Hastings Surface Water Management Plan (SWMP)€¦ · AECOM Study Report 2 The Flood Maps for...

Water

Hastings Borough Council March 2011

Hastings Surface Water Management Plan – Study Report Hollington Old Lane flooded in 2009 – Source: EA

Executive Summary ........................................................................................................................................................................ 1

Glossary .......................................................................................................................................................................................... 3

Acronyms ........................................................................................................................................................................................ 8

Introduction and Background........................................................................................................................................................ 9 Introduction ......................................................................................................................................................................... 9 Background ....................................................................................................................................................................... 10

1 Preparation Stage ........................................................................................................................................................... 13 1.1 Identify the need for a SWMP study .................................................................................................................... 13 1.2 Establish Partnership ........................................................................................................................................... 13 1.3 Scope the SWMP ................................................................................................................................................ 14

2 Risk Assessment Stage .................................................................................................................................................. 17 2.1 Strategic Assessment .......................................................................................................................................... 17 2.2 Intermediate Assessment .................................................................................................................................... 18 2.3 Detailed Assessment ........................................................................................................................................... 26 2.4 Map and Communicate Risk ................................................................................................................................ 27

3 Options Stage .................................................................................................................................................................. 33 3.1 Identify Measures ................................................................................................................................................ 33 3.2 Assess Options .................................................................................................................................................... 37

4 Implementation and Review Stage ................................................................................................................................ 48 4.1 Prepare Action Plan ............................................................................................................................................. 48 4.2 Implement and Review Action Plan ..................................................................................................................... 53

General Conclusions and Recommendations............................................................................................................................ 54 Conclusions ....................................................................................................................................................................... 54 Recommendations ............................................................................................................................................................ 54

Table 1.1: Hastings SWMP – Working Group Structure and Representatives ..................................................................... 14 Table 1.2: Partners‟ Programmes linked to the Hastings SWMP ......................................................................................... 15 Table 2.1: Information used to inform the Strategic Assessment .......................................................................................... 17 Table 2.2: Maps produced as part of the Strategic Assessment........................................................................................... 18 Table 2.3: Information used to inform the Intermediate Assessment .................................................................................... 18 Table 2.4: Maps produced to inform the Intermediate Assessment of the flood hotspots ..................................................... 20 Table 2.5: Maps produced to summarise outcome of Site Visits .......................................................................................... 21 Table 2.6: Summary of the findings of the Intermediate Assessment ................................................................................... 22 Table 2.7: Summary of the Conclusions and Recommendations of the Intermediate Assessment ...................................... 24 Table 2.8: Summary of Modelling results in relation to Overtopping of the Dams and Surcharging of Culvert at Upper Glen Road

.......................................................................................................................................................................................... 26 Table 2.9: Differences between AStSWF and FMfSW ......................................................................................................... 27 Table 2.10: EA Surface Water Flood Maps - National and Local (Hastings) Uncertainty Levels ............................................ 29 Table 2.11: List of Maps/Sketches produced to inform the Hastings SWMP .......................................................................... 30 Table 3.1: Summary of Options identified during the Risk Assessment Stage ..................................................................... 33 Table 3.2: Short-listing Criteria Recommended by Defra ..................................................................................................... 34 Table 3.3: Application of Short-listing Criteria to Flood Hotspot 1......................................................................................... 34 Table 3.4: Application of Short-listing Criteria to Flood Hotspot 2......................................................................................... 35 Table 3.5: Application of Short-listing Criteria to Flood Hotspot 3......................................................................................... 36 Table 3.6: Application of Short-listing Criteria to Flood Hotspot 4......................................................................................... 37 Table 3.7: Summary of Assessment of Shortlisted Options for Flood Hotspot 1 .................................................................. 38

Table of Contents

Table 3.8: Summary of Assessment of Shortlisted Options for Flood Hotspot 2 .................................................................. 39 Table 3.9: Summary of Assessment of Shortlisted Options for Flood Hotspot 3 .................................................................. 40 Table 3.10: Summary of Assessment of Shortlisted Options for Flood Hotspot 4 .................................................................. 43 Table 3.11: Summary of Borough-wide studies/investigations ............................................................................................... 44 Table 3.12: Summary of Preferred Options to be taken forward to Implementation Stage ..................................................... 46 Table 3.13: Summary of Agreed Complementary Actions to Improve Surface Water Management across Hastings ............ 47 Table 4.1: Summary of Ranked Options for Implementation ................................................................................................ 49 Table 4.2: Summary of Ranked Complementary Actions for Implementation ...................................................................... 50 Table 4.3: Chronological order of activities required to progress options and complementary actions identified ................. 51 Table 4.4: Additional work identified post completion of Hastings SWMP Study .................................................................. 53 Figure 1: Framework for undertaking a SWMP Study.......................................................................................................................9 Figure 2: Location of Hastings within East Sussex ......................................................................................................................... 10 Figure 3: Overview of Hastings ....................................................................................................................................................... 10

AECOM Study Report 1

Hastings Borough Council appointed AECOM Ltd as consultant for the Hastings Surface Water Management Plan in June 2010.

This appointment followed the initial technical support provided by AECOM to HBC‟s successful bid for DEFRA funding.

The Hastings Surface Water Management Plan has been undertaken following the guidelines set out in the “Surface Water

Management Plan Technical Guidance” published by Defra in March 2010. Four well defined phases are identified in the

guidance and have been followed as part of this study. These stages are: Preparation, Risk Assessment, Options,

Implementation and Review.

The Preparation Stage of the study built on the identification of the need for a Surface Water Management Plan, completed as

part of the original bid for Defra funding, by establishing a robust partnership between all organisations with responsibilities for

flood risk or drainage management across the Borough. The partners for the Hastings Surface Water Management Plan are:

Hastings Borough Council (lead partner), East Sussex County Council (lead local flood authority), Southern Water, Environment

Agency and Rother District Council.

Once the partnership was in place, a working group was formed with representatives of the partners. The group‟s remit was to

contribute effectively to the production of the Surface Water Management Plan by sharing relevant data and attending

meetings/workshops as necessary. The overall aim of the study, as agreed with the partners, was to prepare a robust plan to

reduce the number of properties at risk of surface water flooding in Hastings through the implementation of cost-effective local

solutions. It is envisaged that the partnership formed as part of the Hastings Surface Water Management Plan will remain active

following the completion of this study and will aim to deliver the solutions identified as part of the Surface Water Management

Plan.

A series of objectives that captured the aspirations of the different partners were set out as part of the Preparation Stage. These

objectives, in conjunction with an understanding of the data readily available to inform the study were used to establish the level

of assessment required for the study thus completing the Scoping Phase.

The Risk Assessment Stage of the Hastings Surface Water Management Plan started with the Strategic Assessment Phase

which relied on historical flooding information, the Strategic Flood Risk Assessment for Hastings, LiDAR Data and the Areas

Susceptible to Surface Water Flooding Map produced by the EA. The analysis of this information identified sixteen medium to

large flood hotspots across the Borough which were presented to the working group for review. Upon review of the initial

conclusions it was agreed that further assessment was required but given the budget and time limitations associated with the

study, as per Defra conditions, it was agreed by the working group that four flood hotspots would be looked at in more detail as

part of the Intermediate Assessment Phase.

The Intermediate Assessment started with the identification of the top eight flood hotspots across Hastings by the working group.

A selection criteria based on accepted methods applied for other similar Defra funded studies was then applied to these locations

to identify the top four flood hotspots across the Borough. The selected locations were then subject to more detailed analysis

which included a site visit by the working group aimed at identifying the issues on the ground from the perspective of all partners

as well as establishing any quick solutions to the problems. The output of the intermediate assessment was a series of

conclusions, recommendations and the identification of various options to be investigated further. Among the recommendations

was the need to undertake a detailed assessment of the Upper Hollington Stream aimed at improving the understanding and

management of the existing water retaining structures.

The Risk Assessment Stage was completed with the Map and Communicate Risk phase which involved the production of a

Borough-wide asset register aimed at identifying all flood risk and drainage management assets across Hastings regardless of

ownership. The asset register was the result of a lengthy consultation process with all partners which included attendance at a

workshop aimed at reviewing the information collated, addressing any gaps in the data and agreeing the criticality of the assets

from a surface water flood risk perspective. Details of the maintenance regime of the various assets across the Borough have

also being included. It is envisaged that the asset register will be used by Hastings Borough Council and East Sussex County

Council to inform their flood risk management role and therefore it is essential that any gaps/uncertainties are removed and it is

kept up to date.

Executive Summary


The Flood Maps for Surface Water released by the Environment Agency in November 2010 have refined the understanding of

the areas deemed at risk of flooding from surface water across Hastings. It is, however, recognised by all partners that whereas

these revised maps provide a good general representation of the areas at risk, they do not capture all of the known problem

locations. Consequently, it was agreed within the working group that these maps would be used as the best available information

for the area until such time when East Sussex County Council issues the “locally agreed surface water flood risk information”.

The Options Stage included the identification of possible mitigation measures or solutions to the issues identified during the Risk

Assessment Stage. A number of Borough-wide and flood hotspot-specific measures were outlined to provide solutions in the

short, medium and long term. These were short-listed and subsequently assessed through a variety of methods (including

detailed overland flow modelling) and to different levels of detail in order to establish the preferred options for implementation.

The various options selected to be taken forward to the Implementation Stage are outlined below:

- Borough-wide

- Education

- Flood Resistance/Resilience Measures

- Flood Hotspot 1

- Modify Ground Profile around Priory Meadows Shopping Centre

- Flood Hotspot 3

- Install Trash Screen at the culvert entrance at Ashbrook Park, Upper Church Road

- Retrofit SUDS at Hollington Primary School

- Clear debris and improve understanding & use of water management structures

In addition to the above options, a number of complementary actions aimed at improving the management of surface water flood

risk have been identified and progressed in principle as outlined below:

- Seek SUDS Retrofitting Opportunities

- Maintain an up-to-date Borough-wide asset register

- Review maintenance regime for all assets in accordance with their criticality

- Devise a suitable flood response and report procedure

- Seek opportunities to reduce the risk of surface water flooding affecting critical infrastructure

The Implementation and Review Stage contains an action plan which outlines the steps required to deliver and monitor the

implementation of the various options agreed. The action plan included in the final version of this report has being reviewed and

approved by the various partners as well as Hastings Borough Council scrutiny committee.

It is envisaged that the working group formed to inform the production of the Hastings Surface Water Management Plan will

continue to work together post completion of the study to progress the delivery of the various options and complementary

actions. Furthermore, it is foreseen that East Sussex County Council (lead local flood authority) will take a primary role in

managing flood risk across Hastings.


Antecedent Conditions:

The pre-existing condition before a rain event (e.g. waterlogged soil)

Areas Susceptible to Surface Water Flooding

Areas identified by the Environment Agency (in 2008) as susceptible to surface water flooding under extreme events (1 in 200

year return period)

Brownfield site:

Any land or site that has been previously developed

Catchment

The area contributing flow or runoff to a particular point on a watercourse

Catchment Flood Management Plan

Environment Agency produced documents providing an overview of the flood risk across each river catchment and estuary and

recommended ways of managing those risks now and over the next 50-100 years

Chance of Flooding

Describes the frequency of a flood event occurring in any given year. This can also be described as an annual probability

Climate change

A long-term variation in global temperature and weather patterns both natural and as a result of human activity, primarily

greenhouse gas emissions

Combined Sewer Network

A unified sewerage system that combines surface water and foul discharges

Cost Benefit Analysis (CBA)

Analysis which quantifies in monetary terms the costs and benefits of a proposed scheme, including items for which the market

does not provide a readily available monetary value

Critical Infrastructure

Infrastructure which is considered vital or indispensable to society , the economy, public health or the environment, and where its

failure or destruction would have large impact

Culvert

Covered channel or pipe that forms a watercourse below ground level, or through a raised embankment

Deep (as identified on the Flood Maps for Surface Water)

Areas where surface water is expected to flow or pond at a depth greater than 0.3 m, as identified on the Flood Maps for Surface

Water

Defra

UK Government department responsible for policy and regulations on the environment, food and rural affairs

Designing for Exceedance

An engineering approach which aims to plan for and manage flows which are larger than the designed capacity of infrastructure

during rainfall events

Development

The carrying out of building, engineering, mining or other operations in, on, over or under land or the making of any material

change in the use of any buildings or other land

Digital Elevation Model (DEM)

A model of the elevation of the ground surface and includes building, vegetation etc

Glossary


Digital Terrain Model (DTM)

A model of the terrain of the earth‟s surface („bare earth‟)

Dry Valleys

A valley originally produced by running water but now waterless

Enmained

Watercourse designated as a Main River

Environment Agency (EA)

Government Agency charged with the protection of the environment

Environmental Agency Flood Zones

They indicate land at risk by referring to the probability of flooding from river and sea, ignoring the presence of defences. Flood

zones are defined in Table D.1 of Planning Policy Statement (PPS) 25: Development and Flood Risk

Escarpment

The long continuous steep face of a ridge or mountain

Exceedance Flows

Excess flow that appears on the surface once the capacity of the underground drainage system is exceeded

Flood defence

Flood defence infrastructure, such as flood walls and embankments, intended to protect an area against flooding, to a specified

standard of protection

Flood Estimation Handbook (FEH)

Software offering guidance on rainfall and river flood frequency estimation in the UK

