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EASTBOURNE AREA
SURFACE WATER MANAGEMENT PLAN
Quality Management
ii
Quality Management DOCUMENT INFORMATION
Title: Surface Water Management Plan for Eastbourne Area
Owner: East Sussex County Council
Version: 1.3
Status: Final
Project Number: WBESWM File Name: SWMP_Halcrow_Report_for_Eastbourne.doc
REVISION HISTORY
Summary of Changes Completed by Date of Issue Version
Draft Report Oliver Evans / Chris Downs 0.1
Final Report Oliver Evans / Chris Downs 31/01/12 1.3
AUTHORS
Name Organisation and Role
Chris Downs Halcrow Project Manager
Oliver Evans Halcrow Deputy Project Manager
REPORT DELIVERY APPROVALS
Name Title Signature Date
Chris Downs Project Manager, Halcrow
Elliot Gill Technical Director, Halcrow
Imran Bukhari Project Director, Halcrow
Nick Claxton Head of Flood Risk Management, ESCC
PARTNER APPROVAL
Name Title Signature Date
Peter Padget Engineering, Eastbourne Borough Council
Graham Kean Engineering, Wealden District Council
John Challoner County Sewerage Engineer, Southern Water
Peter Amies Environment Agency
DISTRIBUTION
Name Organisation and Role
Nick Claxton Head of Flood Risk Management, East Sussex County Council
Peter Padget Engineering, Eastbourne Borough Council
Graham Kean Engineering, Wealden District Council
John Challoner County Sewerage Engineer, Southern Water
Peter Amies Environment Agency
RELATED DOCUMENTS
Doc Ref Document Title Author Date of Issue Version
PFRA Preliminary Flood Risk Assessment for East Sussex
Oliver Evans / Chris Downs
June 2011 1
Quality Management
iii
Halcrow Group Limited has prepared this report in accordance with the instructions of East Sussex County Council, for their sole and specific use. Any other persons who use any information contained herein do so at their own risk.
Executive Summary
iv
Executive Summary
According to the Environment Agency, East Sussex County Council (ESCC)
was ranked 35th in the National Assessment of Flooding in England with
approximately 8,000 properties at risk of flooding. This national assessment
led to funding and prompted the study to verify the national view. The Lead
Local Flood Authority (LLFA) ESCC is responsible for managing surface water
flood risk within the County and SWMPs are an excellent tool in assist with
this. ESCC and partners agreed that a SWMP for the Eastbourne Area was
required because of the historic flooding and the predicted future flood risk
identified on the Environment Agency’s national mapping. ESCC therefore
commissioned this SWMP to gain an understanding of surface water flood risk
in Eastbourne (including Wannock and Polegate) and provide an Action Plan
to help reduce it.
The approach taken to deliver the Eastbourne Area Surface Water
Management Plan (SWMP) was based on that detailed in the related technical
guidance prepared by Defra (see Section 9). This standard approach was
enhanced and adapted using the skills and local knowledge of the partners
plus the experience from Halcrow of working across the UK on similar work.
The SWMP Action Plan and accompanying study report has been developed
by ESCC as a strategic tool, which would facilitate the local and coordinated
management of surface water flood risk within the Eastbourne catchment
area. It provides a preliminary understanding of surface water flood risk as
well as identifying potential preferred options to mitigate or reduce flood risk.
This tool will assist East Sussex County Council, Eastbourne Borough
Council, Wealden District Council and Southern Water & Environment Agency
in making subsequent sustainable surface water management decisions,
which are evidence, risk based, future proofed, joint funded where appropriate
and founded upon partnership working.
This report builds on previous studies undertaken by ESCC and has been
delivered using a tiered four phase approach as suggested in the guidance;
SWMP Document Status January 2011
This document has been produced to explain the preparation and present the
findings of the Eastbourne Area Surface Water Management Plan (SWMP) as
well as the associated Action Plan. The Action Plan will remain a live document
allowing the LLFA & RMAs to continue to monitor action delivery, develop
existing actions and add new ones, in collaboration with SWMP partners and
other relevant stakeholders.
Executive Summary
v
i.e. Phase 1 – Preparation; Phase 2 – Risk Assessment; Phase 3 – Options;
and Phase 4 – Implementation.
Phase 1: Preparation
The first phase focused on preparing and scoping the requirements of the
study. ESCC, as the Lead Local Flood Authority (LLFA), had already
established a flood risk partnership with Eastbourne Borough Council,
Wealden District Council, the Environment Agency and Southern Water to
facilitate the delivery of the SWMP. Through meetings with the partners, the
specific roles, of each, was clarified, the data sharing approach developed and
the issue of how the partnership would engage with stakeholders was agreed
in principle. The early setting-up of the partnership enabled prompt
agreement on the approach to the SWMP and the definition of the objectives.
Partners held various data, which were brought together in a GIS environment
to be shared immediately. The maps produced from this GIS dataset gave an
improved understanding of the flood risk, allowing general approaches to be
considered and an Action Plan to be developed, which will help manage and
reduce surface water flood risk going forward. This, in turn allowed an
informed judgement to be made on the level of assessment required for the
Risk Assessment Phase (Phase 2). .
Phase 2: Risk Assessment
The risk assessment phase did comprise of two distinct stages. The first
stage was to identify the intermediate hotspots, which were potential flood risk
areas determined by using the already plotted data, and review them with the
partners to confirm the most critical to consider further. The second stage,
took these high priority intermediate areas and modelled their flood risk.
The first stage identified intermediate hotspots using surface water flood risk
mapping provided by the Environment Agency along with other available data.
This was illustrated in the form of a “storyboard” (see Appendix B), using
tabulated data, text and flood risk mapping. This simple summary
presentation aided the capture of known local flood risk. It was then used, in
addition to the Environment Agency’s surface water modelling results and
historic flooding, to score and rank each hotspot. This process resulted in
highlighting thirty six. These hotspots in total contained approximately 6,000
properties predicted to be at risk of surface water flooding during a 1 in 200
year event, however since this is only predicted flood risk it is thought this
number maybe lower in reality.
Executive Summary
vi
Figure ES1 – Figure of Hotspots
It was agreed with the partners that the top four ranked intermediate hotspots
represented the key flood risk areas and it would be these taken forward to the
second, detailed risk assessment stage. The four high priority locations
identified were:
Mill Stream Gardens, Willingdon
Langney
Firle Road and Arndale Shopping Centre in Eastbourne Town Centre
Bourne Stream / Motcombe Park east of Eastbourne Town Centre
Executive Summary
vii
These four key hotspots carried forward to detailed risk modelling were seen
as the most likely to result in improved flood risk understanding and the
identification of potential flood risk reducing options from detailed modelling.
In the second stage computer modelling was used to analyse the impact of
heavy rainfall events across South Wealden and the Eastbourne Area by
assessing flow paths, flood depths, flow velocities and catchment response.
Halcrow used an existing Southern Water drainage-system computer model
and improved it to simulate flood pathways to gain an understanding of the
surface water flooding, which would be critical for option selection in Phase 3.
Figure ES2 – Extract of Detailed Flood Map
Phase 3: Options
Supported by the understanding developed in Phase 2, an option assessment
process was undertaken for each of the four top ranked hotspots areas to
reduce the associated surface water flood risk in each of them. For each
hotspot, outline solutions were developed, modelled and tested to understand
the degree of flood protection they provided.
Initially, large engineering solutions were considered to reduce flooding in the
hotspot areas. These were based on traditional fluvial flood defence
approaches such as large flood storage areas. Eastbourne was well served by
potential open areas upstream and existing storage areas downstream of the
main built-up areas. However, constraints in the topography upstream, the
Executive Summary
viii
lack of space in the developed areas and limitations on conveyance to make
use of the downstream storage areas, made these more traditional measures
impractical, and they were not progressed further.
Therefore, the computer models of the drainage systems and flood pathways
were used to assess more locally based options. These options made use of
limited modifications to the local drainage system and associated
infrastructure and were developed to an initial feasibility level. Several
possible options for further development were identified, one of which is likely
to result in the removal of properties from the Southern Water’s register of
sewer-flooded property. Further details on the options can be found in Section
6 of this report.
It was anticipated that schemes offering more than 1:25yr standard of
protection (SoP) would not be economically viable for the key hotspots and,
for the purposes of this high-level appraisal, the design SoP for all scheme
options was limited to 1:25yr (except where noted below). It was assumed that
if lower SoP scheme options were seen to deliver economic advantage, a
higher SoP could be examined at a later appraisal stage.
The outcome of the option appraisal (i.e. preferred scheme options for the four
key hotspots giving a 1:25yr standard of protection) is summarised in the
flowing table.
Table 1 – Preferred Engineering Solutions
Hotspot Preferred Engineering Solution Total
Damages
(£k)
Cost of
Scheme
(£k)
Benefit /
Cost Ratio
A –
Willingdon
Kerb raising of the western kerb on
Millstream Gardens with a Super Gully
located outside the shops on
Farmlands Avenue and a high-level
overflow along the existing footpath
490 - 770 48 10.2 – 16.0
B – Langney No detailed modelling or optioneering undertaken due to complexity of flooding
mechanisms (see Section 3.1.3)
C –
Eastbourne
Town Centre
Divert the 1050mm dia surface water
sewer at Bedfordwell Rd to Eastbourne
Park Lakes. 96 - 256 251 0.4 – 1.0
D – Bourne
Stream
Surface water storage in Motcombe
Park with highway flooding removed
from Star Road by capturing overland
flow on Upperton Road.
30 - 80 33 0.9 – 2.4
Executive Summary
ix
In addition to specific actions to manage issues identified in the intermediate
hotspots and their Critical Drainage Areas, there are a number of generic
actions. These generic actions should be implemented catchment-wide to
ensure the long-term, sustainable management of surface water flooding.
They will reduce the risk of the associated flooding and reducing its impact
when it occurs next. Further details of the preferred specific and generic
actions for intermediate hotspots and their Critical Drainage Areas are outlined
in Chapters 7 and 8 of this report.
To conclude the preferred proposed solution for each detailed hotspot for the
1 in 25 year rainfall event are as detailed in Table 1 above.
Phase 4: Implementation and Review
During this phase the list of actions resulting from the risk assessment and
optioneering work were brought together in the Action Plan comprising of 44
actions formalised under the following types of action:-
Engagement
Investigation
Structural Flood Reduction Measures
Non Structural Flood Reduction Measures
Data
Procedural
This Plan identified the actions required to progress the implementation of the
preferred potential options identified for the hotspots and their Critical
Drainage Areas within the SWMP boundary as set out in Phase 3. Actions
include Southern Water to progress the preferred proposed solution for
surface water storage in Motcombe Park and Eastbourne Borough Council to
lead on the investigation of the ownership and potential maintenance of the
Bourne Stream. Also included In addition to this, the action plan identified
actions that will assist ESCC in delivering its responsibilities as LLFA under
the Flood and Water Management Act. The final version of the Action Plan
was developed with key inputs from the partners. Their input helped with the
refinement of actions and setting the criteria for delivering them, which
included detailing those responsible, the timings and potential costs. An
example of this was Southern Water providing details of their OFWAT funding
programme, so this could be reflected in the cost section of the Action Plan for
the options. During this stage intermediate and short duration actions (typically
between one to three months long) were undertaken to aid the development of
the Plan.
Executive Summary
x
Recommendations
It is recommended to implement the Action Plan detailed in Appendix F of this
SWMP report, and to ensure both the Action Plan and the Strategic
Environmental Assessment are periodically updated according to the latest
guidance and findings of publicised reports as they become available.
The SWMP Partnership should continue beyond the completion of the SWMP
in order to discuss the implementation of the proposed actions. The partners
should hold regular monitoring meeting to consider how the actions are
progressing and what needs to be done to drive the delivery of the Action Plan
forward.
Successful implementation of the Action Plan is likely to require additional
resources and funding from the partners.
.
Glossary
xi
Glossary
Term Definition
Aquifer A source of groundwater comprising water bearing rock, sand or gravel capable of yielding significant quantities of water.
AMP Asset Management Plan
Asset Management Plan
A plan for managing water and sewerage company (WaSC) infrastructure and other assets in order to deliver an agreed standard of service.
AStSWF Areas Susceptible to Surface Water Flooding
BGS British Geological Survey
Catchment Flood Management Plan
A high-level planning strategy through which the Environment Agency works with their key decision makers within a river catchment to identify and agree policies to secure the long-term sustainable management of flood risk.
CFMP Catchment Flood Management Plan
CIRIA Construction Industry Research and Information Association
Civil Contingencies Act
This Act delivers a single framework for civil protection in the UK. As part of the Act, Local Resilience Forums must put into place emergency plans for a range of circumstances including flooding.
CLG Government Department for Communities and Local Government
Climate Change Long term variations in global temperature and weather patterns caused by natural and human actions.
Culvert A channel or pipe that carries water at or below the level of the ground.
Defra Department for Environment, Food and Rural Affairs
DG5 Register A water-company held register of properties which have experienced sewer flooding due to hydraulic overload and which are 'at risk' of sewer flooding more frequently than once in 20 years.
DTM Digital Terrain Model
EA Environment Agency
FCERM National Strategy for Flood and Coastal Erosion Risk Management
FMfSW Flood Map for Surface Water. Environment Agency’s second generation surface water flood risk mapping dataset.
Flood Defence Infrastructure used to protect an area against floods such as floodwalls and embankments; they are designed to a specific standard of protection (design standard).
Flood Risk Area An area determined as having a significant risk of flooding in accordance with guidance published by Defra and WAG.
Flood Risk Regulations
Transposition of the EU Floods Directive into UK law. The EU Floods Directive is a piece of European Community (EC) legislation to specifically address flood risk by prescribing a common framework for its measurement and management.
Floods and Water Management Act
Part of the UK Government's response to Sir Michael Pitt's Report on the Summer 2007 floods, the aim of which is to clarify the legislative framework for managing surface and groundwater flood risk in England.
Fluvial Flooding Flooding resulting from water levels exceeding the bank level of a main river
Glossary
xii
Term Definition
FRR Flood Risk Regulations
IDB Internal Drainage Board
Indicative Flood Risk Areas
Areas determined by the Environment Agency as indicatively having a significant flood risk, based on guidance published by Defra and WAG and the use of certain national datasets. These indicative areas are intended to provide a starting point for the determination of Flood Risk Areas by LLFAs.
IUD Integrated Urban Drainage
LDF Local Development Framework
Lead Local Flood Authority
Local Authority as defined in the FWMA responsible for taking the lead on local flood risk management
LiDAR Light Detection and Ranging – digital topographic data captured by plane flight
LLFA Lead Local Flood Authority
Local Resilience Forum
A multi-agency forum, bringing together all the organisations that have a duty to cooperate under the Civil Contingencies Act, and those involved in responding to emergencies. They prepare emergency plans in a co-ordinated manner.
LPA Local Planning Authority
LRF Local Resilience Forum
Main River A watercourse shown as such on the Main River Map, and for which the Environment Agency have duties and powers
NRD National Receptor Dataset – a collection of risk receptors produced by the Environment Agency
Ordinary Watercourse
All watercourses that are not designated Main River, and which are the responsibility of Local Authorities or, where they exist, IDBs
Partner A person or organisation with responsibility for the decision or actions that need to be taken.
PFRA Preliminary Flood Risk Assessment
Pitt Review Comprehensive independent review of the 2007 summer floods by Sir Michael Pitt, which provided recommendations to improve flood risk management in England.
Pluvial Flooding Flooding generated from a rainfall event and from water flowing over the surface of the ground; often occurs when the soil is saturated and natural drainage channels or artificial drainage systems have insufficient capacity to cope with additional flow.
PPS25 Planning Policy Statement 25: Development and Flood Risk
PA Policy Area
Policy Area One or more Critical Drainage Areas linked together to provide a planning policy tool for the end users. Primarily defined on a hydrological basis, but can also accommodate geological concerns where these significantly influence the implementation of SuDS
Receptor In flood risk management, a receptor is defined as anything that is affected by flooding such as people, property, transport links and habitats.
