 risklocally or more widely in a catchment by storing water or managing run-off. The policy has been applied toan area (where the potential to apply the policy exists), but would only be implemented in specific locationswithin the area, after more detailed appraisal and consultation.

Table 3. Policy options


Upper Yeo and Cary

Sub-area 1

The issues in this sub-area

Fluvial flooding is focused onparticular isolated communities.This reflects the relatively small andsteep watercourses which dominatethe sub-area.

Some communities adjacent to theRiver Yeo, in particular Ilchester,have suffered fluvial flooding. Othervillages (such as Queen Camel andWest Camel) have suffered fromcomplex fluvial and surface waterproblems.

In the Upper Cary flooding problemsare generally isolated, although theexact mechanism of flooding isoften poorly understood, and isprobably a combination of surfacewater, fluvial and sewer problems.Sewer flooding has been recordedspecifically in Somerton.

Recent flooding in this sub area hasbeen strongly driven by localsurface water problems,exacerbated by some farmingpractices which have increased fieldrun-off locally.

Our key partners are:

West Dorset District Council

South Somerset District Council

Somerset County Council

The number of current properties atrisk in the 1% annual probabilityflood event is 517. This is expectedto increase to 825 properties in thefuture 1% annual probability floodevent.

The vision and preferred policy

Policy Option 3 - we are generallymanaging flood risk effectively

Our current level of investment inthis area is low, and in the UpperYeo area is focussed in areas wherewe have undertaken works. Thismaintenance and flood warning rolemust continue in this sub-area.

As our current investment in thearea is relatively low (in the UpperCary this is generally focussed onreactive debris clearance), it will notbe possible to reduce it furtherwithout undermining ourmaintenance and flood warning roleor without increasing flood risk.

Many of the risks in the Upper Caryrelate to sewer problems.

At the present time we cannotgenerally justify increasing actionsto address climate change or reduceflood risks further. The scatterednature of the problems makes suchinvestment unlikely to be economic.

Proposed actions to implement thepreferred policy

• Work with communities toincrease flood awareness, pre-flood planning and promote floodwarning.

• Review maintenance activities toensure best value for money.

• Investigate ways to support floodresistance and resiliencemethods to individual propertieswhere other options are notpractical. Communities mayinclude Queen Camel, WestCamel, Somerton and Babcary.


Yeovil


Yeovil is situated on a relatively highplateau well above the floodplain ofthe adjacent River Yeo.

Fluvial flooding occurs on varioussmall streams but the majority ofthe problems are related to surfacewater and sewer flooding. Historicrecords show many cases of sewerflooding.

Road access to Yeovil from theA303, a major trunk road into theSouth West, can be affected byflooding.

The current number of properties atrisk in the 1% annual probabilityflood event is 19. This is expectedto increase to 145 properties in thefuture 1% annual probability floodevent.





Natural England


Policy Option 4 - we are alreadymanaging the flood risk effectivelybut we may need to take furtheractions to keep pace with climatechange

Given the high density of propertiesin the town, we envisage that it willbe possible to direct furtherinvestment to respond to increasingrisks due to climate change.However unlike some policy units,Yeovil is generally at lower risk ofmajor flooding particularly whencompared to Taunton andBridgwater.

In the future the main problems inYeovil may be related to higherintensity summer storms whichoverwhelm the local sewers andsmaller streams.



• Investigate the current and futurecapacity of the existing surfacewater drainage systems in Yeovil,focusing on the effects of climatechange. Develop a surface watermanagement plan withconsideration of receivingwatercourses and climatechange.

• Investigate existing criticaltransport links into Yeovil andtheir vulnerability and resilienceto flooding. Implementimprovements where practical.

Sub-area 2

➜ The River Yeo avoids the main part of the town, here passing under the A30 to the east.


Sub-area 3

Upper and North WestParrett, and Upper Isle


Fluvial flooding is relatively limitedin this sub-area. This reflects therelatively small and steepwatercourses which dominate thearea.

Some communities, namelyCrewkerne, Martock, SouthPetherton, Ilminster, Donyatt, Seaand Ilton, do have localisedproblems, exacerbated (particularlyin Crewkerne) by small culvertedwatercourses which are prone toblockage or are undersized. Sewerflooding has been recordedspecifically in Ilminster and Chard.Some isolated problems existelsewhere.

South Petherton flooding has beenexacerbated by farming practices,


Sedgemoor District Council


Taunton Deane District Council



Natural England

National Farmers Union

Farming and Wildlife Advisory Group(FWAG)

contributing to localised floodingwell outside of the fluvial floodplainarea.

