cheshire east council strategic flood risk assessment

Cheshire East Council Strategic Flood Risk Assessment

Final Report August 2013

Cheshire East Council Spatial Planning Team 1st Floor Westfields Sandbach CW11 1HZ

Cheshire East Council SFRA - Final Report - v4.0.doc i

JBA Project Manager Chris Isherwood JBA Consulting Bank Quay House Sankey Street WARRINGTON WA1 1NN

Revision History Revision Ref / Date Issued Amendments Issued to

Draft (Level 1 SFRA) Report Version 1.1 05 February 2013

Cheshire East Council Environment Agency United Utilities

Draft (Level 2 SFRA) Report Version 2.2 30 April 2013

Inclusions of comments made by Cheshire East Council 19/02/2013 and United Utilities 21/02/2013 on report version 1.1.


Final SFRA Report Version 3.0 19 June 2013

Inclusions of comments made by Cheshire East Council 05/06/2013 on report version 2.2.


Final SFRA Report Version 4.0 19 August 2013

Final comments by Council Members 02/08/2013 on report version 3.0.


Contract This report describes work commissioned by Stuart Penny, on behalf of Cheshire East Council, by a letter dated 9 October 2012. Cheshire East Council’s representative for the contract was Stuart Penny of the Spatial Planning Team. Chris Isherwood of JBA Consulting carried out this work.

Prepared by ................................................ Chris Isherwood BSc DipWEM MSc CEnv MCIWEM C.WEM

Chartered Senior Analyst

Reviewed by ............................................... Howard Keeble MPhil BEng BSc CertBusStud CEng CEnv CSci MICE MCIWEM C.WEM

Principal Engineer

Approved by ................................................ Gary Deakin BSc CEng MICE

Director

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Purpose This document has been prepared as a draft report for Cheshire East Council. JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by the Client for the purposes for which it was originally commissioned and prepared. JBA Consulting has no liability regarding the use of this report except to Cheshire East Council.

Acknowledgements JBA would like to thank all Council, Environment Agency and United Utilities' staff for their time and commitment to providing data and discussing the issues identified during the course of this study. Particular thanks is given to Allan Clarke, as the Project Manager, for his valuable guidance and direction throughout the study process.

Copyright © Jeremy Benn Associates Limited 2013

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Executive Summary As set out in the NPPF and its supporting Technical Guidance, Cheshire East Council as a Local Planning Authority are required to undertake a Strategic Flood Risk Assessment (SFRA) to support the preparation of their Local Plan.

The SFRA forms an essential reference tool providing the building blocks for future strategic planning. Cheshire East Council should use the evidence provided in this SFRA to inform their knowledge of flooding, refine information on the Flood Map and determine the variations in flood risk from all sources of flooding. The SFRA should form the basis for preparing appropriate policies for flood risk management within the area.

The primary objective of the SFRA is to enable Cheshire East Council to apply the Sequential and Exception Test in the development allocation and development management process set out in the NPPF.

The NPPF requires that all development is steered to areas of lowest flood risk, where possible. Development is only permissible in areas at risk of flooding in exceptional circumstances where it can be demonstrated that there are no reasonable available sites in areas of lower risk and that the benefits of that development outweigh the risks from flooding. Such development is required to include mitigation and management measures to minimise risk to life and property should flooding occur.

The original SFRAs were prepared by the former Districts of Crewe and Nantwich, Macclesfield, Congleton and Cheshire County Council under Planning Policy Statement 25 (PPS25). However, since their production new legislation, policies, strategies and flood risk evidence have emerged. In October 2012, Cheshire East Council commissioned JBA Consulting to review, update and consolidate each of the SFRAs into one document in accordance with Government’s development planning guidance.

The Level 1 SFRA builds upon existing District SFRAs collating all flood risk evidence into one document. The core output of this study is a series of maps and GIS datasets, which include a narrative of flood risk issues across the District.

The Level 2 SFRA includes a community flood risk review focusing on Principal Towns, Key Service Centres and New Settlements outlined in the Councils Local Plan document ‘Shaping our future: A Development Strategy for Jobs and Sustainable Communities’. The community review provides a detailed but high level overview of flood risk for each community and Strategic Sites proposed. Using this analysis, development recommendations have been provided on site-specific FRAs and appropriate flood risk management within that community.

The SFRA study area predominantly covers the Cheshire Plain, a flat, lowland area, which is characterised by watercourses running in well-defined floodplains and localised areas of hilly terrain. To the northeast, the study area covers part of the western Peak District, an upland area forming the southern end of the Pennines. This area has steep topography, and is characterised by steep sided valleys and large numbers of minor watercourses.

The main source of flood risk in the study area is from main rivers and Ordinary Watercourses. Whilst the overall level of risk from these sources is low, there are a number of major town centres such as Crewe, Macclesfield and Congleton where risk is greater due to the presence of a densely urban population. In these urban areas, watercourses can often be modified with straightened and culverted sections common, especially where rivers flow underneath major railway and road infrastructure.

The Environment Agency has hydraulically modelled the majority of main rivers in the study area providing detailed flood risk information in the form of Flood Zones. There is however, a vast number of rivers and small Ordinary Watercourses not modelled or have indicative Flood Zones based on broad scale modelling outputs. In these locations, flood risk information is poor or incomplete.

Due to the flat nature of the topography there is likely to be extensive surface water flood risks across the District resulting from an extreme rainfall event. To the north east, steeper topography is likely to result in surface water flooding along well defined flow-paths. Flooding in

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these areas has the potential to represent a significant hazard to people due to its velocity and depth.

The complex hydraulic interactions in the urban environment also increase the risk of surface water flooding. Urban watercourse connectivity, sewer capacity, and the location and condition of highway gullies all have a major role to play and in many cases urban watercourses have been culverted over and are likely to be in poor condition. A blockage or collapse of one of these culverts could represent a significant flood risk to adjacent properties. There is very little detailed information on these flood mechanisms. The Council has produced a Surface Water Management Plan that identifies high risk areas throughout the District, however further detailed analysis is required going forward.

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Contents 1 Introduction............................................................................................................. 1

1.1 Commission .............................................................................................................. 1 1.2 Cheshire East SFRA ................................................................................................. 1 2 Understanding Flood Risk ...................................................................................... 3

2.1 Sources of Flooding .................................................................................................. 3 2.2 Likelihood and Consequence .................................................................................... 4 2.3 Risk .......................................................................................................................... 5 3 The Planning Framework and Flood Risk Policy .................................................. 6

3.1 Introduction ............................................................................................................... 6 3.2 Legislation ................................................................................................................ 7 3.3 Planning Policy ......................................................................................................... 9 3.4 Flood Risk Management Policy ................................................................................. 11 3.5 Roles and Responsibilities ........................................................................................ 13 4 Flood Risk in Cheshire East ................................................................................... 16

4.1 Flood Risk Datasets .................................................................................................. 16 4.2 Fluvial Flooding ........................................................................................................ 16 4.3 Surface Water Flooding ............................................................................................ 19 4.4 Groundwater Flooding .............................................................................................. 23 4.5 Canal Flood Risk ...................................................................................................... 25 4.6 Reservoir Flood Risk................................................................................................. 30 4.7 Flood Risk Management ........................................................................................... 30 5 Development and Flood Risk ................................................................................. 32

5.1 Introduction ............................................................................................................... 32 5.2 The Sequential Approach .......................................................................................... 32 5.3 Local Plan Sequential & Exception Test .................................................................... 33 5.4 Development Site Assessment.................................................................................. 34 5.5 Community Review ................................................................................................... 35 5.6 Development Management Sequential & Exception Test........................................... 68 5.7 Site-Specific Flood Risk Assessment ........................................................................ 70 5.8 Sustainable Drainage Systems ................................................................................. 72 5.9 Emergency Planning ................................................................................................. 73 6 Conclusions and Recommendations ..................................................................... 77

6.1 Conclusions .............................................................................................................. 77 6.2 Recommendations for Further Work .......................................................................... 77 Appendices .......................................................................................................................... I A SFRA Flood Risk Maps ........................................................................................... I B Historical Flood Events .......................................................................................... II C Critical Drainage Areas ........................................................................................... III D Development Site Assessment Spreadsheet ........................................................ IV E NPPF Flood Zone and Vulnerability Classifications and Compatibility ............... V F Glossary of Terms .................................................................................................. VI

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List of Figures Figure 1-1: Cheshire East SFRA Study Area ......................................................................... 2 Figure 2-1: Flooding from all Sources .................................................................................... 3 Figure 2-2: Source-Pathway-Receptor Model ........................................................................ 4 Figure 3-1: Key documents and strategic planning links - Flood Risk ..................................... 6 Figure 3-2: PFRA Process ..................................................................................................... 7 Figure 3-3: Cheshire East CFMP Policies .............................................................................. 11 Figure 3-4: RFRA Flood Risk Rank ........................................................................................ 12 Figure 4-1: Residential Properties within Flood Zone 3 .......................................................... 18 Figure 4-2: United Utilities Historical Flood Records............................................................... 21

Figure 4-3: SWMP Risk Areas ............................................................................................... 23 Figure 4-4: Areas Susceptible to Groundwater Flooding ........................................................ 24 Figure 4-5: Canals in Cheshire East ...................................................................................... 26 Figure 4-6: Canal Hazard Zone - Congleton........................................................................... 29 Figure 4-7: Canal Hazard Zone - Nantwich ............................................................................ 29 Figure 5-1: Flood Risk Management Hierarchy ...................................................................... 32 Figure 5-2: Local Plan Sequential Approach to Allocation ...................................................... 33 Figure 5-3: Development Management Sequential Test Process ........................................... 70 Figure 5-4: SuDS Management Train Principle ...................................................................... 73

List of Tables Table 2-1: NPPF Flood Zones ............................................................................................... 5 Table 3-1: Key LLFA Duties under the FWMA ....................................................................... 8

Table 4-1: Flood Source and Key Datasets ............................................................................ 16 Table 4-2: Settlements and Rivers ......................................................................................... 17 Table 4-3: Properties at Risk from Surface Water Flooding .................................................... 20 Table 4-4: Canal Flooding Mechanisms ................................................................................. 25 Table 4-5: Incidents of Historical Canal Breaches and Overtopping Events ............................ 26 Table 4-6: Canal and Rivers Trust Assets and Condition Grades ........................................... 27 Table 4-7: Canal Breach Modelling Methodology ................................................................... 28 Table 5-1: Development Site Assessment Summary .............................................................. 35 Table 5-2: Strategic Development Site Assessment Summary ............................................... 37

Table 5-3: Recommended National Precautionary Sensitivity Ranges.................................... 71 Table 5-4: UKCP09 Change Factors...................................................................................... 72 Table 5-5: Flood Warning and Evacuation Plans.................................................................... 75 Table 6-1: Recommended Further Work ................................................................................ 77

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Abbreviations ABD ............................... Areas Benefitting from Defences

AEP ............................... Annual Exceedance Probability

AMP ............................... Asset Management Plan

AStGWF ......................... Areas Susceptible to Groundwater Flooding

AStSWF ......................... Areas Susceptible to Surface Water Flooding

CDA ............................... Critical Drainage Area

CEC ............................... Cheshire East Council

CFMP ............................ Catchment Flood Management Plan

CSO ............................... Combined Sewer Overflow

DCLG ............................. Department of Communities and Local Government

ELR................................ Employment Land Review

FDGiA ............................ Flood Defence Grant in Aid

FEH ............................... Flood Estimation Handbook

FMfSW ........................... Flood Map for Surface Water

FRA ............................... Flood Risk Assessment

FRM ............................... Flood Risk Management

FRMP ............................ Flood Risk Management Plan

FRR ............................... Flood Risk Regulations

FWMA ............................ Flood and Water Management Act

GIS ................................ Geographical Information Systems

HS2................................ High Speed 2

LFRMS........................... Local Flood Risk Management Strategy

LLFA .............................. Lead Local Flood Authority

LPA ................................ Local Planning Authority

LRF ................................ Local Resilience Forum

MMU .............................. Manchester Metropolitan University

NFCDD .......................... National Flood and Coastal Defence Database

NPPF ............................. National Planning Policy Framework

PFRA ............................. Preliminary Flood Risk Assessment

PPG ............................... Planning Policy Guidance

PPM ............................... Planned Preventative Maintenance

PPS ............................... Planning Policy Statement

RBMP ............................ River Basin Management Plan

RFF................................ Regional Resilience Forum

RFRA ............................. Regional Flood Risk Appraisal

RMA............................... Risk Management Authority

RSS ............................... Regional Spatial Strategy

SA .................................. Sustainability Appraisal

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SAB ............................... SUDS Approval Board

SFRA ............................. Strategic Flood Risk Assessment

SFRM ............................ Strategic Flood Risk Mapping

SHLAA ........................... Strategic Housing Land Availability Assessment

SIRS .............................. Sewerage Incident Register System

SoP ................................ Standard of Protection

SuDS ............................. Sustainable Drainage Systems

SWMP ........................... Surface Water Management Plan

uFMfSW ......................... updated Flood Map for Surface Water

WFD .............................. Water Framework Directive

WIRS ............................. Wastewater Incident Register System

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1 Introduction

1.1 Commission Cheshire East Council (CEC) commissioned JBA Consulting in October 2012 to review, update and consolidate the Strategic Flood Risk Assessments (SFRAs) prepared by the former Districts of Crewe and Nantwich, Macclesfield, Congleton and Cheshire County Council in accordance with Government’s development planning guidance. The Cheshire East SFRA provides an updated and combined review of flood risk and development planning issues throughout the Cheshire East area.

1.2 Cheshire East SFRA As a Lead Local Flood Authority (LLFA) and Local Planning Authority (LPA), CEC requires an SFRA to develop the evidence base for their Local Plan and to inform the Sustainability Appraisal (SA). The aims and objectives of the SFRA are:

To form part of the evidence base and inform the Sustainability Appraisal (incorporating the Strategic Environmental Assessment) for the Cheshire East Local Plan.

To assist in the preparation of, and to make recommendations of, appropriate policies for management of flood risk within the Cheshire East Local Plan.

To understand flood risk from all sources and to investigate and identify the extent and severity of flood risk throughout the Cheshire East area. This assessment will enable the Council to steer development away from those areas where flood risk is considered greatest, ensuring that areas allocated for development can be developed in a safe, cost effective and sustainable manner.

To enable the Council to meet its obligations under the National Planning Policy Framework (NPPF) and technical guidance.

To assess the suitability of potential development site allocations across the Borough including assessment of the direct and indirect impacts on flood risk.

To provide reference and a policy development user guide, to advise and inform wider stakeholders, including the public, private and commercial developers in order for them to understand their obligations under the latest planning guidance.

To supplement current policy guidelines and to provide a straightforward risk based approach to development management in the area. This is aimed at Councillors (including Parish / Town Councils), the public and developers.

To provide a reference document to which all parties involved in development planning and flood risk can reliably turn to for initial advice and guidance.

To develop a report that forms the basis of an informed development management process that also provides guidance on the potential risk of flooding associated with future planning applications and the basis for site specific Flood Risk Assessments (FRAs) where necessary.

To identify land required for current and future flood management that should be safeguarded as set out in the NPPF.

1.2.1 Report Format

The Cheshire East SFRA has been prepared in one report covering flood risk policy, flood risk issues and development guidance. The structure of the report has been written in sections, supported by mapping, which will enable users to identify and focus on their particular requirements and areas of interest. The first sections of the report focus on setting the scene and include a general overview to flood risk management and planning polices, which influenced development of this SFRA. This is then developed to include an overview of the flood risk issues across Cheshire East. The strategic assessment of risk has been undertaken in two stages:

1. Stage (or level) 1 – Collated readily available flood risk information in order to provide a spatial assessment of flood risk from all sources across the Borough. This involved updating the existing information, already gathered during the SFRAs prepared for the


former Districts of Crewe and Nantwich, Macclesfield, Congleton and Cheshire County Council. This stage also includes a review of strategic development options identified by Cheshire East Council to allow the application of the Sequential Test.

2. Stage (or level) 2 - Built on the information collected in Stage 1. Stage 2 included consideration of the detailed nature of flood hazards (including flood probability, depth and velocity). It takes into account the presence of flood risk management measures such as flood defences, and focuses on areas of high risk that coincided with development pressures and aspirations throughout the Borough. The aim of this assessment was to develop the understanding of risk in key areas and to inform the application of the Exceptions Test where required.

1.2.2 Study Area

Cheshire East is the third largest Unitary Authority in the northwest, next to Manchester and Liverpool. The authority covers an area of 1,116km² and is bounded to the west by Cheshire West and Chester Council, and eleven other councils including Derbyshire County Council, Shropshire Council, Newcastle-under-Lyme Borough Council, Staffordshire Moorlands District Council, Staffordshire County Council, High Peak District Council, Stockport Metropolitan Borough Council, Trafford Metropolitan Borough Council, Manchester City Council and Warrington Borough Council.