Glossary
xiii
Term Definition
Resilience Measures
Measures designed to reduce the impact of water that enters property and businesses; could include measures such as raising electrical appliances.
Resistance Measures
Measures designed to keep flood water out of properties and businesses; could include flood guards for example.
Risk In flood risk management, risk is defined as a product of the probability or likelihood of a flood occurring, and the consequence of the flood.
Risk Management Authority
As defined by the Floods and Water Management Act;
(a) the Environment Agency,
(b) a lead local flood authority,
(c) a district council for an area for which there is no unitary authority,
(d) an internal drainage board,
(e) a water company, and
(f) a highway authority.
RMA Risk Management Authority
Sewer Flood Mitigations
Flooding Local Improvement Projects. Non-return valves and pump devices installed to prevent sewage ‘back-surging’ into basements in times of heavy rainfall and allow the property’s sewage to flow properly into the sewer network.
Sewer Flooding Flooding caused by a blockage or overloading in an urban sewerage system.
SFRA Strategic Flood Risk Assessment
Significant Harmful Consequences
Memorable past floods or otherwise registered on a national scale (such as the summer 2007 event) even if only occurring over a relatively small area
SMP Shoreline Management Plan
Stakeholder A person or organisation affected by the problem or solution, or interested in the problem or solution. They can be individuals or organisations, includes the public and communities.
SuDS Sustainable Drainage Systems
Sustainable Drainage Systems
Methods of management practices and control structures that are designed to drain surface water in a more sustainable manner than some conventional techniques.
Surface Water Rainwater (including snow and other precipitation) which is on the surface of the ground (whether or not it is moving), and has not entered a watercourse, drainage system or public sewer.
SWMP Surface Water Management Plan
WAG Welsh Assembly Government
WaSC Water and Sewerage Company
Contents
xiv
Table of Contents
Phase 1: Preparation
15
Quality Management ..................................................................................................................... ii
DOCUMENT INFORMATION ................................................................................................. ii
REVISION HISTORY .............................................................................................................. ii
AUTHORS .............................................................................................................................. ii
REPORT DELIVERY APPROVALS ........................................................................................ ii
PARTNER APPROVAL .......................................................................................................... ii
DISTRIBUTION ...................................................................................................................... ii
RELATED DOCUMENTS ....................................................................................................... ii
Executive Summary ..................................................................................................................... iv
Glossary ....................................................................................................................................... xi
1.0 Introduction ........................................................................................................................ 20
1.1 What is a Surface Water Management Plan? ............................................................. 20
1.2 Background ................................................................................................................ 22
1.3 Objectives ................................................................................................................... 23
1.4 Study Area .................................................................................................................. 24
1.5 Links with Other Plans and Policies ............................................................................ 25
1.5.1 Environment Agency FCERM National Strategy ................................................ 27
1.5.2 Local Strategies ................................................................................................. 28
1.5.3 Preliminary Flood Risk Assessment (PFRA) ...................................................... 28
1.5.4 Strategic Environmental Assessment ................................................................ 29
1.5.5 Strategic Flood Risk Assessments (SFRA) ........................................................ 29
1.5.6 Catchment Flood Management Plan (CFMP) .................................................... 29
1.5.7 Planning Documents .......................................................................................... 30
1.6 Roles & Responsibilities of Partners ........................................................................... 34
1.6.1 East Sussex County Council .............................................................................. 34
1.6.2 The Borough and District Councils ..................................................................... 35
1.6.3 Environment Agency .......................................................................................... 37
1.6.4 Southern Water ................................................................................................. 38
1.7 Powers and Responsibilities of Businesses and Local Households ............................ 38
1.7.1 Utility and Infrastructure Providers ..................................................................... 38
1.7.2 Property Owners and Residents ........................................................................ 38
1.7.3 Riparian Ownership ........................................................................................... 39
1.8 Responsibilities of Parish Councils and Communities ................................................. 39
1.8.1 Parish Council Emergency Self-Help Plans ....................................................... 40
1.9 LLFA ........................................................................................................................... 40
2.0 Phase 1: Preparation ......................................................................................................... 42
2.1 Introduction ................................................................................................................. 42
2.2 Partnership ................................................................................................................. 42
Phase 1: Preparation
16
2.3 Data Collection ........................................................................................................... 43
2.4 Data Review ............................................................................................................... 44
2.4.1 Topography ....................................................................................................... 44
2.4.2 Geology ............................................................................................................. 46
2.4.3 Watercourses .................................................................................................... 47
2.4.4 Sewerage Network & Ownership ....................................................................... 50
2.4.5 Highways Drainage Data ................................................................................... 51
3.0 Phase 2a: Intermediate Risk Assessment ........................................................................ 52
3.1 Introduction ................................................................................................................. 52
3.1.1 Surface Water Flooding from Surface Runoff..................................................... 53
3.1.2 Surface Water Flooding from Surcharged Manholes and Gullies ....................... 54
3.1.3 Flood Risk from Groundwater ............................................................................ 55
3.1.4 Flood Risk from Ordinary Watercourses ............................................................ 58
3.1.5 Flood Risk Interactions with Surface Water ....................................................... 59
3.1.6 Effect of High Fluvial Levels on Surface Water Flooding .................................... 59
3.1.7 Effect of High Tidal Levels on Surface Water Flooding ...................................... 60
3.1.8 Residual Flood risk ............................................................................................ 61
3.1.9 Flooding of Basements ...................................................................................... 61
3.1.10 Land Use ......................................................................................................... 61
3.1.11 Significant Infrastructure .................................................................................. 61
3.1.12 Historic Flooding Incidents ............................................................................... 62
3.1.13 Proposed Future Development ........................................................................ 64
3.1.14 Surface Water Related Schemes ..................................................................... 66
3.2 Source, Pathways and Receptors ............................................................................... 67
3.3 Introduction to Hotspots and Maps ............................................................................. 68
3.3.1 Critical Drainage Areas of hotspots .................................................................... 69
3.4 Selection of Hotspots and Prioritisation ....................................................................... 71
4.0 Phase 2b: Detailed Risk Assessment ............................................................................... 73
4.1 Modelling & Detailed Assessment ............................................................................... 73
4.1.1 Introduction ........................................................................................................ 73
4.1.2 Model Updates .................................................................................................. 74
4.1.3 1D updates ........................................................................................................ 74
4.1.4 Broad scale 2D mesh generation ....................................................................... 74
4.1.5 Rainfall profiles and application to model ........................................................... 75
4.1.6 Model sensitivity and model validation ............................................................... 75
5.0 Phase 2c: Communicate Risk ........................................................................................... 77
5.1 Mapping Outputs ........................................................................................................ 77
5.1.1 Eastbourne Area Flood Depth Map .................................................................... 77
5.1.2 Detailed Hotspot Flood Depth Maps .................................................................. 79
Phase 1: Preparation
17
5.1.3 Detailed Hotspot Flood Hazard Maps ................................................................ 79
5.2 Summary of Flooding Mechanisms for Detailed Hotspots ........................................... 82
5.2.1 Hotspot A – Mill Stream Gardens, Willingdon .................................................... 82
5.2.2 Hotspot B – Langney ......................................................................................... 82
5.2.3 Hotspot C – Firle Road & Arndale Shopping Centre, Eastbourne ...................... 82
5.2.4 Hotspot D – Bourne Stream & Star Inn, Eastbourne .......................................... 82
6.0 Phase 3: Options ............................................................................................................... 84
6.1 Objectives ................................................................................................................... 84
6.2 Measures .................................................................................................................... 85
6.3 Arndale Shopping Centre ............................................................................................ 85
6.4 Eastbourne Lakes ....................................................................................................... 86
6.5 Preferred Options ....................................................................................................... 87
6.6 Options Prioritisation ................................................................................................... 88
6.7 Strategic Environmental Assessment .......................................................................... 88
7.0 Phase 4: Implementation and Review .............................................................................. 90
7.1 Action Plan ................................................................................................................. 90
7.2 Implementation Programme ........................................................................................ 93
7.3 Action Prioritisation ..................................................................................................... 93
7.4 Ongoing Monitoring .................................................................................................... 93
8.0 Conclusion ......................................................................................................................... 95
8.1 Review Objectives ...................................................................................................... 95
8.2 Recommendations ...................................................................................................... 96
8.3 Ownership of the SWMP Action Plan .......................................................................... 96
9.0 References ......................................................................................................................... 97
Phase 1: Preparation
18
Appendices
Appendix A – Data Review ...................................................................................................................... A
Data Review ................................................................................................................................. A1
Historic Flooding Data ................................................................................................................. A2
Planning Document Review ......................................................................................................... A3
Appendix B – Hotspot Area Selection ................................................................................................... B
Intermediate Hotspots Storyboard ............................................................................................... B1
Hotspot Prioritisation .................................................................................................................... B2
Appendix C – Risk Assessment: Technical Details ............................................................................. C
Environment Agency Model Review ............................................................................................ C1
Groundwater Flood Risk Technical Note ..................................................................................... C2
Appendix D – Maps .................................................................................................................................. D
Appendix E – Option Assessment Details............................................................................................. E
Appendix F – Action Plan ........................................................................................................................ F
Action Plan ................................................................................................................................... F1
Action Plan Programme ............................................................................................................... F2
Appendix G – Planner, Emergency Planner & Public Briefing Note .................................................. G
Appendix H –Environmental Assessments ........................................................................................... H
Strategic Environmental Assessment .......................................................................................... H1
Habitats Regulations Assessment Screening ............................................................................. H2
Phase 1: Preparation
19
Figures
Figure ES1 – Figure of Hotspots
Figure ES2 - Extract of Detailed Flood Map
Figure 1-1 - SWMP wheel
Figure 1-2 – Study Area
Figure 1-3 - Delivery of local FCERM
Figure 1-4 - Eastbourne Key Diagram reproduced from the EBC Core Strategy
Figure 2-1 – Phase 1: Preparation Phase of the SWMP Process
Figure 2-2 – Flood Risk Partnership
Figure 2-3 (Map 1 in Appendix D) – LiDAR Data
Figure 2-4 (Map 3 in Appendix D) – Aquifers
Figure 2-5 (Map 4 in Appendix D) - Watercourses
Figure 2-6 (Map 5 in Appendix D) – Lakes
Figure 2-7 (Map 6 in Appendix D) - Southern Water Sewerage Network
Figure 3-1 – Phase 2a: Risk Assessment Phase of SWMP Process
Figure 3-2 – Photo of Surface Runoff Flooding
Figure 3-3 – Photos showing flooding from manholes
Figure 3-4 – Photos showing groundwater flooding
Figure 3-5 (Map 8 in Appendix D) – Groundwater Flood Risk in Low-lying Areas
Figure 3-6 (Map 9 in Appendix D) – Groundwater Flood Risk
Figure 3-7 (Map 10 in Appendix D) – Fluvial Flood Risk
Figure 3-8 (Map 11 in Appendix D) – Historic Surface Water Flooding Incidents
Figure 3-9 (Map 12 in Appendix D) – EBC Core Strategy Area against SWMP Hotspot Areas
Figure 3-10 (Map 13 in Appendix D) – Hotspots in the Eastbourne Area
Figure 3-11 (Map 14 in Appendix D) – Critical Drainage Areas in the Eastbourne Area
Figure 4-1 – Phase 2b: Detailed Risk Assessment Phase of the SWMP Process
Figure 4-2 – InfoWorks 2D Mesh
Figure 5-1 – Phase 2c: Communicate Risk Phase of the SWMP Process
Figure 5-2 – Extract of the Eastbourne Area Flood Depth Map
Figure 5-3 – Extract of Flood Depth Map (Maps 16 & 18 in Appendix D)
Figure 5-4 – Extract of Flood Hazard Map (Maps 17 & 19 in Appendix D)
Figure 6-1 – Phase 3: Options Phase of the SWMP Process
Figure 7-1 – Phase 4: Implementation Phase of the SWMP Process
Many of the figures in the main report are included full size (A3 generally) in Appendix D
Phase 1: Preparation
20
1.0 Introduction
1.1 What is a Surface Water Management Plan?
A Surface Water Management Plan (SWMP) is a plan which outlines the
preferred surface water management strategy in a given location. In this
context, surface water flooding describes flooding from sewers, drains,
groundwater, and runoff from land, small watercourses and ditches that occurs
as a result of heavy rainfall.
This SWMP study has been undertaken by Halcrow on behalf of East Sussex
County Council (ESCC) in partnership with key local partners who are
responsible for surface water management and drainage in the area. The key
local partners are: Eastbourne Borough Council (EBC), Wealden District
Council (WDC), Southern Water and the Environment Agency. The SWMP
Partners have worked together to understand the causes and effects of
surface water flooding and agree the most cost-effective package of measures
for managing surface water flood risk for the long term.
This document will act as the basis for a long-term action plan to manage
surface water and will influence further investigation, future capital investment,
maintenance, public engagement and understanding, spatial planning and
emergency planning.
A Surface Water Management Plan (SWMP) focuses on reducing flood risk for
both existing and future development. This integrated approach allows the
planning of effective surface water management measures, which will
ultimately contribute towards the development of vibrant future sustainable
communities. A SWMP attempts to look at how surface water management
will be delivered over the next 100 years. The SWMP is subject to a review
every five years, so it can reflect local changes and take account of national
developments in the management of surface water flooding.
In this context, the SWMP Defra guidance document (see Section 9 -
References) provides a definition of surface water flooding as:
“flooding from sewers, drains, groundwater, and runoff from land, small watercourses and ditches that occurs as a result of heavy rainfall.”
In more detail, this includes:
Surface water, or pluvial, flooding where runoff from high intensity
rainfall is ponding or flowing over the ground surface before it enters
the underground drainage network or watercourse, or cannot enter it
because the network is full to capacity, thus causing flooding.
Phase 1: Preparation
21
Flooding from groundwater where groundwater is defined as all sub-
surface water in direct contact with the ground or subsoil.
Sewer flooding which occurs when the capacity of underground
systems is exceeded due to heavy rainfall, resulting in flooding inside
and outside buildings. Note that the normal discharge of sewers and
drains through outfalls may be impeded by high water levels in
receiving waters as a result of wet weather or tidal conditions. (Sewer
flooding in ‘dry weather’ resulting from blockage, collapse or pump
failure is excluded.)
Flooding from open-channel and culverted watercourses which receive
most of their flow from the urban area and perform an urban drainage
function.
Overland flows from the urban/rural fringe entering the urban area.
Overland flows resulting from groundwater sources.
The approach to the SWMP is defined in the Defra guidance document (see
Section 9 - References). The four main phases (e.g. Preparation, Risk
Assessment, Options, and Implementation and Review), as well as the
subsets of these and the key tasks, are identified in the SWMP wheel (Figure
1-1).
Figure 1-1
Phase 1: Preparation
22
1.2 Background
Surface water flood risk is poorly understood with relatively few records of
flooding or understanding of the key assets which impact on surface water
flow. Responsibility for managing flood risk is historically unclear, being split
between the local planning authorities, the County Council, the Environment
Agency and water companies. The problem of surface water flood risk
management is given greater urgency because it is expected that heavy
storms will increase in frequency, groundwater levels will show greater
fluctuation and tide-locking will become a greater risk as a result of climate
change.
The extensive, nationwide flooding during summer 2007 led to the Pitt Review
being undertaken (see Section 9 – References). These floods were a
reminder that intense rainfall events can occur anywhere and that
stakeholders need to work in partnership if better understanding of urban flood
risk and preparation for future flood events is to be achieved. Sir Michael Pitt
recommended that local authorities should collate and map the main flood risk
management and drainage assets (over and underground), including a record
of their ownership and condition (Recommendation 16). He also
recommended that SWMPs be adopted, particularly where surface water flood
risk is high (reflected in Recommendation 18).
Informed by the ‘Integrated Urban Drainage (IUD) Pilots’ and the flooding
events which occurred in summer 2007, Defra set out its intention to use
SWMPs as the primary vehicle to manage surface water flood risk in England.