Recent flooding in the Upper Isle sub-area has been strongly driven by localsurface water problems, exacerbatedby some farming practices whichhave increased field run-off locally.

Flooding in the higher area of theNorth West Parrett has been limitedto local surface water problems. Inthe lower area there are very limitedassets at risk. However the tidalembankments do protect some lowsuburbs of Bridgwater from floodingas well as the occasional farm.



Policy Option 3 - we are generallymanaging existing flood riskeffectively.

Our current level of investment inthis sub-area is low, and is focusedin areas where we have undertakenworks (especially tidal embankmentswhich protect limited parts ofBridgwater). This maintenance andflood warning role must continue.

As our current investment in theseareas is relatively low, it will not bepossible to reduce it further withoutundermining our maintenance andflood warning role. Under thechosen policy, our present activities(primarily reactive maintenance,bank inspection and maintenanceand flood warning) will continueand are economically justified whencompared to existing risks.




• Work with the farming communityto encourage best practicefarming and soil management.Pay particular attention towater/run-off management on afarm scale and water quality.

• Investigate ways to support floodresistance and resiliencemethods to individual propertieswhere other options are notpractical. Communities mayinclude Martock, Merriott,Ilminster, Ilton and surroundingvillages, Cannington andsurrounding villages.


Upper Tone


Fluvial flooding is relatively limitedin this sub-area. This reflects therelatively small and steepwatercourses which dominate thearea. Some villages, such asHillfarrance, situated on the lowerpart of the catchment have sufferedfluvial flooding in the past, althoughwork has been undertaken toaddress this particular risk.

Recent flooding in this sub-area hasbeen strongly driven by local surfacewater problems, exacerbated bysome farming practices which haveincreased field run-off locally.



West Somerset District Council


Wessex Water

Natural England,

National Farmers Union

Farming and Wildlife Advisory Group(FWAG)

Sewer flooding has been recordedspecifically in Wellington andWiveliscombe. Some isolatedproblems exist elsewhere.



Policy Option 3 - we are generallymanaging existing flood riskeffectively.

Our current level of investment inthis sub-area is very low. Thismaintenance and flood warning rolemust continue. As our currentinvestment in the sub-area is low(generally focussed on reactivedebris clearance), it will not bepossible to reduce it further withoutincreasing flood risk.

At the present time we cannotgenerally justify increasing actionsto address climate change or reduceflood risks further. The scatterednature of the problems makes suchinvestment unlikely to be economic.




• Investigate the current and futurecapacity of the existing surfacewater drainage systems includingat Wellington and Wiveliscombe,focusing on the effects of climatechange. Develop a surface watermanagement plan withconsideration of receivingwatercourses and climatechange.

• Work with the farming communityto encourage best practicefarming and soil management.Pay particular attention towater/run-off management on afarm scale and water quality.

• Investigate ways to support floodresistance and resiliencemethods to individual propertieswhere other options are notpractical. Communities mayinclude Wellington, Tonedale andWaterrow.

Sub-area 4


Sub-area 5

Taunton


Historically flooding in Taunton hasbeen dominated by the River Tone.In the 20th century the 1960 floodevent was the most severe, reportedto have flooded nearly 500properties in the town. In responseto this flooding the Taunton flooddefence scheme was constructed inthe 1960s and the scheme wasfurther upgraded in the 1990s.

Since the scheme was built in the1960s there have been no majorflood events in Taunton although thedefences were tested in October2000.





Wessex Water

Currently there are 1,500 propertiesat risk from a 1% annual probabilityflood event. This is expected toincrease to 3,320 properties in thefuture 1% annual probability floodevent.

Most of the remaining risks inTaunton are related to tributaryflooding. Areas such as NortonFitzwarren, Bathpool and areasaround Tangier are at risk. The levelof flood risk to areas affected bytributary flooding is uncertainalthough significant.


Policy Option 5 - we can generallytake further action to reduce floodrisk.

The policy has been selected forTaunton as significant risks toexisting properties adjacent to thetributaries remain.

Work is presently ongoing to addressone of the main tributaries (theHalse Water) which flows throughNorton Fitzwarren. However risksremain on the other key tributaries.

There are also relative weaknessesin the River Tone defences asidentified in recent studies. Theseshould be addressed.

Taunton is subject to majorregeneration. Opportunities should,and are, being taken to address thedeficiencies in the River Tonedefences in connection with theredevelopment of the town.

Tributary flooding is significantlymore difficult to address and the riskis spread throughout the sub-area.