Flood Hotspots

Locations identified as being prone to flooding

Flood Maps for Surface Water

Areas identified by the Environment Agency (in 2010) as prone to surface water flooding under two scenarios, the 1 in 200 year

and 1 in 30 year return period events. The Flood Maps for Surface Water are a refinement of the Areas Susceptible to Surface

Water Flooding maps produced in 2008

Flood Probability

The estimated likelihood of a flood of a given magnitude occurring or being exceeded in any specified time period

Flood risk

An expression of the combination of the flood probability and the magnitude of the potential consequences of the flood event

Flood Risk Assessment (FRA)

A study to assess the risk of a site or area flooding, and to assess the impact that any changes or development in the site or area

will have on flood risk

Flood Risk Management Plan

A plan for the management of a significant flood risk. The plan must include the objectives of the plan and the method by which

those objectives may be achieved

Floods and Water Management Bill

This Bill, passed in April 2010, aims to clarify the legislative framework for managing surface water flood risk in England

Fluvial Flooding

Flooding caused by rivers


Foul Sewer Network

Sewer network collecting any foul discharges

Greenfield

Previously undeveloped land

Ground Contours

Show depression or elevation of ground forms in an area

Groundwater

Water in the ground, usually referring to water in the saturated zone below the water table

Groundwater flooding

Flooding caused by groundwater escaping from the ground when the water table rises to or above ground level

Groundwater Vulnerability

A measure of the vulnerability of groundwater stores to contamination

Highways Agency

The national body responsible for managing, maintaining and improving England‟s motorways and trunk roads

Less Susceptible to Surface Water Flooding

Areas which are susceptible to surface water flooding with a modelled indicative depth of between 0.1 m and 0.3 m, as identified

on the Areas Susceptible to Surface Water Flooding maps

LiDAR

Data set that provides a 3D image of the surface of the earth using a “Light Detection And Ranging” technique

Local Development Documents (LDDs)

Documents that set out the spatial strategy for local planning authorities which comprise development plan documents

Local Development Framework (LDF)

Framework which forms part of the statutory development plan and supplementary planning documents which expand policies in

a development plan document or provide additional detail

Local Planning Authority (LPA)

Body responsible for planning and controlling development, through the planning system

Local Resilience Forums (LRF)

Multi-agency forums, bringing together all organisations who have a duty to co-operate under the Civil Contingencies Act, and

those involved in responding to emergencies

Main River

A watercourse designated on a statutory map of Main rivers, maintained by the Environment Agency

Mitigation measure

A generic term used in this guide to refer to an element of development design which may be used to manage some risk to the

development, or to avoid an increase in risk elsewhere

Moderately Susceptible to Surface Water Flooding

Areas which are susceptible to surface water flooding with a modelled indicative depth of between 0.3 m and 1.0 m as identified

on the Areas Susceptible to Surface Water Flooding maps

More Susceptible to Surface Water Flooding

Areas which are susceptible to surface water flooding with a modelled indicative depth of more than 1.0 m, as identified on the

Areas Susceptible to Surface Water Flooding maps


Ordinary watercourse

A watercourse which is not a private drain and is not designated a Main river

Permitted Development Rights

Qualified rights to carry out certain limited forms of development without the need to make an application for planning permission,

as granted under the terms of the Town and Country Planning (General Permitted Development ) Order 1995

Pluvial Flooding (Surface water flooding)

Flooding which occurs due to water pooling on or flowing over the surface before it reaches a drain or watercourse

Resilience Measures

Measures designed to reduce the impact of water that enters property and businesses

Resistance Measures

Measures designed to keep flood water out of properties and businesses

Riparian Owners

Land owners with land or property alongside a river or other watercourse

Risk

The probability of a flood occurring multiplied by the consequence of the flood

Runoff

Water flow over the ground surface to the drainage system

Sewers for adoption

Standard for new drainage systems in England & Wales to be used as a guide to assist developers in preparing their submission

to a sewerage undertaker before they enter into an Adoption Agreement under Section 104 of the Water Industry Act 1991

Shallow (as identified on the Flood Maps for Surface Water)

Areas where surface water is expected to flow or pond at a depth greater than 0.1 m, as identified on the Flood Maps for Surface

Water

Shoreline Management Plan (SMP)

Policy framework that assesses and manages risks to people and to the developed, historic and natural environment associated

with coastal processes, on a large-scale

Sewer Network

Entire sewer network, comprising of combined, foul and surface water sewers

Standard of protection

The estimated probability of an event occurring which is more severe than those against which an area is protected by flood

defences

Strategic Flood Risk Assessment (SFRA)

A study to examine flood risk issues on a sub-regional scale, typically for a river catchment or local authority area during the

preparation of a development plan

Source Protection Zone (SPZ)

Defined areas showing the risk of contamination to selected groundwater sources used for public drinking water supply, from any

activities that might cause pollution in the area

Springs

A small stream of water flowing naturally from the earth

Supplementary Planning Document (SPD)

Local Development Document that provides further detail of policies and proposals in a „parent‟ Development Plan Document


Surface Water

Water collected or flowing over the ground not contained within a watercourse. Usually results from heavy rainfall

Sustainable Drainage Systems (SUDS)

A sequence of management practices and control structures, often referred to as SUDS, designed to drain surface water in a

more sustainable manner. Typically, these techniques are used to attenuate rates of runoff from potential development sites

Watercourse

Any natural or artificial channel that conveys surface water

Water Cycle Strategy (WCS)

Provides a plan and programme of Water Services Infrastructure implementation. It is determined through an assessment of the

environment and infrastructure capacity for: water supply; sewage disposal; flood risk management; and surface water drainage

Water Framework Directive

A European Community Directive (2000/60/EC) of the European Parliament and Council designed to integrate the way water

bodies are managed across Europe

Watershed

Line depicting the area within which all surface water will drain into an area of interest, such as a town or village. For the

assessment of surface water this boundary is defined from the topography


AStSWF Areas Susceptible to Surface Water Flooding

CA Complementary Action

CFMP Catchment Flood Management Plan

CS Infoworks CS, Sewer Network Model

DEFRA Department for Environment, Flood and Rural Affairs

DTM Digital Terrain Model

EA Environment Agency

ES Emergency Services

ESFP East Sussex Flood Partnership

ESCC East Sussex County Council

FEH Flood Estimation Handbook

FMfSW Flood Maps for Surface Water

GIS Geographical Information System

HA Highways Agency

HBC Hastings Borough Council

LiDAR Light Detection And Ranging

mOD Metres Ordinance Datum

OP Options

PFRA Preliminary Flood Risk Assessment

RA Risk Assessment

RDC Rother District Council

SEA Strategic Environmental Assessment

SMP Shoreline Management Plan

SFRA Strategic Flood Risk Assessment

SSSI Sites of Special Scientific Interest

SUDS Sustainable Drainage Systems

SW Southern Water

SWMP Surface Water Management Plan

WFD Water Framework Directive

Acronyms


Introduction

Hastings Borough Council (HBC) was successful in a Defra bid for funding to tackle surface water flooding in the Borough. The

bid was produced by AECOM on behalf of HBC and was based on the Areas Susceptible to Surface Water Flooding Map

(AStSWF) published by the Environment Agency (EA) as well as the Strategic Flood Risk Assessment (SFRA) for the area and

local knowledge shared by HBC, EA and East Sussex County Council.

The funding awarded to Hastings Borough Council has been used to produce a Borough-wide Surface Water Management Plan

(SWMP) as well as funding the delivery of some of the solutions identified on the ground.

The Hastings SWMP was based upon the guidance contained within Defra‟s „Surface Water Management Plan Technical

Guidance‟ (hereafter referred to as „the Defra Guidance‟), dated March 2010.

The Defra guidance includes a framework for undertaking SWMPs illustrated by the wheel diagram below:

Figure 1: Framework for undertaking a SWMP Study

Introduction and Background

Map and

communicate risk


Background

Study Area Overview

Hastings Borough is located within East Sussex on the south east coast of England. The Borough has an area of 3,066ha, the

majority of which is used for residential purposes.

Figure 2: Location of Hastings within East Sussex

The main settlements within the Borough include the Town Centre, Old Town, St Leonards, St Helens, Hollington, West Marina

and Bulverhythe.

Figure 3: Overview of Hastings


Hastings is located where the sandstone beds, at the heart of the Weald, meet the English Channel, forming tall cliffs to the east

of the town. Hastings Old Town is in a sheltered valley between the East Hill and West Hill. The town spreads westwards and

northwards forming a single urban centre with the more suburban area of St Leonards-on-Sea to the west. Roads from the Old

Town valley lead towards Clive Vale and the former village of Ore, from which "The Ridge", marking the effective boundary

between Hastings and Rother, extends north-westwards towards Battle. Beyond Bulverhythe, the western end of Hastings is

marked by low-lying land known as Glyne Gap, separating it from Bexhill-on-Sea.

The beach is mainly shingle, although wide areas of sand are uncovered at low tide. The town is generally built upon a series of

low hills rising to approximately150 m above sea level at "The Ridge" before falling back in the river valley further to the north.

There are three Sites of Special Scientific Interest (SSSI) within the Borough; Marline Valley Woods (an ancient woodland of

pedunculate oak-hornbeam which is uncommon nationally), Combe Haven (site of biological interest, with alluvial meadows, and

the largest reed bed in the county, providing habitat for breeding birds) and Hastings Cliffs To Pett Beach (The site runs along the

coast and is of both biological and geological interest).

From a socio-economic perspective, the history of Hastings paints it as a thriving seaside town enjoying economic success and a

prosperous society. However, in recent decades, the town has experienced a sustained economic decline, leading to an increase

in social problems and the development of distinct pockets of deprivation. According to the national indicators of deprivation,

Hastings is the most deprived town in the South East and one of the most deprived areas in the country1. Flooding Sources

Experience has shown that the vast majority of flooding problems in Hastings Borough cannot be attributed to a single source but

are largely as a result of a combination of factors such as tide locking, surface water runoff, groundwater, high river flows,

hydraulic overloading of the sewer network, blocked gullies, etc.

The various sources likely to have an impact in terms of flooding within the Borough are summarised below.

Sea: The tidal influence along the Combe Haven extends from just upstream of Filsham Nature Reserve to the river mouth at

Bulverhythe. Along this stretch flooding can be caused by a combination of high tides and significant river flows that, on their

own, may not cause any difficulties to the system.

Rivers: Hydraulically, Hastings forms part of the Cuckmere and Sussex Havens Catchment. However, the only major fluvial

catchment draining the Borough is the Combe Haven. The Combe Haven lies to the north-east of Bexhill and to the west of

Hastings. Its catchment is predominantly rural in nature and covers an area of 5,150ha extending over Rother and Hastings.

The main rivers identified within the Borough are Combe Haven, Spring Ditch, Decoy Pond, Pebsham Stream, Hollington

Stream, South Saxons Sewer and Bexhill Road Sewer. From these the Hollington Stream, directly linked to surface water

flooding, is known to have produced significant flooding in the recent past.

Some minor watercourses also exist in the Borough; however, these are reported not to have caused any flooding problems in

the past.

Sewers: Flooding can occur when the flow entering a sewer exceeds its hydraulic capacity thus surcharging the system. The

sewer network draining Hastings is largely combined along the low lying stretches (coastal area) which has historically

manifested in flooding occurring in these areas. Problems with capacity can be further compounded by high tides preventing

outfalls from discharging treated effluent effectively. Groundwater: High groundwater levels and resultant spring flows are

recognised as a source of flooding along the coastal strip of Hastings. This high water table in the gravel beds can be pushed

higher still by the tide, resulting in complex and difficult to predict flooding where no obvious watercourse or source is identified.

This is the case in low lying parts of St Leonards and Bulverhythe.

1 Safer Hastings Partnership (2008) Hastings Community Safety Plan 2008-11. Available at

http://www.saferhastings.co.uk/CSPlan_cropped%20to%20size%20smaller_file.pdf

http://www.saferhastings.co.uk/CSPlan_cropped%20to%20size%20smaller_file.pdf


Overland Flow: Due to its topography (surrounded by hills), overland flow is a well recognised problem across the Borough, as

recognised by the AStSWF maps. The impact of overland flow can be compounded by high river flows, blockages, high tides and

groundwater emergence as has been recognised to be the case across Hastings.

Artificial Sources: There are a number of artificial sources across the Borough; however, these do not have a history of flooding

and under normal working conditions are unlikely to contribute to flooding from any other sources.


The preparation stage was the first and arguably the most important step in the preparation of the SWMP as it established the

foundations over which the SWMP was undertaken.

This stage was divided in three well defined parts:

- Identify the need for a SWMP study

- Establish Partnership

- Scope the SWMP

1.1 Identify the need for a SWMP study

The objective of this initial step was to identify whether there was a need for a SWMP taking into consideration flooding history,

existing modelling information, anecdotal evidence, etc.

In the case of Hastings Borough this need had already being recognised by Defra and the EA by the award of funding for the

production of a Borough-wide SWMP following the successful submission of a bid to tackle surface water flooding.

1.2 Establish Partnership

The objective of this part of the SWMP was to identify the organisations that should be involved in the study as well as clarify

their roles and responsibilities.