This intention was published in the Future Water Strategy (see Section 9 –
References) and included a specific surface water drainage consultation at the
same time (see Section 9 – References). The SWMP concept is recognised
and promoted within Planning Policy Statement 25 (PPS25) (see Section 9 –
References).
In response to the Pitt Review recommendations and government requests to
upper tier authorities to develop strategic level partnerships with key
stakeholders to develop and integrate flood risk management within their
areas, ESCC established the East Sussex Flood Partnership (ESFP) in
January 2010. The ESFP membership is representative of the Risk
Management Authorities (RMAs) (as defined in the Flood and Water
Management Act) in East Sussex and comprises:
the County Council in its role as Highway, Emergency Planning and
Lead Local Flood Authority;
the Districts and Borough Councils;
Phase 1: Preparation
23
the Environment Agency;
Romney Marsh area Internal Drainage Board; and
Southern Water.
The Flood and Water Management Act 2010 received Royal Assent on 08
April 2010. The Act implements those recommendations made by Sir Michael
Pitt which require primary legislation. The Act takes forward proposals from
the Pitt Review that unitary and county local authorities will lead new local
flood risk management activities as the Lead Local Flood Authority (LLFA).
The LLFA’s responsibility in relation to a SWMP is to lead in its production and
ensure that it is periodically reviewed and updated. The Act also included the
recommendation for local authorities to establish and maintain a record of
assets. The Act proposes that a good SWMP will inform the LFRM (Local
Flood Risk Management) strategy.
East Sussex County Council (ESCC) consulted with its SWMP Partners and
they agreed that a SWMP for Eastbourne area was appropriate and would
result in an understanding of the mechanisms of surface water flooding with
the potential to identify mitigation measures.
The SWMP Action Plan and accompanying study report is seen by ESCC as a
basic tool, which will facilitate the initial strategic and coordinated
management of surface water flood risk within the Eastbourne catchment area
to be undertaken by the RMAs. It will provide a preliminary understanding of
surface water flood risk as well as potential options to mitigate or reduce it.
This tool will assist the main stakeholders in making subsequent sustainable
surface water management decisions that are evidence-based, risk-based,
future-proofed and inclusive of stakeholder participation. This is to become a
‘live’ document with actions being undertaken in the following 5 years before
the next full review of the SWMP.
1.3 Objectives
The objectives of the SWMP are to:
Map all current and potential surface water flood risk areas from any
source and engage the community and stakeholders to share
knowledge
Establish and consolidate partnerships between key drainage
stakeholders to facilitate the sharing and exchange of data, skills,
resources and learning, and closer coordination to utilise cross-
boundary working opportunities
Phase 1: Preparation
24
Determine current and future surface water flooding impacts to help
establish the priorities and compare various mitigation measures
Develop a strategy to inform the provision of drainage for new
development and minimise its impact on the receiving drainage
system.
Develop an implementation plan to show how partners and
stakeholders will work together to finance and implement the preferred
strategy
Develop a framework to periodically review the plan and monitor the
effectiveness of chosen solutions
Identify effective and affordable measures to mitigate surface water
flood risk which achieves the maximum possible benefit at the least
possible cost irrespective of asset owner.
Deliver outputs to enable a real change on the ground rather than just
reports and models, whereby partners and stakeholders take
ownership of their flood risk and commit to delivery and maintenance
of the recommended measures and actions;
1.4 Study Area
The indicative study area for the SWMP has been agreed by the Partners.
The study boundary has purposely included all urban areas fringing
Eastbourne (including Wannock & Polegate) which is all of EBC and part of
WDC.
This boundary however, is indicative, so other local drainage assets or
features outside the study area have been included where appropriate. An
example of this is the Pevensey Outfalls to the east of the study area, which is
the major outfall for the study catchment.
Phase 1: Preparation
25
Figure 1-2 – Study Area
1.5 Links with Other Plans and Policies
Key studies relevant to the Eastbourne Area SWMP are the Eastbourne
Borough, southern Wealden District and Cuckmere Catchment Strategic Flood
Risk Assessment (SFRA) and the Catchment Flood Management Plan
(CFMP) which provide information on areas at risk from all sources of flooding
and can help inform the SWMP on flood risk management decisions. Also the
Shoreline Management Plan for Eastbourne provides a large-scale
assessment of risk to people and development from coastal processes and
identifies the proposed approach to shoreline management (i.e. no works,
maintain, improve).
Specific information from all of these studies currently available for the
Eastbourne area have been fed into the SWMP to ensure the wider picture
has been considered for this study.
Phase 1: Preparation
26
The FWMA must also be considered in the context of the EU Floods Directive,
which was transposed into law by the Flood Risk Regulations 2009 (the
Regulations) on 10 December 2009. The Regulations require three main types
of assessment/plan:
Preliminary Flood Risk Assessments (maps and reports for Sea,
Main River and Reservoirs flooding) to be completed by LLFAs and
the Environment Agency by the 22 December 2011. Flood Risk
Areas, at potentially significant risk of flooding, will also be identified.
Maps and management plans will be developed on the basis of these
flood risk areas.
Flood Hazard Maps and Flood Risk Maps. The Environment
Agency and LLFAs are required to produce Hazard and Risk maps
for Sea, Main River and Reservoir flooding as well as ‘other’ relevant
sources by 22 December 2013.
Flood Risk Management Plans. The Environment Agency and
LLFAs are required to produce Flood Risk Management Plans for
Sea, Main River and Reservoir flooding as well as ‘other’ relevant
sources by 22 December 2015.
Phase 1: Preparation
27
Figure 1-3 illustrates how this SWMP fits into the delivery of local Flood and
Coastal Erosion Risk Management (FCERM), and where the responsibilities
for this lie.
Figure 1-3 - Delivery of local FCERM
1.5.1 Environment Agency FCERM National Strategy
The Flood and Water Management Act 2010 requires the Environment
Agency to develop a national flood and coastal erosion risk management
strategy for England as part of its strategic overview role for flood and coastal
erosion risk management (FCERM) in England. The Environment Agency has
Environment Agency (National Strategy)
Produce a National Strategy for FCERM as part of full strategic
overview role for all FCERM (Main river, ordinary watercourse,
sea water, surface runoff, groundwater, coastal erosion and flood
risk from reservoirs). Support lead local authorities and others in
FCERM by providing information and guidance on fulfilling their
roles.
Defra
Flood and Coastal Erosion Risk Policy
Overview
Planning
Delivery
PFRAs SWMPs CFMPs SMPs
Lead Local Flood Authorities – Local Strategies
surface water, groundwater, ordinary
watercourses
EA – Main River and
Coastal
LLFAs - surface water
and groundwater
Water companies, reservoir owners, highways
authorities
Third Party assets (i.e. riparian owners)
SEAs
SFRAs
Phase 1: Preparation
28
developed this new strategy jointly with Defra to ensure it reflects current
Government policy.
The strategy sets out what needs to be done by all those involved in flood and
coastal erosion risk management to reduce the likelihood of flooding and
coastal erosion, and to manage its consequences. It provides a statutory
framework within which communities, the public sector and other
organisations will work together to manage flood and coastal erosion risks.
The strategy is central to the implementation of the Flood and Water
Management Act 2010, and provides a framework for managing all sources of
flood and coastal erosion risk in a co-ordinated way.
The strategy builds upon existing approaches to FCERM. It further promotes
the use of a wider range of measures to manage risk in a co-ordinated way
that balances the needs of communities, the economy, and the environment.
The aim of the strategy is to give a framework for FCERM that is not
prescriptive but instead encourages innovation and proportionate approaches,
and enables LLFAs to take the necessary local actions.
1.5.2 Local Strategies
The Flood and Water Management Act 2010 (FWMA) requires LLFAs to
produce Local Flood Risk Management Strategies (LFRMS). The Flood Risk
Regulations 2009 also require a Flood Risk Management Plan (FRMP) of
Flood Risk Areas by December 2015. The Action Plan from the SWMP will
feed into the LFRMS to assist in setting the strategic objectives for the whole
County.
1.5.3 Preliminary Flood Risk Assessment (PFRA)
This study focused on surface water flood risk for the whole of East Sussex
County. An assessment on the EA’s NRD (National Receptor Dataset) and
the EA’s FMfSW (Flood Map for Surface Water) dataset undertaken by the
EA, indicated parts of the Eastbourne area were highlighted as being an ‘area
above the flood risk threshold’. This meant a significant enough proportion of
receptors were deemed at risk of surface water flooding. The results of this
assessment concluded there is surface water flood risk within Eastbourne and
South Wealden, but it is not significant on a national or continental scale.
The assessment drew attention to the significant rainfall event in August 2006
which resulted in highway flooding of Terminus Road in the town centre, and
identified that low-lying areas of Eastbourne will be at higher flood risk in the
future due to tide-locking of the sea outfalls.
Phase 1: Preparation
29
1.5.4 Strategic Environmental Assessment
The Strategic Environmental Assessment (SEA) Directive (2001/42/EC) is
implemented in the UK by ‘The Environmental Assessment of Plans and
Programmes Regulations 2004 (Statutory Instrument No.1633)’. Its objective
is ‘to provide for a high level of protection of the environment and to contribute
to the integration of environmental considerations into the preparation and
adoption of plans and programmes with a view to promoting sustainable
development’.
The flood risk management plans required under the Flood Risk Regulations
2009 fall under the scope of the SEA Directive.
As part of the preparation of the SWMP a Strategic Environmental
Assessment was undertaken to consider the environmental effects of the
proposed options. This also included an appropriate assessment in terms of
the Habitats Directive, which was seen as necessary due to the proximity of
the Pevensey Levels. The Levels are located directly downstream from the
study area and are designated as a SSSI and RAMSAR site.
1.5.5 Strategic Flood Risk Assessments (SFRA)
A SFRA provides information on areas at risk from all sources of flooding. The
SFRA should form the basis for flood risk management decisions, and
provides the basis from which to apply the Sequential Test and Exception Test
(as defined in PPS25) in the development allocation and development
management process. The SFRA Level 1 historical data has been reused to
inform this SWMP, however, the Level 2 has not been used since it focuses
purely on tidal flood modelling and no relevant information was identified for
this SWMP.
1.5.6 Catchment Flood Management Plan (CFMP)
The CFMP is a strategic planning tool through which the Environment Agency
works with other key decision-makers within a river catchment to identify and
agree policies for sustainable flood risk management. The study area is
covered in the Cuckmere and Sussex Havens CFMP – Sub Catchment 6 -
Polegate/Eastbourne and Willingdon/Pevensey
This CFPMP states that the Polegate area is likely to see significant urban
development over the next 10-15 years. Together with the effects of climate
change, this development is likely to increase the level of flood risk above
existing levels. The plan also states that surface water and groundwater
flooding are a problem in Willingdon; this is caused in part by runoff from the
South Downs and by long lengths of culverted watercourses, which are of
insufficient size and in poor condition.
Phase 1: Preparation
30
The EA’s preferred policy for this sub-catchment is that, although current flood
risk is low, it is expected to increase in the future, and therefore there may be
a need to take further actions to keep pace with climate change.
Their key messages are that existing flood risk in this sub-catchment is from a
combination of fluvial, surface water and urban drainage problems due mainly
to constricted culverts and channel blockages. The current drainage system is
at full capacity. Any increase in runoff is likely to lead to more frequent and
deeper flooding. The consequences of increased flooding (due to climate
change, rises in sea level or changes in land use) would be all the more acute
in low-lying areas where extra effort will be necessary to manage this risk.
1.5.7 Planning Documents
In order to understand the context, and the potential interaction between
various sectors such as the built environment and transport infrastructure, we
conducted a review of selected national policies, and local planning policies
(mostly under production) to inform the ESCC SWMP action plan. The policy
documents reviewed were:
Flood and Water Management Act 2010 (amended 2011)
Eastbourne Borough Council Core Strategy (ongoing)
Eastbourne Town Centre Area Action Plan (ongoing, at Submission Stage)
Eastbourne County Council Local Transport Plan-3 (2011-2026)
Eastbourne Park Area Action Plan Supplementary Planning Document (ongoing)
Wealden Borough Council Core Strategy (ongoing)
A detailed review of various planning documents relating to Eastbourne
Borough Council, Wealden District Council and the East Sussex County
Council is contained in Appendix A. The key messages from each policy
document relevant to the present study are shown in Table 1-1 below.
Policy/ Plan Key pointers/ Message for the SWMP (in italics)
Eastbourne
Borough Council
Core Strategy –
Eastbourne Plan
The document lists policies on various development aspects. Of
interest will be the proposals, such as new/ intensification of
development in the Neighbourhood areas- as most of these areas are
contained within either an Intermediate or Detailed surface water
flooding hotspot identified through this ECC SWMP study modelling
exercise.
Map 1 combines the proposed EBC Core Strategy Areas for Change
and Development, with our modelled hotspot areas at risk for surface
Phase 1: Preparation
31
Policy/ Plan Key pointers/ Message for the SWMP (in italics)
water led flooding. This map should be used to interpret potential Core
Strategy Key areas at risk of flooding. The identified risk may be
exacerbated if the Core Strategy Areas do not sufficiently incorporate
surface water runoff attenuation methods. For example the Detailed
Hotspot areas within the town centre have been identified as Key
Areas of change, and for residential and retail land-use intensification.
Refer to Appendix A for the proposed Neighbourhood Core Strategy
Areas, and whether these areas lie within the hotspots.
This exercise attempts to highlight the critical need for a combined
approach between the planners and the surface water management
team, at an early stage of an area development. The suggested
planning approach goes beyond S106 contributions, and the need to
incorporate effective methods within key local development
documents.
Eastbourne Town
Centre AAP
The AAP sets out vision and series of objectives to improve the retail
offering; the public realm; accessibility; maintain the cultural heritage;
and develop the area for mixed use. The document identifies 7
character areas within the town centre for potential development, and
identifies 5 Development Opportunity sites, most of which also fall
within the SWMP hotspots. The five sites are:
i) Land at the junction of Terminus Road and Ashford Road.
ii) Land adjoining the railway station and the Enterprise Centre
iii) Land between Upperton Road and Southfields Road
iv) Land at the south-eastern end of the Arndale Centre
v) Land at the former Coop on Terminus Road
It is worth noting that most of the Development Sites proposed in the
area are located in the Surface Water Flooding Hotspots, but even as
a generic point, the AAP document does not address any risk relating
to surface water runoff and this aspect is not included as part of the
‘key components for development’ section of the AAP document.
Eastbourne Park
AAP SPD
The document, under production, presents a vision for the wet
floodplain area up to the year 2026. To be adopted as a
Supplementary Planning Document, that will guide future development
in the area from a planning perspective, it emphasises the need to
maintain and/ or enhance the ecological function of the Park, as well
as expand the flood water storage capacity at Shinewater, West
Langney, Broadwater and Southbourne areas of the Park.
ESCC LTP3 The plan, a mandatory obligation for the County Council, outlines the
Vision, Objectives and Strategy for maintaining and enhancing the
Phase 1: Preparation
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Policy/ Plan Key pointers/ Message for the SWMP (in italics)
transport infrastructure and the transport services within the County.
The Sustainability appraisal of the Plan recommends the following
which relate to surface water runoff from road surfaces:
· Consider options to alleviate highways runoff that may pollute local
water bodies
· Need for the SWMP to take transport infrastructure related surface
water runoff into consideration
The LTP document stresses the need to consider transport
infrastructure as an integral component in surface water management,
in addition to the built-up area from buildings. It is important to include
car park surfaces and similar public space areas relating to transport
infrastructure (e.g., bus stands). Joint working between the surface
water management team and the LTP team is recommended.
Wealden District
Core Strategy
Similar to the Eastbourne Borough Core Strategy, this document
discusses development proposals and the policies that will direct
growth in the next 15 years.
Only part of this District area is included in the Eastbourne Area
SWMP Study area boundary, nevertheless it is worth noting that
substantial residential development is planned for the area- in various
phases, both as intensification and as urban extensions. The impact of
these built areas on the risk mapping may be worth considering for the
SWMP study.