It is predominately rural and contains the railway town of Crewe, the old mill towns of Macclesfield, and Congleton and the market towns of Nantwich, Knutsford and Sandbach, as well as Middlewich, Wilmslow, and smaller settlements such as Poynton, Alderley Edge, Holmes Chapel and Prestbury. The Cheshire East area has a total population of around 370,127 (Census, 2011).

Cheshire East has good transport and communication links to large cities including Manchester, Liverpool and Birmingham. The M53, M56 and M6 motorways provide national transport links to the north and south of the UK. The A51 provides a direct link to Chester and North Wales, and the A500 links to Stoke-on-Trent and the West Midlands. The West Coast Mainline (railway) travels through Cheshire East. The rail hub based in Crewe provides access into and out of the area providing a rail gateway to the northwest with links to London, Scotland, Birmingham and Manchester, in addition to more local stations across Cheshire East. Figure 1-1: Cheshire East SFRA Study Area


2 Understanding Flood Risk

2.1 Sources of Flooding Flooding is a natural process and can happen at any time in a wide variety of locations. It constitutes a temporary covering of land not normally covered by water and presents a risk when people, human and environmental assets are present in the area that floods. Assets at risk from flooding can include housing, transport and public service infrastructure, commercial and industrial enterprises, agricultural land and environmental and cultural heritage. Flooding can occur from a combination of many different sources. As outlined in Figure 2-1, major sources of flooding include:

Fluvial (rivers) - inundation of floodplains from rivers and watercourses; inundation of areas outside the floodplain due to influence of bridges, embankments and other features that artificially raise water levels; overtopping or breaching of defences; blockages of culverts; blockages of flood channels/corridors.

Tidal - inundation of floodplains by the sea or estuaries; overtopping of defences; breaching of defences; other flows (e.g. fluvial surface water) that could pond behind flood defences due to tide locking; wave action.

Surface water - surface water flooding covers two main sources including sheet run-off from adjacent land (pluvial) and surcharging of piped drainage systems (public sewers, highway drains etc.)

Groundwater – caused by the water table rising after prolonged rainfall to emerge above ground level remote from a watercourse; most likely to occur in low-lying areas underlain by permeable rock (aquifers); groundwater recovery after pumping for mining or industry has ceased.

Infrastructure failure - reservoirs; canals; industrial processes; burst water mains; blocked sewers or failed pumping stations.

Different types and forms of flooding present a range of different risks and the flood hazards of speed of inundation, depth and duration of flooding can vary greatly. With climate change, the frequency, pattern and severity of flooding are expected to change and become more damaging. Figure 2-1: Flooding from all Sources


2.2 Likelihood and Consequence Flood risk is a combination of the likelihood of flooding and the potential consequences that arise. It is assessed using the source – pathway – receptor model as shown in Figure 2-2 below. This is a standard environmental risk model common to many hazards and should be the starting point of any assessment of flood risk. However, it should be remembered that flooding may result from many different sources and via numerous pathways, and not simply those shown in the illustration below. Figure 2-2: Source-Pathway-Receptor Model

The primary sources of flooding are high rainfall or higher than normal river or sea levels. The most common pathways for flooding are rivers, drains, sewers, overland flow and river and coastal floodplains and their defence assets. Receptors may include people, property and the environment. All three elements must be present for flood risk to arise. Mitigation measures have little or no effect on sources of flooding but they can block or impede pathways or remove receptors.

The planning process is primarily concerned with the location of receptors, taking appropriate account of potential sources and pathways that might put those receptors at risk. It is, therefore, important to define the components of flood risk in order to apply this guidance in a consistent manner.

2.2.1 Likelihood

Likelihood of flooding is expressed as the percentage probability based on the average frequency measured or extrapolated from records over a large number of years. A 1% probability indicates the flood level that is expected to be reached on average once in a hundred years, i.e. it has a 1% chance of occurring in any one year, not that it will occur once every hundred years. Table 2-1 provides an example of the flood probabilities used to describe Flood Zones as defined in the NPPF Technical Guide.

Considered over the lifetime of development, such an apparently low frequency or rare flood has a significant probability of occurring. For example:

A 1% flood has a 26% (1 in 4) chance of occurring at least once in a 30-year period - the period of a typical residential mortgage

And a 49% (1 in 2) chance of occurring in a 70-year period - a typical human lifetime


Table 2-1: NPPF Flood Zones

Flood Zone

Annual probability of flooding

1 This zone comprises land assessed as having a less than 1 in 1,000 annual probability of river or sea flooding in any year (<0.1%).

2 This zone comprises land assessed as having between a 1 in 100 and 1 in 1,000 annual probability of river flooding (1% – 0.1%) or between a 1 in 200 and 1 in 1,000 annual probability of sea flooding (0.5% – 0.1%) in any year.

3a This zone comprises land assessed as having a 1 in 100 or greater annual probability of river flooding (>1%) or a 1 in 200 or greater annual probability of flooding from the sea (>0.5%) in any year.

3b This zone comprises land where water has to flow or be stored in times of flood. This includes land that would flood with an annual probability of 1 in 20 (5%) or greater in any year, or is designed to flood in an extreme (0.1%) flood.

2.2.2 Consequence

The consequences of flooding can result in fatalities, property damage, and disruption to lives and businesses. In addition, the consequence of flooding may have severe implications for people (e.g. financial loss, emotional distress, health problems). Consequences of flooding depend on the hazards caused by flooding (depth of water, speed of flow, rate of onset, duration, wave-action effects, water quality) and the vulnerability of receptors (type of development, nature, age-structure of the population, presence and reliability of mitigation measures etc). Flood risk is then expressed in terms of the following relationship:

Flood risk = Probability of flooding x Consequences of flooding

2.3 Risk Flood risk is not static, as it cannot be described simply as a fixed water level that will occur if a river overtops its banks or, for example, from a high spring tide that coincides with a storm surge. It is, therefore, important to consider the continuum of risk carefully. Risk varies depending on the severity of event, the source of the water, the pathways of flooding (such as the condition of flood defences) and the vulnerability of receptors.

2.3.1 Actual Risk

This is the risk 'as is' taking into account any flood defences that are in place for extreme flood events (typically these provide a minimum Standard of Protection (SoP)). Hence, if a settlement lies behind a fluvial flood defence that provides a 1% SoP then the actual risk of flooding from the river in a 1% Annual Exceedance Probability (AEP) event is generally low.

Actual risk describes the primary risk from a known and understood source managed to a known SoP. However, it is important to recognise that risk comes from many different sources and that the SoP provided will vary within a river catchment. Hence, the actual risk of flooding from the river may be low to a settlement behind the defence but moderate from surface water, which may pond behind the defence in low spots and is unable to discharge into the river during high water levels.

2.3.2 Residual Risk

Even when flood defences are in place there is always a possibility that these could be overtopped or that they could fail or breach. Where there is a consequence to that occurrence, this risk is known as residual risk. Defence failure can lead to rapid inundation of fast flowing and potentially deep floodwaters, which may pose significant risk to people, property and environment behind the defence.

Whilst the actual risk of flooding to a settlement that lies behind a fluvial flood defence that provides a 1 in 100-year SoP may be low, there will always be a residual risk from flooding if these defences overtopped or failed that must be taken into account. Because of this, it is never appropriate to use the term "flood free".


3 The Planning Framework and Flood Risk Policy

3.1 Introduction The main purpose of this section of the SFRA is to provide an overview of the key planning and flood risk policy documents that have shaped the current planning framework. This section also provides an overview, and puts in context, the Council’s responsibilities and duty in respect to managing local flood risk. This includes consideration of the requirements of the Flood Risk Regulations (FRR) 2009 and the Floods and Water Managements Act (FWMA) 2010.

Figure 3-1 illustrates the links between legislation, national policy, statutory documents and flood risk assessments. The figure shows that whilst the key pieces of legislation and policy are separate, they are closely related and their implementation should aim to provide a comprehensive and planned approach to asset record keeping and improving flood risk management within communities.

It is intended that the non-statutory Surface Water Management Plans (SWMPs) and SFRAs can provide much of the base data required to support the delivery of statutory flood risk management tasks as well as supporting Local Authorities in developing capacity, effective working arrangements and informing Local Flood Risk Management Strategies (LFRMS) and Local Plans, which in turn help deliver flood risk management infrastructure and new development at a local level. Figure 3-1: Key documents and strategic planning links - Flood Risk


3.2 Legislation

3.2.1 EU Floods Directive & the Flood Risk Regulations European Flood Directive (2007) sets out EU’s approach to managing flood risk and aims to improve the management of the risk floods pose to human health, the environment, cultural heritage and economic activity.

The Directive was translated into English law by the Flood Risk Regulations (FRR) 2009 and outlines the requirement for the Environment Agency and Lead Local Flood Authorities (LLFA) to create Preliminary Flood Risk Assessments (PFRAs), with the aim of identifying significant Flood Risk Areas. Figure 3-2: PFRA Process PFRAs cover the entire area for local flood risk (focusing on ordinary watercourses, surface water and groundwater flooding). Where significant Flood Risk Areas are identified using a national approach (and locally reviewed), the LLFA will then be required to undertake flood risk hazard mapping and Flood Risk Management Plans (FRMPs) as illustrated in Figure 3-2.

The FRMP will need to consider objectives for flood risk management (reducing the likelihood and consequences of flooding) and measures to achieve those objectives.

The Environment Agency have implemented one of the exceptions for creating PFRAs etc for main rivers and coastal flooding, as they already have mapping (i.e. Flood Map) and plans (i.e. Catchment Flood Management Plans, CFMPs) in place to deal with this. The Environment Agency therefore focused their efforts on assisting LLFAs through this process.

Cheshire East Preliminary Flood Risk Assessment

The Cheshire East PFRA was published in June 2011 as required under the FRR. Whilst information collected as part of the PFRA process did categorise two historical flood events as having significant harmful consequences in the district, the PFRA did not identify a Flood Risk Area using the national significant thresholds set by Defra. As a result, the next stages of the PFRA process, the requirement to develop flood risk hazard mapping and Flood Risk Management Plans, do not apply to CEC.

That said, the Environment Agency are currently in the process of updating their national Flood Map for Surface Water (uFMfSW), which is expected to meet the requirements for flood risk hazard mapping and will be available to CEC later in 2013. As illustrated by Figure 3-1, the updated national map should be informed by the SWMP.

3.2.2 Flood & Water Management Act

The Flood and Water Management Act (FWMA) was passed in April 2010. It aims to improve both flood risk management and the way we manage our water resources.

The FWMA creates clearer roles and responsibilities and instils a more risk-based approach. This includes a new lead role for Local Authorities in managing local flood risk (from surface water, ground water and ordinary watercourses) and a strategic overview role of all flood risk for the Environment Agency.

The content and implications of the FWMA provide considerable opportunities for improved and integrated land use planning and flood risk management by Local Authorities and other key partners. The integration and synergy of strategies and plans at national, regional and local scales, is increasingly important to protect vulnerable communities and deliver sustainable re-


generation and growth. Table 3-1 provides an overview of the key LLFA responsibilities under the FWMA. Table 3-1: Key LLFA Duties under the FWMA

Responsibility Description Start Date

Local Strategy for Flood Risk Management

A LLFA is required to develop, maintain, apply and monitor a local strategy for flood risk management in its area. The local strategies will build on information such as national risk assessments and will use consistent risk based approaches across different Local Authority areas and catchments. The local strategy will not be secondary to the national strategy; rather it will have distinct objectives to manage local flood risks important to local communities.

October 2010

Investigating Flood Incidents

A LLFA has a duty to investigate and record details of significant flood events within their area. This duty includes identifying risk management authorities and their functions and how they intend to exercise those functions in response to a flood. The responding risk management authority must publish the results of its investigation and notify any other relevant risk management authorities.

April 2011

Asset Register

A LLFA has a duty to maintain a register of structures or features, which are considered to have an effect on flood risk, including details on ownership and condition as a minimum. The register must be available for inspection and the Secretary of State will be able to make regulations about the content of the register and records.

April 2011

Works Powers

The Act provides a LLFA with powers to do works to manage flood risk from surface runoff, groundwater and on ordinary watercourses, consistent with the local flood risk management strategy for the area.

December 2011

Designation Powers

The Act provides a LLFA with powers to designate structures and features that affect flooding or coastal erosion. The powers are intended to overcome the risk of a person damaging or removing a structure or feature that is on private land and which is relied on for flood or coastal erosion risk management. Once a feature is designated, the owner must seek consent to alter, remove, or replace it.

August 2012

SuDS Approving

Body

The Act establishes each LLFA as a SuDS Approving Body (the “SAB”). The SAB would have responsibility for the approval of proposed drainage systems in new developments and redevelopments, subject to exemptions and thresholds. Approval must be given before the developer can commence construction. The SAB would also be responsible for adopting and maintaining SuDS that serve more than one property, where they have been approved. Highways authorities will be responsible for maintain SuDS in public roads, to National Standards.

Expected April 2014

A full progress report on the implementation of the FWMA can be found on the Defra website.1

3.2.3 Water Framework Directive & Water Environment Regulations

The purpose of the Water Framework Directive (WFD) is to deliver improvements across Europe in the management of water quality and water resources. The WFD requires all inland and coastal waters to reach “good ecological status” by 2015 through a catchment-based system of River Basin Management Plans (RBMPs), incorporating a programme of measures to improve the status of all natural water bodies. There is an exception for “heavily modified water bodies”,

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which are required to achieve “good ecological potential”. The Water Environment Regulations (2003) transposed the WFD into law in England and Wales. The Environment Agency is leading on the delivery of the WFD.

Cheshire East is within the North West River Basin District and the Environment Agency published the final North West River Basin Management Plan in December 2009. The main responsibility for CEC is to work with the Environment Agency to develop links between river basin management planning and the development of Local Authority plans, policies and assessments. In particular, the programme of actions (measures) within the RBMP highlights the need for:

Water Cycle Strategies, Considering the WFD objectives (achieving good status or potential as appropriate) in

the spatial planning process, including LDDs and Sustainable Community Strategies, and

Promoting the use of Sustainable Drainage Systems (SuDS) in new development.

3.3 Planning Policy

3.3.1 National Planning Policy Framework

The National Planning Policy Framework (NPPF) was published in March 2012, as part of reforms to make the planning system less complex and more accessible, to protect the environment and to promote sustainable growth. It replaces most of the Planning Policy Guidance Notes (PPGs) and Planning Policy Statements (PPSs).

The NPPF is guidance for Local Planning Authorities to help them prepare Local Plans and take development management decisions. The NPPF states that Local Plans

“...should be supported by a Strategic Flood Risk Assessment and develop policies to manage flood risk from all sources, taking account of advice from the Environment Agency and other relevant flood risk management bodies, such as Lead Local Flood Authorities and Internal Drainage Boards. Local Plans should apply a sequential, risk-based approach to the location of development to avoid, where possible, flood risk to people and property and manage any residual risk, taking account of the impacts of climate change.” (Para 100)

Technical guidance on flood risk has been published alongside the NPPF and sets out how the policy should be implemented, although it is stated that this is an interim measure.

Whilst the NPPF concentrates on high level national policy and avoids prescriptive guidance, the PPS25 Practice Guide still applies. The Sequential Test has also been carried forward from PPS25 and must be performed when considering the placement of future development and for planning application proposals. The Sequential Test is used to direct all new development (through the site allocation process) to locations at least risk of flooding, giving highest priority to Flood Zone 1.

The Environment Agency has produced a useful guide2 on the impacts of the NPPF on flood and coastal change risk management and development. They have also published a technical note3, which provides guidance on how to apply the Sequential Test as per the NPPF and in relation to allocation of land, individual planning applications, windfall sites, and renewable energy projects, redevelopment of an existing single property and change of use.

3.3.2 Regional Spatial Strategy

The Regional Spatial Strategy (RSS) for the North West was approved in September 2008. The document contains Policy EM5: Integrated Water Management that sets out that plans and strategies should have regard to RBMPs, Water Company Asset Management Plans (AMP), CFMPs and RFRA.

2 Environment Agency (2012) National Planning Policy Framework – Flood and Coastal Change Risk Management -

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It also sets out that Local Planning Authorities and developers should protect the quantity and quality of surface, ground and coastal waters and manage flood risk by:

Working with water companies and the Environment Agency when planning the location and phasing of development.

Producing sub-regional or district level SFRAs. Designing appropriate mitigation measures into any scheme, which exceptionally must

take place in current and future flood risk areas. Requiring new development to incorporate SuDS and water efficiency within existing

developments. Raising people's awareness of flood risk and the impacts of their behaviour and lifestyles

on water consumption.

The North West RSS and remaining Cheshire Structure Plan policies were revoked on the 20th May 2013 by ‘The Regional Strategy for the North West (Revocation) Order 2013. These are no longer part of the Statutory Development Plan.

3.3.3 Localism Act

The Localism Act was given Royal Assent in November 2011 with the purpose of shifting power from Central Government back to Councils, communities and individuals. The Government proposes that now RSS are abolished, this provides the opportunity for Councils to re-examine the local evidence base and establish their own local development requirements for employment, housing and other land used through the plan making process.