1.2.1 Partners

Partners are organisations with responsibilities for decisions and actions to be taken. For the development of the Hastings

SWMP they were:

- Hastings Borough Council (HBC) – lead organisation

- Environment Agency (EA)

- Southern Water (SW)

- East Sussex County Council (ESCC)

- Rother District Council (RDC)

The level of involvement of RDC was limited as it was established early in the process that there was little correlation between

surface water flood risk in Hastings and Rother. This conclusion was reached following a review of the catchment extents which

suggested that the political borders presented a good correlation to the catchment boundaries and therefore any surface water

problems in one area could not be attributed to what happens in the other.

1.2.2 Stakeholders

A stakeholder is anyone affected by or interested in the problem or solution. Therefore anybody reading this report would fall into

this category. There are a number of organisations that could be regarded as key stakeholders due to their direct involvement in

the prevention, response or management of surface water flooding across the Borough. These include:

- Emergency Services (ES)

- Highways Agency (HA)

- Statutory Undertakers (apart from Southern Water – partner)

- East Sussex Flood Partnership (ESFP)

1.2.3 SWMP Working Group

A working group was formed with representatives of the partners to steer/assist the SWMP study. In order to ensure the SWMP

would complement the existing local processes/structures, representatives from a number of associated disciplines were

identified and invited to form part of the working group. The following table provides a summary of the members of the working

group as well as the various disciplines/sectors represented:

1 Preparation Stage


Table 1.1: Hastings SWMP – Working Group Structure and Representatives

Organisation Representatives Discipline/Sector

Hastings Borough Council Virginia Gilbert / Nick Sangster Natalie Bumpus Brian Williamson/ Charles Sharrod

Amenities, Waste & Leisure (Project Lead) Spatial Planning Emergency Planning

Environment Agency Ian Nunn Les Norman

Asset Management Flood Risk Management

Southern Water John Challoner Sewerage

East Sussex County Council Nick Claxton Mark Andrew Derek Ireland

Flood Risk (Lead Local Flood Authority) Structures Highways

Rother District Council Alan Dodge Civil Engineering – General

AECOM David Pope / Galo Pinto Flood Risk Management (Project Consultant)

The group met periodically (approximately once a month) to review progress and agree the way forward for the study. In addition

to the regular progress meetings, a series of special events (workshops, site visits, etc) were undertaken during the study with

active participation from all members of the working group.

Links between the Hastings SWMP working group and the East Sussex Flood Risk Group (led by ESCC) were maintained

through HBC and ESCC representatives sitting on both committees. This approach ensured consistency on the work undertaken

across East Sussex and aimed to facilitate the fulfilment of the responsibilities of ESCC as lead local flood authority.

1.2.4 Partner‟s Commitments

All partners expressed their intention of working together to contribute to the production of a robust Surface Water Management

Plan for Hastings. Furthermore, they indicated their willingness to share information as well as attend working group meetings

and other associated events when requested. A data sharing protocol was agreed and signed by all the partners to facilitate the

release of information for the study.

The production of a memorandum of understanding was also discussed within the working group but deemed unnecessary as all

partners were committed to contribute effectively to the delivery of the SWMP.

It was agreed by all partners that in order to deliver the project in the required timeframe, decisions would be taken within the

working group whenever possible. It was, however, recognised that higher level discussions might be required within the

partners‟ organisations at times.

1.3 Scope the SWMP

The objective of this part of the Surface Water Management Plan (SWMP) was to clarify what approach the study should take

based on the available information and the objectives set by all partners involved.

1.3.1 Aim

The overall aim of the SWMP was to prepare a robust plan to reduce the number of properties at risk of surface water flooding in

Hastings through the implementation of cost-effective local solutions.

1.3.2 Objectives

The following general objectives were identified by the working group:

- Produce a robust SWMP following the guidelines set out in Defra‟s „Surface Water Management Plan Technical Guidance‟

(herein referred to as „the Defra Guidance‟), dated March 2010.

- Determine the locations of the main flood risk management and drainage assets as well as identify their ownership and

condition by producing a borough-wide asset register in GIS format.

- Develop an asset maintenance/action plan with the aim of ensuring all main flood risk management and drainage assets are

adequately maintained by the relevant organisation.


- Map current and potential surface water flood risk areas, irrespective of source, and engage the community and all

stakeholders to share this knowledge.

- Determine the potential consequences of surface water flooding, now and in the future, so that priorities can be established

with regards to the merits of different mitigation strategies. The outcome of the SWMP should inform any further bidding

process for flood protection funding.

- Identify effective, affordable, achievable and cost-beneficial measures to mitigate surface water flood risk which achieve

multiple benefits where possible. Emphasis should be made on finding suitable local solutions that could be implemented with

the collaboration of the community.

- Work with the EA to improve the flood warning service in light of the outcome of the study.

- Inform the strategic and emergency planning across Hastings to reduce the risk posed by surface water flood risk to members

of the public now and in the future.

- Link the SWMP with other schemes being managed/promoted by partners and other stakeholders with the aim of maximising

the opportunities to deliver solutions on the ground.

- Develop an implementation plan showing how partners and stakeholders will work together to finance and implement the

preferred strategy.

- Tie-in the SWMP with other EA/Defra studies as well as other SWMPs being undertaken across the country to ensure best

practice is observed.

- Periodically review the plan and monitor the effectiveness of chosen solutions.

1.3.3 Links to Partners Programmes

The following existing programmes were identified by the partners as having links to the SWMP:

Table 1.2: Partners‟ Programmes linked to the Hastings SWMP

Organisation Existing Programmes

Hastings Borough Council EA sponsored Coastal Pathfinder (Climate Change) Climate Change Adaptation Study Bulverhythe Flood Defences – Emergency Planning

Environment Agency Catchment Flood Management Plan SUDS Retrofitting Pilot Project Hollington Stream Rapid Response Catchment Action Plan

Southern Water Flood Relief Scheme at Collier Road Pollution Reduction Scheme at Old Roar Gill Bathing Water Risk Study

East Sussex County Council ESCC Preliminary Flood Risk Assessment

Rother District Council None

In addition to the above partners programmes, East Sussex County Council established East Sussex Flood Partnership (ESFP)

in January 2010. This group which includes all the partners of the Hastings SWMP was created 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..

Although not governed by formal agreement, the ESFP‟s terms of reference focus on the delivery of the requirements of the

Flood and Water Management Act and the County Council‟s statutory duty as a Lead Local Flood Authority.

1.3.4 Engagement Plan

It was agreed that Hastings Borough Council would lead the stakeholder engagement, which would comprise the following tasks:

- Internal liaison with Councillors (HBC)

- A briefing to Councillors/HBC Officers to present the study

- A workshop with residents and relevant stakeholders in areas where recommendations are being made


- An event for the general public

It is envisaged that any comments made by residents will be considered by the working group and will inform the continuous

revision of the SWMP. It is important to note that the SWMP should be a live document and that the working group created will

continue working together post-completion of the study with the aim of delivering the objectives set out as part of the Hastings

SWMP.

1.3.5 Data Availability

All partners were consulted with regards to the data available to inform the production of Hastings SWMP. A data register

capturing the information available to inform the study from all partners was compiled and is included as Appendix 1A.

1.3.6 Level of Assessment

The Hastings SWMP was based on the Defra Guidance which identifies three levels of assessment as potentially required to

inform the SWMP. The study followed a sequential approach which started by the application of the Strategic Assessment at

Borough-wide level and included the detailed assessment of specific locations within Hastings.


The Risk Assessment Stage aims to identify the reasons behind surface water flooding problems across the Borough with the

intention of mapping and communicating the risk and therefore is a vital part of the SWMP process.

During the scoping of the SWMP, it was recognised that in order to maximise efficiency in terms of the financial and time

constraints for the study the Risk Assessment Stage for the Hastings SWMP should be undertaken in phases:

- Strategic Assessment

- Intermediate Assessment

- Detailed Assessment

The final phase of the Risk Assessment Stage involves mapping and communicating the risk identified throughout the different

phases of this Stage of the SWMP.

2.1 Strategic Assessment

The objective of this phase was to identify broad locations which are considered to be more vulnerable to surface water flooding

with the aim of implementing a risk based approach to the assessment of flood risk and options for implementation.

The Strategic Assessment phase involved the following steps:

- Collate information for the Strategic Assessment

- Undertake Strategic Assessment

2.1.1 Collate information for the Strategic Assessment

The strategic assessment was based on existing information, as outlined by the Defra guidance. The principal sources of data

and information considered as part of the Hastings SWMP Strategic Assessment are summarised below:

Table 2.1: Information used to inform the Strategic Assessment

Data Source Coverage Comments

Historical Flooding

HBC 1969/85; 1993/2003;

2006/2009 Periods missing. No detailed information available

ES 1997/2010 (May) Inconsistent level of detail

EA Main Rivers Flooding Extents only

SW 1988/2010 (March)

AStSWF EA National FMfSW were released at the end of November 2010 and therefore were not available to inform this phase of the

assessment

LiDAR Data EA Borough-wide Some small areas around the Borough boundary missing

Hastings Strategic Flood Risk Assessment

(SFRA) HBC Borough-wide Completed in April 2008

2.1.2 Undertake Strategic Assessment

The strategic assessment made use of the information listed above which was entered into a Geographical Information System

(GIS) to facilitate the overlying of the different layers of information.

2 Risk Assessment Stage


As part of the Strategic Assessment stage the following Borough-wide maps were created:

Table 2.2: Maps produced as part of the Strategic Assessment

Drawing Number Title

60156460/RA/001 Hastings Flooding History

60156460/RA/002 AStSWF + Hastings Flooding History

60156460/RA/003 Factors Influencing Flood Risk

60156460/RA/004 LiDAR Topographic Information

By bringing together the information collated for the assessment, it was possible to identify surface water flood hotspots across

the Borough. A total of 16No. medium to large flood hotspots areas were identified during this initial assessment. These areas

are shown in Sketch 001 (Maps section).

The flood hotspots areas identified were discussed during a progress meeting of the working group and a consensus reached in

terms of the top eight priority areas. It was agreed by the working group that to ensure transparency these eight areas would be

subject to a priority scoring system to establish the top four areas to be looked at in more detail as part of the intermediate stage.

It is important to recognise the perceived lack of detail/consistency of the historical records provided by the different partners. As

a result of these inconsistencies and despite efforts to select only the relevant records for this study, some level of inaccuracy

might remain in this stage of the assessment.

2.2 Intermediate Assessment

The objective of this phase was to gain an improved understanding of surface water flooding, identify localised flood hotspots and

associated suitable mitigation measures as well as inform the decision making process with regards to the need for further

assessment.

The Intermediate Assessment phase involved the following steps:

- Collate information for Intermediate Assessment

- Undertake Intermediate Assessment

- Determine whether more detail assessment is required

2.2.1 Collate information for Intermediate Assessment

The intermediate assessment was informed by the output of the strategic assessment and by the following information made

available by partners and key stakeholders:

Table 2.3: Information used to inform the Intermediate Assessment


Extent of Sewer Network SW Borough-wide GIS layer provided

Location of Pumping Stations SW Borough-wide Only pumping stations operated by SW

included

Flood Hotspot Locations as identified by sewer modelling

SW Borough-wide GIS layer provided

Schematic of Pumping Arrangements SW Borough-wide

Alignment of Main Rivers EA Borough-wide

Alignment of Ordinary Watercourses EA/HBC (SFRA)

Borough-wide

Hydraulic modelling results and reports EA Combe Haven

including Hollington Stream

1-D ISIS and 2-D Tuflow model


Table 2.3: Information used to inform the Intermediate Assessment (continued)


NFCDD Information EA Borough-wide Coastal assets not included

Location of Gullies ESCC Borough-wide GIS layer provided

Location of Culverts ESCC Borough-wide

Location of Highway Structures >1m diam ESCC Borough-wide

Location of Reservoirs in Operation HBC Borough-wide

Areas subject to Escarpment HBC/EA (SFRA)

Borough-wide

Location of Existing Ponds HBC

(SFRA) Borough-wide

Location of Dry Valleys HBC/EA (SFRA)

Borough-wide

Location of Springs HBC/EA (SFRA)

Borough-wide

Maintenance Records and Regimes

EA Borough-wide NFCDD and general information only

SW Borough-wide General information only

ESCC Borough-wide General information only

HBC Borough-wide General information only

Site Specific Flood Risk Assessments HBC Flood hotspots No recent FRAs submitted for development

within these areas

Locations of proposed new residential and employment development

HBC Borough-wide

Aerial Photography HBC Borough-wide

Contour lines HBC Borough-wide 5 metre contours

Location of critical infrastructure HBC Borough-wide

Cuckmere and Sussex Havens Catchment Flood Management Plan

EA Catchment-wide Brief mention of surface water flood risk but

number of people deemed to be affected during an extreme event seems low (70)

Rother District Council (RDC) SFRA RDC District-wide No relevant information for Hastings found

East Sussex Local Flood Warning Plan EA County-wide

Emergency Plan 2010 HBC Borough-wide

Bulverhythe 2007 flood response document HBC Bulverhythe and

surrounding areas

Bulverhythe Flood Evacuation Plan Oct 2009

HBC Bulverhythe and

surrounding areas

Multi Agency Flood Plan for Sussex (Part 1) ESCC Sussex

Site visits to the top four flood hotspots Working

group Flood hotspots one

to four Undertaken by representatives of the various partners on 18

th August 2010

Discussions held with representatives of SW, EA, ESCC, RDC and HBC

Working group

Borough-wide Aimed at gaining a better understanding of

flooding issues across Hastings

It must be noted that whereas additional items of data might have been provided by the various partners, the use and reference

of the information used for this stage of the assessment followed the guidelines set out by Defra. Therefore there might be some

data/information that was made available but was not deemed directly relevant for this particular phase of the SWMP.


