Exe Catchment Flood Management Plan - Exmoor · Environment Agency Exe Catchment Flood Management Plan 1 Introduction I am pleased to introduce our summary of the Exe Catchment Flood

managingflood risk

Summary Report June 2012

Exe Catchment Flood Management Plan

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June 2012

Environment Agency Exe Catchment Flood Management Plan 1

Introduction

I am pleased to introduce our summary of the Exe Catchment Flood

Management Plan (CFMP). This CFMP gives an overview of the flood

risk in the Exe catchment and sets out our preferred plan for

sustainable flood risk management over the next 50 to 100 years.

The Exe 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 primary source of flooding in the Exe catchment isfrom rivers, particularly where prolonged periods ofrainfall lead to a saturated catchment. There is also arisk of significant tidal flooding around the Exe estuaryand problems associated with tide-locking of thetributary streams. The greatest number of people andproperties at risk are in Exeter and Tiverton and on thetowns around the estuary. Historically, it is in theselocations that the greatest numbers of properties havebeen flooded in the past.

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: Devon CountyCouncil, Natural England, South West 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 alternatively paper copies can be viewed at any ofour offices in South West Region.

Richard CresswellSouth West Regional Director

2 Environment Agency Exe 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 Headwaters and high ground sub-area 12

2 Greater Exeter sub-area 14

3 Tiverton sub-area 16

4 Cullompton sub-area 18

5 East of Exeter sub-area 20

6 Exe Estuary sub-area 21

7 Mid Exe and Creedy sub-area 23

Map of CFMP policies 25

Contents


The purpose of a CFMP in managing flood riskCFMPs 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 Exe CFMP comprises thecatchments of the River Exe and itstributaries, as well as those of thecoastal streams that drain direct tothe Exe estuary. The catchmentextends across several differentlandscape types, from Exmoor in thenorth, the wide floodplains and rivervalleys to the north of Exeter, to thesmaller tributary streams of theestuary to the south.

The area is environmentally rich,containing a large number ofstatutorily designated sites. Thereare two Areas of Outstanding NaturalBeauty (AONB), three Special Areasof Conservation (SAC), 31 Sites ofSpecial Scientific Interest (SSSI), and146 Scheduled Monuments.

The Exe CFMP covers an area of some1,500 square kilometres (580 squaremiles). Annual rainfall ranges frommore than 2,300mm (90in) in uplandareas to less than 800mm (32in) onthe coast - the England and Walesaverage is 920mm (36in).

Catchment overview

In the north of the catchment, theRivers Exe and Barle rise on the openwet moorland of Exmoor and flowsouth-east through steep sidedwooded valleys. The rivers areconfined within steep, narrow valleysthat, in the upper reaches, respondrapidly to rainfall.

Then the Exe floodplain widensthrough the gently undulating Devonlandscape past Tiverton to Exeter.Just upstream of Exeter, the Exe isjoined by two major tributaries, theCreedy, to the west, and the Culm, tothe east. The wide floodplains of thelower reaches of the Exe and Culmprovide considerable floodwaterstorage, this attenuates and reducespeak flows.

The Exe finally flows into the Exeestuary immediately to the south ofExeter. The River Clyst and a numberof smaller tributary streams also flowdirectly into the estuary, both to thewest and to the east.

The main areas of urbandevelopment are to the south of thecatchment. In addition to Exeter,these urban areas include Tiverton,Cullompton, Crediton (which is not atrisk of flooding), and the townsaround the Exe estuary, principallyExmouth to the east, and Dawlish tothe west. The remainder of thecatchment is predominantly rural,with smaller villages and minorsettlements, and is dominated byagriculture, particularly grazing.

The geology of the Exe catchmentspans 400 million years. The oldestrocks - Devonian siltstones,sandstones and shales - are in theuplands of Exmoor. Permo-Triassicsandstones, mudstones andbreccias are found in the middle andeastern parts of the catchment. Withsands and muds being deposited inthe Exe Estuary as the most recentgeological activity.


Map 1. Location and extent of the Exe CFMP area

© Crown Copyright. Environment Agency 100026380.