Additionally the Act places a duty to cooperate on Local Authorities, including statutory bodies and other groups, in relation to planning of sustainable development. This duty to cooperate requires Local Authorities to

“...engage constructively, actively and on an ongoing basis in any process by means of which development plan documents are prepared so far as relating to a strategic matter.” (Provision 110)

The Act also provides new rights to allow Parish or Town Councils to deliver additional development through neighbourhood planning. This means local people can help decide where new homes and businesses should go and what they should look like. Local Planning Authorities will be required to provide technical advice and support as neighbourhoods draw up their proposals.

3.3.4 Local Plan

The Council is currently developing its new Local Plan, which will be the Development Plan for Cheshire East and form the basis of planning decisions until 2030. It will contain planning strategy, policies and site allocations and will be accompanied by an Infrastructure Delivery Plan that will set out transport, social and other infrastructure required to support development. The latest stage of consultation on the new Cheshire East Local Plan ran from 15 January to 26 February 2013, and included two main documents relevant to this SFRA:

Shaping our Future: A Development Strategy for Jobs and Sustainable Communities Shaping our Future: Policy Principles Document

The Development Strategy sets out the proposed overall number of new homes and employment land that will be needed; it suggests levels of development for the main towns and identifies proposed strategic development sites. The Policy Principles document sets out proposed policy principles to make sure that new development helps deliver objectives for enterprise and growth, stronger communities, better connectivity and a sustainable environment.

The Council aim to publish the final version of the Local Plan (the submission draft Core Strategy of the Local Plan) for consultation in summer 2013, which will be followed by an independent public examination by a Government-appointed inspector.

Prior to adoption of the new Local Plan, the Saved Policies from the Congleton Local Plan, Crewe and Nantwich Local Plan, Macclesfield Local Plan, Cheshire Structure Plan, Cheshire

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Waste Plan and Cheshire Minerals Plan will continue to be used to determine planning applications.

3.4 Flood Risk Management Policy

3.4.1 Catchment Flood Management Plans

A Catchment Flood Management Plan (CFMP) is a key tool within spatial planning. As well as providing a detailed overview of flood risk from multiple sources, they develop complementary policies for long-term management of flood risk within the catchment that take into account the likely impacts of climate change, the effects of land use and land management, deliver multiple benefits and contribute towards sustainable development. This is critical when areas under development pressure coincide with high flood risk.

Chosen policies and actions highlight where to avoid development in those areas deemed inappropriate, to reduce flood risk now and in the future. They also indicate when water should be allowed to flood or where current flood risk measures should be reduced. Development should therefore be focused towards the more 'sustainable' areas in terms of lower risk of flooding or where flood risk management is considered viable within the short and long-term plans. Therefore if development has been proposed in flood risk areas and the chosen policy is not to take further action to reduce flood risk, then developments will find it difficult to rely on Environment Agency led flood risk management (FRM) infrastructure investment and there will be a great reliance on private (developer) funding to reduce risk. In this instance, development may not be viable.

As part of the CFMP process each CFMP area was divided up into broad areas (known as ‘policy units’), which represent areas of similar characteristics, flood mechanisms and flood risks. Each policy unit was then assessed to decide which policy will provide the most appropriate level and direction of flood risk management both now and in the future. Whilst the policy unit simplifies direct action over vast areas of land, in reality, the chosen policy may only focus on a small urban or rural area within that policy unit. Cheshire East is located in two CFMP catchments; the Upper Mersey and the Weaver Gowy. Figure 3-3 illustrates the CFMP policies covering the district. Figure 3-3: Cheshire East CFMP Policies


The six CFMP policies include:

Policy 1 - No active intervention (including flood warning and maintenance) and continue to monitor and advise.

Policy 2 - Reduce existing flood risk management actions (accepting that flood risk will increase over time).

Policy 3 - Continue with existing or alternative actions to manage flood risk at the current level.

Policy 4 - Take further action to sustain the current level of flood risk into the future (responding to the potential increases in risk from urban development, land use change and climate change).

Policy 5 - Take further action to reduce flood risk. Policy 6 - Take action to increase the frequency of flooding to deliver benefits locally or

elsewhere (which may constitute an overall flood risk reduction, e.g. for habitat inundation).

It is important to note that Policy Options 4 and 5 do not automatically equate to the Environment Agency, or others, taking action on the ground. Policy responses indicate a long-term direction of travel and do not reflect the likelihood of any particular area qualifying for funding for a scheme under the priority scoring system.

3.4.2 North West Regional Flood Risk Appraisal Figure 3-4: RFRA Flood Risk Rank The North West Regional Flood Risk Appraisal (RFRA) for the North West RSS was published in October 2008. The RFRA identifies the potential flood risk issues that are of regional significance as illustrated in the adjacent figure. It also sets out flood risk rankings produced by the Environment Agency that, although they have their limitations, provide Local Authorities with an indication of the type and scale of fluvial and tidal flood risk management challenge they face.

Although the RSS has been abolished, the mechanisms of flood risk have not changed and they will still need to be addressed at a strategic level.

As illustrated in the RFRA, flood risk does not respect administrative boundaries and there are a number of Local Authorities in the North West that are hydraulically connected. Strategic flood risk management studies such as CFMPs provide some of this evidence base. However, they are mainly focused on providing a long-term direction of travel of flood risk management and subsequent action will still be required depending on a number of factors, including available resources or schemes qualifying for funding.

There are also clear links between the RFRA and the CEC SFRA with the flood risk data it provides across the North West and regional guidance it offers. The RFRA still has a major role to play in influencing local planning by


considering flood risk strategically and help develop regional approaches and partnerships.

3.4.3 National and Local Flood Risk Management Strategies

The FWMA establishes that flood risk will be managed within the framework of National Strategies for England and Local Strategies for each LLFA area.

The national strategy for England has been developed by the Environment Agency with the support and guidance of Defra. It sets out principles for how flood risk should be managed and provides strategic information about different types of flood risk and which organisations are responsible for their management. The Act requires risk management authorities (local authorities, internal drainage boards, sewerage companies and highways authorities) to act consistently with the national strategy in carrying out their flood and coastal erosion risk management functions.

LLFAs have responsibility for developing a Local Flood Risk Management Strategy (LFRMS) for their area covering local sources of flooding. The local strategy produced must be consistent with the national strategy. It will set out the local organisations with responsibility for flood risk in the area, partnership arrangements to ensure co-ordination between these, an assessment of the flood risk and plans and actions for managing the risk.

The Cheshire East LFRMS is currently being prepared and the findings of this SFRA and the Cheshire East SWMP should help inform its development.

3.5 Roles and Responsibilities The new and emerging responsibilities for the Risk Management Authorities (RMA) under the Flood and Water Management Act and the Flood Risk Regulations are summarised below.

3.5.1 Environment Agency as a RMA

The Environment Agency has a strategic oversight role for all forms of flooding. Has the power to request information from any partner in connection with its risk

management functions. Must exercise its flood or coastal erosion risk management functions in a manner

consistent with the National Strategy and Local Strategies. Must be consulted on Local Strategies, if affected by the strategy, by the LLFA.

3.5.2 Cheshire East Council as LLFA

Must develop, maintain, apply and monitor a strategy for local flood risk management. This must be consulted on with all RMAs, the public and all other partners with an interest in local flood risk.

The Act also imparts several other responsibilities on LLFAs. o Required to coordinate local flood risk management between relevant authorities

and partners. o Empowered to request information from others when it is needed in relation to

their flood risk management functions. o Where it considers this necessary or appropriate, the LLFA must investigate

flooding incidents in its area. o Duty to establish and maintain a record of structures within its area that have a

significant impact on local flood risk. o Empowered to designate structures and features that affect flooding. o The LLFA must establish a SuDS Approval Body – this provision has yet to be

commenced. o LLFAs have powers to undertake works to manage flood risks from surface

runoff and groundwater. Powers in relation to Ordinary Watercourses remain with district authorities.


o Must exercise its flood and coastal erosion risk management functions in a manner consistent with the National Strategy and the Local Strategy.

o Permitted to agree the transfer of responsibilities for risk management functions (except the production of a Local Strategy) to other RMAs.

o Local Authorities and other RMAs must aim to contribute to sustainable development.

LLFAs should consider flooding issues that require collaboration with neighbouring LLFAs and other RMAs.

In order to contribute to the provision of a co-ordinated and pragmatic approach to flood risk management across the study area, CEC have developed a number of work groups and forums to liaise with our most important stakeholders at the appropriate organisational level.

CEC initially set up a Flood and Water Management Task Group, which includes representatives from the Environment Agency, and United Utilities. The task group includes key staff from the following departments within CEC: Emergency Planning, Building Control, Highways, Geographical Information Systems (GIS), Greenspaces, Finance and Environmental Planning. The terms of reference for this group will be reviewed as core Flood Risk Management functions are embedded.

As well as setting up the Task Group, CEC has set up strategic partnerships with Cheshire West and Chester Council, Warrington BC, Halton BC and St Helens BC, to ensure that lessons are learnt and knowledge is shared. The Cheshire and Mid Mersey Partnership Group also serves to ensure consistency amongst the councils, so that data and information relating to FRM functions can be shared in an effective manner.

The Flood Task Group and the Strategic Alliance between councils will be developed in the future as more of the requirements of the legislation become enacted.

3.5.3 United Utilities as a RMA

Duty to act in a manner that is consistent with the National Strategy and have regard to Local Strategies.

Must be consulted on Local Strategies, if affected by the strategy, by the relevant LLFA. Duty to be subject to scrutiny from LLFAs.

3.5.4 Highways Authority (CEC) as a RMA

Duty to act consistently with the National Strategy and Local Strategies. The Highways Authority has responsibility for ensuring effective drainage of local roads

in so far as ensuring drains and gullies are maintained. Must be consulted on Local Strategies, if affected by the strategy, by the relevant LLFA. Duty to be subject to scrutiny from LLFAs.

3.5.5 The Public

Must be consulted on Local Strategies by the LLFA. The public have a key role in ensuring Local Strategies are capable of being successfully

delivered within the community. They should actively participate in this process and be engaged by the LLFA.

3.5.6 Riparian Owners A riparian owner is someone who owns land or property alongside a river or other watercourses including a culvert. A watercourse is any natural or artificial channel through which water flows, such as a river including where rivers flow through a culvert, brook, beck, or mill stream.

Riparian owners have statutory responsibilities, including:

Maintaining river beds and banks; Allowing the flow of water to pass without obstruction;


Controlling invasive alien species.

Further guidance for riverside property owners can be found in the Environment Agency’s helpful booklet ‘Living on the Edge4’ published in 2012.

3.5.7 Developers

Have a vital role in ensuring effective local flood risk management by avoiding development in areas at risk of flooding. Local Strategies should form a key element of local planning guidance.

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4 Flood Risk in Cheshire East

4.1 Flood Risk Datasets This section of the SFRA provides a strategic overview of flood risk from all sources within the study area. The information contained is the best available at the time of publication and is intended to provide the Council with an overview of risk. Where further detail is available, then the source of information is provided. The table below provides a summary of the key datasets or studies used in this SFRA according to the source of flooding.

Stage1 SFRA Flood Risk Maps have been produced using the information listed below. These can be found in Appendix A. Table 4-1: Flood Source and Key Datasets

Flood Source Datasets / Studies

Fluvial

Environment Agency Flood Map Cheshire East PFRA Upper Mersey and Weaver Gower CFMPs Environment Agency Hydraulic River Models

Pluvial (surface water runoff)

Environment Agency Surface Water Flood Maps Cheshire East SWMP Flood Risk Areas Cheshire East PFRA

Sewer United Utilities Historical Flood Records (SIRS, WIRS & DG5) United Utilities Hydraulic Sewer Modelling Outputs Cheshire East SWMP

Groundwater Environment Agency Groundwater Susceptibility Maps Canal Canal and Rivers Trust Asset Register Reservoir Environment Agency Reservoir Flood Maps

Flood Risk Management Infrastructure

Environment Agency NFCDD United Utilities Assets Canal and Rivers Trust Asset Register Cheshire East Council Asset Register

4.2 Fluvial Flooding Fluvial flooding is associated with the exceedance of channel capacity during higher flows. The process of flooding on watercourses depends on a number of characteristics associated with the catchment including geographical location and variation in rainfall; steepness of the channel and surrounding floodplain; and infiltration and rate of runoff associated with urban and rural catchments.

The Cheshire East SFRA study area predominantly covers the Cheshire Plain, a flat, lowland area created by the deposition of glacial tills, sands and gravels during the retreat of the ice sheets approximately 10,000 years ago. This area is characterised by watercourses running in well-defined floodplains and localised areas of hilly terrain. To the northeast, the study area also covers a small area of the western Peak District, an upland area forming the southern end of the Pennines. This area has steep topography, and is characterised by steep sided valleys and large numbers of minor watercourses.

The study area falls within the catchments of the Rivers Weaver and Gowy, and the River Mersey. There are also a number of large tributaries, which flow from west to east through the study area. Table 4-2 lists the key towns and villages and the main rivers and tributaries which run through them.


Table 4-2: Settlements and Rivers

Settlements Main Rivers Other Key Tributaries Alderley Edge Mobberley Brook Common Car and Pott Brook Bollington River Dean Harrop Brook Congleton River Dane Dane-in-Shaw, Howty and Loach Brook Crewe River Weaver Valley Brook , Wistaston Brook, Wells Green Brook, Homes Chapel River Dane River Croco and Alum Brook Knutsford Birkin Brook Knutsford Macclesfield River Bollin Spencer Brook and Collar House Brook Middlewich River Croco Sanderson Brook Nantwich River Weaver Cheer Brook, Edleston Brook Poynton Poyton Brook Booth Green Brook Sandbach River Wheelock Arclid, Lawton and Hassall Brook Wilmslow River Bollin River Dean, Handforth Brook

Cheshire East contains a number of ordinary watercourses. ‘Ordinary Watercourses’ are any watercourses that are not designated a ‘Main River’. These watercourses can vary in size considerably and can include rivers and streams and all ditches, drains, cuts, culverts, dikes, sluices, sewers (other than public sewers within the meaning of the Water Industry Act 1991) and passages, through which water flows.

Prior to the enactment of the FWMA, the responsibility for managing flood risk from these watercourses was often not clearly identified. As a result, their conditions are likely to be highly variable. Consequently, it is likely that there will be several locations where structures on Ordinary Watercourses will be in a significant state of disrepair. Furthermore, the condition of the assets will continue to deteriorate over time.

4.2.1 Historical Flooding

The Cheshire East PFRA carried out a full review of historical flood events, primarily from reviewing The Chronology of British Hydrological Events database5 and the Environment Agency’s Catchment Flood Management Plans (CFMPs). The results are provided in Appendix B.

4.2.2 Environment Agency Flood Map

The Environment Agency’s Flood Map is the main dataset for predicting the location and extent of fluvial flooding through Cheshire East. This is supported by the Weaver Gowy and the Upper Mersey CFMPs and a number of detailed hydraulic river modelling reports which provide further detail on flooding mechanisms.

The Environment Agency Flood Map provides flood extents for the 1 in 100-year fluvial, 1 in 200-year tidal and the 1 in 1000-year fluvial and tidal flood events. Flood zones were originally prepared by the Environment Agency using a methodology based on the national digital terrain model (NextMap), derived river flows (Flood Estimation Handbook (FEH)) and two dimensional flood routing. Since their initial release, the Environment Agency has regularly updated their zones with detailed hydraulic model outputs as part of their flood risk mapping programme.

The Flood Map is precautionary in that it does not take account of flood defences (which can be breached, overtopped or may not be in existence for the lifetime of the development) and, therefore, represent a worst-case extent of flooding. They do not consider sources of flooding other than fluvial and tidal, and do not take account of climate change.

This SFRA uses the Environment Agency Flood Map issued in September 2012. Using the Environment Agency Flood Zone 3, the number of residential properties potentially at risk from

5 http://www.dundee.ac.uk/geography/cbhe/


the 1 in 100-year fluvial flood event has been identified6. Figure 4-1 illustrates the distribution and total number of dwellings at risk in each parish area.

In Cheshire East 1,800 residential properties have been identified to be within Flood Zone 3. The towns with the most properties at risk include Congleton, Crewe and Alsager with 223, 176 and 173 residential properties respectively. Like the Flood Zones, these counts include the properties that may be protected, to some extent, by flood defences. Figure 4-1: Residential Properties within Flood Zone 3

Functional Floodplain

The PPS25 Practice Guide defines functional floodplain as Flood Zone 3b and is described as land where water has to flow or be stored in times of flood and includes water conveyance routes and flood storage areas. The functional floodplain is usually defined by more frequent flood extents, such as the 1 in 20-25 year flood outlines, but does not include currently developed land or areas that benefit from raised flood defences, infrastructure or buildings.

As part of this SFRA, the Environment Agency provided all their available hydraulic river models for the area. These models, however, did not include any results for the 1 in 20 or 25 year flood event outlines. It was therefore decided, as a precautionary approach, that Flood Zone 3 would be used as a surrogate outline with the following edits made below. The indicative functional floodplain was then sent to CEC for review and agreement. It is recommended that further analysis is carried during detailed site specific FRAs to improve the understanding and assessment of the actual functional floodplain.