2.2.2 Undertake Intermediate Assessment

The intermediate assessment started by using the output of the strategic assessment stage (top eight flood hotspots - as agreed

by the working group) and applying a priority scoring system to establish the top four flood hotspots which were the focus of the

intermediate assessment stage.

The priority scoring system used for this study was based on scoring systems used for other SWMPs and adjusted/modified to

reflect the type/quality of data available for this study. Among the factors considered for the scoring system were:

- Flooding History (number of incidents/internal/external)

- Number of properties within AStSWF (FMfSW were not available to inform this process)

- Location of critical infrastructure

- Flood Hotspots areas identified by sewer modelling

- Consequences of flooding (businesses/residences)

A detailed description of the scoring system adopted as well as a summary of the scoring itself is included as Appendix 2A.

Following the application of the priority scoring system, the top four flood hotspots were found to be:

- Town Centre (flood hotspot 1)

- Old Town (flood hotspot 2)

- Hollington Stream (flood hotspot 3)

- Warrior Square (flood hotspot 4)

The assessment undertaken for the above flood hotspots as part of this phase included a review of the data/information listed

above (Table 2.3) as well as the preparation of a series of maps/sketches.

As part of the Intermediate Assessment phase the following maps were created for the top four flood hotspots:

Table 2.4: Maps produced to inform the Intermediate Assessment of the flood hotspots


60156460/RA/1X0 Hastings Flood Hotspot X (AStSWF + Hastings Flooding History)

60156460/RA/1X1 Hastings Flood Hotspot X (Factors Influencing Flood Risk+ Hastings Flooding History)

60156460/RA/1X2 Hastings Flood Hotspot X (Sewer Network + Ground Contours)

60156460/RA/1X3 Hastings Flood Hotspot X (Aerial Photograph)

60156460/RA/1X4 Hastings Flood Hotspot X (Gullies)

X denotes the number assigned to the flood hotspot (1 to 4)

The above maps were used to inform a site visit carried out by the working group and aimed at sharing knowledge as well as

identifying reasons behind flooding at these locations. The site visits were undertaken on 18th

August 2010 and represented a

very important step in understanding the issues associated with these areas. The site visit briefing note (included as Appendix

2B) provides more details on the way the site visits were undertaken.

A site visit report was prepared for each of the top four flood hotspots. These reports summarise the findings of the intermediate

assessment carried out for each of these sites and are complemented by additional maps (see Table 2.5). The site visit reports

are also included as Appendix 2B.


Table 2.5: Maps produced to summarise outcome of Site Visits


60156460/RA/2X0 Historical Flooding Issues

60156460/RA/2X1 Potential Mitigation Measures

(X denotes the number assigned to the flood hotspot (1 to 4))

The intermediate assessment undertaken for the four flood hotspots is summarised in the table below.


Table 2.6: Summary of the findings of the Intermediate Assessment

Flood Hotspot

Reasons behind Historical Flooding

Predominant Flooding

Mechanisms

Likely Implications of Surface Water Flooding

Possible mitigation measures Comments

1. Town

Centre - Infrastructure failure/

capacity exceeded

- Natural valley

location

- Ground profile

- Overland flooding

(thresholds lower

than road – Town

Centre)

Significant duration/depth of flooding at Town Centre. Significant disruption caused to businesses and residents

Short Term: Flood resistance / resilience; education Medium Term: Modify ground profile; increase capacity of storm outfall Long Term: Replace the combined sewer system; increase number of surface water outfalls.

Further investigation required to improve understanding of links between pumping station and existing outfalls.

2. Old Town - Infrastructure

blockages/capacity

exceeded

- Natural valley

location

- Ground profile

- Overland flooding

(thresholds lower

than road –

George Street)

- Sewer capacity

exceeded /

blockages

Significant duration/depth of flooding at junction between The Bourne and Rock-a-Nore Road. Significant disruption caused to businesses

Short Term: Flood resistance / resilience; education Medium Term: Improve SUDS; increase capacity of storm outfall Long Term: Replace the combined sewer system;

make use of disconnected section of storm sewer; increase number of surface water outfalls.

3. Hollington

Stream - Channel blockages

- Sewer/culvert

capacity exceeded

- Inadequate use of

existing water

management

structures

- Nature of catchment

(Rapid Response)

- Sewer/culvert

capacity

exceeded as

outfalls unable to

discharge into

Hollington Stream

Significant duration/depth of flooding at junction between Battle Road and Upper Church Road as well as the southern edge of Hollington Old Lane. Significant disruption caused to residents

Short Term: Flood resistance / resilience; education; install trash screen; clear debris and improve understanding & use of water management structures Medium Term: Implementation of SUDS; increase

capacity of river channel Long Term: Additional storm water attenuation

Further investigation required to improve understanding of water management structures at upstream end of the catchment.

4. Warrior

Square - Infrastructure failure/

capacity exceeded

- Natural valley

location

- Sewer capacity

exceeded/failures

Isolated locations likely to experience significant depth/duration due to local topography (basements). Potential significant disruption to some businesses and residents

Short Term: Flood resistance / resilience; education Medium Term: Improve SUDS Long Term: Replace the combined sewer system; increase number of surface water outfalls


2.2.3 Determine whether more detailed assessment is required

This part of the intermediate assessment was informed by the review of the information made available by different sources and

the output of the site visits undertaken with representatives of the different partners.

The intermediate assessment concluded that there was a need to undertake detailed assessment for flood hotspot 3 – Hollington

Stream in order to gain a better understanding of the water management structures located at the upstream end of this

catchment. No other areas were found likely to benefit significantly from further assessment at this stage of the process.

The following table has been created to facilitate the presentation of the conclusions reached and recommendations made

following completion of the Intermediate Assessment.


Table 2.7: Summary of the Conclusions and Recommendations of the Intermediate Assessment

Flood Hotspot

Level of Understanding of

flooding mechanisms

Data available to facilitate improved understanding of flooding mechanisms

Possible Detailed Assessment Techniques (Benefits and Constraints)

Conclusions Recommendations

1. Town

Centre

Generally good

understanding of

flooding mechanisms

and areas at risk

- Sewer Network Models

(Infoworks CS)

An Infoworks 2-D model could be built combining the existing sewer network model with a digital terrain model. Benefits: Improved understanding of likely flood pathways and receptors as well as indication of depth, velocity, rate of onset and duration of flooding Constraints: Potentially costly and time consuming. Unlikely to inform any short term solutions.

Whereas an Infoworks 2-D model would be desirable, it is unlikely to provide any real value to the identified short term solutions. Additionally, the FMfSW provide some of the details that could be obtained from the Infoworks 2-D model.

- Do not undertake any

additional modelling at this

stage.

- Review FMfSW and continue

with Options Stage

2. Old Town Generally good understanding of flooding mechanisms and areas at risk


(Infoworks CS)





stage.


with Options Stage

3. Hollington

Stream

Reasonable understanding of flooding mechanisms and areas at risk. However, this could be improved by establishing condition and operation regime of water management structures at upstream end.

- ISIS/Tuflow (1-D/2-D)

model of Hollington

Stream (recently

completed by EA)

- MIKE 11 (1-D) model of

Hollington Stream (built

by Faber Maunsell in

2008 to inform the

Hastings SFRA)

Refinement of the recently completed ISIS/Tuflow model to identify the most appropriate operation regime for the water management structures at the upstream end of Hollington Stream Benefits: Identification of optimum operation regime for water management structures and potential for increased channel capacity. Constraints: To be effective needs to be accompanied by maintenance/operation plan which will depend on human intervention.

The refinement of the model will improve significantly the understanding of the operation of the water management structures. This will in turn enable the implementation of action plans aimed at reducing flood risk downstream by maximising storage upstream. The cost of this work is likely to be relatively low due to the amount of information readily available and the timeframe for completion should be relatively short.

- Proceed with the refinement

of the existing ISIS/Tuflow

model (detailed

assessment)

- Seek to improve emergency

response by contributing

effectively to the Hollington

Stream Rapid Response

Catchment Action Plan


Table 2.7: Summary of the Conclusions and Recommendations of the Intermediate Assessment (continued)

Flood Hotspot

Level of Understanding of

flooding mechanisms

Data available to facilitate improved understanding of flooding mechanisms

Possible Detailed Assessment Techniques (Benefits and Constraints)

Conclusions Recommendations

4. Warrior

Square

Generally good understanding of flooding mechanisms and areas at risk


(Infoworks CS)





stage.


with Options Stage


2.3 Detailed Assessment

The intermediate assessment concluded that there was potential for significant benefits arising from a better understanding of the

water management structures at the upstream end of the Hollington Stream catchment and the role they have on flood risk

(fluvial/surface water) in the area. A detailed assessment was therefore undertaken to complement the knowledge of this section

of the stream directly linked to flood hotspot 3.

The Detailed Assessment phase involved the following steps:

- Select modelling approach

- Develop modelling approach

- Quantify current and future flood risk

2.3.1 Select modelling approach

It was discussed and agreed within the working group that the modelling work should use as basis the hydraulic model for the

Combe Haven catchment (including Hollington Stream) completed in January 2010 by the Environment Agency. The modelling

work was therefore undertaken using a combination of ISIS (1-D) and Tuflow (2-D). This was deemed to be the most appropriate

tool to achieve the objectives set out above as in this area the risk of surface water flooding is directly related to fluvial flooding.

2.3.2 Develop modelling approach

The base model was reviewed and refined locally using historical information on the dams. No significant changes to the base

model were, however, undertaken.

2.3.3 Quantify current and future flood risk

The refined model enabled the formulation of a recommended operation regime aimed at maximising the storage volume

upstream of the dams thus reducing the surcharging of the culverts further downstream and making space for surface water to

enter the river network.

Additionally, the various scenarios run as part of the modelling process facilitated the identification of capacity limits for the dams

under low and high return period events. The modelling work undertaken as part of the detailed assessment phase is

summarised in Table 2.8 and described in detail in Appendix 2C.

Table 2.8: Summary of Modelling results in relation to Overtopping of the Dams and Surcharging of Culvert at Upper Glen Road

Return Period (Years)

Settings Overtopping Culvert Surcharge

Dam 1 Dam 2 Channel Section

Dam 1 Dam 2 Upper Glen

Rd Gardens

100

Fully Open Original Original No (Fb 2.9m) No (Fb 1.3m) Yes Yes

Original Fully Open Original No (Fb 1.4m) No (Fb 2.1m) Yes Yes

Fully Open Fully Open Original No (Fb 2.9m) No (Fb 2.1m) Yes Yes

¼ Opening ¼ Opening Original No (Fb 1.1m) Yes (nominal)

(0.01 m) Yes Yes

¼ Opening ¼ Opening Modified No (Fb 1.1m) No (at risk) (Fb <0.1m)

Yes Yes

5 ¼ Opening ¼ Opening Original No (Fb 2.5m) No (Fb 1.9m) No (at risk) Yes (nominal)

⅛ Opening ⅛ Opening Original No (Fb 1.1m) No (Fb 0.1m) No No (at risk)

20 ¼ Opening ¼ Opening Original No (Fb 1.6m) No (Fb 1.2m) Yes Yes

⅛ Opening ⅛Opening Original No (Fb 1.1m) Yes (0.6 m) No (at risk) No (at risk)

(Fb= Freeboard; Original= set up as per Original model; Dam 1= northern dam; Dam 2= southern dam)


2.4 Map and Communicate Risk

The final phase of the risk assessment stage involves mapping the areas identified as likely to be at risk of surface water flooding

and communicating this risk to the spatial and emergency planning teams of Hastings Borough Council as well as the relevant

stakeholders.

2.4.1 Map Surface Water Flooding

Mapping of the areas deemed susceptible to surface water flooding across Hastings was undertaken to:

- Help engage stakeholders on surface water flood risks

- Inform the spatial planning process

- Inform emergency planning functions

- Identify whether critical infrastructure is at risk from surface water flooding The information used to map surface water flood risk was refined throughout the production of the study as described below:

2.4.2 Areas Susceptible to Surface Water Flooding (AStSWF)

These are the first generation of EA Surface Water Flood Maps which were used as the basis for the ranking of settlements

deemed to be at risk of flooding from surface water by Defra as part of their initial funding allocation to tackle surface water flood

risk.

As far as the Hastings SWMP is concerned, these maps were the basis for the Preparation and Risk Assessment Stages of the

study. Furthermore, they were referred to when outlining potential solutions as part of the Options Stage of the study.

2.4.3 Flood Maps for Surface Water (FMfSW)

These are the second generation of EA Surface Water Flood Maps which were officially released at the end of November 2010.

These maps are generally deemed to provide a better representation (in comparison to the first generation) of surface water flood

risk as a result of significant refinement in the modelling process undertaken. It is important to note, however, that the FMfSW do

not supersede the AStSWF which should still be referred to as these maps represent a valid starting point, particularly in areas

where drainage networks are liable to blockage or are tide-locked.

As far as the Hastings SWMP is concerned, due to amount of work already undertaken using the AStSWF as basis, the use of

these refined maps was focused towards informing the mapping and communicating phase rather than revisiting the assessment

previously undertaken. In the absence of the locally agreed surface water information, to be confirmed by the lead local flood

authority (ESCC) as part of the Preliminary Flood Risk Assessment (PFRA), these maps should be referred to as they represent

the primary source of national derived information.

