West Cornwall Catchment Flood Management Plan...Cornwall catchment, but particularly in the areas of...

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managing flood risk Summary Report June 2012 West Cornwall Catchment Flood Management Plan

Transcript of West Cornwall Catchment Flood Management Plan...Cornwall catchment, but particularly in the areas of...

Page 1: West Cornwall Catchment Flood Management Plan...Cornwall catchment, but particularly in the areas of Hayle, Helston, Par and St Blazey, Penzance, Perranporth, St Austell, St Ives and

managingflood risk

Summary Report June 2012

West Cornwall Catchment Flood Management Plan

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We are the Environment Agency. It’s our job to look after yourenvironment and make it a better place – for you, and forfuture generations.

Your environment is the air you breathe, the water you drinkand the ground you walk on. Working with business,Government and society as a whole, we are making yourenvironment cleaner and healthier.

The Environment Agency. Out there, making your environmenta better place.

Published by:

Environment Agency

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Tel: 0870 8506506

Email: [email protected]

www.environment-agency.gov.uk

© Environment Agency

All rights reserved. This document may be reproduced

with prior permission of the Environment Agency.

June 2012

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Environment Agency West Cornwall Catchment Flood Management Plan 1

Introduction

I am pleased to introduce our summary of the West Cornwall

Catchment Flood Management Plan (CFMP). This CFMP gives an

overview of the flood risk in the West Cornwall catchment and sets

out our preferred plan for sustainable flood risk management over

the next 50 to 100 years.

The West Cornwall CFMP is one of 77 CFMPs for Englandand Wales. Through the CFMPs, we have assessedinland flood risk across all of England and Wales for thefirst time. The CFMP considers all types of inlandflooding, from rivers, ground water, surface water andtidal flooding, but not flooding directly from the sea(coastal flooding), which is covered by ShorelineManagement Plans (SMPs). Our coverage of surfaceand ground water is however limited due to a lack ofavailable information.

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.

Flood risk affects people and property across the WestCornwall catchment, but particularly in the areas ofHayle, Helston, Par and St Blazey, Penzance,Perranporth, St Austell, St Ives and Truro. Various floodevents have demonstrated that while the numbers ofproperties at risk across West Cornwall may berelatively low compared with other areas of the country,the risk to life, and community disruption caused byflooding can be significant.

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: CornwallCouncil, 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

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2 Environment Agency West Cornwall 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 Fal and Carnon sub-area 12

2 St Austell Bay sub-area 14

3 South Coastal Rivers sub-area 16

4 North Coastal Rivers sub-area 18

5 Fal Estuary sub-area 20

6 Carbis Bay sub-area 22

7 The Lizard sub-area 24

8 Cape Cornwall sub-area 25

Map of CFMP policies 26

Contents

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Environment Agency West Cornwall Catchment Flood Management Plan 3

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.

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4 Environment Agency West Cornwall Catchment Flood Management Plan

The West Cornwall CFMP lies next tothe East Cornwall CFMP at the mostsouth-westerly point of mainlandBritain. The CFMP area is made up ofone relatively large catchment, theRiver Fal and many other smallerriver catchments. The Fal Estuary isthe one major estuary in the WestCornwall catchment, with smallerestuaries at Hayle and Helford.

The West Cornwall CFMP covers anareas of some 1,500 squarekilometres (600 square miles).Annual rainfall ranges from morethan 1,400mm (55in) over higherground to less than 1,000mm (40in)on the coast. The England and Walesaverage is 920mm (36in).

The topography of West Cornwall isvaried. The main upland areas arethe Land’s End peninsula, theCarnmenellis uplands (near

Catchment overview

Camborne and Redruth) and theHensbarrow Downs (to the east ofthe area), from which a large numberof rivers spring. The remainder of thearea is made up of rolling farmland,valleys and heaths which form anumber of discrete river catchments,many of which are small and steep.

Most of the catchment is rural, withonly eight per cent urban. Theprincipal urban centres are Penzanceand St Ives in the far west,Camborne, Redruth and Truro in thecentre, Falmouth to the south, andPar and St Austell on the southcoast, at the eastern extent of thearea.

Just over 300,000 people live in thearea, with the main employmentsectors being the manufacturing andservice industries, and tourism. Thetraditional economic activities of

agriculture, mining, and fishing havebeen in decline for some years,however they still contribute to theeconomy today.

The West Cornwall catchment isenvironmentally rich with manyimportant environmental locations,and some high quality river systems.There are two Areas of OutstandingNatural Beauty, 12 Special Areas ofConservation, one Special ProtectionArea (SPA), 76 Sites of SpecialScientific Interest (SSSIs) and 701Scheduled Monuments. The area hasa rich mining heritage recognised byWorld Heritage status for mininglandscape, with component sites inor adjacent to floodplains at HayleHarbour and Perranaworthal.