The following areas are not included in an area of functional floodplain:

6 Residential properties at risk have been identified using a GIS query. Initially OS MasterMap building polygons that

intersect Flood Zone 3 were selected. The selected buildings were then used to count NRD property points with the theme Dwelling.


Land already benefiting from raised flood defences as identified in the Environment Agency’s Areas Benefiting from Defences (ABD) GIS layer;

Currently developed land where no flood alleviation function has been defined. Major transport infrastructure (e.g. motorways and railways).

4.3 Surface Water Flooding Surface water flooding, in the context of the Cheshire East SFRA, includes:

Surface water runoff (also known as pluvial flooding) Sewer flooding

Surface water flooding can occur anywhere where ground levels and profiles tend to cause surface water to flow and accumulate. However, there are certain locations where the probability and consequence of these mechanisms are more prominent due to the complex hydraulic interactions in the urban environment. Urban watercourse connectivity, sewer capacity, and the location and condition of highway gullies all have a major role to play in surface water flood risk.

Whilst effort is taken to describe each source of surface water flooding below, it should be acknowledged that once an area is flooded during a large rainfall event, it is often difficult to identify the route, cause and ultimately the source of flooding without undertaking further site specific and detailed investigations.

4.3.1 Pluvial Flooding

Pluvial flooding of land from surface water runoff is usually caused by intense rainfall that may only last a few hours. In these instances, the volume of water can prove to be too great from the rural land to infiltrate in a short amount of time resulting in water flowing over land. Within urban areas, this intensity is too great for the urban drainage network resulting in excess water flowing along roads, through properties and ponding in natural low spots. Areas at risk can therefore lie outside of the fluvial flood zones.

Pluvial flooding within urban areas will typically be associated with events greater than the 1 in 30-year design standard of new sewer systems. Some older sewer and highway networks will have even less capacity than the 1 in 30-year event. There is also a residual risk associated with these networks due to possible network failures, blockages or collapses.

The Environment Agency has produced two national surface water flood maps aimed at helping to identify those areas where localised, flash flooding can cause problems even if the Main Rivers are not overflowing. Both maps are extremely helpful in supplementing the fluvial Flood Map by identifying areas in Flood Zone 1, which may have critical drainage problems.

4.3.2 Areas Susceptible to Surface Water Flooding Map

The first-generation national map, the Areas Susceptible to Surface Water Flooding (AStSWF) released in 2008, shows areas where surface water would be expected to flow or pond during an extreme rainfall event with a 1 in 200 chance of occurring. The simplified modelling method adopted excludes the underground sewerage, drainage systems, smaller over ground drainage systems and the impact of buildings. The first-generation map was a preliminary provided to:

Local Resilience Forums (LRFs) and Regional Resilience Teams for use in their functions that relate to emergencies as defined and required by the Civil Contingencies Act 2004, and

LPAs for land use planning purposes.

The AStSWF map is separated into areas at less, intermediate or high susceptibility of surface water flooding. The areas identified as 'highly' susceptible will flood first, flood deepest and flood during lower rainfall events. These areas will also tend to be predominantly located in valleys, in the Main River floodplain, behind defences or raised structures or on flat low-lying land, which are generally also at fluvial risk.


4.3.3 Flood Map for Surface Water

The Environment Agency updated their national methodology in 2010 and released their second-generation national map, the Flood Map for Surface Water (FMfSW). The revised model included a number of improvements to the AStSWF including:

Two storm events (1 in 30-year and 1 in 200-year) National drainage rates to represent the sewer system The influence of buildings

The resulting flood extents of each storm event were categorised as two zones:

Shallow Surface Water Flooding - flooding greater than 0.1m Deep Surface Water Flooding - flooding greater than 0.3m

The Environment Agency chose the 0.3m threshold as it represents a typical value for the onset of significant property damages. It is also at this depth that moving through floodwater (driving or walking) may become more difficult; both of which may lead users to consider the need to close roads or evacuate areas.

4.3.4 Locally Agreed Surface Water Information

During the Cheshire East PFRA, the Council were required by the Environment Agency to agree an appropriate dataset that represents the risk from surface water in their area. Both the FMfSW and the AStSWF were reviewed against the available historic flooding information provided by United Utilities and the previous SFRA data.

In general, during the PFRA only a loose correlation was found between either of the datasets and the historic flooding information. Therefore, for the purposes of the PFRA, the AStSWF dataset was used as the locally agreed surface water information. This is because it was thought to represent a more conservative assessment of the level of risk and is therefore more appropriate for a high level strategic study such as the PFRA. Table 4-3 shows the number of properties at risk from surface water flooding as identified in the PFRA. Table 4-3: Properties at Risk from Surface Water Flooding

Property Type Total Number of Properties

Less Risk (>100mm)

Intermediate Risk (>300mm)

More Risk (>1m)

All 557,382 34,200 13,900 1,876 Residential 440,560 25,900 10,200 1,231 Non-Residential 116,822 8,300 3,700 645 Properties counted using the AStSWF map

4.3.5 Sewer Flooding

Combined sewers extend across urban areas and convey waste and surface water to treatment works. On these systems Combined Sewer Overflows (CSOs) provide an overflow release from the drainage system into local watercourses or large surface water systems during times of high flow and intense rainfall. Some areas may also be severed by separate foul and surface water sewers. Foul sewers convey waste water to a treatment works whilst surface water discharges to local watercourses.

Flooding from the sewer network mainly occurs when flow entering the system, such as an urban storm water drainage system, exceeds its available discharge capacity. The system may then become blocked or it cannot discharge due to a high water level in the receiving watercourse. Pinch points and failures within the drainage network may restrict flows further. Water then begins a surcharge of the sewer network emerging at ground levels through manholes, potentially causing flooding to highways and properties. It should be noted that sewer flooding in 'dry weather' resulting from blockage, collapse or pumping station mechanical failure (for example), is the sole concern of the drainage undertaker.


The water company that serves the administrative area is United Utilities. United Utilities were consulted on flood risk associated with their assets and provided a number of datasets. The three main datasets associated with historical flood incidents include:

Sewerage Incident Register System (SIRS) - Feb 1990 to June 2008 Wastewater Incident Register System (WIRS) - April 2008 to August 2012 DG5 Register - October 2012

United Utilities SIRS and WIRS datasets provide a register of all incidents related to United Utilities wastewater assets from 1990. The WIRS system replaced the SIRS in 2008. The raw incident data has filtered to only include records that are flooding related (foul, surface water and sewer surcharge). In the majority of incidents, blockage of the underground system has been the root cause, resulting in flooding to properties and highways.

United Utilities also provided their “DG5 Register”, which is a Register of properties in their area that have suffered internal or external flooding from overloaded public sewers. The register is only a “snap shot” in history of those properties on the register at the time it was supplied, and properties may have been added or removed since it was supplied. The DG5 register was provided in October 2012. For United Utilities to remove a property from the DG5 register the flooding problem should be resolved or an investigation undertaken to prove that the public sewer was not the source of the flooding. Figure 4-2 illustrates the geographical distribution of DG5 records across the study area along with the total number of historical flooding incidents recorded in United Utilities SIRS and WIRS databases for each parish area. Figure 4-2: United Utilities Historical Flood Records

Whilst the DG5 register and the SIRS and WIRS datasets can give an idea of those areas at risk, they are purely identifying locations that have flooded previously and issues may have been resolved through United Utilities ongoing sewer improvements programme. The datasets do however provide a useful dataset for model verification or using alongside alternative data sources such as the Environment Agency's AStSWF or FMfSW.


4.3.6 Cheshire East Surface Water Management Plan

CEC published the Cheshire East Level 1 Surface Water Management Plan (SWMP) in July 2012. The SWMP project brought together existing flood risk information from CEC, the Environment Agency and United Utilities (as discussed in the sections above) to assess the surface water flood risk across the study area, first through a strategic review of flood risk and then an assessment of particular sites potentially at high risk from flooding.

The strategic review of flood risk across the study area has indicated that the overall level of surface water flood risk is moderate. In particular:

Due to the flat nature of the topography there is likely to be extensive surface water flooding resulting from an extreme rainfall event. This flooding is unlikely to be deep or fast flowing, except in localised areas, and only small numbers of properties are likely to be affected.

Deep flooding is only likely to be experienced where there are localised low-points, such as natural closed depressions, or manmade features, for example underground car parks or subways.

In a small number of locations, steep topography is likely to result in surface water flooding along well defined flow-paths. Flooding in these areas has the potential to represent a significant hazard to people due to its velocity and depth.

There are likely to be a number of locations throughout the study area where surface water and fluvial flooding mechanisms are likely to interact. In these areas it may be difficult to identify the exact source of any flooding, and CEC and the Environment Agency will have to work together to manage these issues.

There are a large number of Ordinary Watercourses within the study area, some of which run through urban areas. In many cases these watercourses have been culverted over and are likely to be in poor condition. A blockage or collapse of one of these culverts could represent a significant flood risk to adjacent properties.

Although the general classification of risk across the study area is moderate, there are a number of locations where flooding poses a high risk to people and/or property. 55 individual Risk Areas were identified where the level of risk is considered to be high enough to warrant further investigation. Figure 4-3 illustrates the locations of the 55 risk areas and their attributed level of risk.

The results of the site specific review for the risk areas indicate that:

During and after an extreme rainfall event it is likely that there will be extensive, shallow flooding, but unlikely to significantly affect large numbers of properties.

Flooding in most areas is unlikely to represent a significant hazard to people due to its shallow depth and low velocity. Much flooding will be ‘nuisance flooding’ of highways, low-lying areas and properties with basements / cellars.

There are numerous minor watercourses across the study area. The majority of these watercourses are very small and are unlikely to represent a significant risk to people or property as they are located in rural or sparsely inhabited areas. In some cases, localised areas are at significant risk from flooding from these minor watercourses. However, due to the flat nature of the topography, these flood risks are generally limited in scope and will not represent a significant hazard to people.

Along the eastern edge of the study area, where there is steep topography, areas are likely to experience greater levels of surface water runoff and flooding. In some cases high velocity flows could represent a hazard to people, particularly when flow-paths form along roads and through properties. These flood mechanisms have been experienced before where a culvert running underneath properties in Bollington have resulted in significant damages.


Figure 4-3: SWMP Risk Areas

4.3.7 Critical Drainage Areas

One of the requirements of the SFRA is to identify the location of Critical Drainage Areas (CDAs) to inform development policies and the need for detailed SWMPs.

For the purpose of this SFRA a CDA is considered to be an area contributing surface water runoff, either as direct overland flow or from the existing sewer network, which causes flooding at locations within that area. The risk of flooding is thereby confirmed, either by historical evidence, or through numerical modelling or other detailed form of analysis. A CDA therefore has areas within it where surface water flood risk exists (flood prone areas within a CDA) and areas where properties, although not directly at risk, contribute to that flood risk (upstream areas in a CDA directly affecting flood-prone areas).

CEC have already prepared a high level SWMP, discussed in Section 4.3.6 above, identifying flood prone areas across the borough (Figure 4-3). This SFRA will therefore identify CDAs as those areas contributing to the high risk areas listed in the SWMP.

Further information on CDAs is provided in Appendix C.

4.4 Groundwater Flooding Groundwater flooding is caused by the emergence of water from beneath the ground, either at point or diffuse locations. The occurrence of groundwater flooding is usually local and unlike flooding from rivers and the sea, does not generally pose a significant risk to life due to the slow rate at which the water level rises. However, groundwater flooding can cause significant damage to property, especially in urban areas, and can pose further risks to the environment and ground stability.


There are several mechanisms that increase the risk of groundwater flooding including prolonged rainfall, high in bank river levels, artificial structures, groundwater rebound and mine water rebound. Properties with basements or cellars or that are located within areas susceptible to groundwater flooding are at particular risk.

The Environment Agency's CFMPs do not consider groundwater flooding to be a significant issue in CEC’s administrative boundary, as there is little historic evidence to suggest that groundwater flooding is an issue worth further investigation.

Development within areas susceptible to groundwater flooding will generally not be suited to SuDS and proposals for infiltration drainage; however, this is dependent on a detailed site investigation and risk assessment. Further guidance is discussed in Section 5.6.

The Environment Agency’s national dataset, Areas Susceptible to Groundwater Flooding (AStGWF), provides the main dataset used to assess the future risk of groundwater flooding. The AStGWF map uses four susceptible categories to show proportion of each 1km grid square where geological and hydrogeological conditions show that groundwater might emerge. It does not show the likelihood of groundwater flooding occurring.

Figure 4-4 illustrates the AStGWF map. It shows that the probability of groundwater flooding is very high in Nantwich, and parts of Crewe and Knutsford. The probability of future groundwater flooding tends to be lower in the north east of the study area. There could however be localised problems, which will not be identified on this strategic map. Figure 4-4: Areas Susceptible to Groundwater Flooding


4.5 Canal Flood Risk There are six canals running through Cheshire East as illustrated in Figure 4-5. The Canal and Rivers Trust are responsible for the care and enhancement of all five canals, including:

1. Llangollen Canal 2. Macclesfield Canal 3. Peak Forest Canal 4. Shropshire Union Canal (plus the Middlewich Branch) 5. Trent and Mersey Canal 6. Wardle Canal (Middlewich)

The risk of flooding along each canal is dependent on a number of factors. As they are manmade systems and heavily controlled, it is unlikely they will respond in the same way as a natural watercourse during a storm event. Flooding is more likely to be associated with residual risks, similar to those associated with river defences, such as overtopping of canal banks, breaching of embanked reaches or asset (gate) failure as highlight in Table 4-4. Each canal also has significant interaction with other sources, such as the main rivers that feed them and the minor watercourses or drains that cross underneath.

The risks associated with these events are also dependent on their potential failure location with the consequence of flooding higher where floodwater could cause the greatest harm due to the presence of local highways and adjacent property. The focus should be on areas adjacent to raised embankments. The pound length of the canal also increases the consequence of failure, as flows will only cease due to the natural exhaustion of supply.

Stop plank7 (log) arrangements, stop gates and the continued inspection and maintenance of such assets by the Canal and Rivers Trust manage the overall risk of an event. Table 4-4: Canal Flooding Mechanisms

Potential Mechanism Significant Factors

Leakage causing erosion and rupture of canal lining leading to breach

Embankments Sidelong ground Culverts Aqueduct approaches

Collapse of structures carrying the canal above natural ground level

Aqueducts Large diameter culverts Structural deterioration or accidental damage

Overtopping of canal banks Low freeboard Waste weirs

Blockage or collapse of conduits Culverts

4.5.1 Historical Flooding

Table 4-5 provides a list of the known canal flood incidents in Cheshire East as a result of canal breaching and overtopping. Figure 4-5 identifies the location of these incidents.

Although not in Cheshire East, a recent breach occurred along the Trent and Mersey Canal in September 2012, when the canal at Dutton burst its banks8. The cause in this case was high groundwater levels and surface water that could not freely drain underneath the canal. The banks became saturated and a land slide occurred.

A similar pattern of historical events can be seen in Table 4-5, where interactions with other sources (surface water runoff and culverts) crossing underneath the canal have resulted breaches along major embankments.

7 wooden boards for dropping into grooves at a narrows; to permit drainage for maintenance work on a canal section or

to isolate a leaking section 8 http://www.bbc.co.uk/news/uk-21292298


Figure 4-5: Canals in Cheshire East

Table 4-5: Incidents of Historical Canal Breaches and Overtopping Events

Location Description Result Date Marbury Embankment failure from leakage through

subsidence Breach 21/07/1907

Bollington Suspected embankment failure from leakage Breach 29/02/1912 Disley Breach Embankment failure at culvert Breach 1941 Church Minshull Piping / Leak failure Breach 12/10/1958 Bollin Aqueduct Aqueduct embankment failure Breach 02/08/1971 Disley Embankment failure at culvert Breach 16/07/1973 Stanthorne/ Middlewich

Unknown Breach 1991

Audlem Breach / Hawkes Moor

Embankment failure at culvert Breach 21/12/2000

Bollington Embankment

Piping failure caught before embankment breach

Breach 2001

Baddiley Embankment failure from exfiltration into embankment from inverted siphon

Breach 05/06/2006

Combs Feeder Blockage within the culvert Overtopping 13/12/2008 Grindley Brook Culvert Failure Breach 27/07/2009 Combs Feeder Overtopping of feeder channel caused by

blockage Breach 08/08/2009

Dane Feeder Unknown Overtopping 07/04/2010 Dane Feeder Unknown Overtopping 13/04/2010


4.5.2 Canal Hazard Zones

As part of the SFRA the Canal and Rivers Trust have provided their Asset Register9, which includes a comprehensive database of their assets including locks, weirs, sluices, aqueducts, embankments, reservoirs, flood gates and retaining walls. For each asset the Canal and Rivers Trust have recorded a number of details including its Planned Preventative Maintenance (PPM) programme and condition grade. A summary of the condition grades for each asset group are summarised in Table 4-6. Table 4-6: Canal and Rivers Trust Assets10 and Condition Grades11

Asset Type No. Condition Grade (number of) A B C D E Unknown Very Good

Good Fair Poor Bad

Locks 96 0 4 60 32 0 0 Canal Weirs 24 1 3 16 4 0 0 River Weirs 0 0 0 0 0 0 0 Weired Locks 1 0 1 0 0 0 0 Sluices 42 1 2 8 20 6 5 Aqueducts 26 0 1 14 10 0 1 Culverts 189 4 17 112 26 6 24 Major Embankments 57 0 3 42 11 0 1 Minor Embankments 7 0 1 0 0 0 0Reservoirs 3 1 1 1 0 0 0 Flood Gates 3 0 0 0 0 3 0

The location of major embankments in poor or bad condition, where aqueducts or culverts run underneath, can be used to identify locations where the probability of breaching could be considered higher.