Legend

Exe CFMP

Urban areas

Main rivers

Railway

Motorway

Okehampton

Bovey Tracy

Exeter

0 4 8 12 16Kilometres

Barnstaple

SouthMolton

Tiverton

Crediton

Wellington

Cullompton

Honiton

Sidmouth

Exmouth

Dawlish

N

➜Coastguards rescueresidents from a floodedcaravan park at DawlishWarren in December 2000 Photo: Guy Newman/Apex


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 ayear period. It is expressed as apercentage. For example, a 1% floodhas a 1% chance or 0.01 probabilityof occurring in any one year, and a0.5% flood has a 0.5% chance or0.005 probability of occurring in anyone year.

Hydraulic modelling, to determineflood extent, depth and velocity, wascarried out for the River Exeupstream as far as the confluencewith the River Batherm at Bampton,the River Culm upstream toWhimple. This ensured coverage ofthe main urban areas at risk: Exeter,Tiverton and Cullompton, as well asother settlements along thesereaches. In areas outside the extentof our model coverage, we haveused Flood Zone 2 and Flood Zone 3outlines.

The primary source of flooding in theExe catchment is from rivers,particularly when prolonged periodsof rainfall fall on saturated ground.

There is also a risk of significanttidal flooding around the estuary,with problems associated with tide-locking of the tributary streams.

The greatest number of people andproperty at risk is from the River Exein Exeter and Tiverton, and thetowns around the Exe estuary,particularly Exmouth. Historically, itis in these locations that thegreatest numbers of properties havebeen flooded.

The most significant recorded floodsoccurred in 1960, when severeflooding in Exeter affected morethan 1,000 properties. It was as aresult of this flooding that thecurrent flood alleviation scheme inExeter was constructed.

Our current flood risk managementactivities are focussed on the keysites and ensure the continuingmaintenance and operation of theflood defences. With the Exeter,Tiverton and Exmouth defences inplace, estimated annual averagedamages for the towns are reducedto less than a third of what theywould be without defences.

Overview of the current flood risk

The main risks to people, propertyand the environment across thecatchment are from the rivers andthe tide.

In total, approximately 11,000properties in the Exe catchment areat risk from a 1% annual probabilityflood. This assumes there are nodefences. This represents 10% of allproperties in the Exe catchment.However, this also includes keycommunity assets such as schools,care homes, ambulance, police andfire stations, health centres and ahospital.

Numerous sites designated for theirnatural or historic environmentalvalue are also affected by flooding,including the Exe Estuary Ramsar, aSpecial Protection Area (SPA) andSSSI site.

The main rail line to the South Westnear Exeter and along the Exeestuary is at risk of flooding, as arethe main water and waste watertreatment works at Exeter.

What is at risk?

Table 2. Critical infrastructure at risk:

55 electricity substations, 4 water treatment works, 5 railway lines, 5 A roads, and 1 motorway

Number of properties at risk Locations

2,000 to 5,000 Exeter, Exmouth

1,000 to 2,000 Tiverton

500 to 1,000 Starcross

250 to 500 Dawlish Warren, Cullompton

100 to 250 Stoke Canon and Cowley, Bampton, Dawlish, Exminster, Lympstone, Topsham


Table 1. Locations of towns and villages with 100 or more properties at risk in a 1% annual probability river flood

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

150 - 500

501 - 1,000

1,001 - 2,000

2,001 - 3,000

3,001 - 4,000

Exe CFMP

Main rivers


Exeter

Tiverton

Cullompton

Exmouth

Bampton

Stoke Canon

TopshamLympstoneExminster

Dawlish Warren

Starcross

N


How we currently manage the risk

Our activity is prioritised on a riskbasis. Our main activities include:

• Flood risk mapping – A major partof the programme is Flood ZoneImprovements and HazardMapping. This is focused onimproving the mapping at high-risk locations.

• Managing development – Ourdevelopment control teamsupports the planning process byensuring that new developmentshave the appropriate flood riskassessments and follow PPS25(Government Planning PolicyStatement on Development andFlood Risk).

• Flood warning – A warning systemin place for Exeter and Tivertonincludes loudhailers and leafletdrops. Elsewhere in thecatchment, registered propertiesreceive a direct message viaphone, email or fax. Major

Incident Plans have beendeveloped for specific areas ofExeter and Tiverton.