Table 1-1 – Key messages from planning documents
Figure 1-4 overleaf is reproduced from the Eastbourne Core Strategy
document to indicate spatial proposals.
Phase 1: Preparation
33
Figure 1-4 - Eastbourne Key Diagram reproduced from the EBC Core
Strategy
Phase 1: Preparation
34
1.6 Roles & Responsibilities of Partners
All Risk Management Authorities must cooperate in the exercise of their flood
and coastal erosion risk management functions.
Each Risk Management Authority has its own distinctive roles and
responsibilities. We all recognise the benefits of working together to achieve
our common interests and to comply with the relevant acts.
1.6.1 East Sussex County Council
East Sussex County Council is the Lead Local Flood Authority for East Sussex
and has a strategic role in overseeing the management of local flood risk
associated with surface water runoff, ordinary watercourses such as streams,
ditches and groundwater.
It is also under a duty to ensure that the relevant duties under the Flood and
Water Management Act are discharged, this includes (subject to
commencement):
Meeting the requirements of the flood risk regulations,
Developing and applying a local flood risk management strategy
Reporting on local flood incidents where appropriate
Maintaining a register of assets likely to have a significant effect on flood risk
The regulation of SuDS applications via the Drainage Approval Body (anticipated October 2012)
Under the Land Drainage Act (1991) the County Council will have powers of
consenting and enforcement in respect of minor watercourses (as of 6 April
2012)
The County Council has a significant drainage role in the exercise of its duties
as a Highway Authority. Under the Highways Act (1980), the County Council is
under a duty to ensure that highway drainage systems are clear and that
blockages on the highway are cleared where reasonably practicable.
ESCC plays a leading role in emergency planning under the Civil
Contingencies Act. When a serious or wide-spread flooding incident occurs in
Sussex, ESCC’s Emergency Planning Team together with other emergency
responders from the Sussex Resilience Forum (SRF) undertakes a range of
actions to support affected communities and help limit the impacts of the flood.
In order to do this effectively and in a co-ordinated way the team produces and
contributes to multi-agency plans for responding to flooding events, including
the SRF Multi-Agency Flood Plan covering all locations in Sussex, and site-
Phase 1: Preparation
35
specific plans for Uckfield, Lewes, Seaford & Newhaven, Bulverhythe, Rye
Bay, and Pevensey Bay, Normans Bay and Eastbourne.
1.6.2 The Borough and District Councils
The Borough and District Councils are community leaders and posses a
detailed understanding of the nature of flood risk that communities face in their
jurisdiction. They are also identified as having responsibilities under the
following:
Flood and Water Management Act 2010;
Land Drainage Act 1991;
The Planning Acts ;
Coast Protection Act (1949); and
Emergency planning.
i. Responsibilities under the Flood and Water Management Act
Though the Flood and Water Management Act 2010 provides the LLFA with
powers to undertake works for the management of flood risk from surface
runoff and groundwater, powers to undertake works on ordinary
watercourses remain with either district or unitary authorities, or internal
drainage boards, but all works must be consistent with the Local Strategy.
These powers are discretionary and the Councils’ policy is generally to
exercise them where property is at risk of flooding. The District and Borough
Councils may also give guidance and assistance on flooding issues to
residents. Under planning legislation, Borough and District Councils operate
their development planning and control functions, having due regard to
PPS25. As well as the statutory powers mentioned above, some
Boroughs/Districts have kept records of flood events and carried out both
maintenance and new works within their district. The extent of these activities
varies considerably between Councils, due to the variance of technical
resource and capacity of each Council.
Specifically, District and Borough Councils also have the following new
responsibilities:
Power to designate structures and features that affect flooding or coastal erosion;
Duty to act consistently with local and national strategies;
Phase 1: Preparation
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ii. Responsibilities under the Land Drainage Act
From the 6th of April 2012, District and Borough Councils have no
responsibilities (except when it is a landowner) under the Land Drainage Act.
They do however have a number of permissive powers, which they can
employ in support of the Lead Local Flood Authority. These include:
Permissive powers to maintain or improve existing works or to construct new works in order to help prevent, mitigate or remedy flood damage; and
Advise the LLFA on land drainage consent applications.
iii. Responsibilities as a Planning Authority
District and Borough Councils’ planning function affects Flood Risk
Management in three key ways:
Considering flooding concerns in developing local plans
Working with the SuDS Approval Body in ensuring that planning applications and drainage applications are complementary
Considering flood risk assessments submitted in support of applications on which the Environment Agency do not require to be consulted
iv. Responsibilities as a coastal erosion risk management authority
Broadly, the Coast Protection Act 1949 provides for coast protection
authorities with general powers to execute coast protection work and provides
authorities with powers to authorise others to undertake such work.
The largely permissive coast protection powers have to be considered
alongside a range of pre-existing, and continuing, common law and local
statutory/non-statutory duties including:
Planning shoreline management activities with input from the Environment Agency.
Delivery of coastal erosion risk management activities including maintenance and repair work.
Working alongside the Environment Agency to develop and maintain coastal flood and erosion risk information.
Maintain a register of assets and other features that help to manage coastal risks.
Implement, manage, maintain and monitor shoreline management plans to understand and manage coastal flood and erosion risks.
Phase 1: Preparation
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Assist communities in planning for the future and taking appropriate steps to adapt to changing flood and coastal erosion risks.
v. Responsibilities as an Emergency Planning authority
District and Borough Councils are ‘Category 1’ responders to emergencies
and members of the East Sussex Resilience Forum. This means that they
have duties to:
undertake risk assessments;
manage business continuity;
carry out emergency planning;
share information and cooperate with other responders; and
warn and advise the public during times of emergency.
Furthermore, in the event of an emergency, district and borough councils have
additional roles and responsibilities regarding coordinating, supporting and
managing emergency support during and after the flooding event.
1.6.3 Environment Agency
The Environment Agency has a specific role in providing strategic overview on
flood risk matters and advice and guidance to the Lead Local Flood
Authorities. The EA is a non departmental public body of Defra and is under a
duty to prepare the national flood risk strategy and it retains responsibility for
managing coastal and main river flooding. It is also the competent body
responsible for implementing the water framework directive in England and
Wales by the development of river basin management plans.
The National Strategy identifies the following strategic actions for the
Environment Agency:
Use strategic plans like the Catchment Flood Management Plan and the Shoreline Management Plan to set the direction for Flood Risk Management;
Support the creation of Flood Risk Regulations by collating and reviewing the assessments, plans and maps that Lead local flood authorities produce;
Providing the data, information and tools to inform government policy and aid risk management authorities in delivering their responsibilities;
Support collaboration, knowledge-building and sharing of good practice including provision of capacity-building schemes such as trainee schemes and officer training;
Phase 1: Preparation
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Manage the Regional Flood and Coastal Committees (RFCCs) and support their decisions in allocating funding for flood defence and flood resilience schemes;
Report and monitor on flood and coastal erosion risk management;
Provide grants to risk management authorities to support the implementation of their incidental flooding or environmental powers;
The Environment Agency maintains a number of FRM assets (tidal, main
fluvial and ordinary watercourses) and acts as the Internal Drainage Board for
three Internal Drainage Districts in the County: the Lower Ouse, the Cuckmere
and the Pevensey levels.
1.6.4 Southern Water
Southern Water is statutory water supply and sewerage undertaker and
supplies freshwater and collects and treats wastewater in East Sussex. As
sewerage undertaker it is responsible for public combined and surface water
sewers which are essential to effective flood risk management in the county. It
is a public company regulated by the Environment Agency and, financially by
OFWAT.
1.7 Powers and Responsibilities of Businesses and Local Households
1.7.1 Utility and Infrastructure Providers
Utility and infrastructure providers such as Network Rail, energy companies
and telecommunication companies are not risk management authorities.
However, they have a crucial role to play in flood risk management as their
assets can be important consideration in planning for flooding. Moreover they
may have assets such as culverts which it is important to share with flood risk
management authorities. They already maintain plans for the future
development and maintenance of the services they provide and it is important
that they factor in flood risk management issues into this planning process.
This will ensure that their assets and systems are resilient to flood and coastal
risks and that the required level of service can be maintained in the event of
an incident. Utility and infrastructure providers may wish to invest time and
resources into developing and delivering the local flood risk management
strategy, to realise the significant benefits for them and their customers that
follow from flood risks being effectively managed.
1.7.2 Property Owners and Residents
It is the responsibility of householders and businesses to look after their
property, including protecting it from flooding. While in some circumstances
other organisations or property owners may be liable due to neglect of their
own responsibilities, there will be many occasions when flooding occurs
despite all parties meeting their responsibilities. Consequently it is important
Phase 1: Preparation
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that householders whose homes are at risk of flooding, take steps to ensure
that their house is protected.
These steps include:
Check whether their household is at risk from flooding from the river,
coast or local flood sources;
Ensure that preparations have been made in the event of a flood;
Take measures to ensure that their house is protected from flooding,
either through permanent measures such as sealants in the wall or
temporary measures such as floodsax or flood guards;
Take measures to make sure the house is resilient to flooding so that if
it does occur it does not cause too much damage;
Where possible take out flood insurance.
1.7.3 Riparian Ownership
Landowners, householders or businesses whose property is adjacent to a
river or stream or ditch are likely to be riparian owners with responsibilities.
Riparian owners have a right to protect their property from flooding and
erosion but in most cases will need to discuss the method of doing this with
the Environment Agency. They also have responsibility for maintaining the bed
and banks of the watercourse and ensuring there is no obstruction, diversion
or pollution to the flow of the watercourse. Full details can be found in the EA
document ‘Living on the edge’.
1.8 Responsibilities of Parish Councils and Communities
Flooding events can affect whole communities with households which do not
suffer from internal flooding still potentially being trapped as roads are blocked
or having to help support and provide shelter to their neighbours who have
suffered from flooding.
District and County Councillors have a key role in helping the Parish Councils
and communities understand their role and ensuring affected communities are
properly represented in discussions about local activities.
Communities know better than anyone the level of flood risk that they face and
can make important contributions to helping manage the levels of flood risk.
Parish councils can be the best way of letting residents know that they should
be aware of flood risk and to check with East Sussex County Council and the
Phase 1: Preparation
40
Environment Agency as to the extent of the risk. Finding out through the
community has the advantage of being provided the information in context so
as to know the extent to which residents should be concerned.
1.8.1 Parish Council Emergency Self-Help Plans
If a parish is at risk from flooding it is advisable to create an Emergency Plan
which details who can be contacted to lead and assist in an emergency, what
equipment is available and where can be used as emergency accommodation.
1.9 LLFA
As the designated LLFA, East Sussex County Council is responsible for
leading local flood risk management across the County. Given this is a new
duty, much of the local knowledge and technical expertise necessary for the
Council to fulfil its duties as LLFA currently lies with partner organisations. It is
therefore crucial that they continue the good partnership building processes
they have already started to ensure effective and consistent management of
local flood risk throughout the County.
Aside from forging partnerships, coordinating and leading on local flood
management, there are a number of other responsibilities and powers that
have arisen for LLFAs from the Flood & Water Management Act and the Flood
Risk Regulations. This report provides information and evidence to assist the
LLFA in undertaking their responsibilities, and exercising their powers,
although it should be noted that at the time of writing some enabling sections
of the Act had yet to commence. The key legislative responsibilities and
powers invested in LLFAs are:
Investigating flood incidents – LLFAs have a duty to investigate and
record details of local flood events within their area which exceed the
threshold set by the LLFA.
Asset Register – LLFAs also have a duty to maintain a register of
structures or features which are considered to have an effect on local flood
risk, including details on ownership and condition as a minimum. The
register must be readily available for inspection. The Secretary of State
will be able to make regulations about the content of the register and
records, and these details will be made available to the public.
Drainage Approval Body (yet to be commenced) – The Flood and
Water Management Act establishes an Approval Body at County or Unitary
authority level (in this case East Sussex County Council) to ensure
national standards of sustainable drainage are enforced. Developers will
be required to gain approval for their proposed drainage systems before
they can begin construction. The SuDS Approving Body will then be
Phase 1: Preparation
41
responsible for adopting and maintaining SuDS which serve more than
one property (other than on public roads which are the responsibility of the
Highways Agency (trunk roads) and the Highway Authority (local
network)).
Local Strategy for Flood Risk Management – LLFAs are required to
develop, maintain, apply and monitor a local strategy for flood risk
management in their areas. The local strategy will build upon information
such as national risk assessments and will use consistent risk based
approaches across different local authority areas and catchments.
Designation powers – LLFAs, as well as the Environment Agency, have
powers to designate structures and features that affect flooding or coastal
erosion in order to safeguard assets that are relied upon for flood or
coastal erosion risk management. This includes assignment of features on
private land with a duty to inform the land owner and having enforcement
powers for the unauthorised alteration of privately owned designated
features.
Works powers – LLFAs have powers to undertake works to manage local
flood risk, consistent with the local flood risk management strategy for the
area.
Transfer of powers – In April 2012 there will be a transfer of powers 23
(regulatory role for the consenting regime of ordinary watercourses) and
25 (enforcement powers to be removed from the district and boroughs to
the county council).
The Flood and Water Management Act 2010 (FWMA) presents a number of
challenges for policy makers and the flood and coastal risk management
authorities identified to co-ordinate and deliver local flood risk management
(surface water, groundwater and flooding from ordinary watercourses). ‘Upper
Tier’ local authorities (Lead Local Flood Authorities – LLFA) have been
empowered to manage local flood risk through new responsibilities for flooding
from surface and groundwater.
The FWMA reinforces the need to manage flooding holistically and in a
sustainable manner. This has grown from the key principles within Making
Space for Water (Defra, 2005) and was further reinforced by the summer 2007
floods and the Pitt Review (Cabinet Office, 2008). It implements several key
recommendations of Sir Michael Pitt’s Review of the summer 2007 floods,
while also protecting water supplies to consumers and protecting community
groups from excessive charges for surface water drainage.
Phase 1: Preparation
42
2.0 Phase 1: Preparation
Figure 2-1 – Phase 1: Preparation Phase of the SWMP Process
2.1 Introduction
This Phase focuses on establishing a partnership for the SWMP, data
collection and determining appropriate objectives for this study. The Partners
were asked to consider the need for an Eastbourne Area SWMP.
2.2 Partnership
For the purposes of the SWMP study a partnership was established
comprising Eastbourne Borough Council (EBC), Wealden District Council
(WDC), the Environment Agency and Southern Water. Figure 2-2 shows the
organisations forming the SWMP partnership.
East Sussex County Council (ESCC) consulted with its SWMP Partners and
they agreed that a SWMP for the Eastbourne area was appropriate and would
Phase 1: Preparation
43
result in an understanding of the mechanisms of surface water flooding with
the potential to identify mitigation measures.
Figure 2-2 – Flood Risk Partnership
2.3 Data Collection
A list of potential data sources was issued to the Partners. With their input this
list has been developed to reflect what useful data was available for the
SWMP. As data was received, it was logged into an Incoming Data Register,
with date of receipt, contact name and licence information details. A quality
scoring of the data was determined in line with the SWMP Defra guidance
document (see Section 9 - References) as follows:
1. No known deficiencies – not possible to improve in the near future.
2. Known deficiencies – best replaced as soon as new data is available.
3. Assumed – based on experience and judgement.
4. Grossly assumed – an educated guess.
The register of data received for the SWMP Scoping Study is presented in
Appendix A, with key datasets summarised in Table 2-1 overleaf:
Phase 1: Preparation
44
Data Source
Eastbourne historic flooding incidents and hotspot areas EBC
Wealden land drainage database and hotspot areas WDC
Environment Agency Geostore data – main rivers, drainage paths, historic flood map, national receptors database, indicative surface water mapping
ESCC
Eastbourne Park Compensatory Flood Storage Scheme Report EBC
LiDAR EA
SO753 Polegate Willingdon 2007 model EA
Southern Water Sewer System GIS, Maps, and historical incidents Southern Water
EBC- Eastbourne Park and Flooding Report EBC
Southern Water sewer model & recorded flooding locations Southern Water
Table 2-1: Summary of key datasets received
There seems to be no other significantly important datasets which are
outstanding from the SWMP data collection process.