There are several major embankments through Cheshire East, which will cause significant damage if they were to fail due to the presence of local highways, adjacent property and the distance between available stop planks. Two locations have been chosen to assess the impacts of canal breaching in more detail and include:

Macclesfield Canal through Congleton, and the Shropshire Union Canal through Nantwich.

A "Canal Hazard Zone" has been created for each area to show land that could potentially be affected by flooding in the event of breaching of major canal embankments. This is based on broad scale modelling techniques and should only be taken as an indication of the extent of potential flood risk. The methodologies used to derive the risk of canal overtopping and breach are outlined in Table 4-7.

It is accepted that a major breach failure is unlikely due to ongoing maintenance by the Canal and Rivers Trust. However, due to the number of assets in poor and bad condition, history of canal flooding in the area and number current properties and future development sites at risk, it was considered that a breach assessment would help increase the understanding of flooding mechanism from all sources in Cheshire East.

9 Canal and Rivers Trust Asset Register dated 04/01/2012 10 Some of these assets are not owned by the Canal and Rivers Trust. Other owners include the Environment Agency

and riparian owners. 11 Some assets have not been attributed with a condition grade. No further information has been provided on the

condition grading system.


Table 4-7: Canal Breach Modelling Methodology

Task Approach Comment Identify breach locations

Major embankments in poor or bad condition with culverts and highways running underneath.

These are the only areas through Cheshire East in which the canal is raised above urban areas.

Calculate breach volume

Estimating the volume of water per impounded length using average depth and width.

Impounded length is the distance either side of breach to the nearest stop log. Average depth of 1.25m. Average width calculated using GIS for each impounded length.

Create JFLOW model

Import breach location and potential discharge volume into JFLOW

The breach used a standard hydrograph. Breach extents were created every hour.

There are a number of assumptions made within the canal breach methodology.

The SFRA does not attempt to calculate the probability of such events occurring, as this would be too detailed for this level of assessment and as such, the SFRA has adopted a more precautionary approach where data is uncertain.

The impounded length of the canal has been calculated using the first set of stop planks either side of the breach location. This is contrary to what was seen in the breach at Durham where the predefined stop plank locations could not be used because the velocities were too high, and so stop log locations were sought further away from the breach. However, due to the significant distances between stop plank locations through Cheshire East this approach, whilst potentially optimistic, was the best use of available information.

The mapping in figure 4-6 and 4-7 (below) is intended to provide an indication of the likely impact of selected failure scenarios. It is not intended that inundation mapping provides a comprehensive analysis of all failure scenarios and further site specific analysis will need to be considered at all sites located within the vicinity of a canal system. Developers should be aware that any site that is at or below canal bank level may be subject to canal flooding and this should be taken into account when building resilience into low level properties.


Figure 4-6: Canal Hazard Zone - Congleton

© Crown copyright, All rights reserved. 2013 Licence number 0100031673

Figure 4-7: Canal Hazard Zone - Nantwich

© Crown copyright, All rights reserved. 2013 Licence number 0100031673


4.6 Reservoir Flood Risk A reservoir is usually an artificial lake where water is stored for use. Some reservoirs supply water for household and industrial use, others serve other purposes, for example, as fishing lakes or leisure facilities. Like canals, the risk of flooding associated with reservoirs is residual and is associated with failure of reservoir outfalls or breaching. This risk is reduced through regular maintenance by the operating authority. Reservoirs in the UK have an extremely good safety record with no incidents resulting in the loss of life since 1925.

The Environment Agency is the enforcement authority for the Reservoirs Act 1975 in England and Wales. All large reservoirs must be regularly inspected and supervised by reservoir panel engineers. Local Authorities are responsible for coordinating emergency plans for reservoir flooding and ensuring communities are well prepared. Local Authorities will work with other members of the Local Resilience Forum (LRF) to develop these plans.

4.6.1 Reservoir Flood Maps The Environment Agency has prepared reservoir flood maps for all large reservoirs that they regulated under the Reservoirs Act 1975 (reservoirs that hold over 25,000 cubic meters of water).

The maps show the largest area that might be flooded if a reservoir were to fail and release the water it holds but do not give any information about the depth or speed of the flood waters. CEC Emergency Planners will have access to this information so they can develop effective Emergency Plans. However this is not available to the public due to the sensitivity of the information and therefore has not been provided within this SFRA. Reservoir flood maps can be viewed online only and can be found on the Environment Agency’s website12.

The FWMA updates the Reservoirs Act, reducing the capacity at which reservoirs will be regulated from 25,000m³ to 10,000m³. These reservoirs will not have been covered by the Environment Agency’s inundation maps.

4.7 Flood Risk Management The aim of this section of the SFRA is to identify existing flood risk management (FRM) assets and proposed FRM schemes through Cheshire East. The location, condition and design standard of existing assets will have significant impact on actual flood risk mechanisms. Whilst future schemes in high flood risk areas carry the possibility of reducing the probability of flood events and reducing the overall level of risk. Both existing assets and future schemes will have a further impact on the type, form and location of new development or regeneration through the district.

4.7.1 Environment Agency Assets

Both the Upper Mersey and Weaver Gowy catchments have benefitted from engineering schemes put in place by the Environment Agency over the last 30 to 50 years, including raised defences, concrete walls, pumping stations and flood basins. There are over 10km of existing major defences across Cheshire East, with 3.5km, 4.5km and 2.1km in Crewe and Nantwich, Macclesfield and Congleton respectively. A number of these defences provide a 1 in 100-year standard of protection, protecting existing properties in Bollington and Congleton.

In addition to these engineering schemes, the Environment Agency carryout a number of other flood risk management activities in the catchment that help to reduce the probability of flooding, and those that address the consequences of flooding. These include:

Maintaining and improving existing flood defences, structures and water courses. Enforcement and maintenance where riparian owners carry out work detrimental to flood

risk. Identifying and promoting new flood alleviation schemes where appropriate.

12http://maps.environment-

agency.gov.uk/wiyby/wiybyController?x=357683.0&y=355134.0&scale=1&layerGroups=default&ep=map&textonly=off&lang=_e&topic=reservoir

http://www.environment-agency.gov.uk/business/sectors/64253.aspx

http://www.environment-agency.gov.uk/business/sectors/64253.aspx

http://www.direct.gov.uk/en/Governmentcitizensandrights/dealingwithemergencies/preparingforemergencies/DG_176587


Working with Local Authorities to influence the location, layout and design of new and redeveloped property and ensuring that only appropriate development is allowed on the floodplain.

Operation of Flood Warnings Direct and warning services in areas of Congleton, Nantwich, Macclesfield and Bollington.

Promoting awareness of flooding so that organisations, communities and individuals are aware of the risk and are prepared in case they need to take action in time of flood.

Promoting resilience and resistance measures for those properties already in the floodplain.

4.7.2 United Utilities Assets

During this SFRA, the United Utilities Catchment Manager was consulted on current and future schemes within Cheshire East. In some cases, United Utilities aim to reduce the risk of flooding by increasing the size of some sewer pipes and building tanks underground, which can store the storm water during times of peak flow and then pump it back into the system when the water has subsided.

Under AMP5, OFWAT requires United Utilities to offer mitigation to all properties at risk of flooding by 2013. This includes providing door blocks and such like. This will go some way to reducing the consequences of sewer flooding, although it is the consequences rather than the probability of such an event that will be reduced. United Utilities are currently developing their business plan for AMP6 (2015-2020) and were unable to provide any further details.

4.7.3 Cheshire East Council Assets

As LLFA, CEC will own and maintain a number of assets throughout the district including culverts, bridge structures, trash screens, highway drains and gullies. The majority of these assets are likely to lie along Cheshire’s many Ordinary Watercourses, especially within urban areas where they have been culverted or diverted. These assets can have flood risk management functions as well as affect flood risk if they become blocked or fail.

As part of their FWMA duties, CEC has a duty to maintain a register of structures or features that are considered to have an effect on flood risk, including details on ownership and condition as a minimum. CEC are at the early stages of developing this register, which will be an ongoing process including asset identification, data collection, site visits and flood risk assessment.

The CEC LFRMS should outline how the Council intend to manage these assets or features including their ongoing maintenance programme. Where assets of features are located in a high risk area or have been assessed to have the potential to effect flood risk, the Council should prioritise and focus any maintenance or upgrades.

4.7.4 Future Flood Risk Management Schemes

The Environment Agency’s Medium Term Plan (MTP) has been agreed for 2013/14 and includes three studies in Cheshire East. These include investigation works with a particular focus on surface water flooding connected with main river levels and surveys on the local drainage networks. The aim of these studies is to provide CEC with the opportunity to identify areas of the network that are at significant risk of failure and enable CEC to target resources where needed most, produce prioritised works programmes and prepare future funding bids. The three studies include:

1. Coppice Road / Wistaston Road (Crewe and Nantwich) Surface Water Flood Alleviation Scheme led by Cheshire East Council

2. Newcastle Road (Astbury Marsh, Congleton) Surface Water Flood Alleviation Scheme led by Cheshire East Council

3. Church Lawton and Kidsgrove (Congleton/Newcastle under Lyme) joint investigation with Cheshire East Council and Staffordshire County Council

A number of potential studies did not make it on to the MTP including Flood Risk Management Strategies for the Bollin (covering Macclesfield and Prestbury) and Congleton areas. In addition, a number of studies are also underway this year via the RFCC Local Levy funding and include communities at Bollington, Brereton and Bradfield Green.


5 Development and Flood Risk

5.1 Introduction This section of the SFRA provides a strategic assessment of the suitability of potential site allocations across the Borough, including direct and indirect impact of flood risk on development.

The information and guidance provided in this section (supported by the SFRA mapping) can be used by the Council to inform the Sustainability Appraisal (incorporating the Strategic Environmental Assessment Directive) of the Local Plan. This also provides the basis for which to apply the Sequential Approach in the development allocation and development management process.

5.2 The Sequential Approach The NPPF Technical Guide provides the basis for the Sequential Approach. It is this approach, integrated into all stages of the development planning process that provides the opportunities to reduce flood risk to people, property and the environment to acceptable levels.

The approach is based around the flood risk management hierarchy, in which actions to avoid, substitute, control and mitigate flood risk is central. For example, it is important to assess the level of risk to an appropriate scale during the decision making process, (starting with this SFRA). Once this evidence has been provided, positive planning decisions can be made and effective flood risk management opportunities identified.

Figure 5-1 illustrates the FRM hierarchy with an example of how these may translate into the Council’s management decisions and actions. Figure 5-1: Flood Risk Management Hierarchy

The overall aim of the Sequential Approach should be to steer new development to low risk Flood Zone 1. Where there are no reasonably available sites in Flood Zone 1, the flood risk vulnerability of land uses and reasonably available sites in Flood Zone 2 should be considered, applying the Exception Test if required.

Only where there are no reasonably available sites in Flood Zones 1 or 2 should the suitability of sites in higher risk Flood Zone 3 be considered. This should take into account the flood risk vulnerability of land uses and the likelihood of meeting the requirements of the Exception Test if required.

There are two different aims in carrying out the Sequential Approach depending on what stage of the planning system it is being carried out i.e. LPAs allocating land in Local Plans or determining planning applications for development.


The next Sections of the report are split between the two key users to provide a guided discussion on why and how the Sequential Approach should be applied, including the specific requirements for undertaking Sequential and Exception Testing.

5.3 Local Plan Sequential & Exception Test As the LPA, CEC should seek to avoid inappropriate development in areas at risk of flooding by directing development away from areas at highest risk and ensuring that development does not increase risk. Where possible, development can help reduce risk from flooding to existing communities and development.

At a strategic level, this should be carried out as part of the Core Strategy and/or allocation of sites for development during the Local Plan period by applying the risk-based approach to the allocation of development to avoid flood risk to people and property and to also manage any residual risk. Flood risk will need to take climate change into account. This should be achieved by:

1. Applying the Sequential Test and if necessary, the Exception Test, 2. Safeguarding land to prevent development in areas required for current and future flood

management; and, 3. Use opportunities offered by new development to reduce the causes and impacts of

flooding.

Figure 5-2 illustrates the Sequential and Exception Tests as a process flow diagram using the information contained in this SFRA to assess potential development sites against the NPPF Flood Zone and development vulnerability compatibilities (see Appendix E).

This is a stepwise process, but a challenging one, as a number of the criteria used are qualitative and based on experienced judgement. The process must be documented and evidence used to support decisions recorded. Figure 5-2: Local Plan Sequential Approach to Allocation


This SFRA provides the main evidence required, along with the LPA Core Strategy and Sustainability Appraisal, to carry out this process. This process also enables those sites requiring the Exception Testing to be identified.

For the Exception Test to be passed:

a) It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk; and,

b) A site-specific flood risk assessment (FRA) must demonstrate that the development will be safe for its lifetime, taking account of the vulnerability of its users, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall.

Although actually passing the Exception Test will require the completion of a site-specific FRA, the Council should be able to assess the likelihood of passing the test at the Local Plan level by using the information contained in this SFRA to answer the following questions:

1. Can development within higher risk areas be avoided through avoidance or substitution? 2. Is flood risk associated with possible development sites considered too high; and will this

mean that the criteria for Exception Testing are unachievable? 3. Can risk be sustainably managed through appropriate techniques without compromising

the viability of the development? 4. Can the site and those people who live and work there remain safe during times of flood

if developed?

Where it is unlikely that the Exception Test can be passed due to few wider sustainability benefits, flood risk is considered too great, or the viability of the site is compromised by the flood risk management work required, then the Council should consider avoiding the site all together.

Once the process has been completed the Council should then be able to revisit and update the Sustainability Appraisal with the allocation of development sites, as well as prepare flood risk policy including the requirement to prepare site-specific FRAs for all allocated sites that remain at risk of flooding.

5.4 Development Site Assessment The overall Development Strategy13 for Cheshire East is to provide a minimum of 300 hectare of land for business, general industrial and storage and distribution uses over the period 2010 to 2030, to support growth of the local economy. The strategy also requires sufficient land to be provided to accommodate at least 27,000 homes between 2010 and 2030.

This will be phased as follows:

2010 to 2015 - at least 1,150 homes each year (5,750 total) 2016 to 2020 - at least 1,250 homes each year (6,250 total) 2020 to 2030 - at least 1,500 homes each year (15,000 total)

A total of 7,153 new homes have been completed, under construction or have full or outline planning permission as of 31 March 2012. This leaves 19,847 new homes required to meet the housing numbers anticipated for 2030. A number of potential development sites have been identified by the Council through the Development Strategy:

Preferred Strategic Sites, Alternative Strategic Sites, and New Settlements

The Council have also undertaken two assessments to identify potential housing and employment sites, including the:

Strategic House Land Availability Assessment (SHLAA) sites – 2013, and Employment Land Review (ELR) sites - 2012

13 Cheshire East Council (2012) Shaping our future: A Development Strategy for Jobs and Sustainable Communities


During the recent consultation on the Cheshire East Local Plan Development Strategy and Emerging Policy Principles documents the Council received responses that have revealed a number of possible strategic sites that developers and landowners consider suitable for inclusion in the Local Plan as well as other strategic sites that have been brought to the attention of the Council in the past few months as the plan-making process has progressed. These sites have either not previously featured in Local Plan consultations or have changed significantly since previous consultations. These sites have also been reviewed and are labelled ‘Possible Additional Sites Proposed by Developer and Land Interests’.

In order to inform the first part of the Sequential Approach, illustrated in Figure 5-2, this SFRA has carried out a high level screening exercise overlaying all potential development sites provided against Flood Zones 1, 2, 3a and 3b. As an extra layer of information, each site has been reviewed against the Environment Agency's AStSWF map to help identify those sites in Flood Zone 1 that may have critical drainage problems, as required in the NPPF.

A detailed Excel spreadsheet can be found in Appendix C, which provides a breakdown of each site and the area (ha) and percentage cover of the fluvial and surface water flood zones. A summary of this spreadsheet is illustrated in Table 5-1. Table 5-1: Development Site Assessment Summary

Proposed Development Sites

Number of Sites Within*

Total Sites

Medium Risk of surface water flooding

Flood Zone 2

Flood Zone 3a

Flood Zone 3b

Strategic Sites 43 18 10 15 46 Alternative Strategic Sites 43 12 8 10 45 SHLAA 2013 504 167 123 124 905 ELR 35 19 16 14 53 Possible Additional Sites Proposed by Developer and Land Interests

42 23 16 20 50

*Sites within Flood Zone 3b will also be in Flood Zone 3a. Sites within Flood Zone 3a will also be in Flood Zone 2.