The AStSWF and the FMfSW were reviewed and discussed by the working group and found to provide a good representation of

the areas deemed to be at risk of surface water flooding across Hastings. It is accepted, however, that there are some areas with

a flooding history which are not shown as “at risk” and therefore, it is expected that these will be captured as part of the locally

agreed surface water information for the area.

The differences between the AStSWF and the FMfSW are summarised in Table 2.9.

Table 2.9: Differences between AStSWF and FMfSW

Properties AStSWF FMfSW Why different/same?

Annual Probability

Rainfall

1 in 200

chance

1 in 30 and 1 in

200 chance

1 in 30 added to allow a better understanding of lower

consequence, more frequent events such as the onset of sewer

flooding.

Storm Duration 6.5 hrs 1.1 hr profile 1.1 hr produced on average higher results than other durations

piloted

Rainfall Profile 50% summer 50% summer Recommended profile from the Flood Estimation Handbook (FEH)


Table 2.9: Differences between AStSWF and FMfSW (continued)

Properties AStSWF FMfSW Why different/same?

Reduction to

rainfall amount to

represent

infiltration

0

Reduction to

39% in rural

areas and 70%

in urban areas

AStSWF did not consider infiltration

Reduction to

rainfall amount to

represent sewer

flow

0

Reduction of

0mm/hr rural,

12mm/hr urban

AStSWF did not consider effects of sewers

Manning‟s „n‟ 0.1 0.1 rural, 0.03

urban

Urban value reduces now as buildings are included in DTM.

Previously n was increased to account for lack of building

representation

DTM

Infoterra bare

earth LIDAR

and Geo

Perspectives

EA 2010

Composite

(SAR, EA

LIDAR and

PGA2 LIDAR)

with OS 2009

Mastermap

Buildings (DTM

raised by 5m)

Access to EA LIDAR available

Model Resolution 5m 5m Modelling at smaller resolution (for example 2m) was impracticable

at a national scale with the model used due to processing demands.

Model Domain

Size 5 km x 5 km 5 km x 5 km

5km x 5 km provides a reasonable balance between high intensity

local storms and larger less intense events

Buildings Not

represented

Represented in

the DTM using

the 2009 OS

Mastermap

Buildings layer

Earlier work identified that the presence of buildings improved the

routing of flow in urban areas. Use high buildings based upon the

DTM elevation plus 5m. Building outlines are best represented by

OS Mastermap polygons

Flood Depth

Threshold Bands

- 0.1 to 0.3m

(less)

- 0.3 to 1m

(intermediate)

- >1m (more)

- >0.1m

- >0.3m Consultation with partners resulted in 2 bands being produced

The guidance provided to accompany the FMfSW highlighted the importance of establishing the levels of confidence associated

with the EA Surface Water Flood Maps in relation to the local conditions. This exercise was undertaken with the working group

and the results are included in Table 2.10.


Table 2.10: EA Surface Water Flood Maps - National and Local (Hastings) Uncertainty Levels

FMfSW AStSWF

Topic Source of Uncertainty

Confidence

Level National

Confidence

Level Local

(Hastings)

Source of Uncertainty Confidence

Level National

Confidence

Level Local

(Hastings)

Data

DTM accuracy Data ground level compared to real

ground level High High

Data ground level compared to real ground level

Medium Medium

DTM

resolution

Average ground level applied to 5m x 5m grid compared to real ground level

Medium - High Medium - High Average ground level applied to 5m x 5m grid compared to real ground level

Medium Medium

Consideration

of Buildings

MasterMap building position in degraded DTM compared to reality

Medium Medium N/A N/A N/A

Hydrology

How realistic is rainfall profile Medium Medium How realistic is rainfall profile Medium Medium

How well storm duration reflects worst case

Medium - High Medium - High How well storm duration reflects worst

case Medium - Low Medium - Low

Other main

data Inputs The EA intends to continue to build up their understanding of uncertainty of other inputs

Mo

de

l

Type How well does JFLOW route the water High High How well does JFLOW route the

water High High

Urban or Rural

Area

Are all urban areas in reality represented as urban in the model

High High N/A N/A N/A

Infiltration

Assumptions

How representative Urban and rural factors are compared to reality

Medium Medium How representative is no infiltration Very Low Very Low

Drainage

Assumptions

How representative 12mm/hr is compared to reality

Medium - Low Medium - Low How representative is 0mm/hr

compared to reality Very Low Very Low

Other major

model variable

assumptions

The EA intends to continue to build up their understanding of uncertainty of other variables / assumptions

Roughness How representative is the global use of

Mannings n values of 0.1 (rural) and 0.03 (urban)

Medium Medium How representative is the blanket use

use of Mannings n value of 0.1 Low Low


The local assessment of uncertainty associated with the EA surface water flood maps was found to be very similar to the national

assessment undertaken by the EA. It was concluded therefore that the FMfSW provide a refined understanding of surface water

flooding issues across Hastings and therefore should be used as the primary point of reference in the absence of locally agreed

surface water flood risk information.

2.4.4 Other Sources of Flood Mapping Information

In addition to the EA Surface Water Flood Maps, other hydraulic models were used/developed during the preparation of the

Hastings SWMP and to inform relevant maps. These are summarised below:

- Overland flow model for Hollington Primary School which provides a better understanding of the overland flow paths and flood

receptors around flood hotspot 3

- Hydraulic modelling of Upper Hollington Stream which assisted the understanding of the water management structures (dams)

in the area but was not used to inform the mapping process as this was not the purpose of this model.

The various maps and sketches produced as part of the study are summarised below and included in the mapping section. All

maps are supported by a GIS database system which is available to Hastings Borough Council.

Table 2.11: List of Maps/Sketches produced to inform the Hastings SWMP

Drawing No. Title

001 Hastings Flooding History

002 AStSWF + Hastings Flooding History

003 Factors Influencing Flood Risk

004 LiDAR Topographic Information

005 Potential areas for SUDS (Borough wide)

006(A) FMfSW (1 in 200) + Hastings Flooding History

006(B) FMfSW (1 in 30) + Hastings Flooding History

007(A) Critical Infrastructure + FMfSW (1 in 200)

007(B) Critical Infrastructure + FMfSW (1 in 30)

110 - 114 Flood Hotspot 1 covering (AStSWF, flooding history, factors influencing flood risk, sewer network, ground contours, aerial photography and gullies)

115(A) and (B) Flood Hotspot 1 FMfSW (1 in 200) and (1 in 30) respectively including flooding history







210 and 211 Flood Hotspot 1 covering (historical flooding issues and potential mitigation measures respectively, as identified during the walkover survey with the working group)




Table 2.11: List of Maps/Sketches produced to inform the Hastings SWMP (continued)

Drawing No. Title


SKETCH 001 Flood Hotspots

SKETCH 025 FHS 1 Medium Term Solutions

SKETCH 026 Upper Hollington Stream Maintenance (with annotation)

SKETCH 027 Flood Resistance Recommendations - Example Properties

Note: It is important to note that whereas more drawings/sketches were produced throughout the study to inform discussion, the ones listed above summarise the process.

2.4.4.1 Borough-wide Asset Register

During initial discussions with Hastings Borough Council and the working group, it became apparent that in order to improve the

understanding of the existing flood risk management and drainage infrastructure across Hastings, a Borough-wide asset register

needed to be created.

The reasoning behind this requirement was the perceived lack of information as to the ownership and maintenance regimes

associated with the various assets across the Borough.

The asset register was produced using a GIS system and was informed by significant amount of data provided by the various

partners. Due to the nature of the information included in the asset register, the use of GIS software (ArcView) is required to

interrogate the asset register. The asset register includes a criticality rating for all assets aimed at providing an indication as to

their importance from a surface water flood risk point of view. Also included is an indication of the current maintenance regime for

all assets, as advised by the relevant partners. Appendix 2D includes summaries on how the asset register was put together from

a technical perspective and how to interrogate it from a user point of view.

The main constraint in producing the asset register was the lack of detail/consistency of the asset records provided by the

different partners. As a result of these inconsistencies and despite efforts to provide a standard minimum level of information for

every asset, a few gaps remain for certain assets.

To complement the asset register, the production of a Borough-wide asset maintenance plan was originally discussed with the

working group. Unfortunately due to the number of assets identified across the Borough and the varying quality/level of detail of

the records available for the different assets, it was deemed impractical to obtain maintenance information for all assets. A

generic summary of typical maintenance periods for the assets in Hastings has been produced and is included in Appendix 2E.

2.4.5 Communicate Risk

One of the most important parts of the process is communicating the risk identified during the various stages of assessment. For

the Hastings SWMP, the following steps were identified as part of this phase of the study:

- Communicate risk to spatial planning

- Communicate risk to emergency planning

- Communicate risk to other stakeholders

2.4.5.1 Communicate risk to spatial planning

The findings of the Hastings SWMP are being communicated to the spatial planning team by:

- Supplementary Planning Note on Surface Water Flood Risk: this was produced in coordination with the working group to

provide additional guidance to the planning team of Hastings Borough Council on how to deal with planning applications in

areas deemed susceptible to surface water flooding. The Supplementary Planning Note on Surface Water Flood Risk is

included as Appendix 2F


- Mapping of Surface Water Flood Risk: the various maps produced as part of the Hastings SWMP should inform the spatial

planning process and eventually be incorporated in a revised version of the Strategic Flood Risk Assessment (SFRA). Refer to

the mapping section for a full description of the maps and copies of them.

- Involvement in the working group: the spatial planning team are represented in the working group and given the commitment

of all partners to maintain the group beyond the completion of the Hastings SWMP study, it is envisaged that they will continue

to play an important role in shaping how surface water flood risk is managed across Hastings.

- Workshop for Hastings Borough Council Officers: it is envisaged that as part of the communications strategy for the Hastings

SWMP, a workshop/presentation will be given to councillors and Hastings Borough Council officers. The key messages for the

spatial planning team will be reiterated during this event.

2.4.5.2 Communicate risk to emergency planning

The findings of the Hastings SWMP are being communicated to the emergency planning team by:

- Mapping of Surface Water Flood Risk: the various maps produced as part of the Hastings SWMP should inform the

emergency planning process and any emergency action plans for the Borough. Refer to the mapping section for a full

description of the maps and copies of them.

- Involvement in the working group: the emergency planning team are represented in the working group and given the

commitment of all partners to maintain the group beyond the completion of the Hastings SWMP study, it is envisaged that they

will continue to play an important role in shaping how surface water flood risk is managed across Hastings.

- Workshop for Hastings Borough Council Officers: it is envisaged that as part of the communications strategy for the Hastings

SWMP, a workshop/presentation will be given to councillors and Hastings Borough Council officers. The key messages for the

emergency planning team will be reiterated during this event.

In addition to the above, a review of the procedures in place to deal with flood reports was carried out in close liaison with the

emergency planning team. As a result of this review the following documents, included as Appendix 2G, were produced:

- Procedure “to answer“ flood incident reports

- Flood Response Plan

- Flood Incident Report Form

2.4.5.3 Communicate risk to other stakeholders

The findings of the Hastings SWMP are being communicated to other stakeholders by:

- Mapping Critical Infrastructure likely to be affected by Surface Water Flooding: two maps and associated summary tables

were produced to identify critical infrastructure likely to be affected by surface water flooding during the 1 in 30yr and the 1 in

200 yr return period events. The tables are included as Appendix 2H and the maps in the mapping section.

In addition to the above, the following documents were drafted with the aim of informing the understanding of the general public

to flood risk and actions they should consider to minimise the impacts of flooding events.

- Flood Information Pack

- Flood Resistance/Resilience Measures These are discussed in more detail in the Options Stage of this report.


The Stage of the SWMP aims to identify and assess the options to mitigate/reduce the risk of surface water flooding across the

Borough with the intention of finding the most appropriate mitigation measures which can be agreed and taken forward to the

Implementation Stage. To achieve this objective the Options Stage was divided in two phases:

- Identify measures

- Assess Options

3.1 Identify Measures

The purpose of this phase is to formulate and short-list the various options to be assessed. The Identify Measures Phase

involved the following steps:

- Identify measures

- Short-list measures

3.1.1 Identify Measures

As part of the risk assessment stage, a number of measures were identified as possible mitigation to the risk of surface water

flooding in the short, medium and long term for the top four flood hotspots. These are summarised below:

Table 3.1: Summary of Options identified during the Risk Assessment Stage

Flood Hotspot Possible mitigation measures

Short Term Medium Term Long Term

1. Town Centre - Flood resistance / resilience

- Education

- Modify ground profile

- Increase capacity of storm

outfall

- Replace the combined sewer

system

- Increase number of surface

water outfalls

2. Old Town - Flood resistance / resilience

- Education

- Improve SUDS

- Increase capacity of storm

outfall

- Replace the combined sewer

system

- Make use of disconnected

section of storm sewer


water outfalls.

3. Hollington

Stream - Flood resistance / resilience

- Education

- Install trash screen

- Clear debris and Improve

understanding & use of

water management

structures

- Improve maintenance of

sewer/culvert system along

Hollington Old Lane

- Implementation of SUDS

- Increase capacity of river

channel

- Additional storm water

attenuation

4. Warrior

Square - Flood resistance / resilience

- Education

- Improve SUDS - Replace the combined sewer

system


water outfalls

3 Options Stage


3.1.2 Short-list measures

In order to establish what options should be taken forward to the next stage of the Options Appraisal process, the Defra

Guidance recommends a short listing criteria which is summarised below.