2.4 Data Review
2.4.1 Topography
LiDAR (Light Detection And Ranging) data of 2m resolution was downloaded
from the Environment Agency Geomatics website and covered the entire
study area. Both the ‘raw’ unfiltered LiDAR and filtered LiDAR (where, for
example, buildings and trees have been stripped from the raw LiDAR) were
obtained. The filtered LiDAR was merged to create the initial digital terrain
model (DTM) shown in Figure 2-3 and this gives an indication of the ‘bare
earth’ topography.
Phase 1: Preparation
45
Figure 2-3 (Map 1 in Appendix D) – LiDAR Data
The LiDAR data shows that a large proportion of the study area is low lying
with ground levels of between 1 to 3m AOD. This corresponds mainly to the
fields and parklands along the downstream reaches of the main rivers through
the study area. However, the eastern, coastal part of Eastbourne town is also
quite low-lying, with ground levels of between 2 to 5m AOD, although there
are occasional ‘islands’ of high ground such as at Roselands, which is
between 8 to 9m AOD. Around the west and north of the study area, the land
starts to rise, reaching approximately 35m AOD at Stone Cross to the north,
and over 100m AOD along the South Downs hills to the west. At Warren Hill
ground levels reach 157m AOD, at Downside they reach between 170 to
200m AOD, and at Willingdon 194m AOD.
Phase 1: Preparation
46
2.4.2 Geology
An overview of the study area geology was obtained from the British
Geological Survey Solid and Drift Geology maps. The maps were available in
hardcopy and as GIS layers provided by the British Geological Survey.
The maps show that the SWMP study area overlies a complex geology. The
bedrock geology is a series of rock layers, with the chalk hills of the South
Downs, Gault (mudstone, sandstone and limestone) through much of the
centre of the study area, then a band of Lower Greensand, and finally Weald
Clay underlying the north east, apart from a little area which protrudes over
the Tunbridge Sands belt to the north. Overlying deposits of Head (probably
old river deposits) occur in the valleys of the South Downs hills, while the low-
lying area in the centre of the SWMP study area is filled with Alluvium, apart
from some outcroppings of Gault and Lower Greensand. Along the shorefront,
there is a narrow stretch of Upper Greensand in front of the south part of
Eastbourne town, whereas, to the north, in front of the Alluvium, is a wider
band of Storm Gravel Beach Deposits.
Map 2 in Appendix D shows the bedrock and superficial geology of the
SWMP area, based on the GIS data provided by the British Geological
Survey. The permeability of the geology is summarised in Figure 2-4 by
identifying rock types as major or minor aquifers; very low permeability
geology (such as the clays) is not marked.
Phase 1: Preparation
47
Figure 2-4 (Map 3 in Appendix D) – Aquifers
Chalk and Greensand are generally high permeability rock which, when
overlaid with the Environment Agency’s Groundwater Vulnerability maps,
correspond closely to the location of major aquifers. The Alluvium and Storm
Gravel Beach Deposits are also permeable and are classified as a minor,
more local aquifer.
2.4.3 Watercourses
Under Section 93 of the Water Resources Act 1991, principal rivers or locally
significant watercourses in England and Wales were classified as main rivers
and are the responsibility of the Environment Agency. The Environment
Agency also administers the Pevensey Levels Internal Drainage Board (IDB)
which covers the ordinary watercourses in the Pevensey Levels area. It is
assumed that the remaining ordinary watercourses are normally the
responsibility of riparian owners. The responsibility for Critical Ordinary
Watercourses transferred from local authorities to the Environment Agency in
2003.
A GIS layer of main rivers is available from the Environment Agency Geostore
website; this has been combined with ordinary watercourses taken from OS
Phase 1: Preparation
48
Mastermap. The principal water features of the SWMP study area are shown
in Figure 2-5.
Figure 2-5 (Map 4 in Appendix D) - Watercourses
The study area surrounds the Willingdon Levels marshes where a number of
ordinary watercourses and drainage ditches are featured. Through the town
the drainage ditches are predominantly culverted, but on reaching the central
Willingdon Levels area they become open watercourses and lakes within a
greenfield area known as Eastbourne Park.
The drainage system is gravity operated, apart from those ordinary
watercourses draining to Lottbridge pumping station. The system currently
suffers from tide-locking about 50% of the time, where water cannot discharge
into the sea due to the outfalls being below the high tide water level. During
winter, there are times when the rate of discharge is lower than the rate at
which water drains into the system from the catchment and hence the lakes
and pasturelands beside the streams act as flood storage.
Phase 1: Preparation
49
The Eastbourne Park area is located in the heart of the Borough, and contains
several lakes that form a compensatory flood storage scheme. It was
developed to provide a mechanism to compensate for the impact on surface
water drainage of any new development in Eastbourne. The scheme was
constructed in the early 1990s to provide protection up to the 1 in 100 year
rainfall event.
The lakes comprise Broadwater, Shinewater, Southbourne and West Langney
which interact with either ordinary watercourses or EA Main River. Figure 2-6
shows the location of all lakes constructed as part of the flood storage
scheme.
Figure 2-6 (Map 5 in Appendix D) – Lakes
Phase 1: Preparation
50
2.4.4 Sewerage Network & Ownership
Southern Water has provided details of their sewerage network system which
is shown in Figure 2-7.
Figure 2-7 (Map 6 in Appendix D) - Southern Water Sewerage Network
The majority of Eastbourne and south Wealden comprise a combined
sewerage system with some local separately sewered areas predominantly in
areas which were developed over the last 30 years.
The majority of the sewers are owned by Southern Water, however, there are
areas within the study boundary where the picture is less clear:-
a) The Bourne Stream, running along the A259 which marks out the historical
path of the Bourne Stream. The majority of the length of this watercourse
is of unclear status and this needs to be resolved by the partnership.
Phase 1: Preparation
51
b) Pashley Road / Cherry Gardens Road
c) Private systems. Many private sewers and laterals outside of the property
curtilage which connect to an existing public sewer were transferred to
Southern Water on 1st October, 2011. Unfortunately, however, these are
largely unmapped.
d) North Polegate
2.4.5 Highways Drainage Data
Highway drain gully data was obtained from the Highway Authority (East
Sussex County Council & local network). Overlaying this with the Southern
Water sewer network map showed that most of the gullies were located in
roads with surface or combined sewers, so it is currently assumed they
connect directly into the sewer system. Highways data supplied thus far are
shown as Map 7 in Appendix D.
Highways Agency data indicated there are some key flood risk areas along the
A27, the most significant being the junction of the A27 and A2270 (Eastbourne
Road).
Phase 1 of the action plan process formed a strong working relationship
between Eastbourne Borough Council, Wealden District Council, Southern
Water and the Environment Agency. Through this partnership a
comprehensive data collection exercise was undertaken which is discussed in
detail in Section 2.3. Objectives were agreed with the partners during an
inception meeting which can be found in Section 1.3.
Phase 2a: Intermediate Risk Assessment
52
3.0 Phase 2a: Intermediate Risk Assessment
Figure 3-1 – Phase 2a: Risk Assessment Phase of SWMP Process
3.1 Introduction
This phase focuses on the source-pathway-receptor model for giving a broad
overview to surface water flood risk in Eastbourne and South Wealden.
Phase 2a: Intermediate Risk Assessment
53
3.1.1 Surface Water Flooding from Surface Runoff
(Source: BBC Website, Eastbourne flooding 2006)
Figure 3-2 – Photo of Surface Runoff Flooding
In urban areas, surface water flooding occurs when intense rainfall is unable
to soak into the ground and when road gullies and/or pipes have insufficient
capacity to allow all surface water to enter the drainage network.
In these conditions surface water builds up locally if the ground terrain is flat,
or travels following prevailing terrain gradients. Surface water flooding is likely
to occur at locations where surface water flow paths converge, at local dips in
the ground, dry valleys and/or at overland obstructions.
Runoff is the main mechanism of surface water flooding but can be
exacerbated by the lack of maintenance of drainage infrastructure.
The impact of urbanisation (i.e. the expansion of impermeable areas (roof
areas and paved areas)), has resulted in increased runoff volumes and peak
flows reaching drainage networks. This increase has, in many cases,
exceeded the available capacity of the drainage networks (which were not
necessarily designed for extreme storm events) and has severely increased
the likelihood of surface water flooding.
Current estimates in accordance with UKCIP09 (see Section 9 - References)
indicate that climate change could increase peak rainfall intensities by up to
30% by 2115. It has been found as part of this study that large scale surface
water flood reduction schemes are not economic for the Eastbourne
catchment and therefore local based schemes were progressed. These local
schemes generally have a short design life and therefore climate-change
future-proofing of them is not necessary. The design horizons of the schemes
proposed in this report are discussed in greater detail in Section 6.1.
Phase 2a: Intermediate Risk Assessment
54
3.1.2 Surface Water Flooding from Surcharged Manholes and Gullies
The photo in Figure 3-3 show a typical situation where the water pressures in
a pipe network system are high enough to remove manhole covers.
(Source: EBC, Star Inn flooding)
Figure 3-3 – Photo showing flooding from manholes
In addition to surface water flood risk from surface runoff (see Section 3.1.1),
surface water flooding can also occur as a result of surface water inundating
foul or combined sewers causing sewer flooding from manholes and gullies.
This is the result of extreme storm events where the overwhelmed sewerage
system surcharges manholes and gullies in the critical low-spots within the
catchment, as shown in Figure 3-3.
Flooding out of manholes and gullies can originate from surface water drains
and sewers, combined sewers, or foul sewers. These are defined below:
a) Surface water drains and sewers carry only surface water originating from
roofs, pavements and roads, not foul water.
b) Foul sewers do not normally carry surface water. In some circumstances,
however, surface water runoff is able to enter the foul system, which can
result in overflowing of manholes and flooding of property.
c) Combined sewers carry both foul water and surface water originating from
roofs, pavements and roads.
Figure 2-7 in Section 2.4.4 shows the distribution between surface water
drains, foul sewers and combined sewers in the Eastbourne area.
Sewer flooding appears to be the highest risk for the older networks of sewers
in the town centre, which are designated as ‘foul’. However, the absence of
Phase 2a: Intermediate Risk Assessment
55
surface water sewers in the study areas and local knowledge confirm that they
are actually acting as combined sewers and were designed as such.
Inundation as well as direct surface water connection were significant factors
in combined sewer overloading during the 2006 storm. The situation is likely to
deteriorate further under the effects of climate change, where rainfall intensity
is predicted to increase by 30% in the next 100 years.
The same effects of climate change and future development proposals are
applicable to this form of flood risk (from overflowing manholes and gullies) as
for surface water flooding from surface runoff. Sewer flooding arising from
surface water inundation can provide additional drivers (social, environmental
and economic) for the improvement of surface water systems.
3.1.3 Flood Risk from Groundwater
Figure 3-4 – Photos showing groundwater flooding
Groundwater flooding occurs when the water table rises above the ground
surface. This is normally the result of persistent rainfall over a long period.
The water table is the level at which the ground changes from saturated
(where the soil contains as much water as it can hold) to unsaturated (where
the soil has some spare capacity). Rainfall soaks into the soil and, if
sufficiently persistent, eventually fills it up so that it cannot hold any more
water; in this case, distinguishing between whether it is surface water flooding
because it cannot infiltrate or groundwater flooding because the water table
has reached the surface becomes difficult to discern.
Groundwater flooding does not necessarily occur after a local rainfall event;
rainfall falling further away may cause the groundwater to rise over a much
wider area, e.g. due to an extensive aquifer, and thus cause groundwater
flooding at other locations. Again, if the ground is already saturated and
causing groundwater flooding, then any further local rainfall will be unable to
infiltrate and result in surface water flooding.
Phase 2a: Intermediate Risk Assessment
56
High groundwater levels can also cause springs to occur, where water
travelling through permeable rocks emerges from a hillside, or where it
reaches a more impermeable rock and is forced to the surface. This is the
case on the South Downs to the west of Eastbourne.
The water table in the low lying areas of Eastbourne close to the sea is
dominated by tidal levels. Consequently, the water table around Eastbourne
centre is an average of 0.14m AOD (which is the mean sea level at this
location). Figure 3-5 gives an indication of the areas in Eastbourne where
existing ground levels are less than 0.14m AOD.
Figure 3-5 (Map 8 in Appendix D) – Groundwater Flood Risk in Low-lying
Areas
Phase 2a: Intermediate Risk Assessment
57
Figure 3-6 below shows the historic flooding locations as well as the likely
areas which will experience groundwater flooding.
Figure 3-6 (Map 9 in Appendix D) – Groundwater Flood Risk
The cross-section line on the above figure relates to the cross sections which
have been undertaken as part of the technical note on groundwater flood risk
which can be found in Appendix C.
If sea water levels rise by 1.05m over the next 100 years (in accordance with
the latest climate change guidance from UKCIP09), then the water table in
Eastbourne town centre and Eastbourne Park will rise by a similar amount.
Traditionally it had been thought that at locations where the water table is near
the surface there is a risk that ground water will enter the sewer network
through pipe joints or cracked pipes. This results in reduced capacity of the
drainage system. Southern Water has reported that this has been a common
occurrence in the Langney area of Eastbourne.
Phase 2a: Intermediate Risk Assessment
58
However, they are increasingly finding that this traditional explanation is not
the case. Instead, the overloading is caused by:-
a) Surface water flooding as a result, for example, of soakaway failure
entering their system by other means, e.g. manhole covers and sink waste
gullies.
b) Surfacing springs in the slightly higher western part of the catchment,
flowing across the surface and flowing into the highway drains and surface
water sewerage system.
Future development will not affect groundwater flood risk provided that their
foundations do not affect groundwater flow paths. Groundwater levels follow a
seasonal trend which is likely to be amplified by climate change. The lack of
data regarding groundwater flooding within the Eastbourne area means that
this potential risk needs to be investigated further (see Action Plan in
Appendix F).
3.1.4 Flood Risk from Ordinary Watercourses
Figure 2-5 in Section 2.4.3 identifies the locations of ordinary watercourses in
the Eastbourne area.
Ordinary watercourses are all watercourses that are not designated Main
River (watercourses where the Environment Agency has responsibilities and
powers) and which the LLFA will have consent over (currently proposed to be
from April 2012) if works are required to be undertaken.
There are many ordinary watercourses within the study area which have been
reported to have flooded in the past due to lack of capacity and/or due to a
lack of adequate maintenance. The upper parts of the catchment
predominately to the west of Eastbourne on the South Downs, experience
flooding from ordinary watercourses due to the high runoff rates and short lag
time during a short rainfall event. The lower part of the catchment
experiences localised flooding from drainage ditches potentially caused, or at
least worsened, by partial blockages or excessive vegetation within the
watercourse, or due to a poor maintenance regime. It is important that the
relevant authority identifies these assets in the future for prioritised
maintenance in parallel to the task of populating the risk asset registers. The
LLFA will have the power to serve notice (currently proposed to be from April
2012) on a riparian owner to maintain watercourses and ditches necessary for
the proper operation of the surface water drainage system within the
Eastbourne area.
Phase 2a: Intermediate Risk Assessment
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In accordance with UKCIP09, climate change will increase peak flows in
watercourses by about 20% over the next 50 to 100 years. This implies the
capacity of watercourses, and drainage ditches may not be sufficient in the
future. New development could also worsen this situation unless effective
policies are put in place now.
3.1.5 Flood Risk Interactions with Surface Water
Surface water flood risk can be increased as a result of the surface water
drainage system being impacted by high groundwater, fluvial and tidal levels.
This occurs when surface water flows are unable to drain through, for
instance, the soil, via an outfall into an open channel or to sea causing
significant ponding/backing up resulting in localised flooding.