The Council should use this spreadsheet to identify which sites should be avoided during the Sequential Test. It can also be used to assess whether or not employment and housing projections can be met by purely allocating sites in areas at low risk of flooding.

If this is not the case, or where wider strategic objectives require regeneration in areas already at risk of flooding, then the Council should consider the compatibility of vulnerability classifications and Flood Zones (Appendix E) and whether or not the Exception Test will be required before allocating sites.

In this case, the decision making process should be transparent and information from this SFRA should be used to justify decisions to allocate land in areas at high risk of flooding.

5.5 Community Review Where the high level screening exercise has identified a level of flood risk to priority development sites, the Level 2 SFRA is there to provide the Council with additional flood hazard information (such as flood depths, velocities, and likely risk to people), to help inform their strategic planning decisions on site allocation.

Due to local priorities, it was agreed at a Steering Group level that a community review would be carried out as part of the Level 2 SFRA, focusing on Principal Towns, Key Service Centres and New Settlements outlined in the Councils Local Plan document ‘Shaping our future: A Development Strategy for Jobs and Sustainable Communities’ and possible additional sites proposed by developer and land interests. Only sites at high risk of flooding have been included in this review.


The community review will provide a detailed but high level overview of flood risk for each community and Strategic Site proposed within. Supporting A3 flood risk maps for each community area have been provided in Appendix A. Using this analysis, development recommendations will be provided on site-specific FRAs and appropriate flood risk management within that community.

Due to level of detail contained in this chapter, it is not recommended that each site review is read consecutively but users should use Table 5-2 to identify those sites of interest. Table 5-2 also summarises the sources of flooding present with an assigned risk rating. This rating is based on available data collected through the SFRA. In some instances, where data gaps exist (e.g. lack of flood zone information along ordinary watercourses), it was not possible to identify potential sources. A site-specific FRA will be required to confirm risks.


Table 5-2: Strategic Development Site Assessment Summary

Community Strategic Site Name R

epor

t Se

ctio

n

Mai

n R

iver

Ord

inar

y W

ater

-co

urse

Fluvial Flood Zones

Surf

ace

Wat

er

Sew

er

Surc

harg

e

SWM

P R

isk

Are

a

Can

al

Haz

ards

His

toric

al

Floo

ding

R

ecor

ds

2 3a 3b Alsager Twyfords 5.5.3 Alsager Former MMU Campus 5.5.3

Alsager Radway Green 5.5.3

Alsager Fannys Croft 5.5.3

Congleton Back Lane and Radnor Park 5.5.4 Congleton Giantswood Lane to Manchester Road 5.5.4

Congleton Congleton Business Park Extension 5.5.4

Congleton Manchester Road to Macclesfield Road 5.5.4

Crewe Basford West 5.5.1

Crewe Basford East 5.5.1

Crewe West Street / DunwoodyWay 5.5.1

Crewe Crewe Town Centre 5.5.1 Crewe Leighton West/ Barrows Green Phase 2 5.5.1

Crewe East Shavington 5.5.1

Crewe The Triangle 5.5.1

Knutsford Parkgate Extension 5.5.5

Knutsford North West Knutsford 5.5.5

Macclesfield South Macclesfield Development Area 5.5.2

Macclesfield Land east of Fence Avenue 5.5.2

Macclesfield Land between Congleton Road and Chelford Road 5.5.2

Macclesfield Macclesfield Town Centre 5.5.2


Community Strategic Site Name R

epor

t Se

ctio

n

Mai

n R

iver

Ord

inar

y W

ater

-co

urse

Fluvial Flood Zones

Surf

ace

Wat

er

Sew

er

Surc

harg

e

SWM

P R

isk

Are

a

Can

al

Haz

ards

His

toric

al

Floo

ding

R

ecor

ds

2 3a 3b Middlewich Brooks Lane 5.5.6

Middlewich Glebe Farm 5.5.6

Middlewich Land at Midpoint 18 5.5.6

Nantwich Stapeley Water Gardens 5.5.7

Nantwich Kingsley Fields 5.5.7

Nantwich Snow Hill 5.5.7

New Settlement Handforth East 5.5.10

New Settlement Stowford Village A 5.5.10

New Settlement Barthomley Village B 5.5.10

New Settlement Employment Areas 1, 2 and 3 5.5.10

Sandbach Land adjacent to J17 of M6 5.5.8

Sandbach Former Albion Chemicals 5.5.8

Wilmslow Adlington Road 5.5.9

Wilmslow Land to the east of Royal London 5.5.9

Alderley Edge Land North of Beech Road 5.5.9

Crewe Land off University Way 5.5.1

Low Medium High


5.5.1 Crewe Community Review

Crewe Flood Risk Overview

Crewe is located in the upper reaches of the River Weaver. Fluvial flooding can originate from Englesea Brook, Valley Brook, Basford Brook and Swill Brook, which flow in a westerly direction through the town. The floodplains through Crewe are relatively small and exposure to flooding is infrequent. Flood water in this area can be deep, presenting a real hazard in places to people and current properties. Through the town centre, the watercourses have been heavily modified with straightened and culverted sections being commonplace, especially where rivers flow underneath major railway infrastructure.


The only defended reach in this area is a raised masonry channel wall along Valley Brook. Current flood risk management activities by the Environment Agency focus on river asset and channel maintenance. The Environment Agency expect further management work in the future to contain what would otherwise be increasing risk due to climate change. This will be focused on the key ‘flood hotspots’ and making them more resistant to flooding. Flood Warning is not viable in the area because of short lead times.

The national surface water maps indicate the potential for significant surface water flood risks through the northern edge of Crewe. The area has a flat topography and surface water has the potential to affect a significant number of residential properties which predominantly comprise semi-detached housing. The Cheshire East SWMP has identified four high risk areas in Crewe. There is also a number of Ordinary Watercourse through the town with little or no flood risk information.

There are a number of current properties on United Utilities DG5 register. Overlaying property locations with existing flood risk data identifies a potential interaction between the sewer network, main rivers, Ordinary Watercourses and overland flow along Nantwich Road, Dane Bank Avenue, Broughton Lane and Bilton Way.

Crewe Development Strategy

From its inception, Cheshire East has identified Crewe as its biggest spatial priority and has developed the 'All Change for Crewe' strategy in response to this. The Development Strategy seeks to deliver 6,000 new jobs on Basford Strategic Development sites with a mix of uses focusing on high value knowledge and science based industries. The strategy also advocates a retail led redevelopment of the town centre together with other leisure and residential development. It also seeks to develop about 6,500 new homes in and around the town by 2030 together with the regeneration of existing older areas of the town.

Crewe Town Centre Strategic Site

Crewe Town Centre has the potential to provide 200 new homes (including both apartments and family homes), student accommodation, comparison retail and leisure and other commercial uses including offices.

The risk of flooding in the area is low. Valley Brook runs to the south of the town centre, but Flood Zones are narrow. Properties currently at risk are located south of the railway. There is a potential for surface water flooding in the area, with the railway providing an informal barrier to any overland flows. The railway also restricts access and egress to the town centre.

Flood risk is unlikely to pose a significant constraint to development in this area. Site-specific FRAs should focus on surface water flood risk and sewer surcharge exploring the potential impacts of development and appropriate surface water management techniques. The assessment should identify how surface water is to be managed on site and should include SuDS where possible to managing runoff and reduce the amount of surface water entering the combined sewer network.

West Street / Dunwoody Way Strategic Site

The West Street / Dunwoody Way Strategic Site is located to the west of Crewe town centre. It is generally flat and currently occupied by Bombardier for employment use. However, it is possible that during the plan period there may be opportunities for redevelopment, including the provision of up to 700 homes.

The risk of flooding in the area is low. Valley Brook runs to the south of the town centre, but Flood Zones are narrow, with those properties currently at risk located south of the railway. There is a potential for surface water flooding in the area, with the railway providing an informal barrier to any overland flow.

Flood risk is unlikely to pose a significant constraint to development in this area. Site-specific FRAs should focus on surface water flood risk and sewer surcharge exploring the potential impacts of development and appropriate surface water management techniques. The assessment should identify how surface water is to be managed on site and should include SuDS where possible to managing runoff and reduce the amount of surface water entering the combined sewer network.


Basford East Strategic Site

Basford East is a large greenfield site situated to the south east of Crewe and covers approximately 92 hectares. The site itself is bordered by the West Coast Mainline (to the west) and Stoke-on-Trent / Nottingham rail line (to the north), and the A500 Hough-Shavington Bypass to the south. Basford East is a mix of arable, improved grassland and semi-improved grassland which also contains a river habitat. It has been identified for strategic and major industrial and business related development delivering around 4,000 jobs and about 1,000 new homes.

Basford Brook flows through the heart of the site alongside several groupings of ponds providing the greatest source of flood risk. The Brook has been hydraulically modelled in detailed by a third party and outputs have been used to update the Environment Agency’s Flood Map. The current Flood Zones have been classified as functional floodplain in this SFRA and development should be avoided in these areas. Basford Brook has also been identified as a Local Wildlife Site with protected species recorded, adding further weight to avoiding development in the floodplain. Any loss of floodplain will require compensational storage to offset the impacts of development.

As the site is currently Greenfield, SuDS should be used to control runoff to greenfield rates. Improvement could also be sought to reduce impacts downstream.

A detailed site-specific FRA will be required before development can go ahead. As well as managing any risks that remain after master planning, the FRA should also consider future transport infrastructure planned on site including the Crewe Green Link Road South and the High Speed Two (HS2). Any infrastructure planned over the Brook or in the floodplain should be designed to not impact on flood flow. Culverting part or the entire Brook is not recommended.

Basford West Strategic Site

Basford West is a large greenfield site situated in the south east of Crewe. The site is bordered by the West Coast Mainline (to the east) and Crewe Road / Gresty Road (to the north and west) and the A500 Hough-Shavington Bypass (to the south). The site covers approximately 55 hectares of arable, improved grassland and semi-improved grassland, and has been identified to deliver about 2,000 jobs through a new regional warehousing and distribution park and 300 new homes.

According to the flood risk data collected during this SFRA, only the northern edge of the site is at risk from both surface water pooling and fluvial flooding from Basford Brook / Gresty Brook.

Risk should be avoided through careful master planning, placing all development away from the naturally low spot to the north. As the site is currently greenfield, SuDS should be used to control runoff to greenfield rates. Improvement could also be sought to reduce impacts downstream. Ponds could be used at the northern edge of the site to store surface water before discharging into the brook.

Leighton West Strategic Site

Leighton West lies to the north west of Crewe and borders existing residential development to the east and Leighton Hospital to the north. The site has been identified as a new sustainable neighbourhood to support and complement the adjacent Leighton Hospital, including the delivery of 750 new homes. Land adjacent to this site (known as land north of Parkers Road) has planning permission for up to 400 homes.

According to the flood risk data collected during this SFRA, the risk of flooding to the area is low. Leighton Brook runs to the south of the site, but does not increase risk to the site. The brook has not been modelled by the Environment Agency and Flood Zones are still based on broad scale modelling outputs. A detailed hydraulic model of the watercourse is not required as part of the site-specific FRA. As the site is currently greenfield, the FRA should focus on surface water management and SuDS to control runoff to greenfield rates. Improvement could also be sought to reduce impacts downstream.

The Triangle Strategic Site

The Triangle site is located south of Newcastle Road between the villages of Shavington and Wybunbury. The proposed development area is bounded by Newcastle Road to the north, the


rear gardens of houses bounding Dig Lane to the south-west, and the rear gardens of houses bounding Stock Lane to the south-east. The proposed development area is relatively level on greenfield land currently used for agricultural purposes. The site now has outline planning permission for up to 360 dwellings

The site incorporates the upper reach of Cheer Brook. Downstream of Dig Lane, the Brook is classified as a main river. Upstream of Dig Lane, through the site, the Brook is an Ordinary Watercourse. From satellite imagery, the brook originates in the middle of the site. However, it is potentially in culvert, as a second small field drain reappears off Stock Lane. The Environment Agency’s nations surface water maps help illustrate the potential path of the watercourse.

As part of a site-specific FRA, a site investigation should be carried out to identify the upper reaches of the brook and its condition. If a culvert is found, opportunities to open the brook should be assessed. A hydraulic model of the Brook maybe required. Placing development over the culvert, or within the easement for the culvert, should be avoided as access maybe required in the future.

Surface water will have to be effectively managed on site. The site is currently undeveloped and water will naturally tend to drain towards the Brook. SuDS offer opportunities to control runoff to greenfield rates. Improvement could also be sought to reduce impacts downstream.

East Shavington Strategic Site

This site lies on the eastern edge of Shavington village. It comprises approximately 11 hectares of Greenfield agricultural land, which slopes downwards towards Swill Brook and up towards Weston Lane. Swill Brook has been hydraulically modelled by the Environment Agency as part of the Weaver Tributaries Strategic Flood Risk Mapping (SFRM) study, but does not extend as far upstream as the site.

As the site is currently greenfield, water will naturally drain towards the brook. The national surface water maps also indicate that existing residential properties bordering the site to the south could also be at risk from surface water.

Flood risk should be avoided by placing all development outside of the functional floodplain to the north. A site-specific FRA should investigate the impacts of development of surface water runoff and identify appropriate SuDS. SuDS should be used to control runoff to greenfield rates, whilst improvement could also be sought to reduce the risk of flooding to downstream properties.

Land off University Way, Crewe

Land north of University Way has been identified as a possible additional site proposed by developer and land interests. The site is 4ha in size and has the potential to provide 120 new homes. Currently the land is grassed and is bordered by the A5020 and trees to the northern and eastern boundaries. The area is characterised by a mix of uses including employment and university uses to the west. To the east, the site is adjacent to open countryside and woodland. Beyond is Crewe Hall Registered Park and Garden (Grade II listed) and the listed Park Farm House (Grade II) and the Crewe Green Conservation Area.

The site is also boarded by Englesea Brook to east and Valley Brook to the north. Over 30% of the site is within Flood Zone 3. Most of this area has been designated as functional floodplain as part the SFRA and it is recommended that this part of the site is avoided as any loss of floodplain could have a significant negative impact downstream.

However, if development is sough, it is recommended that a site-specific FRA is carried out. This will require the extension of Valley Brook hydraulic river model as it currently only covers half of the site. This will be required to better define Flood Zones 2 and 3. Regardless of the outcome of the modelling, compensational flood storage will be required to offset any impacts of development.

The north east corner of the site is also at risk from surface water flooding which pools on the low lying floodplain. The A5020 forms a critical obstruction to overland flow.


5.5.2 Macclesfield Community Review

Macclesfield Flood Risk Overview

Macclesfield is at risk of fluvial flooding from the River Bollin. From the culvert underneath the railway line (adjacent to the A523), the Bollin is heavily modified / canalised through the town centre with high bank levels. Bank levels will have been raised over the years as development has taken place.

The 1 in 100-year flood remains mostly in bank apart from a number of locations where flood water will overtop due to sections of lower uneven river bank. The town centre is a risk from the extreme 1 in 1000-year fluvial flood event.


The Environment Agency’s vision is to sustain the current level of fluvial protection into the future, while also accepting that specific locations need improvement in order to maintain the standard of existing defences through the town centre.

According to the Cheshire East SWMP, Macclesfield is at high risk of surface water flooding, with fifteen high risk areas identified. Sheet runoff during extreme rainfall events from the open land surrounding the town could be the main cause of flooding. Whilst the national surface water flood map indicates the potential for extensive and deep flooding within this area, affecting a large number of properties, the SWMP classifies most of these areas a low to medium risk. The SWMP concluded that this was mainly due to the lack of supporting historical flood records and a number of areas of local storage available within the highway and local green space.

Incidents of highway flooding and DG5 records collated in this SFRA do show a minor correlation with surface water flow paths and SWMP risk areas. There are also a number of Ordinary Watercourses that run into the centre of Macclesfield from the surrounding open land. These watercourses become culverted as they run through built up areas.

Macclesfield Development Strategy

The Development Strategy looks to provide a long term supply of suitably located employment land to attract new businesses and allow existing businesses to expand in Macclesfield. The strategy has the potential to deliver a vibrant town centre by providing residential, retail, arts, leisure, tourism and cultural facilities and deliver about 3,500 new dwellings in and around the town by 2030. This will provide a mix of housing types and tenures and including affordable and older persons accommodation. In order to deliver sustainable economic growth, it considers a number of development options around the town some of which are in the Green Belt.

Macclesfield Town Centre Strategic Site

Macclesfield Town Centre covers the existing Primary Shopping Area and the surrounding areas. It has been identified as a mixed use development area including the delivery of between 300 and 400 dwellings by 2030.