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Environment Agency West Cornwall Catchment Flood Management Plan 5

Map 1. Location and extent of the West Cornwall CFMP area

© Crown Copyright. Environment Agency 100026380.

Legend

West CornwallCFMP

Urban areas

Main rivers

Railway

Motorway

Newquay

Redruth

0 4 8 12 16Kilometres

Bodmin

St Austell

Truro

Mevagissey

Camborne

Hayle

Falmouth

Helston

Penzance

St Ives

N

The Square, Pentewan in November 1997

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6 Environment Agency West Cornwall Catchment Flood Management Plan

Current and future flood risk

There is a recorded history offlooding within West Cornwall thatdates back to the 1900s. Previousriver flooding incidents include:

• The floods of 1988, in which Trurowas flooded twice and over 60properties were flooded inPerranporth.

• The event of 31 December 2002and 1 January 2003 saw floodingacross the area, includingRedruth and Helston, where over60 properties were affected.

• In addition, St Ives has a longhistory of flooding, with a severeevent in 2002 leading to eightpeople needing emergencyrescue.

High tides contribute to flood risk inWest Cornwall. A major tidal surge in2004 affected many communities onthe south coast.

While the numbers of properties atrisk across West Cornwall may berelatively low compared with otherareas of the country, the risk to life,and community disruption can bejust as great.

There are flood alleviation schemesthroughout the catchment thatreduce flood risk. The main sectionsof defences are located along:

• the St Austell (White) Riverthrough St Austell;

• the Bolingey River throughPerranporth;

• the Angarrack and Hayle Rivers atHayle;

• the River Par and Treffry Canal atPar and St Blazey;

• and around Truro with New Milland Idless dams and Truro tidalbarrage.

Overview of the current flood risk

Today, there are over 5,000properties across the catchment atrisk of flooding from rivers and thetide, at a 1% annual probability(rivers) or 0.5% annual probability(tidal) event, not taking into accountthe effect of flood defences.

Also at risk is the mainline railway(especially at Par and Penzance), theA390 and A39 (at Truro, Par,Perranaworthal and Penzance), twowater treatment works, a fire station,police station and a care home.

Also affected by flooding and floodrisk management activities aredesignated environmental sites suchas the Hayle Estuary and CarrickGladden SSSI, Marazion Marsh SPA,and Loe Pool SSSI.

What is at risk?

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Number of properties at risk Locations

500 to 1,000 Par/St Blazey, Penzance

100 to 500 St Ives, Perranporth, St Austell, Hayle, Truro, Helston, Redruth, Portreath

50 to 100 Penryn, Crowlas, Falmouth

25 to 50 Camborne

Environment Agency West Cornwall Catchment Flood Management Plan 7

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

Table 2. Critical infrastructure at risk:

7 electricity substations, 8 railway lines, 11 A roads, 2 water treatment works

Map 2. Flood risk to property in a 1% annual probability river flood, taking into account current flood defences

© Crown Copyright. Environment Agency 100026380.

Legend

Properties with a 1%chance of flooding

25 - 50

51 - 100

101 - 200

201 - 400

401 - 700

West Cornwall CFMPMain rivers

St Austell

Redruth

Camborne

Falmouth

Hayle

Helston

Penzance

0 4 8 12 16Kilometres

St Blazey

Penryn

Portreath

N

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8 Environment Agency West Cornwall Catchment Flood Management Plan

How we currently manage the risk

• 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 – Where floodforecasting exists, we aim toprovide at least two hoursadvance warning of imminentflooding to people in designatedrisk areas. This however is notrealistic on many of the rivers inWest Cornwall due to their flashynature. The service involves usinga multi-media communicationservice called Floodline Warnings

Direct. This provides a system thatcan target warnings to people viadifferent media methods,including telephone, email andSMS text messaging. We alsoprovide a public access telephoneservice called Floodline thatpeople can ring to check if there isa flood warning for their area.Flood warnings in force are alsolisted on our website. MajorIncident Plans have beendeveloped for Perranporth,Helston, Truro, Penryn and Par / StBlazey.

• Flood defence schemes – We haveflood defence schemes at StAustell (on the Sandy River and StAustell River), Truro, Hayle, St Ives,Helston, Perranporth, Angarrack,Penzance, Par, Penryn andFalmouth.

• Maintenance – We maintainchannels and defences.

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.