Proposed actions to implement the preferred policy

• Work with communities to increase flood awareness, pre-flood planning and promote flood warning.

• Review maintenance activities to ensure best value for money.

• Prepare development guidance for proposed developments in Taunton, identifying methods to reduce runoff rates and include Sustainable Urban Drainage systems (SUDs) in all new developments.

• Investigate the current and future capacity of the existing surface water drainage systems, focusing on theeffects of climate change. Develop surface water management plan with consideration of receivingwatercourses and climate change.

• Investigate existing critical transport links into Taunton and vulnerability and resilience to flooding.Implement improvements where practical.

• Investigate identified marginal deficiencies in River Tone flood defences and implement improvements inconnection with urban regeneration.

• Investigate potential to reduce flood risks from tributary flooding and implement improvements wherepractical.

➜ Taunton town centre narrowly escaped serious flooding from the River Tone in October 2000


Somerset Levels and Moors

Sub-area 6


The flood risks in this sub-area arecomplex and derive from the lowlying topography and the verylimited hydraulic gradient. Floodvelocities are low, resulting in lowflow capacities and extensive fluvialflooding over the lowland area.

The existing internationallyrecognised species and habitatsdepend upon the existing floodmanagement assets. Most assets inthe Somerset Levels and Moorsserve both flood management andwater level management functions,which are essential to theenvironmental interests.

Properties are generally scatteredthroughout the sub-area, withvillages and small communitiesoften situated on land slightlyabove moor level or on theembankments which separate the






Natural England

Internal Drainage Boards

rivers and the moors. Embankedwatercourses act as ‘high levelcarriers’ taking water from the uppercatchment through the low-lyingmoor area.

Across the sub-area, 590 propertiesare at risk of flooding during the 1%annual probability flood event. Thisis expected to increase to 1040properties in the future 1% annualprobability flood event.

Agricultural land is frequentlyflooded in the winter, with roadsflooded, disrupting communicationacross the area. Property floodingoccurs because of high flood levelsin the moors. However thoseproperties along the top of the highlevel carriers are also at risk fromhigh levels in the rivers caused byhigh tides in the Bristol Channel.The extensive network ofembankments is necessary to retainthe current agricultural system.There is a risk of breaching of theembankments, although workscontinue to minimise the risk.

Infrastructure across the moors(such as railways and pylons) isreliant on the continuedmanagement of the system. It isunlikely that railways would besustainable across the moorswithout this protection.

Climate change will have impactsboth in terms of higher river levels(due to higher tide levels in theRiver Parrett and higher flows) andalso more frequent and longerflooding of the moors.


Policy Option 6 - we will take actionwith others to store water or managerunoff in locations that provideoverall flood risk reduction orenvironmental benefits.

By adopting this policy andredistributing water some areas willbe subject to increased floodingwhile others will benefit fromreduced flooding. The aim is toachieve a net overall benefit. Thedistribution of floodwater betweenmoors can be determined to someextent by the use of sluices andother structures on the rivers.

The distribution of floodwater hasdeveloped to some extent byhistorical ‘accident’ rather thandesign. When considering thedistribution of assets across thesub-area it makes sense to directwater to areas which have limitedassets at risk.

By redistributing floodwater,primarily from upstream of Langportto the King’s Sedgemoor Drain, theoverall damage and disruption fromflooding would be reduced. Otherredistribution options may also bepossible, although modelling hasshown that technically not alloptions are feasible.





• Investigate existing transportlinks within the Somerset Levelsand Moors and vulnerability toflooding. Implementimprovements where practical.

Once it is accepted that theembanked system must be retainedthen these must be stable and fit forpurpose if breach risks are to beminimised. Investment is requiredto minimise risks today and into thefuture taking into account theconsequences of climate change.

The overall approach is to promotemore sustainable flood riskmanagement, by better use ofexisting flood storage and use ofexisting gravity systems wherepossible. This will ensure the longterm viability of the system and theassociated important conservationinterests.

• Identify a robust and nationallyagreed economic case forinvestment into the long termsustainability of the SomersetLevels and Moors flood riskinfrastructure.

• Investigate, consult upon, andtrial redistribution of floodwaterwithin the Somerset Levels andMoors.

• Undertake a comprehensivestudy of the geomorphology ofthe River Parrett and River Tone toinform future operations (e.g.dredging) and construction (e.g.tidal sluice).

➜ Flooding on the Levels and Moors


Sub-area 7

Bridgwater


Flood risk in Bridgwater isdominated by high tides in theBristol Channel propagating up theParrett Estuary. The town isrelatively low lying. It is protectedfrom tidal flooding by floodembankments and walls.