The interaction with high groundwater levels has already been described in
Section 3.1.3. The interaction with high fluvial and tidal levels is described in
Sections 3.1.6 and 3.1.7 respectively.
3.1.6 Effect of High Fluvial Levels on Surface Water Flooding
The impact of fluvial flood risk in the Eastbourne area can be seen in Figure
3-7 below which denotes the 1 in 100yr and 1 in 100yr plus climate change
flood extents (taken from Capita Symonds 2007 study (see Section 9 –
References)).
Figure 3-7 (Map 10 in Appendix D) – Fluvial Flood Risk
Phase 2a: Intermediate Risk Assessment
60
The Environment Agency records identify three key flood events, in November
1974, July 1980 and December 2009, which caused flooding along its
designated main rivers in Eastbourne Park. Only the last of these occurred
after completion of the Eastbourne Lakes scheme and the flood extents are
confined to the Park area. According to the “Eastbourne Park and Flooding
Topic Paper No. 3” of April 2002 (see Section 9 – References) no flooding of
residential or commercial property occurred up to that time.
The flood extents of the fluvial events are mainly outside any urban areas and
therefore it seems reasonable to conclude that they do not impact directly on
surface water flood risk. In addition, the peak of surface water and fluvial
events are different for the catchment, so unlikely to occur together (see a
technical note undertaken by Halcrow (see Appendix C), which identifies this
difference for the Eastbourne Lakes).
3.1.7 Effect of High Tidal Levels on Surface Water Flooding
Surface water flooding is exacerbated during tide-locking conditions (when
flap gates at surface water outfalls close to prevent sea water entering the
system) combined with rainfall events. Tide-locking results in surface water
accumulating upstream of the outfalls in the drainage system, which leads to
reduced capacity so a storm event may cause flooding out of manholes and
gullies.
The area most prone to surface water flooding from sewers due to tide-locking
is in the northeast of Eastbourne town centre (Firle Road area) where
localised flooding of the road and occasionally properties has occurred.
Flooding in Eastbourne Park due to tide-locking is minimal due to the
significant floodplain areas and lakes available to store surface water.
Surface water flooding is also exacerbated at locations where sea-water
seepage occurs beneath the existing defences, which contributes to
maintaining a high water table.
The above effects will increase with climate change due to sea level rise as
well as increased storm intensities over the next 100 years. For Hotspot A the
impact of climate change is expected to increase flood risk by between 15-
20%, whilst for Hotspots C & D flood risk will increase by between 50-80%.
The predicted increase in flood risk over the next 100 years for Hotspot C & D
is much higher than Hotspot A since it is also impacted by sea-level rise. In
reality the actual impacts of climate change is considered to be lower than the
model is predicting, since current climate change estimates are considered to
be conservative.
Phase 2a: Intermediate Risk Assessment
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3.1.8 Residual Flood risk
Residual flood risk occurs when the infrastructure that is designed to deal with
local flood risk fails due to poor maintenance, or when a storm event has a
higher return period than that that used for the design. Residual local flood risk
can therefore be the result of drains, pipes and gully blockages due to poor
maintenance or misuse of the drainage system as well as pump failure and
pipe collapse.
The SWMP has highlighted a critical culvert (Bourne Stream) which flows
through the centre of Eastbourne before discharging to Horsey Sewer. The
maintenance of this culvert is essential to minimise the risk of a blockage or
collapse. This is discussed in further detail in Section 5.2.4 and is included in
the Action Plan (see Appendix F).
3.1.9 Flooding of Basements
Basement flooding can be significant due to the low-lying nature of the
properties with relatively high depths of flooding. This study has been unable
to identity any dataset which indicates where basements are located within the
Eastbourne area. Such a dataset needs to be created and this action is
included in the Action Plan (see Appendix F). To help with the protection of
future development, Buildings Regulations (2002) part H on drainage and
waste disposal requires anyone developing a basement with sanitation to
consult with the relevant sewer undertaker to discuss foul flood risk to the
property and to undertake preventative measures.
3.1.10 Land Use
The study area is predominantly urban with a high proportion of densely
developed areas with mixed land-uses. Eastbourne town centre, in the south-
west of the study area, is the most heavily urbanised and includes several
industrial areas. In the centre of the study area there is a large greenfield
space, which contains lakes provided for flood storage (Eastbourne Park
Lakes).
3.1.11 Significant Infrastructure
Significant infrastructure is defined as either ‘Essential Infrastructure’ or
‘Highly Vulnerable Infrastructure in accordance with PPS25. The national and
local significant infrastructure assets within the study area include:
District General Hospital, Police Station, Fire Station and Ambulance
Station
Railway Station and trunk roads
Utilities infrastructure
Phase 2a: Intermediate Risk Assessment
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Residential Establishments (i.e. Care Homes)
Arndale Shopping Centre
3.1.12 Historic Flooding Incidents
A range of information on historic flooding incidents has been collected and
mapped for this study. The local Strategic Flood Risk Assessment (SFRA),
compiled by Scott Wilson in September 2008 (see Section 9 – References),
and covering the borough of Eastbourne and the southern part of the district of
Wealden as far north as Heathfield, was a valuable source of information. This
SFRA sources data from records held by ESCC, EBC, WDC, the Environment
Agency and Southern Water. Where the records held by these organisations
have been updated since the SFRA, the latest version has been obtained for
the present SWMP. Individual meetings have also been held with the partners
and key stakeholders to gain an overview on flooding ‘hotspot’ areas as
defined in Section 3.4.
Data was collected from all partners and other studies and is detailed in
Appendix A. All of the data is illustrated in Figure 3-8 overleaf.
Phase 2a: Intermediate Risk Assessment
63
Figure 3-8 (Map 11 in Appendix D) – Historic Surface Water Flooding
Incidents
Phase 2a: Intermediate Risk Assessment
64
Information from the SFRA relating to historical flooding incidents within the
SWMP study area is extracted and reproduced in Table 3-1 below:
Event Date Details
1836 Records of flooding on the Pevensey Levels date back to
1836, when they were reported flooded, along with much of
the low-lying land in Sussex.
July 1893 A summer storm over Eastbourne resulted in severe flooding
of the town, converting manholes into fountains.
November 1974 Flooding of several properties and roads are recorded in
Eastbourne.
December 1984 Fluvial flooding caused watercourses to overtop resulting in
the flooding of properties and roads in Eastbourne.
March 1995 Surface water flooding in Polegate, Wannock and Willingdon
resulted in 56 properties being inundated as well as flooding
of a number of roads causing disruption, particularly through
the closure of the A22.
A report into this flooding concluded that it was due to a high
intensity rainstorm over saturated catchments leading to high
volumes of runoff. The culverts and channels at points along
Wannock Mill Stream, Mill Stream Ditch and Brook Street
Stream had insufficient capacity and thus flooding ensued.
The current policy (C5) from the CFMP for the Polegate area
is to “take further action to reduce the flood risk now and into
the future”.
August 2006 Internal flooding of Arndale Shopping Centre and significant
highway flooding of Terminus Road caused by an intense
localised rainfall event overwhelming the existing drainage
system.
Table 3-1: Historical Flooding from the Eastbourne and south Wealden
SFRA.
Historic flooding data has been collected from a number of sources, and as
much as possible mapped so that a good overview of flood risk could be
gained (see Figure 3-8, above).
The main problem areas which are emerging from the review of historical
flooding data appear to be Eastbourne town centre, the stretch along the
Bourne Stream route and the Polegate/Willingdon area.
3.1.13 Proposed Future Development
Eastbourne Borough Council through its Core Strategy has made a
commitment to deliver 5, 022 new homes over the 20 years from 2006 to
Phase 2a: Intermediate Risk Assessment
65
2027. Development within the borough is constrained by the sea to the south
east, the South Downs to the west, and the Eastbourne Park flood storage
scheme in the centre. Given these constraints, there is little available land
within the Borough which can be brought forward for development. Therefore,
growth will need to be achieved through urban change and renewal. The
Strategic Housing Land Availability Assessment (SHLAA), which has informed
the Core Strategy, assesses potential sites that may be developed for
housing, considering factors such as how many units they could
accommodate and a timeframe for when these sites could become available.
However, communication with the Council indicates that given the scarcity of
available land there are unlikely to be any major development areas and the
Council are expecting to depend heavily upon windfall sites for
redevelopment.
Wealden District Council aims to deliver 700 new dwellings in the Polegate
and Willingdon settlement between 2006 and 2030. The options for delivering
these were set out in the Core Strategy which was published for consultation
in August 2009. The options cover various ways of distributing the housing
including: growth of existing settlements proportionate to their current size;
focussing the majority of growth on Uckfield, Hailsham and/or Polegate;
growth taking particular account of criteria such as AONB, housing needs and
accessibility; growth focussed on developing villages; and growth to support
reopening the Lewes to Uckfield railway line.
A valuable spatial perspective can be gained by overlaying the areas at risk in
structural and non-structural hotspots with the proposed strategic sites
identified in the Eastbourne Core Strategy. Figure 3-9 represents this overlay,
which may provide evidence to future planning actions in the Borough in
relation to future development impact on surface water flooding.
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66
Figure 3-9 (Map 12 in Appendix D) – EBC Core Strategy Area against SWMP
Hotspot Areas
3.1.14 Surface Water Related Schemes
Based on the information collected and interviews held with the stakeholders,
the present and future schemes to improve flood risk within the study area are
summarised below:
Current Schemes:
Eastbourne Borough Council has recently carried out work to Princes Park
Sluice which consisted of replacing the two old, hard to operate, wind-up
sluices with a tilting weir to enable water to discharge more quickly to sea
via Crumble Outfall.
A similar scheme is proposed for the Crumble Sewer, located at a
bifurcation (i.e. flow is split, either going to Pevensey or to Crumble
Outfalls), where they are proposing to replace the old wind-up sluice with a
tilting weir to feed water to the Princess Park Sluice.
Phase 2a: Intermediate Risk Assessment
67
Weed screens are being installed behind Sainsburys store site on Decoy
Stream, so as to be compliant with the latest legislation – this will stop
weeds going into the culverts and causing blockages. The same has been
done at the Currys store site.
The EA are currently working with Halcrow on a planned closure and
refurbishment of outfalls on the Pevensey Levels.
Future Schemes:
The AMP5 (Asset Management Plan) programme for the regulatory period
2010 to 2015 includes only one scheme involving a package pump for a
DG5 property on Terminus Road.
Eastbourne Park Lake improvements (see Section 6.4)
3.2 Source, Pathways and Receptors
The source-pathway-receptor model is frequently used in assessment of flood
risk, it identifies where the water comes from as the source, the mechanism by
which the flooding reaches the receptor as the pathway, and the object which
experiences the flooding, and normally an adverse effect from it, as being the
receptor. Likely sources, pathways and receptors for flooding are listed in
Table 3-2 below.
Type of flooding Sources Pathways Receptors
Surface water Rainfall Roads
Ditches
Overland
People
Buildings
Environment
Groundwater High water table Aquifers and the
overlying soil
People
Buildings
Environment
Sewer Rainfall
Water discharged
from property
Inundation inflows
in areas of surface
water flooding.
Sewer network People
Buildings
Environment
Table 3-2: Primary sources, pathways and receptors for surface water
flooding
Table 3-3 below indicates the sources, pathways and receptors for flooding
which have a secondary impact on surface water flooding. Although these
sources do not result directly in surface water flooding, they will impact on the
Phase 2a: Intermediate Risk Assessment
68
significance of surface water flooding, through tide-locking of drainage outfalls
for example.
Type of flooding Sources Pathways Receptors
Fluvial Rainfall
High groundwater
resulting in springs
or ephemeral
watercourses
Watercourses
overtopping or
breaching
defences
People
Buildings
Environment
Tidal Wind
Tidal surge
Wave or surge
tide inundating
the land
People
Buildings
Environment
Table 3-3: Secondary sources, pathways and receptors for surface water
flooding.
The source, pathway, receptor model was used as a general approach for the
formation of the storyboard which is discussed in greater detail in the following
section.
3.3 Introduction to Hotspots and Maps
The following terminology is used throughout the SWMP. The spatial scale of
these areas follows a hierarchy and is presented below from the smallest to
largest:
1. Intermediate Hotspot is a discrete area of flooding that affects
houses, businesses and/or local infrastructure. The boundary is
defined by the readily available information on surface water flood risk
(mainly the EA’s FMfSW dataset) and confirmed by partners. These
are areas where future work may be required beyond that to prepare
this SWMP, subject to funding, to identify proposed solutions to
reduce flood risk locally (item in Action Plan)
2. Detailed Hotspot is an intermediate hotspot which has been
prioritised through the ranking process (see Section 3.4) and agreed
by partners as an area with significant surface water flood risk.
Thirty six intermediate hotspots have been identified as a result of undertaking
the Intermediate Risk Assessment and four of them have been identified for
further detailed assessment (see details in Section 4). All hotspots are shown
in Figure 3-10.
Phase 2a: Intermediate Risk Assessment
69
Figure 3-10 (Map 13 in Appendix D) – Hotspots in the Eastbourne Area
3.3.1 Critical Drainage Areas of hotspots
In accordance with SWMP Defra guidance document (see Section 9 -
References) Critical Drainage Areas (CDAs) are specific areas in Flood Zone
1 only, where runoff can cause problems. To determine the CDAs LiDAR was
used to determine the upstream catchment area (in EA’s Flood Zone 1) for
each hotspot, this is shown in Figure 3-11 overleaf.
Phase 2a: Intermediate Risk Assessment
70
Figure 3-11 (Map 14 in Appendix D) – Critical Drainage Areas in the
Eastbourne Area
The CDAs indicate areas where flood risk is to be carefully monitored to
minimise any increase in flood risk to the hotspot areas downstream.
Phase 2a: Intermediate Risk Assessment
71
3.4 Selection of Hotspots and Prioritisation
The selection of hotspots was based on interpreting readily available
information, this included:-
1. Historic Flooding Incidents – records collected by partners on
predominantly surface water flooding.
2. Environment Agency Surface Water Mapping – predicted surface
water flood risk modelled by the Environment Agency in the form of
two datasets:
a. AStSWF (Areas Susceptible to Surface Water Flooding) – first
generation dataset indicating the susceptibility to flooding for
the 1 in 200 year rainfall event.
b. FMfSW (Flood Map for Surface Water) – second generation
flood mapping indicating deep or shallow flooding for the 1 in
30 and 1 in 200 year rainfall events. This dataset is more
accurate than the first generation data since it has taken into
consideration the influence of buildings and the sewer system.
3. Environment Agency AStGWF (Areas Susceptible to Ground
Water Flooding) – indicates the likelihood of groundwater emergence
at a 1km square grid, this dataset was predominantly used for the
PFRA study.
4. Partnership Workshops – detailed information on the frequency,
extent and impact of known flooding within the Eastbourne area.
The above information was presented in a storyboard format (see Appendix
B), which was based around using the source, pathway and receptor
descriptions and was tabled with the partners for discussion. Through the
workshop additional information was collated from partners and all relevant
organisations agreed to the proposed hotspot areas.
A prioritisation method was developed by Halcrow and agreed by ESCC to
determine which of the hotspots had the most significant flood risk and
required further investigation in the Detailed Risk Assessment phase of the
SWMP (see Section 4). The prioritisation process was to classify (low,
medium or high) each hotspot on a set criteria and derive a score which could
then rank the hotspots. The variables used to score the hotspots were:-
1. Number of buildings in the predicted flood risk flood extents created by
Halcrow and the EA
2. Amount of critical infrastructure receptors
Phase 2a: Intermediate Risk Assessment
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3. Number of historic flooding incidents
4. Number of partners agreeing that the hotspot has known flooding
issues
A higher score weighting was applied to the number of historic flooding
incidents and number of agreeing partners, to ensure known actual flood risk
data would be prioritised over predicted flood risk.