The greatest concentration ofproperties at risk of flooding is at Parand St Blazey. Here some 690properties are at risk from river, tidaland surface water flooding. This isset to increase due to rising sealevels.

Penzance has the next highestconcentrations in property at riskwith some 505 properties at riskrespectively.

In addition to these locations, thereare risks of surface water flooding,which can be deep and fast flowing,across much of the catchment.However, further studies followingon from the CFMP are needed by usand our partners to quantify thispotential risk.

Where is the risk?

➜Tregenna Place, St Ives, 14/11/2002

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Environment Agency West Cornwall Catchment Flood Management Plan 9

The impact of climate change and future flood risk

We have considered a range offactors that could influence flood riskover the next 100 years to find outhow flood risks could change in WestCornwall. The factors we have lookedat are climate change, landmanagement and urbandevelopment. We have usedgovernment guidance and othercalculations to test the influence ofeach factor.

We have used the following futurescenario in the West Cornwall CFMP,

• 20% increase in peak flow in allwatercourses due to climatechange.

• 11% increase in river flows due toland use change.

• 5% increase in river flows incertain locations due to urbandevelopment.

We have found that climate changehas the greatest influence on futureflood risk, increasing flood risk fromboth rivers and the tide. Landmanagement also contributes,because of the rural nature of thecatchment. Urban developmentcould affect flood risk significantly inSt Austell, Falmouth and Redruth.

In the future we expect flood depthsto increase but for flood extents toincrease or remain the same. Thismeans that more people andproperty will be affected by floodingin the future. The areas where weexpect flood risk to increase themost are Penzance and Truro (seeFigure 2) .

0

100

200

300

400

500

600

700

800

Par/St. Blazey Penzance St Ives Perranporth St Austell Hayle Truro Helston Redruth Penryn Crowlas Falmouth Camborne

Current Future

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

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10 Environment Agency West Cornwall Catchment Flood Management Plan

Approaches in each sub-area

We have divided the West Cornwall catchment into eightdistinct sub-areas which have similar physicalcharacteristics, sources of flooding and level of risk. We have 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. West Cornwall sub-areas

Fowey

Hayle

Truro

Penryn

Bodmin

Newquay

St IvesRedruth

HelstonFalmouth

Penzance

Camborne

St BlazeySt Austell

Carbis Bay

Mevagissey

Wadebridge

St Columb Road

© Crown Copyright. Environment Agency 100026380.

0 4 8 12 16Kilometres

N

LegendWest Cornwall CFMP

Sub-area

Upper Fal and Carnon (Policy 6)

St Austell Bay (Policy 5)

South Coastal Rivers (Policy 5)

North Coastal Rivers (Policy 5)

Fal Estuary (Policy 4)

Carbis Bay (Policy 4)

The Lizard (Policy 3)

Cape Cornwall (Policy 1)

1

2

3

4

5

6

7

8

9

Future direction for flood risk management

➜ Floods in St John’s Road at Helston, January 2003

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Environment Agency West Cornwall Catchment Flood Management Plan 11

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

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12 Environment Agency West Cornwall Catchment Flood Management Plan

Upper Fal and Carnon

Sub-area 1

The issues in this sub-area

The Upper Fal and Carnon coversthe river catchments of the Fal,Tresillian, Allen and Carnon. All therivers drain into the Fal Estuaryarea. The watercourses have a slowresponse to rainfall. The upperreaches of the rivers will, however,react rapidly for example with waterdraining from the moors. Flood risksare made more complex due to thelegacy of mine and mineralworkings, which can impact onwater drainage, discharge, storageand transfer between catchments.

Villages at risk of flooding includeChacewater, St Dennis, Grampound,Ponsanooth and Tregony. In totalthere are 191 properties at risk of

Our key partners are:

Cornwall Council

Natural England

National Farmers Union

Imerys Ltd

flooding in a 1% annual probabilityflood, with 38 of these located inChacewater. However, schemesprotect properties in Tregony andGrampound schemes up to andincluding the 20% annualprobability flood event. Theschemes from Chacewater toDevoran and at Ponsanooth protectproperties for up to the 2% annualprobability flood event.

Specific flood warnings areavailable on the River Fal fromTrenowth to Tregony, with generalcoverage flood warnings elsewhere.

Critical infrastructure at a high riskof flooding includes an electricitysubstation, a water treatment worksand several roads. The railwaybetween Truro and Plymouth maybe at risk.

The nature of the catchments alsomakes them prone to field run-off,which can be exacerbated throughinappropriate land management.This has caused flooding due to run-off from agricultural land,particularly in the St Stephen area.