Currently there are around 135properties at risk from a 1% annualprobability flood. The number ofproperties is expected to increaseto around 10,000 in the future 1%annual probability flood event.

Modelling has shown that existingrisks due to high tide levels are low,and the current flood defences inBridgwater are generally in goodcondition. However, due to sea levelrise and expected deterioration inthe standard of the defences,further works will be required within20-30 years if risks are to bemaintained at a low level.






Natural England

Records have shown some sewerflooding problems and some limitedfluvial problems which probablyoccur during high tides and highintensity rainfall.


Policy Option 4 - we are alreadymanaging flood risk effectively butwe may need to take further actionsto keep pace with climate change.

Opportunities have and continue tobe taken in relation to improvingflood walls and banks as part of theregeneration of parts of Bridgwater.Policy 4 is recommended as we arealready managing the flood riskeffectively but where we may needto take further actions to keep pacewith climate change. However, weare aware that it will becomeincreasingly difficult to raisedefences in Bridgwater in the futurebecause of the existinginfrastructure levels (e.g. bridges)and there could be potentialdamage to the urban landscape byconstructing high walls along theriver frontage.

A step change may be required inthe future by excluding high tidesfrom the town, with the use of a tidalsluice. This poses a dilemma interms of our, and our partners,investment strategy. The step

change is not required from a floodrisk management perspective now,and flood risk managementinvestment would not beforthcoming.

We are aware that our partners havean emerging vision which sees atidal sluice as a component, butthere is significant uncertaintyregarding funding and theenvironmental and socialimplications. We do see thepotential for significantimprovements associated with asluice, although the environmentalrisks are significant.

There is an opportunity to provideresources for a future tidal sluice byusing resources deriving from theregeneration of parts of Bridgwater.


Proposed actions to implement the preferred policy

• Work with communities to increase flood awareness, pre-flood planning and promote flood warning.

• Review maintenance activities to ensure best value for money.

• Investigate the current and future capacity of the existing surface water drainage systems in Bridgwater,focusing on the effects of climate change. Develop a surface water management plan with considerationof receiving watercourses and climate change.

• Undertake a comprehensive study of the geomorphology of the River Parrett to inform potential futureconstruction (e.g. tidal sluice).

• Undertake studies to address key risks associated with long term flood management in Bridgwater (e.g. inconnection with further defence raising or tidal sluice). Implement recommendations in appropriatephases.

➜ High tide on the Parrett at Bridgwater – the town is a focus for future development in the catchment


Shoreline

Sub-area 8


Flood risks within this sub-area aredominated by coastal processesand tidal flooding. The area is lowlying and protected by tidalembankments. Some of the tidalembankments are in poor conditionand continue to deteriorate, butthere are very few built assets atrisk. At the time of writing there areongoing strategies which areconsidering the long term future ofthis area, where fluvial flood risksare of secondary importance.

There are tidal outfalls in the areawhich allow rainfall falling on thelowland areas to be evacuated tothe Bristol Channel. These assetsare maintained and periodicallyreplaced by us and this willcontinue unless the tidalembankments are realigned.






Policy Option 3 - we are generallymanaging existing flood riskeffectively.This policy is currentlyappropriate for this sub-area, untilsuch time as coastal processesdictate a change of approach.


• To continue current practices andreassess as we learn more aboutthe coastal processes.

➜ Past dredging of the tidal Parrett near Bridgwater – we will study natural processesto inform the need for future operations


Map of CFMP policies

Map of the policies in the Parrett catchment

Wells

ChardYeovil

Street

er

Martock

Honiton

TauntonSomerton

Langport

Williton

Crewkerne

Ilminster

Sherborne

Beaminster

Wellington

Bridgwater

D h

Cullompton

Glastonbury

Castle Cary

Burnham



2

4

5

6

7

8

1

1

3 3

3

Legend

Parrett CFMP

Main rivers

Urban areas

Preferred approach

Policy 1

Policy 2

Policy 3

Policy 4

Policy 5

Policy 6

N

1 Upper Yeo and Cary

2 Yeovil

3 Upper and North West Parrett, and Upper Isle

4 Upper Tone

5 Taunton

6 Somerset Levels

7 Bridgwater

8 Shoreline

The sub-areas

GESW1109BOUT-E-P

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Would you like to find out more about us,or about your environment?

Then call us on 08708 506 506* (Mon-Fri 8-6)

email [email protected]

or visit our website www.environment-agency.gov.uk

incident hotline 0800 80 70 60 (24hrs)

floodline 0845 988 1188

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