Table 3.2: Short-listing Criteria Recommended by Defra

Criteria Description Score

Technical Is it technically possible and buildable?

Will it be robust and reliable? U (unacceptable) – measure eliminated from

further consideration

-2 severe negative outcome

-1 moderate negative outcome

+1 moderate positive outcome

+2 highly positive outcome

Economic Will benefits exceed costs?

Social Will the community benefit or suffer from

implementation of the measure?

Environmental Will the environment benefit or suffer from the

implementation of the measure?

Objectives Will it help achieve the objectives of the SWMP

partnership?

The Defra guidance also recommends that the “Do nothing” and “Do minimum” options are taken forward to the next stage and

that the reasons for short-listing or rejecting any measures should be documented as part of the assessment.

The application of the above short-listing criteria on the top four flood hotspots was undertaken as summarised in the following

tables.

Table 3.3: Application of Short-listing Criteria to Flood Hotspot 1

Option

Te

ch

nic

al

Ec

on

om

ic

So

cia

l

En

vir

on

men

tal

Ob

jec

tiv

es

Ov

era

ll S

co

re

Taken to detailed

analysis? Comments

Do Nothing 2 -1 -2 0 -2 -3 Yes Taken forward to option appraisal stage as

recommended by Defra Guidance

Do Minimum 1 -1 -1 0 -1 -2 Yes Taken forward to option appraisal stage as


Flood resistance / resilience

2 1 1 1 2 7 Yes Technically feasible and financially viable

option that could provide significant improvements

Education 2 1 1 1 1 6 Yes Feasible and potentially inexpensive. The major problem will be public willingness to

implement advice

Modify ground profile 2 -1 1 1 2 5 Yes Technically can be implemented and would

benefit the area

Increase capacity of storm outfall

1 -2 1 1 1 2 No Viable from a technical point but unlikely to

be feasible from a financial perspective

Replace the combined sewer system

2 U 1 1 0 U No Although technically feasible the cost is not

viable.

Increase number of surface water outfalls

1 -2 1 1 1 2 No There could be implications on the

environment (water quality) but the main problem is the financial aspect



Option

Te

ch

nic

al

Ec

on

om

ic

So

cia

l

En

vir

on

men

tal

Ob

jec

tiv

es

Ov

era

ll S

co

re

Taken to detailed

analysis? Comments









implement advice

Improve SUDS 2 -1 1 1 1 4 No Technically can be implemented but would

bring very limited benefits to the area as suggested by revised flood mapping

Increase capacity of storm outfall

1 -2 1 1 1 2 No Viable from a technical point but unlikely to

be feasible from a financial perspective



viable.

Make use of disconnected section of

storm sewer 1 -2 1 1 1 2 No

Technically feasible but will need to be undertaken as part of a wider scheme to

make it workable.






Option

Te

ch

nic

al

Ec

on

om

ic

So

cia

l

En

vir

on

men

tal

Ob

jec

tiv

es

Ov

era

ll S

co

re

Taken to detailed

analysis? Comments









implement advice

Install trash screen 2 1 1 1 1 6 Yes Simple and economical to implement

provided the community is prepared to support the option

Clear debris and improve understanding

& use of water management structures

1 1 1 2 1 6 Yes

Technically possible but management of the structures will depend on human

resources available to facilitate manual operation

Improve maintenance of sewer/culvert system along Hollington Old

Lane

1 -1 1 1 1 3 No

Viable from a technical point of view but likely to bring very limited benefits as there

is an issue with capacity of the system during significant storm events which would

be better addressed by exploring other options

Implementation of SUDS

2 -1 2 2 2 7 Yes Technically can be implemented and could bring about significant benefits to the area.

Increase capacity of river channel

2 -1 1 1 1 5 Yes

Feasible from a technical perspective but option limited to locations upstream of

water management structures due to river channel profile.

Additional storm water attenuation

1 -2 1 1 1 2 No

Likely to be financially unviable due to presence of other underground services and lack of space to accommodate it in

areas susceptible to surface water flooding



Option

Te

ch

nic

al

Ec

on

om

ic

So

cia

l

En

vir

on

men

tal

Ob

jec

tiv

es

Ov

era

ll S

co

re

Taken to detailed

analysis? Comments









implement advice

Improve SUDS 2 -1 1 1 1 4 No Technically can be implemented but would

bring very limited benefits to the area as suggested by revised flood mapping



viable.




3.2 Assess Options

The purpose of this phase is to carry out the necessary assessment of the shot-listed options in order to define the preferred

options to be taken forward to the implementation and review stage. The Assess options Phase involved the following steps:

Identify assessment to be carried out

Undertake assessment of options

Agree preferred options

3.2.1 Identify assessment to be carried out

Following the short-listing process, the various options identified as suitable to be taken forward to the next stage were discussed

in principle by the working group with a view to identify the level of assessment required.

The nature of the options taken forward was such that the need for a detailed cost/benefit analysis was deemed unnecessary

and therefore the assessment of the options was based on engineering judgement, local knowledge and experience of all the

members of the working group. Furthermore, no significant investment warranting the application of such assessment methods is

envisaged by any of the partners in the near future following completion of the study.

3.2.2 Undertake assessment of Options

The assessment of Options was undertaken in close liaison with the working group to ensure all relevant local knowledge from

the partners was taken into consideration. The following tables summarise the process followed to assess the shortlisted options

and the conclusions reached.


Table 3.7: Summary of Assessment of Shortlisted Options for Flood Hotspot 1

Option Further Assessment Undertaken Assessment Conclusions Option Recommendations

Do Nothing - Working group discussions - Likely to have significant financial and personal implications

for Hastings residents as flood risk will increase - Unacceptable

Do Minimum - Working group discussions - Will not bring any benefits to Hastings residents as flooding

will increase with time due to climate change

- Maintaining the current maintenance regime

is deemed inadequate taking into

consideration the problems identified in the

area as well as the likely increase of

flooding in the future due to climate change.


- Working group discussions

- Flood Resistance/Resilience

Measures – Summary Table (see

Appendix 3A)


Measures for individual properties

(see Appendix 3A)

- This option would be beneficial to a significant number of

residential and commercial properties in this flood hotspot.

The only drawback is the limited funding available for

delivering solutions on the ground and therefore the

implementation of this type of measures would have to be

financed by the residents benefiting from them or through

EA/DEFRA grants for property level flood protection.

- Promote actively as part of an education

campaign.

- Deliver a sample solution on the ground, as

per the recommendations made for

individual properties.

- Seek funding through applications for

EA/DEFRA grants for property level flood

protection.

Education




Appendix 3A)

- Flood Advice Pack (see Appendix 3B)

- An education campaign is considered essential to reduce

the risk of surface water flooding across the Borough.

- Carry out a series of public events aimed at

educating local residents on flood risk and

engaging them to contribute to the

successful implementation of solutions on

the ground.

Modify ground profile


- Medium term solutions (see Appendix

3C)

- This option could help mitigate the impact of surface water

flooding to commercial properties around Priory Meadows

shopping centre; in particular those surrounding the square

(i.e. Old cricket ground). Flooding problems in the area are

unlikely to disappear, however, unless there is a significant

change to the ground profiles which could be compromised

by the large amount of underground services present.

- Engage the management company

responsible for the Priory Meadows area

with a view to seek the delivery on the

ground of the suggestions made for the

area. This could be a planning condition for

any further works proposed in the area.








- Maintaining the current maintenance regime

is deemed inadequate taking into

consideration the problems identified in the

area as well as the likely increase of

flooding in the future due to climate change.





Appendix 3A)


Measures for individual properties

(see Appendix 3A)

- This option would be beneficial to a various commercial and

potentially some residential properties in this flood hotspot.

The main drawback is the limited funding available for





- Promote actively as part of an education

campaign.

- Deliver a sample solution on the ground, as

per the recommendations made for

individual properties.


EA/DEFRA grants for property level flood

protection.

Education




Appendix 3A)


- An education campaign is considered essential to reduce

the risk of surface water flooding across the Borough.


educating local residents on flood risk and

engaging them to contribute to the

successful implementation of solutions on

the ground.








- Maintaining the current maintenance regime is

deemed inadequate taking into consideration the

problems identified in the area as well as the likely

increase of flooding in the future due to climate

change.



- Flood Resistance/Resilience Measures –

Summary Table (see Appendix 3A)

- Flood Resistance/Resilience Measures for

individual properties (see Appendix 3A)

- This option would be beneficial to a limited number of

residential properties that have been severely affected by

surface water flooding in the past. The only drawback is the

limited funding available for delivering solutions on the ground

and therefore the implementation of this type of measures

would have to be financed by the residents benefiting from

them or through EA/DEFRA grants for property level flood

protection.

- Promote actively as part of an education campaign.

- Deliver a sample solution on the ground, as per the

recommendations made for individual properties.

- Seek funding through applications for EA/DEFRA

grants for property level flood protection.

Education





- Upper Hollington Stream Maintenance

(see Appendix 3D)

- An education campaign is considered essential to reduce the

risk of surface water flooding across the Borough.

Furthermore, this flood hotspot would benefit from active

monitoring of the stream which could be done by local

residents provided the necessary training is made available.


educating local residents on flood risk and engaging

them to contribute to the successful implementation

of solutions on the ground.

Install trash screen



(see Appendix 3D)

- The installation of a trash screen at the culvert entrance at

Ashbrook Park, Upper Church Road could provide some

benefits if properly maintained.

- This option is generally deemed unacceptable by local

residents who are of the opinion that previous flooding

incidents have been exacerbated by trash screens being

blocked.

- Consideration could be given to containment of the stream

under surcharge conditions, but has not been taken forward

as an option due to the likely cost of containment required

immediately upstream.

- Engage local residents to seek their support and

reach an agreement on the type of trash screen that

could be implemented and its location with a view to

reduce the risk of blockages affecting this culvert.


Table 3.9: Summary of Assessment of Shortlisted Options for Flood Hotspot 3 (continued)


Clear debris and improve

understanding & use of water management

structures



(see Appendix 3D)

- Hydraulic Modelling of Upper Hollington

Stream (see Appendix 2C)

- An improved maintenance regime of the Upper Hollington

Stream would provide hydraulic and environmental benefits to

the stream and the surrounding area.

- The water management structures (dams) can store

significant volumes of water behind them and should be

operated in a way that maximises the benefits for the

properties downstream (see technical note – Appendix 3E).

- The culverts downstream of the dams present significant

constrictions to the flow as they are either surcharged or at

risk of surcharging during most return period events.

Therefore it is important to reduce as much as possible the

amount of flow reaching these culverts by capturing and

storing river flows using the dams. In addition, consideration

could be given to the introduction of sluices at culvert

entrances to reduce surcharge within the culverted sections,

but this has not been taken forward as an option

recommendation due to the likely cost of containment

required immediately upstream.

- Engage local residents to gain their support in the

effective monitoring and clearance of the stream

under the necessary amount of guidance and

supervision from the relevant authority.

- Inform the operations team responsible for the

dams the recommendations made with regards to

their operation following the hydraulic modelling

work undertaken.

- Improve maintenance of the penstocks and

undertake regular tests to ensure they are fully

operational and ready to come into action when

required (under storm conditions)

- Reinforce the message “less debris on the stream =

less flooding” between local residents as part of an

education campaign.



- SUDS Strategy for Hollington Primary

School (see Appendix 3E). This included

an overland flow model of the school and

its vicinity.

- Medium Term Solutions (see Appendix

3C)

- The implementation of SUDS techniques (retrofitting) at

Hollington Primary School would bring potentially significant

benefits not only for the school but also for the surrounding

area from a surface water flooding perspective.

- Three potential solutions have been recommended from a

technical perspective for pricing and potential implementation

depending on funding availability.

- The risk of surface water flooding in the area will not be

eliminated following the retrofitting of SUDS at the school site

due to the significant rainfall runoff generated in other parts of

the catchment.

- Implement at least one of the three recommended

options for retrofitting of SUDS at Hollington

Primary School as part of the SUDS retrofitting

programme of the EA and the Implementation

Stage of the SWMP.

- Promote and implement the remaining two

recommended options for the school at the earliest

possible opportunity.

- Seek future opportunities to retrofit SUDS at the

school site and/or the surrounding area.


Table 3.9: Summary of Assessment of Shortlisted Options for Flood Hotspot 3 (continued)


Increase capacity of river

channel



(see Appendix 3D)

- Hydraulic Modelling of Upper Hollington

Stream (see Appendix 2C)

- This could be done at the upstream end where residential

properties are not in close proximity to the watercourse.

However, due to the nature of the catchment (rapid response)

and the apparent lack of capacity of the culverts downstream

of the dams, there is little point in trying to get more flow

through the culverts. One possible alternative could be to

increase channel capacity immediately upstream of the dams

with the intention of storing more water behind them. This

scenario was modelled and found to have very limited benefit

for the residential area downstream as the culverts become

surcharged even under relatively low return period events. A

more effective and less expensive solution would be to

manage effectively the penstock systems of the dams to

constrict the flow at the upstream end of the catchment

without increasing the channel capacity (see Appendix 3E).

- DO NOT PURSUE. Concentrate on optimising the

use of existing dams/penstock rather than

increasing the capacity of the river channel.