• Flood defence schemes – Wehave flood defences on the RiverExe including at Exeter, on therivers Creedy, Yeo, Culm, Clyst andAlphin Brook, and at Dulverton,Bampton, Tiverton, Exmouth,Lympstone and Dawlish.

• Maintenance – This includesmaintenance of banks andstructures, desilting, clearance ofobstructions and embankmentmaintenance. Spending is dividedalmost equally between works inthe channel to maintain flowcapacity and works to bankstructures. The Exe and ExeEstuary account for 67% ofmaintenance spending; thereminder is used for other mainriver systems including the Culm,Creedy and Clyst. Localauthorities carry out a largeamount of further work.

The distribution of potential floodrisk from rivers and tides isillustrated in Map 2 for a flood with a1% annual probability (0.5% fortides) of occurring or beingexceeded.

In addition to Exeter, Tiverton andExmouth, floods have also affectedsignificant numbers of properties,for example in Stoke Canon,Bampton, Cullompton, Clyst St Maryand Dulverton.

In addition to these locations, thereare risks of surface water flooding.However, further studies followingon from the CFMP are needed by usand our partners to quantify thispotential risk.

Where is the risk?

➜The railway embankment at CowleyBridge near Exeter was washed awayby the River Exe just after it had beenrepaired following an earlier flood Photo: Mark Hill/Apex


The impact of climate change and future flood risk

In the future, flooding will beinfluenced by climate change,changes in land use (for example,urban development) and rural landmanagement. In the Exe catchment,climate change is expected to 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 950mm bythe year 2100. This will increasethe probability of tidal floodingaround the Exe estuary.

Using river models we estimate thatby 2100, around 10,950 propertiesin the key settlements (Figure 2) maybe at risk from a 1% annual

probability flood, rising from thecurrent 8,800 properties. Flood riskfrom rivers increases mainly in thecommunities of Exeter and Tiverton.

The sensitivity testing undertakenshowed that urban developmentcould affect flood risk in thecommunities of Exeter and Tiverton.We found that with estimates ofincreased urban area around thesecommunities, based on LocalAuthority Development Plans, flowswould be expected to increase by2%. For the Clyst and Rockbearecatchments, which include the Eastof Exeter growth areas, flows wouldbe expected to increase by 5%. Withthe rural nature of much of thecatchment we found that run-off fromagricultural land plays a part in floodrisk. An expected increase in run-off,combined with a reduction in the

0

1000

2000

3000

4000

5000

Exeter Tiverton Stoke Canonand Cowley

Bampton

Current Future

Lower Estuary Upper Estuary Cullompton Clyst St Maryand Clyst Honiton

Num

ber o

f Pro

pert

ies

at F

lood

Ris

k

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

time it takes flows to peak, showedthat the expected increase in flowswould be up to 5%.

We have therefore based ourmodelling of future flood risk onclimate change, urban developmentand land management.


Approaches in each sub-area

We have divided the Exe catchment into seven distinctsub-areas which have similar physical characteristics,sources of flooding and level of risk. We have identifiedthe most appropriate approach to managing flood risk foreach of the sub-areas and allocated one of six genericflood risk management policies, 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.

Chard

SeatonExeter

Shaldon

Dawlish

Honiton

Taunton

Exmouth

Sidmouth

Crediton

Williton

Braunton

Tiverton

Axminster

Ilminster

Ashburton

West Hill

Woolacombe

Barnstaple

Wellington

Lyme Regis

Bridgwater

Okehampton

Cullompton

Horrabridge

South Molton

Bovey Tracey

Newton Abbot

Combe Martin

Kingsteignton

i k ll

Great Torrington

NewtonPoppleford

Teignmouth

Ottery St Mary

Budleigh Salterton



N

LegendExe CFMP

Sub-area

Headwaters and highground (Policy 6)

Greater Exeter (Policy 5)

Tiverton (Policy 5)

Cullompton (Policy 5)

East of Exeter (Policy 4)

Exe Estuary (Policy 4)

Mid Exe and Creedy (Policy 2)

1

2

3

4

5

6

7

8

9

Future direction for flood risk management

➜ Flood waters swell the River Exe in December 2000Map 3. Exe sub-areas


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


Headwaters and high ground

Sub-area 1

The issues in this sub-area

This sub area covers thepredominantly rural headwaters andhigh ground of the Exe catchment. Itincludes parts of Exmoor whichdrain to the south. It includes theRiver Batherm catchment, the upperCulm catchment and the upper Clystcatchment (excluding the East ofExeter area).