The vision and preferred policy

Policy Option 6 - we will take actionwith others to store water ormanage run-off in locations thatprovide overall flood risk reductionor environmental benefits.

Significant numbers of properties,residents, and community asset,would benefit from flood riskmanagement actions and relativelysignificant habitat creationopportunities would be provided.Habitat creation opportunitiesinclude wetland creation. Inaddition, reducing flood risk in thisarea would reduce flood riskdownstream and therefore havecumulative social, economic andenvironmental benefits in the FalEstuary area.

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Environment Agency West Cornwall Catchment Flood Management Plan 13

Proposed actions to implement the preferred policy

• Investigate the scope for wetland creation on the Tresillian River upstream of Ladock and Tresillian, andon the River Allen upstream of Truro, which could attenuate flows and reduce flood risk downstream.

• Examine the potential for alterations to the wetlands of Goss Moor and Tregoss Moor to create additionalstorage resulting in flow attenuation in this area and in the Fal Estuary area.

• Support local authorities in the preparation of their Strategic Flood Risk Assessments and associatedLocal Development Framework Plans. Master planning of Sustainable Drainage Systems for any urbanextension of Truro also forms an essential part in delivering this policy.

• Consider the use of disused china clay pits in the Fal catchment to contribute to a reduction in flood riskdownstream in this area.

• Further investigate the links between land management practices, run-off and flood risk. Research impactof mine and mineral workings on flood risk. In particular the impact on water, drainage, discharge,storage and transfer between catchments. This may require a water cycle study for China Clay areas to beincluded in the Minerals Development Plan Document Strategic Flood Risk Assessment.

• Use programmes to raise and maintain awareness of flood risk and self-help measures.

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14 Environment Agency West Cornwall Catchment Flood Management Plan

St Austell Bay

Sub-area 2

The issues in this sub-area

St Austell Bay is subject to floodrisks from river, tides and surfacewater. The area covers thecatchments of the River Par, the StBlazey Stream, the St Austell(White) River and Pentewan Streamas well as the coastline around theBay with small streams in incisedvalleys.

Areas at risk of flooding from riversinclude Par and St Blazey, StAustell, London Apprentice,Luxulyan, Pentewan, Mevagissey,Bugle, Tywardreath Highway andGorran Haven. Surface water is asource of flood risk in manylocations.

There are around 1,380 proprietiesat risk of flooding from the 1%annual probability flood (0.5%tidal), particularly in Par and St.

Our key partners are:

Cornwall Council

Woodland Trust

Land owners

Natural England

Imerys, Goonvean

Mid Cornwall Moors Life Project

Blazey where 650 properties are atrisk and in St. Austell where 230properties could be affected. Thenumber of properties at risk in thesub-area could increase by around75 by 2100.

Critical infrastructure at a high riskof flooding includes three electricitysubstations, a fire station, St Blazeypolice station, a Care Home in Parand two telephone exchanges inMevagissey. The mainline railway,the Newquay branch line, as well asnumerous roads (including theA390) are at risk of flooding.

Flood alleviation schemes reduceflood risk at Par and St Blazey, StAustell and Pentewan.

Whilst the area is served by floodwarning systems, St Austell is not.Furthermore, the flood warningservice on the River Par providesless than two hours notice offlooding. However, there is a MajorIncident Plan in place for Par and StBlazey where over 1,000 people areat risk.

The coastline is mainly made up ofcliffs with limited risks of tidalflooding. However, a number ofpopulated areas have developedalong the coast in lower areaswhere tidal flood risk is an issue.Tide-locking of watercourses wherethey drain into the sea is also aproblem.

The nature of the catchments alsomake them prone to field run-off,which can be exacerbated throughinappropriate land management.This has caused flooding due to run-off from agricultural land in theSticker, Gorran Haven andTywardreath areas.

The vision and preferred policy

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

The chosen policy provides thehighest level of reduction to floodrisk, resulting in significantreductions in economic damages,number of properties, communityassets, residents, vulnerablecommunities, and roads and criticalinfrastructure that are at risk offlooding. This reflects the fact thatthe current level of flood risk in thearea is high and not adequatelydealt with.

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Environment Agency West Cornwall Catchment Flood Management Plan 15

Proposed actions to implement the preferred policy

• Create specific flood warning service on the St Austell River for St Austell, London Apprentice andPentewan. Review flood warning criteria on the River Par.

• Flood Hazard Mapping of Par, St Blazey and at St Austell to improve emergency response information.

• Undertake a flood risk management strategy at St Austell, Par and St Blazey to investigate opportunitiesto improve existing flood alleviation schemes. Surface Water Management Plans (SWMP) produced for StAustell, Mevagissey, Par and St Blazey. Include proposals for implementation.