- Maintaining the current maintenance

regime is deemed inadequate taking

into consideration the problems

identified in the area as well as the

likely increase of flooding in the future

due to climate change.




Summary Table (see Appendix3A)

- Flood Resistance/Resilience Measures for

individual properties (see Appendix 3A)

- This option would be beneficial to a various commercial and

potentially some residential properties in this flood hotspot.

The main drawback is the limited funding available for





- Promote actively as part of an

education campaign.

- Deliver a sample solution on the

ground, as per the recommendations

made for individual properties.


EA/DEFRA grants for property level

flood protection.

Education





- An education campaign is considered essential to reduce the

risk of surface water flooding across the Borough.

- Carry out a series of public events

aimed at educating local residents on

flood risk and engaging them to

contribute to the successful

implementation of solutions on the

ground.


In addition to the assessment of shortlisted options for the top four flood hotspots, a series of Borough-wide studies/investigations

were undertaken with the aim of improving the management of surface water flood risk. These are summarised below:

Table 3.11: Summary of Borough-wide studies/investigations

Title Topics Covered Recommendations

Medium Term Solutions

(see Appendix C)

- Possible improvements to the

drainage arrangements at the Town

Centre

- Potential locations for retrofitting of

SUDS across the Borough.

- Engage the management company responsible for the

Priory Meadows area with a view to seek the delivery on

the ground of the suggestions made for the location.

- Seek future opportunities to retrofit SUDS across the

Borough as per but not limited to the suggestions made.

Asset Register (see Appendix 2D)

- Compilation of flood risk and

drainage management assets across

the Borough (main focus = surface

water flood risk)

- Identification of criticality of assets

from a surface water flood risk

perspective

- Gathering of details on maintenance

regimes for assets across the

Borough

- Ownership and responsibility for keeping the asset

register up to date needs to be established between HBC

and ESCC.

- A system needs to be put in place for communicating any

updates/changes to the asset register between all

partners

- Identify gaps in information and complete them at the

earliest possible opportunity

- Review maintenance regimes to ensure adequate

attention is given to the assets according to their criticality.

- Update the asset register regularly to ensure it remains fit

for purpose.

Flood Advice Pack (see Appendix 3B)

- General and Hastings specific

information/advice with regards to

flooding and what to do before,

during and after a flood event

- Distribute to residents as part of a Borough-wide

education campaign.

- Undertake regular reviews to ensure advice remains

current.

Procedure “to answer“ flood

incident reports (see Appendix 2G)

- Guidelines for call handlers as to

how to take reports of flooding from

members of the public.

- Contact details for key stakeholders

- Inform/train the team responsible for taking these calls to

ensure a consistent and suitable approach.

- Undertake regular reviews to ensure procedures remain

current.

Flood Response Plan (see Appendix 2G)

- Guidelines for call handlers as to

how to direct/action reports of

flooding from members of the public.

This form complements the

procedure “to answer” flood incident

report

- Inform/train the team responsible for taking these calls to

ensure a consistent and suitable approach.


current.

Flood Incident Report Form

(see Appendix 2G)

- Single form to capture details of the

flooding experienced at property

level. This form complements the

procedure “to answer” flood incident

report and the flood response plan.

- Inform/train the team responsible for carrying out post-

flood events interviews to ensure a consistent approach.

- Keep records of flooding incidents in a central location (to

be agreed between ESCC and HBC) to ensure important

reference data is not lost.


current.


Table 3.11: Summary of Borough-wide studies/investigations (continued)

Title Topics Covered Recommendations

Critical Infrastructure likely to be affected by Surface Water

Flooding (see Appendix 2H)

- Critical infrastructure located within

or in close proximity to areas at risk

as identified by the FMfSW.

- Raise awareness between the various stakeholders

responsible for these assets of the risk to surface water

flooding and what could be done to mitigate it.

- Review relevant information when updates on areas at

risk of surface water flooding are issued.

Advisory Planning Note

- Guidelines for the spatial planning

team to ensure surface water flood

risk is considered when assessing

planning applications

- Inform/train the spatial planning team to ensure a

consistent and suitable approach when assessing

planning applications.

- Undertake regular reviews to ensure advice remains

current and fit for purpose.

3.2.3 Agree Preferred Options

Following the short listing and assessment of the various options formulated, a number of preferred options for implementation

were identified by the working group as summarised in Table 3.12.

The preferred options will be complemented by a number of actions aimed at improving the management of surface water flood

risk across the Borough as summarised in Table 3.13.


Table 3.12: Summary of Preferred Options to be taken forward to Implementation Stage

Option Beneficiaries Possible Constraints Possible Solutions

Flood Resistance / Resilience

- All residential / commercial

properties that incorporate these

systems

- Lack of funding to implement these

techniques.

- Unwillingness of residents to incorporate

these systems due to aesthetic or operation

concerns.

- Bid for EA/DEFRA grants for property level flood

protection.


Education - Borough-wide benefits - Lack of interest

- Start with areas affected in the past where there is

likely to be interest and then try to make it

Borough–wide by engaging community groups and

schools.

Modify ground profile

- Flood Hotspot 1 (Town Centre) but

similar criteria could potentially be

applied elsewhere

- Lack of funding to implement recommended

improvements

- Unwillingness of management company to

get involved and contribute

- Bid for EA/DEFRA grants for property level flood

protection (where possible).

- Engage Management Company to ensure key

benefits are highlighted.

- Create a planning condition to be met by anyone

proposing future works in the area affected.

Install trash screen - Flood Hotspot 3 (Hollington Stream) - Unwillingness of residents to accept the

installation of this type of asset.

- Engage local residents to seek their support and

reach an agreement.

Clear debris and improve understanding

& use of water management

structures

- Flood Hotspot 3 (Hollington Stream)

- Insufficient human resources to monitor

regularly the watercourse and associated

structures.

- Mechanical problems with penstocks

- Insufficient notice ahead of a storm event to

allow calibration of penstocks as required

- Engage local community to get their support

- More strict/regular maintenance applied to these

key elements of the dams.

- Set the penstocks to the recommended opening to

maximise storage as default and only change it

when necessary.


- Hollington Primary School and

immediate vicinity (Blackman

Avenue, Hollington Old Lane)

- Lack of funding to retrofit SUDS - Contributions from EA SUDS Retrofitting Project,

HBC and any other partners able to do so.


Table 3.13: Summary of Agreed Complementary Actions to Improve Surface Water Management across Hastings

Complementary Action

Beneficiaries Possible Constraints Possible Solutions

Seek Opportunities to Retrofit SUDS

- Areas where retrofitting is

implemented

- Lack of funding to implement these

techniques.

- Unwillingness of residents to incorporate

these systems.

- Bid for EA/DEFRA grants.


Maintain an up to date Borough – wide asset

register - Borough-wide benefits

- Gaps in information

- Asset register not kept up to date

- Each partner responsible for filling the gaps

associated with their assets.

- Partner in charge of keeping the asset register

current to outline system for regular information

updates to be circulated and incorporated to the

system.

Review maintenance regime for all assets in accordance with their

criticality

- Borough-wide benefits

- Insufficient information on maintenance of

assets

- Lack of human/financial resources to improve

maintenance regime of critical assets

- Partners to be responsible for identifying the

maintenance associated with their assets (if not

done already)

- Seek opportunities for community involvement in

monitoring/maintenance activities.

Device a suitable flood response and report

procedure - Borough-wide benefits

- Call handlers unfamiliar with procedure and

therefore unable to provide consistent advice

- Provide necessary training and background

information to call handlers to facilitate their work.

Seek Opportunities to reduce the risk of

surface water flooding affecting critical infrastructure


- Lack of understanding of the risk from key

stakeholders owners of these critical assets.

- Lack of funding for the implementation of

suitable solutions.

- Engage asset owners to raise their awareness

- Seek the incorporation of flood protection schemes

to the capital programmes for asset management

of the relevant organisations.

Follow the Advisory Planning Note on

Surface Water Flood Risk


- Spatial Planning team unfamiliar with SWMP

and therefore unable to provide consistent

advice

- Provide necessary training and background

information to spatial planning team to facilitate

their work

Explore opportunities to enmain the upper

part of Hollington Stream

- Residents in the Hollington Stream

Catchment

- Lack of human/financial resources to facilitate

this process

- Seek opportunities for community involvement in

monitoring/maintenance activities as this would

reduce costs and time required to deal with issues.


This final stage of the study is about preparing an implementation strategy (i.e. an action plan), delivering the agreed actions and

monitoring implementation of these actions. This stage was undertaken in two phases:

- Prepare Action Plan

- Implement and Review Action Plan

4.1 Prepare Action Plan

The objective of this phase was to prioritise the options to be implemented and schedule the delivery of the various agreed

mitigation measures in coordination with the various partners and other stakeholders. This phase involved the following steps:

- Prepare Action Plan

- Review and publish the Action Plan

4.1.1 Prepare Action Plan

The action plan was prepared using the output of the Options Stage of the study and was informed by discussions with the

working group with regards to possibilities and constraints to fund the identified solutions in the short, medium and long term.

Tables 4.1 and 4.2 summarise the plan of action to deliver the options and associated complementary actions identified as part of

the Hastings SWMP. A number of terms introduced as part of these tables are summarised below:

Priority Ranking: The priority assigned to the option (O) /complementary action (CA) based on the likely benefits on the ground

(number of properties benefiting directly)

Option / Complementary Action: Provides a description of the option/complementary action.

Delivery Responsibility: The organisation(s) identified as directly responsible for organising/supporting the delivery of the option

or complementary action. A lead organisation was identified when more than one organisation were likely to contribute to the

implementation of the action. It is the lead organisation who is ultimately responsible for coordinating the support from others and

delivering on the ground.

Financial Responsibility: The organisation(s) identified as directly responsible for funding the delivery of the option or

complementary action. A lead organisation was identified when more than one organisation were likely to contribute to the

implementation of the action. It is the lead organisation who is ultimately responsible for coordinating the support from others and

delivering on the ground.

Comments: Describes the plan/opportunities for delivery of the option or complementary action.

Timeframe for Delivery: Provides a target date for delivery of the option or complementary action.

4 Implementation and Review Stage


Table 4.1: Summary of Ranked Options for Implementation

Priority Ranking

Option Delivery

Responsibility Financial

Responsibility Comments Timeframe for Delivery

O1

Implementation of SUDS at Hollington Primary School

- EA SUDS

Retrofitting Project

Team (lead)

- HBC

- Hollington Primary

School

- ESCC

- EA SUDS

Retrofitting Project

Team (lead)

- HBC

- It is envisaged that at least one of the recommended SUDS options

will be incorporated in the short term as part of the SUDS

Retrofitting Pilot scheme from the EA

- The working group should seek opportunities to deliver the other

SUDS Options recommended for the area when funding becomes

available.

March 2012

(EA Retrofitting SUDS pilot

scheme)

Review Annually

(other SUDS options)

O2

Flood Resistance / Resilience Measures to be applied across the Borough

- HBC (lead)

- EA

- Residents benefiting

from these

measures

- HBC (lead)

- EA/DEFRA grants

- It is envisaged that some flood resistance / resilience measures at

property level would be installed at pilot locations across Hastings

as part of the delivery stage of the SWMP. However, this depends

on funding being available.

- HBC could apply for EA/DEFRA properly level flood protection

funding which, if successful, would enable the implementation of

these measures at key locations.

March 2012

(pilot locations)

March 2013

(other key locations)

O3

Clear debris and improve understanding & use of water management structures along the Upper Hollington Stream Catchment

- HBC (lead)

- ESCC

- EA

- Local Residents

- HBC (lead)

- EA

- ESCC

- Recent inspections suggest that the penstocks of the dams are not

fully functional and therefore some effort will be required to repair

them.

- Routine clearance operations should ideally be supported by the

local community wherever possible (Localism bill)

June 2011

(restore functionality of

penstocks

August 2011

(review maintenance

arrangements)

O4

Education on Flood Risk to residents across the Borough

- HBC (lead)

- EA

- ESCC

- HBC (lead)

- An education campaign involving workshops / presentations to

residents in the areas affected in the past and the general public

was identified as needed to pass on the messages from the study.

October 2011

(residents in areas affected)

November 2011

(general public)

O5

Modify the ground profile of the pedestrian area surrounding Priory Meadow shopping centre

- HBC (lead)

- ESCC

- EA

- Management

Company

- HBC (lead)

- Management

Company

- Modifications to the existing ground profile at this location could

bring about significant benefits to shops which are significantly

affected by flooding. However, the delivery of this option is

dependent on the support from the Management Company for the

area

Review

(following discussion with

Management Company)

O6

Install trash screen at the culvert entrance at Ashbrook Park, Upper Church Road

- HBC (lead)

- EA

- ESCC

- HBC (lead)

- EA

- ESCC

- The installation of a trash screen at this location could provide

benefits for the area. However, discussions with local residents will

be required to gain their support to this initiative.

- Estimate cost £1,500-2,500 for a trash screen to cover 1350mm

culvert entrance (supply only)

Review


local residents)


Table 4.2: Summary of Ranked Complementary Actions for Implementation

Priority Ranking

Complementary Action

Delivery Responsibility

Financial Responsibility

Comments Timeframe for Delivery

CA1

Seek opportunities to reduce the risk of surface water flooding affecting critical infrastructure

- HBC(lead)

- ESCC

- SW

- EA

- Stakeholders

affected

- Stakeholders

affected

- Protecting critical infrastructure will enable continuous operations

of key services thus minimising the chances of flooding occurring

as a result of infrastructure failure.