The outcome of the scoring process was that intermediate hotspots 6, 12, 22
& 15 required further investigation; this was agreed by ESCC and the
partners. The intermediate hotspots were then renamed detailed hotspots A
(no.6) - Willingdon, B (no.12) - Langney, C (no.22) – Eastbourne Town Centre
& D (no.15) – Bourne Stream. The prioritisation spreadsheet can be found in
Appendix B.
Through the data collection exercise and consultation with ESCC and partners
37 intermediate hotspot areas were identified to be at risk from surface water
flooding. Hotspot prioritisation with the partners, based on flood risk, identified
4 detailed hotspots which were taken forward to the Detailed Risk
Assessment.
Phase 2b: Detailed Risk Assessment
73
4.0 Phase 2b: Detailed Risk Assessment
Figure 4-1 – Phase 2b: Detailed Risk Assessment Phase of the SWMP
Process
4.1 Modelling & Detailed Assessment
During the SWMP process it became apparent that the flooding mechanisms
associated with Hotspot B (Langney) was caused by a complex combination
of surface water and groundwater flooding (see Section 3.1.3), for this reason
it was not modelled, however, recommendations are made in the Action Plan
(see Appendix F).
4.1.1 Introduction
Two Infoworks CS (Collection System) sewer models were provided for the
Eastbourne area by Southern Water. Infoworks CS is a specialist one
dimensional pipe modelling software capable of hydrological modelling of the
urban water cycle. A rainfall profile is applied as inflows to the model based on
FEH (Flood Estimation Handbook) design rainfall and the flow of water is
modelled until it leaves the pipe system.
Phase 2b: Detailed Risk Assessment
74
The existing 1D models were built to model piped flows but did not have an
above ground component. Water was effectively “stored” above ground until
water levels subside below ground level and water is able to return to the
system. Flow routes and the exact location of the storage areas (and therefore
flooding) were therefore disregarded without a 2D mesh component included.
The following sections describe the model updates that have been carried out
within the SWMP to modify the model so that flow routes above ground level
were included, resulting in the model being effectively converted to Infoworks
2D.
4.1.2 Model Updates
A number of updates to the Infoworks model have been carried out to improve
the schematisation of above ground flow routes and improve model detail.
Only minor updates were included within the 1D pipe network in order to
improve model schematisation for modelling surface water. All pumping
station capacities and trigger levels were left as they were included in the
model supplied by Southern Water. The main updates to the model lie within
the inclusion of a 2D domain and associated improvements to modelled flow
routes.
4.1.3 1D updates
The Bourne Stream was imported into the model and the connections
between the sewers and the watercourse were checked to allow the
interactions between the sewer system, overland flows and watercourse to be
represented.
Another change to the 1D model included the addition of tidal levels to the
model outfalls. The tidal levels added to the model were the mean high tide
levels. This ensured a conservative approach assuming that the event could
coincide with a high tide, but without being too conservative by using a spring
tide level.
4.1.4 Broad scale 2D mesh generation
A 2D triangular mesh was added to the model to simulate above ground flood
routing. Meshes were created for the hotspot areas with a maximum triangle
area of 100m2. This was designed to give an indication of flood risk across the
whole hotspot area. Mesh elevations were taken from the most recent
available 2 metre resolution LiDAR data. The following characteristics were
also included in the detailed model area mesh:
A. Buildings were included within the mesh as voids which water cannot
pass through.
B. Kerbs were included as break lines with a height of 0.125m
Phase 2b: Detailed Risk Assessment
75
C. Following sensitivity tests, a mesh roughness of 0.035 (roughness for
floodplains) was applied for Hotspots A and B, this represents the flow
paths following the rivers rather than the roads. A value of 0.016
(roughness for asphalt) was applied for Hotspots C and D; this
represents the urban nature of the catchment with the majority of the
flow paths following the roads.
Figure 4-2 – InfoWorks 2D Mesh
4.1.5 Rainfall profiles and application to model
A rainfall profile was generated using FEH design rainfall. The rainfall profile is
applied to the model in two ways:
A. Through “subcatchments” based on the drainage system and property
layouts (with contributing areas within the “subcatchment” based on
the size of permeable and impermeable areas); and
B. Rainfall applied directly to the 2D mesh outside of “subcatchment”
areas with 50% of the rainfall profile applied after assessing bedrock
permeability and through validation against historical flooding locations
(discussed further in the following model sensitivity section).
4.1.6 Model sensitivity and model validation
Model sensitivity analysis was carried out to assess how each model
parameter affects model results. Sensitivity tests were carried out for:
A. Pipe Roughness
B. Percentage rainfall applied directly to mesh
Phase 2b: Detailed Risk Assessment
76
C. Allowance for gullies
A model was run with increased pipe roughness across the catchment. This
was found to have marginal impact on the extents and locations of flooding
and therefore the original Southern Water model pipe roughness values were
used for the modelling.
The model was calibrated against a GIS layer of historically flooded properties
and known flow paths. To calibrate against this, the model was tested with
different amounts of rainfall (100%, 75%, 50% and 25%) being applied directly
to the mesh. Based on the simulation results and experience from other
SWMPs, it was finally decided that 50% was a suitable percentage to apply to
the model. This produced results which matched many of the historical flood
locations and flow paths but was also a realistic representation of runoff within
the catchment.
As the Southern Water model does not include the gullies, an allowance was
made in the model to allow flow to pass more easily between the 2D surface
and manholes, thus giving a representation of the gullies. The simulation
results showed effectively no change in the depth of flooding on the surface
(+/- 0.001 metre) and therefore the gully representation was not used in the
modelling.
An instability was identified in the Hotspot A model at the downstream end of
the Wannock Mill Stream. On these links there were shown to be large
negative flows. However, through additional analysis and model testing this
did not impact the flows in the area upstream and therefore impact on the
results found, this is discussed further in the Modelling Technical Note in
Appendix C.
In the detailed modelling stage 2D modelling of Southern Water’s sewerage
systems was undertaken for only 3 detailed hotspot areas to understand and
communicate the extent of surface water flood risk and the flooding
mechanisms.
Phase 2c: Communicate Risk
77
5.0 Phase 2c: Communicate Risk
Figure 5-1 – Phase 2c: Communicate Risk Phase of the SWMP Process
5.1 Mapping Outputs
The output from both the Intermediate & Detailed Risk Assessment stages are
maps indicating the surface water flood risk for the Eastbourne area, giving an
in-depth understanding of flood risk for the hotspots.
5.1.1 Eastbourne Area Flood Depth Map
A flood depth map for the Eastbourne area (Map 15 in Appendix D) uses a
combination of the EA’s second generation surface water flood maps (FMfSW)
overlaid with Halcrow’s detailed 2D sewer modelling from the detailed hotspot
areas. This provides a detailed understanding of not only surface water runoff
and flow paths across the catchment, but also flow routes from surcharging
manholes.
Phase 2c: Communicate Risk
78
Figure 5-2 – Extract of the Eastbourne Area Flood Depth Map
Phase 2c: Communicate Risk
79
5.1.2 Detailed Hotspot Flood Depth Maps
Detailed mapping of surface water flood depths for all three hotspots (see
Maps 16 & 18 in Appendix D) was produced, with a blue colour banding for
depths over 150mm (threshold for internal property flooding) and light yellow
to represent flood depths over 50mm. Properties which are surrounded by a
proportion of 150+mm of flood depth are considered to have flooded internally.
The flood outlines shown are deduced from the 2D triangulated mesh and
hence are angular in form.
Figure 5-3 – Extract of Flood Depth Map
5.1.3 Detailed Hotspot Flood Hazard Maps
Detailed mapping of surface water flood hazard for all three hotspots was then
undertaken (see Maps 17 & 19 in Appendix D). Flood hazard is used to give
an indication of the risk to life posed by flood water. The severity of flood
hazard depends on the water depth and velocity, along with an additional
degree of hazard from debris in the water. This reflects the danger to life from
a combination of deep and fast flowing water. For example, shallow water,
when still, does not present a major hazard, but combined with a fast flow is
potentially dangerous.
Phase 2c: Communicate Risk
80
A method for quantifying flood hazard is described in the Supplementary Note
on Flood Hazard Ratings and Thresholds for Development Planning and
Management Purposes – Clarification of Table 13.1 of FD2320/TR2 and
Figure FD2321/TR1 (see Section 9 – References). The formula devised is:
Flood hazard = depth x (velocity+0.5) + debris factor
For most circumstances the debris factor is unknown, but in most modelling
exercises a standard is assumed; further information is detailed in the
Modelling Technical Note in Appendix C
The flood hazard matrix used for the hazard rating is shown in Table 5-1.
Table 5-1 – Flood Hazard Matrix
Depending on the flood hazard value calculated, the severity of the hazard is
indicated by the class into which the value falls, which are shown in Table 5-2.
Phase 2c: Communicate Risk
81
Table 5-2 – Flood Hazard Classification
The flood hazard outlines shown are deduced from the 2D triangulated mesh
and hence are angular in form.
Figure 5-4 – Extract of Flood Hazard Map
Flood Hazard
Rating
Hazard to People Classification
Less than 0.75 Very low hazard - Caution
0.75 to 1.25 ‘Danger for some’ – includes children, the elderly and the
infirm.
1.25 to 2.0 ‘Danger for most’ – includes the general public.
More than 2.0 ‘Danger for all’ – includes emergency services.
Phase 2c: Communicate Risk
82
5.2 Summary of Flooding Mechanisms for Detailed Hotspots
5.2.1 Hotspot A – Mill Stream Gardens, Willingdon
Sloping urban environment with dry valleys which become flooded by the
Wannock Mill Stream during high intensity rainfall events. Localised overland
flow paths between properties and along Millstream Gardens cause further
flooding with water ponding at the junction of Millstream Gardens and
Farmlands Avenue. Surface flood water may also inundate the foul sewer
network.
5.2.2 Hotspot B – Langney
Water levels in the land drainage and the surrounding EA Main River open
sewers prevent the free discharge of the surface water sewers into the
accepting watercourses. This, coupled with relatively high groundwater,
causes backing-up and egress of groundwater into the foul sewerage system
and entry of irregular surface water flows from non-formalised sources (i.e.
poorly sealed manholes) which results in a surcharged system.
5.2.3 Hotspot C – Firle Road & Arndale Shopping Centre, Eastbourne
a) Firle Road - The surface water sewer running along Firle Road
surcharges and floods during high intensity rainfall events. This flooding
mechanism is exacerbated during high tide when the outfall is tide-locked;
this problem is expected to occur more frequently with sea-level rise due to
climate change
b) Arndale Shopping Centre – Twin surcharging combined trunk sewers
running along Terminus Road prevents effective drainage of the shopping
centre and the pedestrianised precinct during high intensity rainfall events.
5.2.4 Hotspot D – Bourne Stream & Star Inn, Eastbourne
a) Bourne Stream - Failure or blockage scenarios of the Bourne Stream
were modelled at locations along the culvert, which is currently in a poor
condition (as indicated by the limited amount of upstream CCTV surveys).
The failure/blockage locations were prioritised for areas with highly
vulnerable infrastructure (i.e. Terminus Rd outside the Train Station and
Arndale Shopping Centre). The results indicated that flood risk would be
increased in the area immediately surrounding and downstream of these
blockage locations. However, since the flood waters contained within the
culvert were effectively removed from the system at the blockage
locations, additional capacity was created further downstream thus
reducing flood risk locally in these areas.
Phase 2c: Communicate Risk
83
b) Star Inn - A change in pipe gradient along the surface water sewer results
in a reduction in capacity at a low-spot, which causes significant flooding of
several properties and the highway.
The maps in this section indicate the flood risk in terms of depth, velocity and
hazard for each detailed hotspot area. Further modelling assessment clarified
the flooding mechanisms for each hotspot as discussed in this section to
inform the optioneering phase.
Phase 3: Options
84
6.0 Phase 3: Options
Figure 6-1 – Phase 3: Options Phase of the SWMP Process
6.1 Objectives
The objective is to form robust schemes to reduce surface water flood risk for
each of the detailed hotspots.
Each proposed scheme has been designed for the 1 in 25 year rainfall event
(unless otherwise stipulated). Significant surface water flows are also likely to
lead to surface water flooding, which has the potential to impact on all
infrastructure, traditional engineering approaches, such as increasing the
diameter of public sewers or constructing separate systems, are not
economically viable or practical on a large scale. For this reason the 1 in 25
Phase 3: Options
85
year design flood alleviation standard was used to test options to ensure cost
effective measures were recommended.
The outputs of this phase is the preferred options for each detailed hotspot
with flood damage calculations, approximate scheme costs and the associated
cost/benefit ratios (see Appendix E).
6.2 Measures
For each hotspot detailed schemes were developed, modelled and tested to
understand the degree of flood protection provided. A broad overview of the
type of options considered for each area is shown below:
Hotspot A (Willingdon) - To control flood waters within Millstream
Gardens road and improve conveyance under the shop on Farmlands
Avenue back into Wannock Mill Stream.
Hotspot C (Eastbourne Town Centre) - Construct a high-level overflow
or divert the surface water sewer to prevent flooding on Firle Road due
to tide-locking.
Hotspot D (Bourne Stream) - Increase capacity of the surface water
sewer upstream of the low-point by storing flows in Motcombe Park.
Details of each option scenario run can be found in Appendix E.
6.3 Arndale Shopping Centre
The modelling results indicated the main flooding mechanism in the Arndale
Shopping Centre area is the surcharging of the twin combined sewers running
along Terminus Road. The surcharging system prevents surface water from
draining away, coupled with the resulting backward-flow of sewage in to the
centre’s drainage system, and the result is localised flooding of both Terminus
Road and partial internal flooding of the Centre.
Possible measure to reduce the flood risk is to install flap values on the local
sewers, which are experiencing surcharging from the trunk sewers. There
would also be a need to consider the installation of removable flood gates on
the two main entrances of the Centre to prevent highway flooding entering the
low-lying shopping centre.
Further investigation into possible flood mitigation measures for the shopping
centre is recommended, for example as a separate feasibility study for the
town centre. Such a study should consult all relevant stakeholders and
consider the development of the western section of Arndale Shopping Centre
Phase 3: Options
86
and the highway modifications of Terminus Road to ensure sustainable
options are identified and flood risk is not increased elsewhere.
6.4 Eastbourne Lakes
EBC raised the issue that the Eastbourne Lakes had not been identified as an
area to consider through the SWMP prioritising process. As there are no
recorded incidences of flooding or receptor to be flooded, the lakes were not
identified as a hotspot. In addition, as the lakes are located downstream of the
main urban area at risk this meant they were judged not to be critical in terms
of the surface water flooding. To confirm that this position was correct a high
level review was undertaken of the discharge to the lakes.
It was reported that the Eastbourne Park flood alleviation scheme was set up
to offer surface water flood protection for Eastbourne due to new
development. Its construction and ongoing maintenance was funded by
development contributions calculated using a formula based on the plan area
of the development site. From a review of the latest information (a Scott
Wilson Report, June 2002), the Eastbourne Park flood alleviation scheme
offers a flood storage to a 1 in 100 year standard of protection, but it will not
be able to maintain this under the effects of climate change without
improvements to the scheme. Potential measures to address this were
recommended as:
a) Construction of new lakes with improvements to the Crumbles outfall.
b) Construction of a new Crumbles outfall
From the high-level review of the discharge to the lakes using the model
developed for the SWMP, it was found that if a significant rainfall event was to
hit the Eastbourne area and the upper fluvial catchment, the lag time for the
surface water to reach the Eastbourne Lakes area would be much less than
the time for the fluvial flood waters to reach the same location (see Halcrow’s
technical note Appendix C). In addition the SWMP model showed that the
volume generated by a storm event was only 30% of that previously
calculated. Therefore, it was considered highly unlikely that discharge from a
surface water and a fluvial flood event would arrive at the lakes at the same
time and even if it did the likely surface discharge volume would be much less
than that used to design the lake scheme. The review recommended that
there is a need to do more work to confirm the actual situation and this should
look at ways of increasing the use of the lakes for surface water flood storage.