• Examine scope for reconnection of channel and floodplain along the St Austell (White) River.

• Support Cornwall Unitary Authority in the preparation of its Strategic Flood Risk Assessments andassociated Local Development Framework documents.

• Examine the scope for wetland creation upstream of Luxulyan. Any eco town located in the River Parheadwaters should incorporate measures to reduce flood flows at Luxulyan and St Blazey.

• Further investigate the links between land management practices, run-off and flood risk.

• Research impact of mine and mineral workings on flood risk.

• Investigate the benefits of using disused china clay pits upstream of St Austell to attenuate flows.

• Create a Major Incident plan for St Austell.

• Use programmes to raise and maintain awareness of flood risk and self-help measures.

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16 Environment Agency West Cornwall Catchment Flood Management Plan

South Coastal Rivers

Sub-area 3

The issues in this sub-area

South Coastal Rivers covers thecatchments of the Rivers Cober, RedRiver and Trevaylor Stream, as wellas the coastline of Mounts Bay. Itincludes the major settlements ofPenzance and Helston and othertowns such as Mousehole, Crowlasand Porthleven.

There are numerous smallcatchments draining directly to thecoast, particularly in the MountsBay area, while the River Cobersprings on high ground to the north-east and drains a greater area.

A number of areas are at risk offlooding from rivers, particularlyHelston, Gulval (Trevarrack)Penzance, Nancledra, Lamorna,Chyandour, Ludgvan and Burras.The nature of the catchments alsomakes them prone to field run-off,which can be exacerbated throughinappropriate land management.

Our key partners are:

Cornwall Council

South West Water

Natural England

National Farmers Union

A number of populated areas havedeveloped along the coast in lowareas, particularly Penzance,Newlyn, Porthleven and Mousehole.In these areas tidal flood risk ismore significant.

There are approximately 1,000properties at risk of flooding underthe 1% (or 0.5% tidal) annualprobability flood, particularly inPenzance where 480 propertiescould be affected and in Helstonwhere 200 properties are at risk.Critical infrastructure at a high riskof flooding includes a watertreatment works, an electricitysubstation, the mainline railwayand various roads.

By 2100, the number of propertiesat risk of flooding could increase byover 150, mainly in Penzance.

Flood alleviation schemes serve toreduce flood risk at Penzance,Helston, Porthleven andMousehole.

Specific flood warnings areavailable on the River Coberbetween Wendron and the coastthrough to Loe Pool with less thantwo hours notice of flooding. Tidalflood warnings are issued for theSouth Cornish coast. There is aMajor Incident Plan in place atHelston, with less than six hoursnotice of major flooding available.

The vision and preferred policy

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

The Chosen Policy providessignificant reductions in economicdamages and the number ofproperties, community assets,residents, vulnerable communities,roads and critical infrastructure thatare at risk of flooding. Furthermore,additional benefits arise from theprotection from flooding of heritage,landscape and pollution risk sites. Itallows the existing high levels offlood risk to be addressed,particularly at Helston where theexisting flood risk managementactions do not adequately deal withriver or surface water flood risks.

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Environment Agency West Cornwall Catchment Flood Management Plan 17

Proposed actions to implement the preferred policy

• Review the quality of flood warning criteria on the River Cober and implement recommendations. Use programmes to raise and maintain awareness of flood risk and self-help measures.

• Undertake Surface Water Management Plans for Penzance, Porthleven, Newlyn, Mousehole, Crowlas andHelston. Include proposals for implementation.

• Review channel maintenance procedures to ensure that targeted maintenance is undertaken to reduceflood risks, particularly upstream of structures.

• Investigate the potential to increase storage capacity at Drift reservoir and investigate the creation ofupstream storage on the Trevaylor Stream and on the River Cober. Implement recommendations.

• Investigate the creation of wetland areas at Marazion Marsh to enhance this SSSI/SPA site and reduceflood risk in the Green Lane area.

• Support local authorities in the preparation of their Strategic Flood Risk Assessments and associatedLocal Development Framework Plans.

• Investigate feasibility of improvements to the flood alleviation scheme in Helston.

• Further investigate the links between land management practices, run-off and flood risk.

• Progress with the outcomes of the Rapid Response Catchment Study.

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18 Environment Agency West Cornwall Catchment Flood Management Plan

North Coastal Rivers

Sub-area 4

The issues in this sub-area

The North Coastal Rivers area is atrisk from both river and tidalflooding. Rivers generally drainmedium sized catchments throughnarrow valleys with limitedfloodplains. Communities at floodrisk from rivers include Perranporth,Portreath, Bridge and GilbertsCoombe.