Flood risk is dispersed across thisarea, with approximately 2,000people and 800 properties withinthe 1% annual probability floodextent. The majority of these are inBampton and Dulverton where flooddefence schemes for a 7% and 2%flood event, respectively, are inplace. There are also significantnumbers of properties at riskelsewhere, for example in Exford,Exebridge, Culmstock and Uffculme.Flood defences are present in theselocations, we estimateapproximately 1,150 properties willbe within the 1% flood extent by2100.

Our key partners are:

West Somerset District Council

Mid Devon District Council

East Devon District Council

Exmoor National Park

Blackdown Hills AONB

Natural England

The 1% flood also affects the A396along the Exe valley, the police andfire stations in Dulverton; as well astwo care homes, two electricity sub-stations and two telephoneexchanges.

The vision and preferred policy

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

There is considerable potential toattenuate and reduce floodwaterthrough changes in land use andland management. Opportunitiesinclude creating wetland featuresand increased tree and hedgeplanting across the floodplain.

Our assessment of catchmenthydrology has identified that theupper Culm catchment is the mosteffective location for changes inland use and land management toreduce peak flows downstream.However, taking action on Exmoor,and in the Lowman and upper Clystcatchments is also likely to have aneffect if carried out over large areasof land.

These changes could potentiallyreduce the flood risk to urban areasfurther downstream, such as Exeter,Tiverton and Cullompton as well asbenefiting Biodiversity Action Planhabitats and species. By allowing

natural features to develop in thefloodplain, this policy could alsoenhance landscape character.

Though this policy involves astrategic increase in flooding inallocated areas, it is not intended toadversely affect the risk toindividual communities. We willcontinue with our currentmaintenance activities in locationswhere the numbers of people andproperty at risk are high (forexample, Bampton and Dulverton).


Proposed actions to implement the preferred policy

• Identify where environmental enhancements will bring the greatest flood risk benefits. Investigate if thelower Culm can provide opportunities for compensatory habitat if sea level rise affects existing high tideroost sites.

• Work with Natural England and others to promote better land management practices.

• Work with partners to use naturalistic features to attenuate surface water flows and manage flood riske.g.Exmoor Ancient Woodland Project, Exmoor Mires project, tree planting and buffer strips, floodplainhedgebanks.

• Ensure land drainage consenting promotes restoration of meanders, rather than hold the current line withhard revetment.

• Continue with current maintenance activities in appropriate locations where the numbers of people andproperties at risk are high (for example, in Bampton and Dulverton).

• Reduce amount and frequency of gravel removals returning gravels to headwaters upstream.

• Monitor hydraulic performance of Bampton flood defence improvements and Shuttern Brook.

• Investigate if the Grand Western Canal can be used for flood storage.

• Identify locations and reduce risk to life from cars becoming stuck in floodwaters in fords and ‘Irishbridges’ (for example, by reviewing signage, depth boards).

• Improve awareness and resilience in communities at risk of fast onset flooding with deep and fast flows.Assess if works to reduce the flood risk are possible.

• Engage with landowners to influence land use changes to deliver flood risk, biodiversity and waterquality benefits. This might involve field scale trials together with a review of the existing knowledgebase.

• Increase floodplain storage and attenuation by increasing wetland habitat, wet woodland (notably atBampton and Dulverton) and hedge planting across the floodplain.

• Oppose inappropriate development within Flood Zone 3 (1% flood extent).

• Investigate ways in which people can be moved out of risk areas. Investigate also if critical infrastructurecan be moved out of risk areas.


Greater Exeter

Sub-area 2


The area covers the urban extent ofExeter, including Exwick, St Thomas,Ide, Alphington and Marsh BartonIndustrial Estate to the west. To thenorth, it includes Stoke Canon atthe confluence of the rivers Exe andCreedy. To the east, and south, thisextends as far as the M5 motorway.