The SWMP process has raised the interest of and eased communication
between the SWMP Partners and this has led to the agreement that a study of
Phase 3: Options
87
the current operation of the lake flood alleviation scheme will be progressed.
The first part of this study is to survey the current condition of the lakes and
their control assets. The survey information will then be used to develop a
model to understand their operation. Finally to use this model to look at how
the lakes should be operated in the future, look at ways of increasing their use
for surface water flood storage, what maintenance/ improvement works are
required to achieve this and how the developer contributions should be
handled in the future going forward.
6.5 Preferred Options
The preferred option for each detailed hotspot is as follows:-
Hotspot A - Kerb raising of the western kerb on Millstream Gardens
with a Super Gully located outside the shops on Farmlands Avenue
and a high-level overflow along the existing footpath.
Hotspot C - Divert the 1050mm diameter surface water sewer at
Bedfordwell Road to Eastbourne Park Lakes.
Hotspot D - Surface water storage in Motcombe Park with highway
flooding removed from Star Road by capturing overland flow on
Upperton Road.
Details of the preferred options, showing their impact on surface water flood
risk are shown in Maps 20, 21 & 22 in Appendix D.
It should be noted that the preferred options presented here are designs in
outline only, and demonstrate a possible workable solution to reduce surface
water flood risk with certain simplifications being made. Progress to detailed
design cannot proceed without more detailed investigation and option
appraisal at each detailed hotspot.
For example Hotspot C (Firle Road, Eastbourne Town Centre) has complex
interactions between the surface water and combined sewerage networks
which are not currently fully understood. Therefore, further work on the
existing integrated urban drainage modelling of the low lying part of the
Eastbourne Catchment with climate change will be required to move it from
strategic to a detailed level. If the further work identifies sufficient drivers to
satisfy OFWAT then, as they are essentially sewerage activities, both the
detailed investigation and the scheme can be included in Southern Water’s
business plan.
Phase 3: Options
88
6.6 Options Prioritisation
The preferred options were tabled with ESCC and the partners and were
prioritised in the Action plan (see Appendix F).
6.7 Strategic Environmental Assessment
The assessment has found that the SWMP offers significant potential to
reduce flood risk that could potentially cause damage to environmental and
cultural heritage assets. Some uncertain effects and one minor negative effect
was predicted. The uncertainty related to the freshwater ecology effects of
diverting a surface water sewer to Eastbourne Lakes and changing the flows
into and capacity of Bourne Stream. Uncertain impacts are also associated
with the new proposed storage area in Motcombe Gardens, which has the
potential to affect the depth of water levels and duration of flooding
downstream. New water storage, even if infrequent, could lead to waterlogging
of soils and affect the ability of terrestrial plant species to survive, albeit on a
small scale. The one minor negative effect identified relates to the temporary
loss of amenity greenspace associated with the proposed storage area at
Motcombe Gardens. However, it is considered that this could be avoided or
mitigated at the EIA stage if these options in Hotspot D are progressed.
For Hotspot A, no important designations for biodiversity, landscape or cultural
heritage or high value agricultural land were found to be in the immediate
vicinity of these options. SWMP options are therefore predicted to have
neutral effects on these SEA objectives. However, by improving surface water
conveyance into Wannock Mill Stream, there are likely to be benefits from
reduced flood risk to infrastructure and properties.
For Hotspot C, there are some significant material assets, landscape features,
amenity areas and heritage assets in the vicinity of the SWMP options, which
would be protected by improved drainage and reduced flood risk. Therefore,
the options score major positive effects for these SEA objectives whereas
minor positive effects are predicted for other SEA objectives. There are
potentially some opportunities to enhance biodiversity through sewer
diversions and habitat enhancement/creation at Eastbourne Lakes.
For Hotspot D, the options should result in reduced flood risk for material
assets and an area of high cultural heritage value; Old Town Conservation
Area. There are uncertain effects on natural resources and biodiversity due to
the uncertain impacts associated with the new proposed storage area in
Motcombe Gardens, which has the potential to affect the depth of water levels
and duration of flooding downstream. Further development of the option will
be needed before these effects can be detailed. In addition, its potential
(positive or negative) impacts on soil and water and habitats and species are
uncertain due to the level of available detail regarding this option at this stage.
Phase 3: Options
89
There is a potential opportunity to create small-scale wetland habitat (e.g.
Biodiversity Action Plan habitat) in the new storage area. Maintenance of the
Bourne Stream should help to conserve flows from the stream into the Horsey
and Crumbles Sewers, which are both designated SNCIs. The proposed
Motcombe Park storage area currently contains a pond but the options would
entail flooding an area of amenity greenspace in addition to the pond, hence a
minor negative score is predicted for the ‘open spaces’ SEA objective.
The SEA concluded by proposing a series of high-level monitoring measures
for the topics of biodiversity, water, cultural heritage, population and human
health and landscape and visual amenity. The SEA with the SWMP can be
made available for public consultation, and if necessary be updated following
consultation comments. Further details on the SEA can be found in Appendix
H.
A combination of options have been considered in this phase with the
preferred options comprising of either; managing overland flow paths,
improving conveyance or creating storage to reduce surface water flood risk.
All reduce flood risk for the designed 1 in 25 year rainfall event as a minimum
and will require further detailed investigation before progressing to detailed
design.
Phase 4: Implementation and Review
90
7.0 Phase 4: Implementation and Review
Figure 7-1 – Phase 4: Implementation Phase of the SWMP Process
7.1 Action Plan
The purpose of Phase 4 of the SWMP is to clearly identify actions and
responsibilities for the ongoing management of surface water flood risk within
the Eastbourne Study area, which have been emerged from Phases 1 to 3.
An Action Plan has been prepared for ESCC (see Appendix F). The purpose
of the Action Plan is to:
Give outline details of the actions;
Phase 4: Implementation and Review
91
Provide an indication of the priority of the actions;
Indicate the potential cost-of and benefit-from delivery, as well as the
potential funding sources;
Identify the timescale for delivery;
Identify the partners or stakeholders responsible for implementing the
actions;
Outline the actions required to implement the preferred options identified in
Phase 3;
Outline actions required to meet some of the requirements for ESCC as
LLFA under the FWMA 2010.
Actions within the Action Plan have been grouped under six headings as
summarised in Table 7-1 below.
Action Type General Description
Engagement Relates to those activities to engage with the
partners, stakeholders and the public generally.
The aim being to share information, promote
collaborative working and to find potential funding
streams.
Investigation To investigate asset condition, ownership and
operation.
Structural Flood
Reduction Measures
Measures where physical interventions are
proposed to reduce flood risk, which ranges from
the Phase 3 options, through support of partner
schemes to SuDs projects.
Non Structural Flood
Reduction Measures
Measures based around improved management of
existing assets or informed control of development
to reduce flood risk.
Data Collecting and assessing data to improve the
understanding of local flood risk leading to a more
effective management of the risk.
Phase 4: Implementation and Review
92
Procedural The procedures that need to be set up and
progressed to help meet the LLFA’s duties and
deliver development management measures.
Table 7-1 - Types of Action within the Eastbourne Area Action Plan
An example of actions from the plan includes Southern Water progressing the
preferred proposed solution for surface water storage in Motcombe Park
subject to the agreement in principle of EBC with details to be included in the
Action Plan.
As identified in Table 7-1, several key actions for ESCC relating to duties and
responsibilities under the FWMA are outlined in Section 1.6. It is likely that
these actions will require consideration of internal functions within the Councils
and the adoption of new systems of data collection and asset management
(e.g. Halcrow’s developed online ‘Flood Portal’ tool).
Building on the understanding of local surface water flood risk gained as a
result of the Phase 1 work and continuing with the SWMP partnership will be
essential to the continued management of surface water across the
Eastbourne area in a joined-up manner.
One of the key drainage assets identified as needing attention from this
SWMP work is the Bourne Stream. As a result of the past changes to drainage
responsibilities, the ownership and the responsibility for this asset has become
unclear. Actions have been identified to determine the responsibility, so that
the asset can have the overdue maintenance it requires to operate effectively.
The culvert may need maintenance in order to permit inspection before asset
ownership can be determined or agreed.
The role of the lakes in Eastbourne Park in alleviating surface water flooding
was considered as part of the SWMP process. They were shown to be
dominated by fluvial rather than surface water flooding. Surface water flooding
in the Eastbourne area was found to be mainly due to runoff from the lower
slopes of the South Downs or rain that fell directly on the urban catchment.
This meant that the Eastbourne Park Lakes located downstream of the
Eastbourne urban area would not directly resolve the conveyance issues
experienced in this urban area. However, the SWMP process brought together
the right partners to start an investigation into the Eastbourne Park storage
scheme. This investigation should consider the mechanism of funding them
from developer contributions, how the currently available fund should be best
used and future contribution utilised. There seems to be a disconnection of the
surface water drainage system from the lakes in some areas. This should be
Phase 4: Implementation and Review
93
considered further as part of the proposed work on the future operation of the
lakes.
As our understanding about surface water flood risk improves and more
information is made available, it becomes increasingly important to be able to
communicate the risk effectively both within ESCC, to other stakeholders and
members of the public. To this end, there is an action related to the future
communication of flood risk and the development of a public awareness plan,
which could be incorporated into a communication plan for the delivery of the
Action Plan.
7.2 Implementation Programme
A strategic level programme has been prepared in a ‘Gantt chart’ format to
show each of the actions from the plan, their priority and timeframes (see
Appendix F). This is seen as a tool to be developed to support future planning
and implementation of the actions.
7.3 Action Prioritisation
A judgement-based approach has been adopted to prioritise the actions in the
Action Plan. This was generally based on considering what impact completing
the action would have on the reduction of flood risk and how quickly it needed
to be undertaken. Therefore, for actions that made a big reduction to flood risk
and needed to be complete within a year they were given a ‘High’ priority.
7.4 Ongoing Monitoring
The SWMP Partnership should continue beyond the completion of the SWMP
in order to manage the implementation of the proposed actions, review
opportunities for operational efficiency and to review any legislative changes.
The partners should hold a monitoring meeting every quarter to consider how
the actions are progressing and what needs to be done to drive the delivery of
the Action Plan forward. It is suggested that each partner should take it in turn
to host the meeting.
The SWMP Action Plan should be officially reviewed and updated once every
six years as a minimum. However, there may be circumstances which might
trigger a review and/or an update of the Action Plan in the interim, examples of
a possible ‘trigger-event’ are:
Occurrence of a surface water flood event;
Additional data or modelling becoming available, which may alter the
understanding of risk within the study area;
Operational decisions by partners that impact on the Action Plan;
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94
Additional (major) development or other changes in the catchment which
may affect the surface water flood risk.
The main output from the implementation phase is the Action Plan. The
approach and form of this Action Plan was developed during this stage. A
Gantt chart was drafted as a tool to be developed to support future planning
and implementation of the actions. The SWMP Partnership should continue
beyond the completion of the SWMP in order to discuss the implementation of
the proposed actions. The partners should hold regular monitoring meeting to
consider how the actions are progressing and what needs to be done to drive
the delivery of the Action Plan forward.
Conclusion
95
8.0 Conclusion
8.1 Review Objectives
To conclude, the objectives outlined in Section 1.3 of the report are presented
in Table 8-1 below with evidence to confirm the status of each option.
Objective Status Evidence
Map surface water flood
risk - engage community
& stakeholders to share
knowledge
Completed
Eastbourne Area Flood Depth Maps show surface water risk
ESCC as part of preparing the PFRA undertook public consultation to capture localised flooding information by hosting a survey on its website for 3 months, and held drop-in sessions in each local authority area
Appendix A – details of data shared
Establish partnerships of
key stakeholders -
facilitating - data, skills,
resource & learning
sharing
Completed
SWMP Partnership formed and data collected in Phase 1 of study
Determine consequences
of flooding - establish
priorities & compare
mitigation measures
Completed Communicate Flooding mechanisms of detailed hotspot areas in Phase 2 (Risk Assessment)
Consider various measures during Phase 3 (Options)
Develop strategy to
inform on development
drainage - minimising
impact on receiving
system
Completed Identified CDAs for all hotspots in Phase 2 (Risk Assessment)
Action plan item for developments to attempt to achieve greenfield runoff
Develop implementation
plan - showing how
partners work together to
finance and implement
Completed Action Plan with proposed funding streams and Gantt Chart for delivery
Develop a periodical
review framework - to
plan & monitor
effectiveness of solutions
Completed Recommendations covering ongoing Monitoring discussed in Phase 4 (Implementation & review)
Identify effective &
affordable mitigation
measures - where
possible achieves
Completed Detailed Hotspots Options tabled detailing costs for damages and proposed schemes to calculate the cost/benefit ratio
Conclusion
96
multiple benefits
Deliver outputs to enable
a real change on the
ground – not just reports
& models - partners take
ownership of their flood
risk & commit to
recommended measures
and actions.
Completed Meeting to finalise agreement on Action Plan and proposed approach for monitoring
Plan Implementation – any possible ‘Quick Wins’
Partner approval signatures of the Final SWMP
Table 8-1 – SWMP Objectives & Evidence
8.2 Recommendations
It is recommended to implement the Action Plan detailed in Appendix F of this
SWMP report. Also it is suggested to ensure both the Action Plan and the
SEA are kept up to date by reviewing against the latest guidance and findings
of publicised reports as they become available.
The SWMP Partnership should continue beyond the completion of the SWMP
in order to discuss the implementation of the proposed actions. The partners
should hold regular monitoring meeting to consider how the actions are
progressing and what needs to be done to drive the delivery of the Action Plan
forward.
For the successful implementation of the Action Plan it is envisaged that
additional resources and funding will be required from within the Local
Authorities.
8.3 Ownership of the SWMP Action Plan
ESCC’s responsibility as the LLFA in relation to this SWMP is to lead in its
production and ensure that it is periodically reviewed and updated. EBC &
WDC will be jointly undertaking the lead role in the delivery of the SWMP
Action Plan.
However, it is accepted that delivery of the Action Plan will, in most cases,
depend on finance to move projects forward and all partners will be expected
to pursue opportunities in order to seek funding that will enable this to happen.
References
97
9.0 References
Surface Water Management Plan Technical Guidance, Defra, March 2010
Learning Lessons from the 2007 Floods, The Pitt Review, June 2008
Future Water – the Government’s Water Strategy for England, Defra, February
2008
Planning Policy Statement 25: Development and Flood Risk, Communities
and Local Government, March 2010 (revision)
UKCP09, UK Climate Impacts Programme (UKCIP), 2009, (www.ukcip.org.uk)
Environment Agency ABD Study for Eastbourne, Capita Symonds, 2007
Eastbourne Park and Flooding Topic Paper No. 3, Eastbourne Borough
Council, April 2002
Eastbourne Borough Council and Wealden District Council Strategic Flood
Risk Assessment Level 1, Scott Wilson, September 2008
Supplementary Note on Flood Hazard Ratings and Thresholds for
Development Planning and Control Purposes – Clarification of Table 13.1 of
FD2320/TR2 and Figure FD2321/TR1. Environment Agency/HR Wallingford,
May 2008.
Living on the edge – a guide to the rights and responsibilities of riverside
occupation. Environment Agency 3rd Edition April 2007.
Appendix A – Data Review
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Appendix A – Data Review
Appendix B – Hotspot Area Selection
V0.10 11/05/2017 B1
Appendix B – Hotspot Area Selection
Appendix C – Risk Assessment Technical Details
V0.10 11/05/2017 D1
Appendix C – Risk Assessment Technical Details
Appendix D – Maps
V0.10 11/05/2017 D1
Appendix D – Maps
Appendix E – Options Assessment Details
V0.10 11/05/2017 E1
Appendix E – Options Assessment Details
Appendix G – Planner, Emergency Planner & Public Briefing Note
I1
Appendix F – Action Plan
Appendix G – Planner, Emergency Planner & Public Briefing Note
I2
Appendix G – Planner, Emergency Planner & Public Briefing Note
Appendix G – Planner, Emergency Planner & Public Briefing Note
I3
Appendix H – Environmental Assessments
Recommended