Surface water is a source of floodrisk in areas such as Redruth,Scorrier, Mount Hawke and CarnBrea Village. Flood risk is alsoincreased in rural areas where landis not managed appropriately.

Our key partners are:

Cornwall Council

Camborne, Pool and Redruth (CPR)Regeneration

South West Regional DevelopmentAgency

English Partnerships

South West Water

Natural England

National Farmers Union

The coastline is predominately madeup of high cliffs and tidal flood riskis limited to low-lying areas on thecoast, such as Porthtowan,Perranporth and Portreath.

There are approximately 850properties at risk of flooding underthe 1% annual probability or 0.5%annual probability flood event,particularly in Perranporth where350 properties are at risk, and inPortreath where 150 propertiescould be affected. Infrastructuresuch as various roads are at risk offlooding. There are flood alleviationschemes at Perranporth, Redruthand Portreath. The number ofproperties at risk of flooding couldincrease by around 90.

A flood warning service is availablefor communities on PerrancoombeStream, the river between Silverwelland Perranporth. There is a MajorIncident Plan for Perranporth butwith less than two hours notice ofsevere flooding. Tidal flood warningsare issued on the north coast.

The vision and preferred policy

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

The chosen policy could providesignificant reductions in economicdamages and the number ofproperties community assets,residents, vulnerable communities,roads and critical infrastructure thatare at risk of flooding. Furthermore,additional benefits arise from theprotection from flooding of heritage,landscape and pollution risk site.

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Environment Agency West Cornwall Catchment Flood Management Plan 19

Proposed actions to implement the preferred policy

• Undertake feasibility studies at Gilberts Coombe, Bridge and Portreath for options to reduce flood risk.Implement recommendations.

• Create specific flood warning service on the Redruth Stream/Portreath Stream for Bridge and Portreath.Create a Major Incident Plan (MIP) for Portreath. Use programmes to raise and maintain awareness of floodrisk and self-help measures. Review flood warning criteria for MIP at Perranporth.

• Review channel maintenance procedures to ensure that targeted maintenance is undertaken to reduceflood risks, particularly upstream of structures.

• Progress the outcomes of the Rapid Response Catchment Study.

• Support the planning authority in the preparation of its Strategic Flood Risk Assessments and associatedLocal Development Framework Documents.

• Implement the Surface Water Management Plan for Redruth.

• Investigate the links between land management practices, run-off and flood risk.

• Undertake research to improve understanding about the impact of mine workings on flood risk on acatchment level.

➜ Flooding in Perranporth 9 February 1974

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20 Environment Agency West Cornwall Catchment Flood Management Plan

Fal Estuary

Sub-area 5

The issues in this sub-area

The Fal Estuary covers thecatchments of the Carnon, Tresillian,Fal, Allen and Kenwyn Rivers. Itincludes the major settlements ofTruro, Falmouth and Penryn.

The area is subject to both flood riskfrom river and tidal water and inplaces these combine to exacerbateflood risk further. There arenumerous small catchments drainingdirectly to the estuary, with otherlarger catchments springing on highground upstream in the Upper Faland Carnon area.

Urban areas particularly at risk offlooding include Flushing, Penryn, StMawes, Truro and Tresillian. In all ofthese places flood risk from tidalwater is the major concern, howeverTruro is also at risk from the riversAllen and Kenwyn. Surface water is asource of flood risk in Falmouth,Penryn and Truro.

Our key partners are:

Cornwall Council

South West Water

Natural England

National Farmers Union

There are approximately 440properties at risk of flooding underthe 1% annual probability (and 0.5%tidal) floodplain, with 220 propertiesat risk in Truro and 90 in Penryn. Anumber of roads are at risk offlooding.

Flood alleviation schemes reduceflood risk at Truro, Penryn, Falmouthand Flushing.

A flood warning service is offered tocommunities along the RiversKenwyn, Allen and Tinney, but withless than two hours notice offlooding provided on the Kenwynand Allen. Tidal flood warnings arealso issued for the South CornishCoast, including the Fal estuary.Emergency plans are in place forTruro and Penryn.

Risk will increase as a result of theimpact of climate change, urbandevelopment and inappropriate landuse management. This will reducethe standard of protection offered byexisting flood alleviation schemes,particularly at Truro. The number ofproperties at risk of flooding couldincrease by over 250, with themajority of this increase expected inTruro.

The vision and preferred policy

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

The chosen policy will preventsignificant future impacts fromflooding, and manages the currentrisks in a sustainable manner,working mainly with existing floodrisk assets. It allows a range of floodrisk management actions to beconsidered, such as sustaining thecurrent flood alleviation scheme atTruro, whilst also considering areasfor potential managed retreat in theFal estuary.