At least 7,000 people and 3,000properties are within the 1% annualprobability flood extent for the RiverExe in Exeter. The majority of theseare in the St Thomas area of Exeter.At risk of flooding are: two carehomes and an ambulance station;


Exeter City Council

Devon County Council


South West Water

Network Rail

Natural England

schools and health centres in StThomas; and Listed Buildings inExeter and Stoke Canon.Infrastructure at risk of floodingincludes more than 30 electricitysub-stations, the main railway line,Pynes Water Treatment Works andCountess Wear Waste WaterTreatment Works and the A377andA379 roads. In the future weestimate that 4,000 properties willbe at risk from a future 1% annualprobability flood.

Defences in Exeter and Stoke Canonwere constructed in the 1960s and1970s following flooding in Exeterin 1960. The defences in Exeter aredesigned to a 1% annualprobability standard of protection.Due to a possible low point indefences at Station Road in Exeterthe actual standard of protectionmay be lower than this at around3.3%. The standard of protection ofthe defences in Stoke Canon is 4%.

A flood warning service is in place inExeter with a lead time ofapproximately four hours. A MajorIncident Plan covering fluvialflooding from the Exe is in place.


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

The Policy chosen would ensuresome continued protection to theschools, health centres and othercritical infrastructure such as theambulance station, electricitysubstations, and the care homeswithin the flood extent.

Taking further action to reduce floodrisk would protect the Exe EstuarySSSI / SPA / Ramsar site frompollution resulting from flooding.This policy would help to managethe risk to historic features withinthe area, such as Exeter Quay,although scheduled bridges mayremain vulnerable to damage.



• Carry out a modelling study to investigate how the flow contributions of the tributaries combine at Exeter.

• Investigate how we can improve the environmental and flood risk management performance of ourexisting systems through Exeter and Stoke Canon.

• Improved flood forecasting and engagement of local partners and community in flood awareness,incident management, and emergency response.

• Evaluate risk to critical infrastructure, especially between Exeter and Stoke Canon: Pynes WTW andmainline railway

• Investigate the risk of flooding to the waste water treatment works in Stoke Canon, Countess Weir, andthe main sewer along the Exeter canal embankment in relation to Flood Risk Management works.

• Work with partners to retro-fit SuDs in problem areas. Including identifying and retro-fitting SuDs whereproblems of highways drainage entering sewerage systems have been identified.

• Ensure spatial planning and development does not increase flood risk (PPS25).

• Investigate ways in which people can be moved out of risk areas over the lifetime of the CFMP.

• Investigate opportunities to restore areas of the North Brook and Pin Brook in Exeter, both to provideenvironmental enhancements and to reduce flood risk.

• Investigate locations and routes for birds to find compensatory high water roosts as the estuary changesand whether this can also provide flood risk benefits. In particular investigate land between Exwick RadialGates and Cowley Bridge for this and for flood attenuation/washlands.

➜ Okehampton Street in Exeter turns into a river in the 1960 floods.


Tiverton

Sub-area 3


Areas of Tiverton are at risk offlooding from the River Exe andRiver Lowman. In total,approximately 3,000 people and1,400 properties are within the 1%flood extent. Of these,approximately 900 people areestimated to be at risk from asignificant or extreme flood hazardof deep and fast flowing floodwater.Furthermore, 44 Listed Buildings,Tiverton Hospital, two schools, a firestation, a care home, a number ofelectricity sub-stations, and parts ofthe A3126 and A396 roads are atrisk from a 1% annual probabilityflood. A quarter of the TidcombeLane Fen SSSI is within the current1% floodplain. In the future we




Emergency Planners

Primary Care Trust

South West Water

estimate that 1,500 properties willbe at risk from a future 1% annualprobability flood.

The River Lowman’s catchment ismuch smaller and more ‘flashy’than the Exe. The standard ofprotection of defences from theLowman is also lower than for theExe. So although approximatelythree-quarters of the properties atrisk from flooding in Tiverton are atrisk from the Exe and only onequarter from the Lowman, overallwe consider the consequences offlooding to people is generallygreater for the Lowman than for theExe.

Flood defences on the Exe and theLowman comprise flood walls,channel improvements and weirs.These provide a standard ofprotection of 1% on the Exe, and2% on the Lowman. Some thirdparty flood risk infrastructure hasbeen put in place on the Lowman asa part of more recent development.

A flood warning service is in place inTiverton – current flood warninglead time is approximately twohours for the River Exe but only onehour for the River Lowman. A MajorIncident Plan covering fluvialflooding is in place in Tiverton.