The town centre is at risk from the River Bollin, which runs along the eastern edge of the site. The Bollin is heavily modified / canalised throughout the town centre. The river has high bank levels which will have been raised over the years as development has taken place. As a result, the Flood Zones are relatively narrow with the 1 in 100-year flood contained within banks except for a few locations (Thorp Street and along Water Street) at risk where flood water will overtop due to sections of lower uneven river bank. Properties along the waterfront are mainly at risk from the extreme 1 in 1000-year flood.

The national surface water maps indicates the potential for runoff to enter the area from the south west and also the potential for significant surface water flood risks through the southern edge of the town centre.. The Cheshire East SWMP has identified two high risk areas on the outskirts of the town centre. The Churchill Way and Bond Street Risk Areas are located at the downstream end of minor watercourses. These are in culvert as they run towards the Bollin. A site assessment carried out in the SWMP indicates that this area is likely to experience extensive flooding. However, this is likely to be predominantly confined to the highway as most of the commercial properties in this area are raised above highway level. A blockage or collapse of both culverts could represent a significant flood risk to the town centre. The roundabout on Churchill Way is likely to be extensively affected as this is a local low point. Deep flooding on roads can represent a hazard to people. How surface water is managed in this area will have impacts on risk to the town centre.

It is recommended that CEC prepares a Flood Management Plan, with support from the Environment Agency, to develop a long term development and flood mitigation strategy for the town centre. This should be linked to the Environment Agency’s aspirations for managing risk from the River Bollin whilst also supporting the Council’s vision for regeneration. A robust review of effective flood management options should be reviewed and assessed against the impacts of climate change and any residential risks that may remain after flood management options have been implemented. The Flood Management Plan should recommend a preferred mitigation strategy across the town centre. This study should then be taken forward into a detailed Project Appraisal Report (PAR) with the aim of outlining a preferred option. Once developed these studies should be used to support the Council’s infrastructure delivery programme and used to


inform individual site-specific FRAs. The Council should also explore opportunities to target sources of appropriate partnership funding.

South Macclesfield Development Area Strategic Site

The South Macclesfield Development Area is a large site that lies on the southern edge of Macclesfield’s urban area, much of which is open fields and scrub land with hedgerow boundaries. Some existing usage is on site including small business uses off Turf Lane, a Council Depot and playing fields with changing rooms. Adjacent neighbouring uses include one and two storey residential properties on Congleton Road (A536) and recent new residential development off Moss Lane. The eastern boundary runs along the rail line and opposite Lyme Green Business Park. The southern boundary is onto farm land, the Council’s waste recycling centre and Dane Moss Landfill Site.

The site has been identified to deliver around 900 dwellings and 5,000 square metres of retail development and 5 hectares of employment land and employment related uses.

According to the flood risk data collected during this SFRA, the site is at risk of surface water flooding with water pooling along field drains. The current site drainage tends to flow in a south-easterly direction before entering a surface water drain that then flows underneath Macclesfield FC football ground along Sherwood Road and into the River Bollin.

The site is situated within Flood Zone 1 and as such a site-specific FRA should focus on surface water flood risks and exploration of the potential impacts of development and appropriate surface water management techniques. SuDS should be explored to control runoff to greenfield rates. Improvement could also be sought to reduce impacts downstream.

The area has significant potential for contamination to be present as it is located adjacent to Danes Moss Landfill site and it includes waste transfer stations and depots. Further investigation is required to assess contamination issues which will restrict viable SuDS.

Land Between Congleton Road and Chelford Road Strategic Site

The site lies to the south west of Macclesfield, and incorporates a large greenfield area from Chelford Road in the north to Congleton Road in the south. The site includes a significant area, but it has been noted that the entire area is not required but it is important to ensure that, over the long term, space remains for future growth. The site has been identified for a phased delivery of between 750 - 1,500 dwellings (at an average of 30 dwellings per hectare), 1,000 square meters of retail and five hectares of employment land.

According to the flood risk data collected during this SFRA the site is at risk of surface water flooding. Whilst the risk on site is low, developing the area could have a significant impact downstream if surface water runoff is not effectively managed. The site lies upstream of a number of high risk areas identified through the SWMP including Tenby Road, Thornton Avenue, Somerton Road and Chiltern Avenue.

Flood risk is unlikely to pose a significant constraint to development in this area. Site-specific FRAs should focus on surface water flood risk and may explore the potential impacts of development and appropriate surface water management techniques. The assessment should identify how surface water is to be managed on site and should include SuDS where possible to managing runoff and reduce the amount of surface water entering the combined network. SuDS offer opportunities to control runoff to greenfield rates. Improvement could also be sought to reduce the risk of flooding to downstream properties.

Land East of Fence Avenue Strategic Site

The site is located to the east of Macclesfield, between the current urban area and the Macclesfield Canal. The site is currently occupied by part of the Kings School and covers an area of around 14 hectares. It has been identified for residential use providing around 150 new homes by 2025 and another 150 homes by 2030.

Although the site is currently within Flood Zone 1, there are a number of surface water drains that can be identified from OS mapping that flow underneath the Macclesfield Canal through the site towards the River Bollin. The Environment Agency’s national surface water maps also indicate possible flood flow routes. The drains seem to be fed by small reservoirs around


Higherfence and from surface water sewers serving residential properties along Cottage Lane and Ecton Avenue.

The actual level of flood risk associated with these drains is currently unknown and should be investigated during a site-specific FRA. There will also be a residential risk associated with the drains as culverts; they could be susceptible to blockage or collapse underneath the canal and through the site. A site investigation should be carried as part of the FRA to define these drains as Ordinary Watercourses or surface water sewers and condition survey carried out. Once the actual level of risk is defined, master planning should be carried out to avoid placing any new development in areas at risk. Flood mitigation may focus on surface water management including SuDS or deculverting the drains through the site.


5.5.3 Alsager Community Review

Alsager Flood Risk Overview

Alsager is at risk from both fluvial and surface water flooding. The two main sources of fluvial flooding include Excalibur Brook and a tributary of the River Wheelock to the north east. The floodplains of both watercourses remain open and undeveloped, reducing the consequences of flooding. Due to sections of culvert, the two areas of greatest risk include the Twyford Factory, Excalibur Primary School and the residential roads between the school and the railway line.

The River Wheelock tributary has not been modelled by the Environment Agency and Flood Zones remain indicative. CEC have suggested the watercourse through the Twyford Factory


has been investigated during a site-specific FRA but these outputs were not available for this SFRA. There will be a residential risk associated with this reach as the watercourse is in culvert as it travels underneath the railway and factory site. The area is also at risk from Excalibur Brook. As the brook is in culvert there is also a residual risk associated with culvert blockage or collapse. Resulting flood water can place a number of residential properties and school at risk.

According to the Cheshire East SWMP, the area of Poplar Drive is a high surface water risk area due to surface water runoff and the presence of the culverted brook. The flat topography of this area makes significant flow through this area unlikely. However, significant ponding along the highway could occur during and after an extreme rainfall event. The SWMP has also identified a United Utilities DG5 scheme on the corner of Linley Grove. The SWMP assumes that this has solved the cluster of flooding problems indicated by the DG5 register of incidents in this area.

Alsager Development Strategy

Future growth in Alsager will be supported by new employment opportunities provided at Radway Green employment area, through the regeneration of about 10 hectares of mainly Brownfield land. This will be complemented by the development of around 1,100 new dwellings by 2030. This level of sustainable growth in the town broadly reflects the aspirations of the Development Strategy and the proximity of the town to the Potteries conurbation and the South Cheshire Green Belt.

Twyfords Strategic Site

This site has accommodated the headquarters of Twyford's Bathrooms since the 1950s including the company's administration, production and warehousing facilities covering an area of approximately 26 hectares. The redevelopment of the site has been identified to include industry, 450 new homes and open countryside.

The site itself lies within the south eastern part of Alsager with extensive road frontages onto both Crewe Road and Linley Lane. This is, in the main, brownfield land within the built-up area of the town although the curtilage does encompass part of a disused railway line and also greenfield land to the north east, which is within the Green Belt.

The Twyford site is located in the upstream catchment of a small Ordinary Watercourse, which is a tributary to Lawton Brook. The watercourse itself is in culvert for most of its length through the site, with only a short open reach before it meets Crewe Road. The watercourse has not been modelled by the Environment Agency and therefore no Flood Zone information is available.

A detailed site-specific FRA should be carried out to assess the actual level of risk associated with the Ordinary Watercourse. This could include the development of a fully hydrodynamic river model. The FRA should also assess the residential risk associated with the watercourse as it could be susceptible to blockage or collapse. A site investigation should be carried out to assess the condition of the culvert in order to inform this assessment.

Once the actual level of risk is defined, master planning should be carried out to avoid placing any new development in areas at risk. Placing further development over the culvert should be avoided as access maybe required in the future. Opportunities to deculvert the watercourse should be assessed as part of the site FRA.

Former Manchester Metropolitan University Campus Strategic Site

The Former Manchester Metropolitan University (MMU) Campus is located to the north west of Alsager covering an area of approximately 22 hectares. The campus has been occupied by MMU since 1992, but they have now made a formal decision to withdraw its facilities and operations from Alsager and relocate them at Crewe. The site has now been identified to provide around 400 new homes.

The site is bounded to the north and west by countryside and to the east by Hassall Road, beyond which is a school, leisure centre complex and associated recreational land set within a predominantly residential area. To the south, the site is bounded by Dunnocksfold Road, beyond which is an area of residential properties.


The overall level of flood risk on the site is low. According to OS mapping there are no drains or watercourses in the vicinity of the site and the national surface water mapping only indicates small pockets of surface water ponding. It is unlikely that a detailed FRA will be required. Focus should be given to the sustainable management of surface water on site including SuDS.

Radway Green Strategic Site

Radway Green is located to the south west of Alsager and to the north east of Junction 16 of the M6 motorway. This site is currently occupied by BAE Systems and has been identified as a redevelopment opportunity providing 10 hectares of employment land.

The site is adjacent to Valley Brook, with only the site north of the railway line at risk. Flood Zones are indicative and are currently based on a broad scale model developed by the Environment Agency. Land south of the railway line is at risk of surface water flooding with the railway line forming a barrier to overland flow. According to OS mapping, there is potentially an Ordinary Watercourse that flows into the area from the south east. This appears to be in culvert underneath the site reappearing at the north face of the railway line before discharging into Valley Brook.

A detailed site-specific FRA should be carried out to assess the actual level of risk associated with the Ordinary Watercourse. This could include the development of a fully hydrodynamic river model. The FRA should also assess the residential risk associated with the watercourse as it could be susceptible to blockage or collapse. A site investigation should be carried out to assess the condition of the culvert in order to inform this assessment.

Once the actual level of risk is defined, master planning should be carried out to avoid placing any new development in areas at risk. Placing further development over the culvert should be avoided as access maybe required in the future. Opportunities to deculvert the watercourse should be assessed as part of the site FRA.

Fanny’s Croft Alternative Strategic Site

Fanny’s Croft Alternative Strategic Site is located to the south of Alsager and has been identified for residential use, which includes the provision for 400 new homes.

The site is currently at risk from Valley Brook that runs along its western border. Flood Zones are however indicative and are currently based on a broad scale model developed by the Environment Agency.

The site is also at risk from Excalibur Brook, which has been hydraulically modelled using ISIS-TUFLOW software by the Environment Agency. The modelling shows flooding occurring upstream of Excalibur Primary School as water backs up at the culvert inlet. Water that spills over bank at the culvert inlet then flows overland through the school grounds and then through the Barley Croft housing estate. Although a number of properties fall within the modelled flood outlines, depths are below 100mm during the 1 in 100-year event. Flood depths surrounding the school and along Audley Road underneath the railway can reach up to 0.5m.

It is initially recommended that this site is not allocated until further detailed flood risk analysis has been carried out by CEC or by the developer.

As the site currently offers a flood storage function for both surface water and excess flows from Excalibur Brook, developing the site could significant impact on surrounding properties if any loss of flood storage is not compensated. Compensational storage may be difficult on site as this could require a large land take reducing the viability of developing the site. A joint venture looking at the suitability of providing storage upstream of the culvert at Excalibur Primary School may be more viable and help reduce risk to existing properties as well as the site.

The FRA should also assess the residential risk associated with Excalibur Brook as it could be susceptible to blockage or collapse. A site investigation should be carried out to assess the condition of the culvert in order to inform this assessment.


5.5.4 Congleton Community Review

Congleton Flood Risk Overview

Congleton is located in the east of the Weaver Gowy catchment on the upper reaches of the River Dane.

The main source of fluvial flood risk is from the River Dane, which runs through the northern half of the town. To the east, Dane-in-Shaw Brook runs westwards to join with the River Dane northeast of the town centre. Floodplains of both watercourses are relatively wide through the town placing a number of properties at risk. Both the Dane and Dane-in-Shaw Brook have Environment Agency registered man-made raised defences through the town centre. Although


providing a standard of protection, there will be a residual risk associated with less probably events such as defence breaching or overtopping. Howty Brook is also a potential source of flooding at its confluence with the Dane and in 1998 Howty Brook culvert blocked and flood flows caused flooding to over 50 properties14. Congleton also has a Flood Warning service covering over 100 properties.

The Environment Agency’s vision for the area is to undertake further appropriate actions that will reduce the high flood risk in Congleton. This will be focusing on making sure the most vulnerable properties are made flood resistant and resilient and encourage sustainable re-development when opportunities arise. The Environment Agency also expects further improvements to the existing flood defences and beneficial land management change would also help to achieve a safer environment.

The Cheshire East SWMP identified a number of high risk areas across Congleton, primarily located along critical surface water flow paths entering the town from the south.

There is also a potential hazard associated with canal flooding from the Macclesfield Canal, which is located high up on the eastern edge of the town. The Canal has a number of major raised embankments with culverts and roads running underneath, factors which increase risks of embankment failure.

Congleton Development Strategy

The Development Strategy sets out the need for high quality employment led growth to accommodate the expansion of existing businesses and attract new investment into Congleton. New housing is seen as important as part of a balanced and integrated portfolio of development to support the town centre and deliver the Congleton Link Road (between the A536 Macclesfield Road and the A534 Sandbach Road). The Congleton Link Road is a vital piece of infrastructure which will provide access to land for employment, commercial and residential development, reduce traffic congestion in the town and improve air quality along the A34.

Back Lane and Radnor Park Strategic Site

The Back Lane and Radnor Park site is a greenfield area located to the north of the west of Congleton, and stretches from Black Firs Lane and Chelford Road to the River Dane. The site has been identified to provide 1,000 new homes, with delivery expected to continue beyond the plan period (approximately 500 homes expected by 2030), 10 hectares of employment land and small scale retail development. The site will also contribute to the Congleton Link Road.

The site is situated on greenfield land and as such the current level of flood risk is low. Only the northern corner of the site is within the River Dane’s Flood Zone 2 and 3. The site does have the potential to contribute to surface water flooding to residential properties to the south, with a strong surface water flow path identified by the national surface water maps.

Flood risk is unlikely to pose a significant constraint to development in this area. Site-specific FRAs should focus on surface water flood risk exploring the potential impacts of development and appropriate surface water management techniques. Risk to future development could be avoided through careful master planning with the functional floodplain remaining undeveloped. The assessment should identify how surface water is to be managed on site and should include SuDS where possible to managing runoff and reduce the amount of surface water entering the combined network.

SuDS offer opportunities to control runoff to greenfield rates. Improvement could also be sought to reduce the risk of flooding to downstream properties. Records show that there is the potential for some areas of infill associated with former ponds, and there may be areas of localised contamination associated with a current farm on site, which could influence the viability of SuDS.

Congleton Business Park Extension Strategic Site

The Congleton Business Park Extension has an area of around 40 hectares and is located on the north western edge of Congleton within the valley of the River Dane. The site is currently situated on greenfield land. To the east the land rises sharply from the Dane Valley and as a

14 Environment Agency (2009) Weaver Gowy CFMP


result the risk of fluvial flooding is low. Only the south west corner of the site is within the River Dane’s Flood Zone 2.

To the north of the site there is a large pond that is fed by a number of field drains, one of which flows from the Giantswood Lane to Manchester Road Strategic Site. OS mapping indicates that the outfall of the pond is in culvert through the site before discharging into the Dane. Development in this area will have to consider this as a source of flooding. This area is also at risk of surface water flooding according to the national surface water map.

Flood risk is unlikely to pose a significant constraint to development in this area. Site-specific FRAs should focus on assessing the risk associated with the small field drain and surface water management. Risk to future development could be avoided through careful master planning. SuDS offer opportunities to control runoff to greenfield rates. Improvement could also be sought to reduce the risk of flooding to downstream properties.

Giantswood Lane to Manchester Road Strategic Site

This site is located to the north of Congleton, covering an area from Giantswood Lane to Manchester Road with surrounding land uses including open countryside, Cranberry Moss and a Sand Quarry. The site has been identified for housing including provision for 850 new homes and small scale retail development.

Whilst the site is currently situated in Flood Zone 1, there are a number of field drains and ponds on site that are a potential source of flood risk. There is, however, very little flood risk information available on these sources. The main drain, which runs through the centre of the site, hydraulically connects the three Strategic Sites in north Congleton and as a result each site must be considered together.