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Environment Agency West Cornwall Catchment Flood Management Plan 21

Proposed actions to implement the preferred policy

• Review Truro flood alleviation scheme and implement measures required to sustain the current scale offlood risk into the future.

• Review channel maintenance procedures to ensure that targeted maintenance is undertaken to reduceflood risks, particularly upstream of structures.

• Use programmes to raise and maintain awareness of flood risk and self-help measures. Review floodwarning criteria on the Rivers Allen and Kenwyn. Create community-based warnings for areas at risk oftidal flooding.

• Support local authorities in the preparation of their Strategic Flood Risk Assessments and associatedLocal Development Framework Plans.

• Undertake Surface Water Management Plans for Truro, Falmouth and Penryn. Include proposals forimplementation.

• Undertake a flood risk management strategy to investigate key opportunities for managed realignment inthe Fal estuary and potential impacts on flood risk and habitat creation.

• Further investigate the links between land management practices, run-off and flood risk.

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22 Environment Agency West Cornwall Catchment Flood Management Plan

Carbis Bay

Sub-area 6

The issues in this sub-area

Carbis Bay area covers thecatchments of the Red River, HayleRiver and Stennack Stream. Itincludes the major settlements ofCamborne, Pool, Hayle and St Ives.

There are around 870 properties atrisk of flooding under the 1%annual probability (or 0.5% tidal)flood, particularly in Hayle where220 properties are at risk.

Our key partners are:

Cornwall Council

Camborne, Pool and Redruth (CPR)Regeneration

South West Regional DevelopmentAgency (SWRDA)

English Partnerships

South West Water

Hayle Harbour Company

Hayle Town Council

Natural England

National Farmers Union

Infrastructure such as the mainlinerailway and various roads are at riskof flooding. The number ofproperties at risk could increase byaround 100.

There are flood alleviation schemesin the main risk locations, including St Ives, Hayle and Angarrack.Defences at Hayle provideprotection for a severe tidal event(0.5 per cent annual probabilityflood event) and from the two riversfor the 1.3 per cent and 2.5 per centannual probability floods. Flood riskin St Ives has been addressed withthe recent completion of a floodalleviation scheme to provideprotection from the StennackStream for up to a 0.6 per centannual probability flood.

A flood warning service on the RiverHayle is provided for communitiesat risk of flooding from Relubbusdownstream and at Hayle. Floodwarnings are offered to propertiesat risk from tidal flooding.

The vision and preferred policy

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

The chosen policy was selected as itprevents significant future impactsof flooding and manages the currentrisks in a sustainable manner,working mainly with existing floodrisk management measures. Theprovision of flood risk managementmeasures is adequate for the currentflood risk situation and theproposed actions will maintain thisinto the future.

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Environment Agency West Cornwall Catchment Flood Management Plan 23

Proposed actions to implement the preferred policy

• Review River Hayle flood alleviation scheme to sustain current standard of service.

• Undertake a flood risk management strategy for the Hayle River to consider how provision of upstreamstorage, wetland creation and setting back of defences could sustain flood risk.

• Investigate the use of existing water bodies and Higher Trevaskis reservoirs upstream of Angarrack toattenuate flows downstream.

• Further investigate the links between land management practices, run-off and flood risk.

• Progress with the outcomes of the Rapid Response Catchment Study.

• Use programmes to raise and maintain awareness of flood risk and self-help measures.

• Support the planning authority in the preparation of its Strategic Flood Risk Assessments and associatedLocal Development Framework Documents.

• Undertake Surface Water Management Plans for Camborne, Pool, St Ives and Hayle. Within thisinvestigate retrofitting Sustainable Drainage Systems and using pumping stations to deal with tide-locking issues. Include proposals for implementation at St Ives and Hayle. Implement the Surface WaterManagement Plan for Camborne and Pool.

➜ Flooding on the A30 at Hayle in February 1974

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24 Environment Agency West Cornwall Catchment Flood Management Plan

The Lizard

Sub-area 7

The issues in this sub-area

The Lizard covers the Helford Rivercatchment and coastal catchmentsto the south.

There are just over 100 properties atrisk of flooding in the 1% annualprobability (and 0.5% tidal) flood,particularly in Coverack where 15properties are at risk and Gweekwhere 12 properties could beaffected. Various roads are also atrisk of flooding.

Flood alleviation schemes arelocated at Gweek, Porthallow,Porthoustock, Coverack andCadgwith.