By taking further action, the 1,500properties and 3,500 people withinthe future 1% flood extent wouldsee their risk of flooding reduced, aswould the schools, hospitals andother critical infrastructure includingthe fire station, electricity sub-station and a care home.

There would still be a risk toapproximately 1,700 properties and4,000 people from an extreme 0.1%flood event. In practice thismagnitude of flooding cannot bereasonably engineered against.



• Investigate how we can improve the performance of our existing systems.

• Investigate ponding of water behind defences in Tiverton.

• Improved flood forecasting and engagement with local partners and community in flood awareness,incident management, and emergency response.

• Ensure spatial planning and development does not increase flood risk (PPS25). There may be anopportunity for improvements to be made to reduce flood risk as part of new developments (for example,developments next to the Lowman). As part of managing future flood risk to new developments, the localauthority may specify a sum of money to be retained specifically for future maintenance purposes.

• Evaluate risk to critical infrastructure: hospital, school, water and sewage treatment works andevacuation centres. Investigate if critical infrastructure can also be moved out of risk areas.

• Investigate ways in which people can be moved out of risk areas.

• Investigate if we can use land next to the River Lowman for flood storage.

• Ensure private flood risk infrastructure is maintained.

• Work with partners to retro-fit SuDs in problem areas. Including identifying and retro-fitting SuDs whereproblems of highways drainage entering sewerage systems have been identified.

• Investigate measures upstream to reduce the flood risk. Look at ways of influencing land use and landmanagement practices in the Lowman catchment.

• Improve awareness and resilience in communities at risk of fast onset flooding with deep and fast flows,and assess if works to reduce the flood risk are possible.

➜ Flooding on the south side of Tiverton


Cullompton

Sub-area 4


The Cullompton area includes all ofurban Cullompton to the west of theRiver Culm extending to Stoneyfordin the east, and approximately 5kmnorth to include Willand, betweenthe Culm and Spratford Stream.

The greatest flood risk in Cullomptonis from the various tributary streamsthat flow through the town into theCulm. The catchments for thesetributary streams are small andrespond rapidly to rainfall.

We estimate that 450 properties and1050 people are at risk from the 1%annual probability flood of the RiverCulm and its tributaries. In additionto the risk to people and property,junctions of the M5 motorway, theA373 and B3181, the main linerailway and a sewage works are alsoat risk from the 1% flood. Anambulance station and two carehomes are also at risk of flooding.



National Farmers Union

Natural England

Land Owners

We estimate approximately 170properties and 400 people will bewithin the future 1% flood extentfrom the River Culm. A further 400properties and 800 people arewithin the 1% flood extent from thetributaries.

In some areas of Cullompton, thestreams have been culvertedthrough housing estates that werebuilt in the 1970’s. This can result inflooding from culverts blocked withdebris during high flows, asoccurred during flooding in 2002.Defences in Cullompton for the RiverCulm consist of channelimprovements, flood relief culvertsand flood banks. These provide a1.7% Standard of Protection.

The River Culm has a relatively slowresponse to rainfall. Flood warningfor Cullompton has a lead time ofapproximately two hours. The floodhazard is low for the majority ofproperties.

There is likely to be a large amountof residential and commercialdevelopment in the Cullompton areain the future, commercial pressuredriven to some extent by distributioncentres around the motorwayjunction.



We consider the risk from thetributaries associated with, forexample, potential blockages toculverts, to be currentlyunacceptable.

By taking further action to reducerisk, we propose to take measurestoresolve these issues both byopening up culverted sections toreduce the risk of blockages, andalso over the longer term toinvestigate ways in which peoplecan be moved out of the risk areas.



• Investigate the River Culm and Spratford Stream response to high flows – particularly the interaction offlows with the M5, and the railway. Identify if hedge and floodplain woodland planting can attenuateflows.

• Prepare an Asset Management Plan to identify where future works may be required to reduce risk toCullompton.

• Work with partners to manage surface water flooding in Cullompton, particularly for new development.Incorporate use of Sustainable Drainage Systems (SuDS).

• Investigate improvements to the tributaries to provide environmental enhancements and to reduce risk ofblockage to culverted sections. Examine the possibility of opening up culverted sections.