Review


stakeholders affected)

CA2

Review maintenance regime for all assets in accordance with their criticality

- ESCC (lead)

- HBC

- EA

- SW*

- Other stakeholders

- All partners and

stakeholders with

responsibility for

maintaining flood

risk and drainage

assets

- A review of the maintenance programmes is essential in light of the

findings of the study and the criticality assigned to assets. This will

ensure the right level of attention is given to assets depending on

their perceived role on flood risk and drainage.

- * It must be noted that the water industry does not have a set

standard for determining the criticality of its assets in respect of surface water flooding.

October 2011

CA3 Seek opportunities to Retrofit SUDS

- HBC (lead)

- ESCC

- EA


- Will vary depending

on nature of the

scheme and

beneficiaries

- Retrofitting SUDS in certain areas across the Borough could

reduce significantly the impact of surface water flood risk.

Therefore the incorporation of these techniques should be actively

encouraged.

Ongoing

CA4

Maintain an up to date Borough – wide asset register

- ESCC (lead)

- HBC

- SW

- EA


- ESCC (lead)

- HBC

- An up to date asset register would facilitate the role of the lead

local flood authority and all partners by removing uncertainty with

regards to the presence, ownership, maintenance regime and

criticality of assets.

Ongoing

(periodical reviews to be

defined by ESCC)

CA5

Devise a suitable flood response and report procedure

- HBC (lead)

- ESCC

- EA

- SW

- HBC (lead)

- A standardised process that enables a consistent response and

reporting of flooding incidents would provide benefits to residents

whilst facilitating the compilation of suitable detailed information to

support future reviews of the SWMP, SFRA and other studies.

September 2011

(regular reviews required)

CA6

Follow the Advisory Planning Note on Surface Water Flood Risk

- HBC (lead) - HBC (lead)

- A consistent approach when assessing planning applications

across Hastings is essential and the Advisory Planning Note, if

followed correctly, should ensure this occurs.

Ongoing

(following publication of the

Hastings SWMP)

CA7

Explore opportunities to enmain the upper part of Hollington Stream

- EA (lead)

- HBC - EA (lead)

- Assigning this responsibility to the EA would streamline response

when issues are identified. This is particularly important given the

rapid response nature of the catchment and the likelihood of

property flooding during significant events.

Ongoing


Table 4.3 was produced to facilitate the understanding of the actions to be undertaken in chronological order when delivering the

options and associated complementary actions identified above. A number of new terms introduced as part of this table are

summarised below:

Task: Numbered to represent the order in which they need to be undertaken (based on estimated completion date)

Completed by: Provides a estimated completion date

Associated with: Links the task with the option or complementary action listed on Tables 4.1 and 4.2

Description: Provides a description of the tasks to be undertaken by the completed by date

Follow up Actions: Describes the actions likely to follow the task as well as an indicative completion date for these actions

Table 4.3: Chronological order of activities required to progress options and complementary actions identified

Task Completed

by Associated

with Description Follow Up Actions

1 Ongoing CA3 Actively promote the retrofitting

of SUDS [HBC, EA, ESCC] - Changes/revisions to SUDS legislation to be

communicated to relevant parties (Ongoing)

2 April 2011 O3 Restore full functionality to

penstocks [EA]

- Raise awareness among operatives with regards

to suggested operation regime (July 2011)

- Seek support from local residents for keeping

clear the stream and its banks (October 2011)

3 June 2011 O1

Define SUDS Option(s) to be

retrofitted [EA SUDS

Retrofitting Project Team, HBC]

- Finalise detailed design of selected option(s) with

preferred contractor and attain any necessary

licences / permits. (September 2011)

- Liaise with Hollington Primary School and

preferred contractor to define timing of works

(October 2011)

- Progress with works (December 2011)

4 July 2011 CA4 Define ownership of the asset

register [HBC, ESCC] - Set up a review programme and communicate it to

relevant parties (Ongoing)

5 July 2011 O5

Discuss benefits and

opportunities for ground

reprofiling with Management

Company [HBC]

- Follow up on initial discussions and if necessary

set the delivery of this option as a planning

condition for any future development in the area.

(October 2011)

6 August 2011

CA7

Hold discussions with the

relevant department within the

EA with regards to enmaining

this section of the stream

- Follow it up depending on outcome on discussions

and continue to pursue it on a regular basis if

necessary

7 September

2011 CA5

Circulate documents to relevant

teams and explain processes

[HBC] - Roll out use of new procedures(October 2011)

8 September

2011 CA6

Circulate documents to

members of the Spatial

Planning team

- Roll out use of the Advisory Planning Note

following publication of the Hastings SWMP

(October 2011)

9 September

2011 CA1

Communicate risk to owners of

critical infrastructure [HBC,

ESCC]

- Discuss opportunities to mitigate the risk and seek

commitment from relevant stakeholders (October

2011)


Table 4.3: Chronological order of activities required to progress options and complementary actions identified (continued)

Task Completed

by Associated

with Description Follow Up Actions

10 September

2011 O6

Discuss opportunities for

installation of trash screen with

local residents [EA, ESCC,

HBC]

- Follow up on discussions with residents and if

outcome is positive seek opportunities to finance

and deliver the trash screen (to be revised

following discussions)

11 September

2011 O4

Carry out event to present

results of the SWMP to the

residents of areas affected and

promote flood risk awareness /

education [HBC]

- Organise a subsequent event for the general

public (October 2011)

- Distribute flood pack to residents (October 2011)

12 October

2011 CA2

Review maintenance

arrangements for all assets

[HBC, ESCC, EA, SW]

- Implement changes to maintenance regimes as

identified during the review (Ongoing)

13 April 2012 O2 Apply for EA/Defra property

level flood protection [HBC] - If successful, progress as per guidance circulated

with application

4.1.1.1 Advice and information to local authority planners

One of the objectives of the Hastings SWMP was to provide valuable information to the spatial planning and development

process. This was achieved by involving a representative of the spatial planning team in the working group and producing the

following outputs that will inform their work:

Advisory Planning Note on Surface Water Flood Risk (see Appendix 2F)

Various Maps showing the areas deemed to be at risk of flooding from this source (see Mapping section)

Identification of areas where SUDS Retrofitting could provide some benefits (see Appendix 3C)

A workshop for HBC officers aimed at describing the study and how it could inform their work

4.1.1.2 Advice and information on emergency planning

Another objective of the Hastings SWMP was to provide valuable information to support emergency planning across the

Borough. This was achieved by involving a representative of the emergency planning team in the working group and producing

the following outputs that will inform their work:

Producing a revised procedure “to answer“ flood incident reports aimed at improving the management of flooding calls (see

Appendix 2G)

Various Maps showing the areas deemed to be at risk of flooding from this source (see Mapping section)

Identification of critical infrastructure deemed susceptible to surface water flood risk (see Appendix 2H)

A workshop for HBC officers aimed at describing the study and how it could inform their work

4.1.1.3 Programme of Further Work and Follow up Actions

Tables 4.1 to 4.3 above provide a summary of the work already identified as required to deliver the options / complementary

actions associated with the Hastings SWMP. It is however, recognised that further work will be required in the future to ensure

the actions identified are delivered and the objectives set out at the beginning of the project are fulfilled. Table 4.4 provides a

summary of the further work likely to be required from the working group post completion of the study.


Table 4.4: Additional work identified post completion of Hastings SWMP Study

Description Responsibility Completed by

Establish whether the Hastings SWMP requires a Strategic Environmental

Assessment (SEA), an Appropriate Assessment (required by the Habitats

Directive), or an Article 4.7 Water Framework Directive (WFD) assessment

- HBC (lead)

- ESCC

- EA

July 2011

Seek to eliminate the gaps in the asset register - ESCC (lead)

- All working group March 2012

Organise regular meetings of the working group (or similar) post completion of the

SWMP Study to continue the partnership and seek solutions to the issues affecting

Hastings Borough

- ESCC (lead)

- All working group Ongoing

Identify opportunities to engage local residents in areas deemed at risk of surface

water flooding to provide support with routine maintenance (Localism bill) - EA (lead)


Seek opportunities to obtain funding through grants for the implementation of

solutions on the ground using the assessment carried out as part of the SWMP - HBC (lead)


Seek opportunities to eliminate the use of combined sewers where possible.

Whereas this is unlikely to be feasible in many areas across Hastings, any

reduction to surface water discharges into the sea will have a positive impact on

water quality.

- SW (lead)

Ongoing

Review effectiveness of solutions implemented as part of the Hastings SWMP - ESCC (lead)


Undertake regular reviews of the SWMP Study and supporting information; in

particular the surface water flood maps from the EA and update any maps/advice

when required.

- ESCC (lead)

- All working group

Annual

Reviews

(May 2012 for

first review)

4.1.2 Review and publish the Action Plan

The action plan identified above has been reviewed and approved for publication by a number of parties including:

- HBC Scrutiny committees

- HBC (lead partner)

- East Sussex County Council (lead local flood authority)

- Environment Agency

- Southern Water

4.2 Implement and Review Action Plan

The objective of this phase is to ensure that the signed off action plan is being delivered by the different partners or other

stakeholders. The main responsibility for this phase falls on the working group created to steer the production of the Hastings

SWMP and which includes representatives from all partners.

It is envisaged that the partnership formed to deliver the Hastings SWMP will continue to work together post completion of the

study to progress and implement the actions identified as well as undertake any further work required. Additionally, it is important

to note that the action plan should be reviewed and updated at least once every six years but there could be circumstances

under which an interim review might be required. These could include:

- A significant flooding incident

- Updated modelling/mapping information becoming available

- Changes to the investment plans for the partners which might have a direct impact on the implementation of options

- Additional Development or other changes in the catchment which might have an influence in surface water flood risk.

AECOM Study Report

As part of the Hastings SWMP a number of general conclusions and recommendations were reached in consultation with the

working group. These are summarised below and do not include those reached as a result of specific assessments carried out to

inform the study.

Conclusions

i. It is recognised by all partners that localised areas across Hastings are at risk of surface water flooding.

ii. The risk of flooding posed by surface water was found to be closely linked to other sources of flooding (rivers, sea, sewers,

groundwater) and to problems with the operation of flood risk and drainage management assets (blockages of gullies,

penstocks, etc).

iii. Despite showing fewer areas across Hastings as likely to be affected by surface water flooding, the FMfSW were found to be

more representative of reality than the AStSWF and therefore are deemed to be the primary source of surface water flood risk

information in the absence of locally agreed surface water information.

iv. Whereas the AStSWF maps and the FMfSW provide useful indication of the areas likely to be affected by surface water

flooding, there are some parts of the Borough that are known to suffer flooding from this source and have not been adequately

represented.

v. It is recognised by all partners that the level of detail and extent of the Hastings SWMP study was limited by financial, time and

information constraints. Furthermore, it is accepted that this study represents the initial stage of an ongoing process aimed at

reducing the risk of surface water flooding affecting Hastings.

vi. The Hastings SWMP identified a lack of consistency in the level of flooding history details provided by different partner

organisations. Whereas efforts were made to overcome this issue by working closely with the working group, some level of

inaccuracy could have remained, in particular when identifying the flood hotspots for assessment.

vii. Despite significant efforts to eliminate any gaps in information associated with the Borough-wide asset register created for

Hastings, there are a number of assets for which data has not been available.

viii. The nature of the potential mitigation measures identified and taken forward for assessment has been somewhat limited by

the financial constraints associated with the partners programmes.

Recommendations

i. It is recommended that the locally agreed surface water information is used to replace the FMfSW as the main reference for

this type of flooding in the area at the earliest possible opportunity. This should ensure that areas not included in the FMfSW

are recognised and added to the relevant mapping which will inform the spatial and emergency planning.

ii. It is recommended that all partners look to promote a “design for exceedence” culture aimed at ensuring that any flows in

excess of the nominal capacity of the different assets are managed in a controlled way and do not put life or properties at risk.

iii. It is recommended that the outputs of the study are circulated to the relevant team of the EA to inform and contribute to the

flood warning service in Hastings. This is particularly important but perhaps a bit complex in the Hollington Stream area due to

the rapid response nature of the catchment and the significant consequences of flooding in the vicinity of Hollington Stream.

iv. It is recommended that any feedback obtained from liaison with the public is taken into consideration by the working group and

appropriate action taken at the earliest possible opportunity with a view to resolving the issue raised.

v. It is recommended that an agreed common level of flood risk record is captured and stored by all partners in their systems as

this would facilitate any future studies across the Borough.

vi. It is recommended that any missing asset data is compiled at the earliest possible opportunity and added to the asset register.

vii. It is recommended that an update of the Hastings SFRA (completed in April 2008) is undertaken at the earliest possible

opportunity in order to incorporate the recent changes to the EA flood zone maps as well as the relevant information on flood

risk posed by surface water as identified by the SWMP.

viii. It is recommended that a review of the capacity of ponds/reservoirs across the Borough is undertaken with the aim of

identifying opportunities to maximise use of this assets to store additional flow when needed thus reducing the amount of flow

reaching the sewer network/watercourses, etc and reducing surface water flooding.

ix. It is recommended that the working group continue to work together following the completion of the SWMP

General Conclusions and Recommendations

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