Our key partners are:

Cornwall Council

South West Regional DevelopmentAgency (SWRDA)

English Partnerships

South West Water

Natural England

National Farmers Union

Flood risk is increased in developedareas where structures such asculverts and bridges are subject toblockage and areas of impermeableground such as roads and car parksincrease surface run-off problemsand increase the volume of waterentering the drainage network. Suchflooding has been recorded atCadgwith, Porth Navas, Coverackand Constantine.

As a result of the impacts of climatechange and inappropriate land usemanagement flood extents anddepths are expected to increase,with flood extents up to 5m greaterin some locations and depthsincreasing by over 0.7m. Thenumber of properties at risk offlooding could increase by around10.

The vision and preferred policy

Policy Option 3 - we are generallymanaging existing flood riskeffectively.

The chosen policy will allowimproved control over futuregeomorphology and will maintainexisting schemes that protectproperties from frequent floodinginto the future.

Proposed actions to implement thepreferred policy

• Review channel maintenanceprocedures to ensure thatmaintenance is only undertakenwhere it is essential to controlflood risks, particularly upstreamof structures.

• Support local authorities in thepreparation of their StrategicFlood Risk Assessments andassociated Local DevelopmentFramework Plans.

• Investigate the links betweenland management practices, run-off and flood risk. Consideroptions for influencing landmanagement practice to reduceflood risk, including encouraginglandowners to join EnvironmentalStewardship programmes.

• Progress with the outcomes ofthe Rapid Response CatchmentStudy.

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Environment Agency West Cornwall Catchment Flood Management Plan 25

Cape Cornwall

The issues in this sub-area

Cape Cornwall covers the north andwest coastal strip of the Penwithpeninsula from Penberth Rivercatchment in the south to just westof St Ives on the north. The areaincludes the communities of St Just,Porthcurno, Sennen and Zennor.

A number of locations arevulnerable to flooding caused byshort, intense rainfall events.Flooding from rivers overtoppingtheir banks and from surface waterrun-off are the biggest risk. Areassuch as Tregeseal have sufferedfluvial flooding in the past while StJust has experienced surface waterflooding when the volume of waterin the built up area has exceededthe capacity of the existing urbandrainage system.

There are currently no floodalleviation schemes and, due to thenature of the rapid response torainfall, it is not possible to offerspecific flood warnings tocommunities using the currenthydrometric infrastructure. Floodwarnings are issued for the NorthCornwall and South Cornwall coasts.Tidal flooding is considered to be ofminimal risk.

Our key partners are:

Cornwall Council

There are 66 properties at risk offlooding under the 1% annualprobability river or 0.5% tidal flood.Some minor roads are also at risk.

As a result of the impacts of climatechange and land use management,the number of properties at risk willincrease by around 5 properties.

The vision and preferred policy

Policy Option 1 - we will continue tomonitor and advise.

The current flood risks are very lowcompared to other areas in theCFMP. Increased flooding bringsonly limited social and economicimpacts, and risk to life does notincrease. Further there are nopotential adverse impacts onenvironmental assets as a result ofincreasing flood risk.

This policy does, however, allow thesituation to continue to bemonitored to allow a change ofpolicy if conditions change fromthose expected.

Proposed actions to implement thepreferred policy

• Any development should becarefully designed not toexacerbate flood risks. Land useplanners should considerdesignating all floodplains asfunctional in order to ensure theyare not constricted, or that thelimited floodplain storage is notreduced. Where development orredevelopment is permitted inflood risk areas it is essential thatrobust warning and evacuationprocedures are secured andmaintained.

• No further action is proposed. Wewill continue to monitor andadvise, particularly with regard tothe Tregeseal Stream and St Just.

Sub-area 8

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26 Environment Agency West Cornwall Catchment Flood Management Plan

Map of CFMP policies

Map of the policies in the West Cornwall catchment

© Crown Copyright. Environment Agency 100026380.

Legend

Main rivers

Urban areas

Preferred approach

Policy 1

Policy 2

Policy 3

Policy 4

Policy 5

Policy 6

West Cornwall CFMP

St Ives

Newquay

St Austell

Bodmin

MevagisseyRedruthTruro

Camborne

Falmouth

Hayle

HelstonPenzance

0 4 8 12 16Kilometres

N

12

3

4

5

6

7

8

1 Upper Fal and Carnon

2 St Austell Bay

3 South Coastal Rivers

4 North Coastal Rivers

5 Fal Estuary

6 Carbis Bay

7 The Lizard

8 Cape Cornwall

The sub-areas

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Environment Agency West Cornwall Catchment Flood Management Plan 27

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GESW0612BWPW-E-E

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