• Investigate ways in which people and infrastructure can be moved out of risk areas.

• Ensure spatial planning and development does not increase flood risk (PPS25).

• Improved flood forecasting and engagement with local partners and community in flood awareness,incident management, and emergency response. Investigate if some level of flood warning coverage maybe feasible on the tributary streams.

• Engage landowners to influence land use and land management practices in the upper Culm catchment.

➜ Flooding of the Leather dressing works, AlexandriaIndustrial Estate, Cullompton - January 1984


East of Exeter

Sub-area 5


The East of Exeter area is apredominantly rural areaimmediately to the east of the city. Itextends as far as the M5 motorwayto the west, Broadclyst to the north,Rockbeare to the east and Clyst StMary to the south, and also includesExeter airport and the nearbybusiness park. The area will seesubstantial future development.

At present, approximately 50properties in the area (in Broadclystand Clyst Honiton) are within the 1%annual probability flood extent of theRiver Clyst. This generally presents alow hazard and a flood embankmentin Clyst St Mary provides a 4%standard of protection.



Exeter City Council

Natural England


Land Owners

We estimate that approximately 90properties will be in the future 1%flood extent. Fluvial flood risk willremain a relatively low hazard.

Exeter is considered both aStrategically Significant City and aPrincipal Urban Area by the SouthWest Regional Spatial Strategy. Assuch it will be a focus for futuredevelopment, in particular the newtown of Cranbrook in East Devon,and possible expansion of theairport and a new rail freightterminal.


Policy Option 4 - we are alreadymanaging the flood risk effectively,but we may need to take furtheractions to keep pace with climatechange.

Future flood risk will be largelydetermined by new development,which consequently must becarefully designed to avoid any longterm impacts.

Proposed actions toimplement the preferredpolicy

• Work with developers and thelocal authority to ensure newdevelopment complies withPPS25.

• Complete the GreenInfrastructure Study to maximiseenvironmental and recreationaluse of the floodplain.

• Influence land use and landmanagement practices in theClyst catchment, which isrelatively shallow and low lyingand has the potential to reduceand attenuate peak flows byholding back floodwater.


Exe Estuary

Sub-area 6


The Exe Estuary covers the townsand infrastructure around the Exeestuary as far as the M5 viaduct. Tothe west of the estuary this includesDawlish, Dawlish Warren,Cockwood, Starcross, Kenton andExminster. To the east of the estuaryit includes Exmouth, Lympstone,Exton and Topsham. The Exe Estuaryis a SSSI, a SPA and a Ramsar siteand includes the Dawlish Warren,SSSI, SAC and National NatureReserve.


Teignbridge District Councils


Network Rail


Highways Agency

South West Water

Natural England


In total, around 2,600 propertiesand 6,000 people are in the 1%annual probability fluvial and 0.5%tidal flood extent. Exmouthaccounts for over half of this total. Anumber of health centres andschools are within the 1% floodextent as are care homes, ListedBuildings and a number ofelectricity sub-stations.

Approximately 2,300 properties arewithin the 10% flood extent. Thecurrent standard of protection offluvial defences in the Exe estuarytowns is greater than this.

We estimate approximately 2,800properties will be in the future 10%flood extent.

In general the catchments for thetributary streams are small and fastresponding. Changes in land useupstream can have an impact onflood risk. The greatest fluvial floodrisk typically occurs at the lower endof these tributaries where peak flowevents in the watercourses coincidewith tide-locking in the estuary.

Whilst there are both fluvial andtidal flood risks, direct tidal risksare addressed by the ShorelineManagement Plan and are likely toplay the greatest role in the future ofcoastal designated sites.


Policy Option 4 - we are alreadymanaging the flood risk effectively,but we may need to take furtheractions to keep pace with climatechange.

Within this sub-area there areopportunities to both retain existingdefences in certain locations and tolook at investigating how we canmove people and infrastructure outof the risk areas. The actions chosenwill allow us to keep pace withclimate change.



• Investigate ways that existing flood defence schemes in urban areas can be managed, taking intoaccount flow and sea level rise since their construction, and in particular considering issues of tide-locking.

• Improved flood forecasting and engagement with local partners and community in flood awareness,incident management, and emergency response.

• Work with partners to retro-fit Sustainable Drainage Systems in problem areas. Identify problemswhere highways drainage enters sewerage systems and retro-fit Sustainable Drainage Systems .

• Ensure spatial planning and development does not increase flood risk (PPS25). This should includeconsideration of climate change adaptation as directed in Planning Policy Statement 1.

• Investigate ways in which people and infrastructure can be moved out of risk areas. The location ofmobile homes / caravan parks in the Dawlish Warren area must be considered. Local DevelopmentFramework documents should identify areas where future river and floodplain restoration may beconsidered especially for locations of present mobile homes and/or caravan parks.

• Investigate measures upstream to reduce the risk. Engage landowners to influence land use and landmanagement practices in the catchments within and upstream of the estuary area.

• Improve awareness and resilience in communities at risk of fast onset flooding with deep and fastflows, and assess if works to reduce the flood risk are possible.


Mid Exe and Creedy

Sub-area 7


This rural area covers the mid Exeand Creedy catchments and thearea to the west of the Exe estuary.

The largest community, Crediton, islocated on high ground between theRiver Creedy and the River Yeo andis not at risk of flooding.


Teignbridge District Council




Natural England

Farmers and Landowners

Properties that are at risk aregenerally dispersed throughout thearea, although in totalapproximately 800 people and 300properties are within the 1% annualprobability flood extent. Weestimate approximately 50 peopleare at risk from deep and fastflowing floodwater.

A number of main roads and therailway line through Crediton arealso at risk of flooding, althoughthere is little other criticalinfrastructure at risk.

There are few flood defences withinthe area. A small amount ofmaintenance debris removaldesilting is carried out.


Policy Option 2 - we will generallyreduce existing flood riskmanagement actions.

In general, the flood risk is relativelyminor and dispersed. There arelocations where we carry outmaintenance work, and to ceaseany flood risk managementactivities altogether would lead toan unacceptable localised risk. Inthese few locations where thenumbers of people at risk areconcentrated we would continuecurrent or alternative maintenance,but overall we would look to reduceactivities.

The Creedy is a relatively fast, steepriver draining a classic undulatingDevon landscape. There may besome localised opportunities forretention of floodwater, but theseare not extensive.



• Review current maintenance activities to identify where they can be reduced to allow the floodplain tonaturalise with potential biodiversity benefits. Continue with current or alternative maintenance activitieswhere the numbers of people and properties at risk are high.

• Reduce amount and frequency of gravel removals. Return gravels to headwaters as a routine part of theseworks.

• With Natural England and others, promote improved land management practices.

• Investigate if embankments can be reduced where doing so would provide a flood risk benefit.

• Ensure that Land Drainage consenting promotes restoration of meanders where appropriate, and allowsthe river to reclaim floodplain.

• Investigate ways in which people and infrastructure can be moved out of risk areas.

• Oppose inappropriate development within Flood Zone 3 and work to ensure that local authoritiesimplement PPS25. Local Development Frameworks should consider designating all floodplain areas asfunctional floodplain.

• Any flood risk management systems required for new communities or any other developments are notexpected to be maintained or adopted by the Environment Agency. However, we may need to considerimprovements where the number of people at risk are concentrated.

• With Devon County Council identify locations and reduce risk to life due to cars becoming stuck infloodwaters at fords and ‘Irish bridges’.

➜ Floods from the River Exe surround a cottage at Bickleigh near Tiverton in December 1994


Map of CFMP policies

Map of the policies in the Exe catchment


Legend

Exe CFMP

Main rivers

Urban areas

Preferred approach

Policy 1

Policy 2

Policy 3

Policy 4

Policy 5

Policy 6

Wellington

Honiton


Okehampton

Bovey Tracy

Exeter

South Molton

Tiverton

Crediton

Cullompton

ExmouthDawlish

Teignmouth

Williton

N

1

2

3

4

5

6

7

1 Headwaters and high ground

2 Greater Exeter

3 Tiverton

4 Cullompton

5 East of Exeter

6 Exe Estuary

7 Mid Exe and Creedy

The sub-areas

GESW0612BWSC-E-E

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Documents

Exe Catchment Flood Management Plan - Exmoor · Environment Agency Exe Catchment Flood Management Plan 1 Introduction I am pleased to introduce our summary of the Exe Catchment Flood