A detailed site-specific FRA must be prepared to assess risk from these sources. It is however recommended that risk could be avoided through careful master planning with green / blue infrastructure used along the path of the drain. Culverting the drain through the site should be avoided. SuDS also offer opportunities to control runoff to greenfield rates, whilst improvement could also be sought to reduce impacts downstream.

Records show that there is potential for some areas of infill associated with former ponds, and there may be areas of localised contamination associated with a current farm on site, which could influence the viability of SuDS.

Manchester Road to Macclesfield Strategic Site

This site is located to the north of Congleton, covering an area from Manchester Road to Macclesfield with surrounding land uses including open countryside, Cranberry Moss and a Sand Quarry. The site has been identified for housing including provision for 550 new homes and small scale retail development.

Whilst the site is currently situated in Flood Zone 1, there are a number of field drains and ponds on site that are a potential source of flood risk. There is, however, very little flood risk information available on these sources. The main drain, which runs through the centre of the site, hydraulically connects the three Strategic Sites in north Congleton and as a result each site must be considered together.

The site also lies near an area of high surface water risk identified through the SWMP. The Galloway Green Risk Area is a new-build estate on the edge of Lower Heath. The national modelling indicates the potential for widespread ponding throughout the estate, which could affect a significant number of properties. The drain discussed above is culverted through the estate with the SWMP identifying a potential residual risk of blockage or collapse.

A detailed site-specific FRA must be prepared to assess risk from these sources. It is however assumed that risk could be avoided through careful master planning with green / blue infrastructure used along the path of the drain. Culverting the drain through the site should be avoided. SuDS also offer opportunities to control runoff to greenfield rates, whilst improvement could also be sought to reduce impacts downstream.

Records show that there is potential for some areas of infill associated with former ponds, and there may be areas of localised contamination associated with a current farm on site, which could influence the viability of SuDS.


5.5.5 Knutsford Community Review

Knutsford Flood Risk Overview

Knutsford is at risk of fluvial and surface water flooding, but the overall level of risk is considered to be low.

The main source of fluvial risk is from Birkin Brook, which forms east of the town at the confluence of Pedley Brook and Marthall Brook. The lateral extent of fluvial Flood Zones are restricted by the narrow valley running northwards on the towns eastern edge. There are very few properties currently at risk.


The Cheshire East SWMP has identified a number of risk areas across Knutsford due to the number of properties located within the Environment Agency’s national surface water map. These areas have however been classified as low level risk areas due to the lack of historical evidence.

Knutsford Development Strategy

The aspiration of the Development Strategy is to maintain the special character of the town, whilst strengthening the range of housing and employment opportunities. To achieve this, the re-use of Brownfield sites and other land within the town will be encouraged, however in order to sustain the town into future decades some re-adjustment of the Green Belt will be required.

Parkgate Extension Strategic Site

The Parkgate Extension Strategic Site is located to the north and east of Parkgate Trading Estate. The site is predominantly greenfield and covers an area of around 20 hectares and is surrounded by Tatton Park, Parkgate Trading Estate, the railway line and a waste water treatment plant.

The site has been identified to provide 6 hectares of employment land with 11 hectares of land safeguarded for future development, including housing.

Birkin Brook flows along the eastern boundary of the site. The Environment Agency has not modelled the brook in detail and the Flood Zones are indicative based on broad scale modelling outputs. A detailed site-specific FRA should be prepared for the site. It is recommended that this should focus on defining the risk associated with Birkin Brook. It is unlikely that a fully hydrodynamic model of the brook is required as development within the functional floodplain should be avoided in the first instance through careful master planning. As the site is currently greenfield, the FRA should also include appropriate surface water management techniques to reduce the impact of development downstream.

North West Knutsford Strategic Site

This site is located to the north west of Knutsford and covers an area of around 45 hectares. It is currently a greenfield site that includes agricultural land and is surrounded by residential properties, open countryside, the Land Rover Car Sales Showroom, the Brookdale Centre and Tatton Park.

The site has been identified to provide 350 new homes, 5 hectares of employment land with 15 hectares of land safeguarded for future development.

The site is currently within Flood Zone 1 and according to the flood data collected through this SFRA there are no other sources of flooding on site. Flood risk is unlikely to pose a significant constraint to development in this area. A site-specific FRA should focus on the management of surface water exploring the potential impacts of development and appropriate SuDS.


5.5.6 Middlewich Community Review

Middlewich Flood Risk Overview

Middlewich is situated between the Rivers Wheelock, Dane and Croco but are considered to be at a lower risk of fluvial flooding, when compared with urban areas elsewhere in the catchment. With a relatively narrow floodplain the rivers pose limited risk to current properties.

Upstream of the railway line, the risk of fluvial flooding is low as floodplains remain open and undeveloped reducing the consequences of flooding. Downstream of the railway line the River Croco is culverted and reappears next to the Trent and Mersey Canal.


At present the risk of flooding has been managed by the Environment Agency by undertaking channel and river asset maintenance. The Environment Agency expects that flood management will continue in the area but may focus on alternative ways of managing risks, such as land management change and flood warning. Appropriate planning is also necessary so that future development does not bring about any additional flood risk issues.

There is a significant risk of surface water flooding along Warmingham Lane, located in the southern part of Middlewich, alongside the Trent & Mersey Canal and the A533. The Environment Agency’s national surface water maps indicate the potential for extensive ponding along the A533 affecting these properties. This is supported by an extensive history of flooding from sewers.

A site assessment undertaken in the SWMP indicates that this area is very flat and it is unlikely that flooding of the extent shown by the national mapping would occur. However, a number of the properties are set below road level and are at risk from localised ponding and runoff from the highway. Several properties have minor flood resilience measures fitted, which suggests that local flooding may be common. A number of local drains and gullies around these properties were also found to be blocked with debris, which is likely to increase the vulnerability of these properties to local flooding.

Further south there is another area of surface water flooding with a number of properties currently on the DG5 register at the junction of Cross Lane and Warmingham Lane. CEC have suggested that United Utilities built a large storage tank 2 – 3 years ago to mitigate the problem and renewed a number of surface water sewers in the area. CEC consider the issue to have been resolved in this area.

Middlewich Development Strategy

The Development Strategy identfiies a level of development that seeks to enable the growth of the town, ensure the delivery of improvements to the town centre and achieve the provision of a wider range of community facilities in the town.

Additional employment land is proposed at Midpoint 18 to generate jobs around the M6 Motorway corridor including the potential development of a Cheshire Enterprise Hub. Provision of housing will occur on Brooks Lane and Glebe Farm. Through these developments, contributions will be sought towards the completion of the Middlewich Eastern Bypass. The Development Strategy also identifies further land that would be suitable for residential development to the north east of the town.

The majority of this land lies, however, in Cheshire West and Chester Borough and cannot therefore be included in the Cheshire East Local Plan. Cheshire West and Chester will be requested to include this land as a development allocation in its Local Plan.

Brooks Lane Strategic Site

The Brook Lane site comprises around 23 hectares of land currently occupied by employment premises and unused/under used areas around 0.5 kilometres to the south of Middlewich town centre. The overall site is bounded by the Trent and Mersey Canal to the west, a residential area to the north, the Sandbach to Northwich railway line to the east and the British Salt settling lagoons to the south.

The site has been identified to provide around 200-400 dwellings, possible marina and small scale retail development.

The northern quarter of the site is currently at risk from Sanderson’s Brook and the River Croco. The confluence of Sanderson’s Brook with the River Croco is in culvert. CEC have suggested that the culvert suffers from siltation, increasing the risk of flooding.

There is a potential interaction with the River Croco and the Trent and Mersey Canal where they run from Brooks Lane, under Kinderton Street, to Finneys Lane. The left bank of the Croco is joined to the right bank of the Canal and the Environment Agency’s hydraulic river model shows a significant volume of flow is exchanged between the two along this reach during times of flood. The maximum flood levels are, however, contained between the left bank of the Canal and the right bank of the Croco.


A detailed site-specific FRA should be prepared for this site focusing on the risk of fluvial flooding from the two main rivers and from surface water flooding. A survey of the culvert must be carried out to confirm its capacity and condition. Development over the culvert should be avoided and if possible opportunities to open up both watercourses should be investigated. However, this may not be possible as access is required at Brook Lane to access the southern area of the site.

Access and egress might be an issue on the site due to the railway line and canal limiting the number of routes to and from the site. As a result, emergency planning must be considered in the FRA. Remediation could also have a significant impact on how flood risk is managed and both should be considered together.

Glebe Farm Strategic Site

Glebe Farm is a greenfield site to the south of Middlewich, which covers an area of around 17 hectares. It has been identified to provide around 500 new homes by 2030.

The site is situated on greenfield land within Flood Zone 1 and as such the current level of flood risk is low and is unlikely to pose a significant constraint to development in this area. The site does however have the potential to contribute to surface water flooding to residential properties to the north, with a strong surface water flow path identified by the national surface water map and SWMP, running from a pond and small field drain.

A site-specific FRA should focus on surface water flood risk exploring the potential impacts of development and appropriate surface water management techniques. There is a separate foul and surface water sewer network serving residential properties to the north, which new development could connect to, but SuDS should be investigated as they offer opportunities to control runoff to greenfield rates, whilst improvement could also be sought to reduce impacts downstream during exceedance events.

Mid Point 18 Extension Strategic Site

This site is located to the east of Middlewich and two miles west of Junction 18 of the M6, at the edge of Middlewich. It is primarily a greenfield site but has been identified to provide a phased delivery of up to 70 hectares of employment land.

The site is situated in between Sanderson’s Brook to the south and the River Croco to the north. A small tributary to the River Croco also flows through the middle of the site. The Environment Agency has modelled all three watercourses in detail and they have well defined Flood Zones.

It is unlikely that flood risk will pose a significant constraint to development in this area. Development within the fluvial Flood Zones should be avoided as they currently provide a flood storage function during extreme events and loss of storage will have an impact downstream especially if more flow reaches the culverts underneath the Sandbach to Northwich railway line downstream. As the site is currently greenfield, development also has the potential to increase surface water runoff rates and flow entering the watercourses. This could also increase risk downstream.

A detailed site-specific FRA should be prepared to help inform the site master plan and outline appropriate surface water management techniques. The River Croco tributary hydraulic model may need extending upstream as it currently does not cover the entire site. SuDS should be investigated as they offer opportunities to control runoff to greenfield rates, whilst improvement could also be sought to reduce flow entering the watercourses and consequently reduce risk downstream.


5.5.7 Nantwich Community Review

Nantwich Flood Risk Overview

Nantwich is located in the upper reaches of the River Weaver. The floodplain is relatively small and exposure to flooding is infrequent. According to the CFMP, flood water in this area can be deep, presenting a real hazard in places to people. However, there are very few current properties at risk as the functional floodplain remains open and undeveloped through the town. Those properties that lie along the edge of the floodplain are at risk during the extreme 1 in 1,000-year flood event.


The Environment Agency expect that further flood risk management work in the future to contain what would otherwise be increasing risk due to climate change. This will be focused on the key ‘flood hotspots’ and making them more resistant to flooding. Flood Warning is not viable because of short lead times. Current flood risk management is focussed on river asset and channel maintenance activities.

There is a risk of fluvial flooding from an ordinary watercourse that runs through the town, which the Environment Agency’s national surface water maps identifies a large number of residential properties at risk. The Cheshire East SWMP also flags this area, but due to the lack of historical flooding evidence it has been classified as a low level risk area. A site assessment undertaken during the SMWP indicates that this area is very flat and that there is unlikely to be a significant upstream catchment for this ponding area. As a result, flooding is likely to be limited and will predominantly affect the highway. No evidence of the watercourse was found on the ground in the risk area but it was found to emerge into open channel downstream of the site. It is considered likely that it is semi-integrated into the local surface water drainage network.

There is a potential hazard associated with canal flooding from the Shropshire Union Canal, which is located high up on the western edge of the town. There are also a number of major raised embankments with culverts and roads running underneath the canal, which increases residual risks of embankment failure.

Nantwich Development Strategy

The Development Strategy recognises that growth is necessary to provide new infrastructure, new employment opportunities and to meet current and future housing needs, including high quality small homes and bungalows. To ensure that the town can grow in the future, land at North West Nantwich is identified as a mixed use site to provide employment land and about 1,000 houses. This site is sustainably located in close proximity to the town centre and provides opportunities to extend the Riverside Park.

In addition, the former Stapeley Water Gardens site is identified to provide 2 hectares of employment land and 250 dwellings and the Snowhill area is identified for regeneration, to include retail, offices, leisure and about 50 dwellings. The identification of both of these sites reflects the support received during the consultation for the development of Brownfield sites and the mixed use development of the former Stapeley Water Gardens site.

Kingsley Fields Strategic Site

Kingsley Fields is located to the north west of Nantwich. The site is bounded by the A51 to the north, the River Weaver to the east, playing fields and Nantwich Football Club stadium to the south and Welshman's Lane to the west. The site is predominantly greenfield and covers an area of around 70 hectares.

The site has been identified to provide around 1,000 new homes by 2030 including a new mixed-use local centre and 2-3 hectares of employment land.

The eastern edge of the site is directly at risk from the River Weaver. The main river has been modelled in detail by the Environment Agency and the resulting Flood Zones are well defined with little obvious difference between the 1 in 100-year and 1 in 1,000-year flood extents. Properties on the right hand bank are protected by higher bank and ground levels, with flood water being stored / a conveyed on the left hand floodplain.

It is unlikely that fluvial flood risk will pose a significant constraint to development in this area as fluvial Flood Zones could easily be avoided by placing all development away from the main river. Loss of functional floodplain on the left hand bank could increase risk downstream or to current properties on the opposite bank if there is little freeboard between peak flood depths and ground levels. Compensational storage will be required to offset any loss of floodplain storage due to development.

There are also two small ordinary watercourses that enter the site adjacent to Holly Farm to the north and Nantwich Football Club stadium to the south. There is very little flood risk information associated with these watercourses and as such they must be assessed as part of a detailed FRA. Culverting either watercourse is not recommended as they should be left open or improved to form part of a wider SuDS scheme.


Snow Hill Strategic Site

The Snow Hill site is predominantly brownfield located within the existing urban area. The site covers an area of about 8 hectares and acts as a key gateway into the town centre occupying a prominent position on the banks of the River Weaver and Nantwich Riverside. The site has been identified as a comprehensive mixed used regeneration opportunity.

The River Weaver poses the greatest risk of flooding to the site. The main river has been modelled in detail by the Environment Agency and the resulting Flood Zones are well defined. Flood Zones are however restricted to the left hand bank. Flood risk should be avoided by placing all regeneration and / or new development on the right hand bank, east of the A530. Development of the left hand bank will require fluvial mitigation in the form of raised ground levels, flood walls or flood resilience depending on the proposed land use and standard of protection required. Compensational storage will be required for any loss of floodplain on the left hand bank. The southern section of the site located on open land south of the A534 should remain as functional floodplain.

The site is also potentially at risk from surface water flooding entering the area from the west down the A534. There is also a residual risk associated with the Shropshire Union Canal as illustrated in Figure 4-7. Any fluvial mitigation measures assessed during a site-specific FRA must consider how they affect flood mechanisms associated with other sources or could be impacted upon by other sources.

Stapeley Water Gardens Strategic Site

The Stapeley Water Gardens site is located approximately 1.5km south east of Nantwich town centre and is bounded to the east by London Road (A51) and to the north by Peter Destapleigh Way (A5301). The site was previously utilised solely for the operation of Stapeley Water Gardens but ceased use in 2011 with only the Angling Centre remaining open. It has now been identified to provide around 250 new homes and 2 hectares of employment land, to include a new garden centre, to replace Stapeley Water Gardens.

According to the flood risk data collected in the SFRA, the level of risk to the site is low and should not pose a significant constraint to development. The site is situated in Flood Zone 1 with no major watercourses nearby. There is a small drain flowing westerly from the site towards the junction of the A529 and A530 and there is potentially at risk of surface water pooling along its length. According to United Utilities, it appears as if the drains discharge into the surface water sewer network.

A site-specific FRA should be prepared for the site focusing on surface water management. A site investigation should be carried out to confirm location and ownership of the surface water drain and collect capacity and condition information.


5.5.8 Sandbach Community Review

Sandbach Flood Risk Overview

Sandbach is primarily at risk from the River Wheelock and three of its tributaries, Arclid Brook, Malkins Lawton Brook and Hassall Brook. Arclid Brook poses the greatest risk as it flows through the town from its source in the north-east at Arclid Green Quarry towards its confluence with the River Wheelock. Malkins Lawton Brook and Hassall Brook also join the Wheelock at the same location. The lateral extent of fluvial flood zones are restricted by the narrow valley and with the functional floodplain of both the River Wheelock and Arclid Brook remaining open and undeveloped through the town, there are very few properties at risk.


The Trent and Mersey Canal runs along the southern edge of Sandbach and provides a significant barrier for fluvial flood flows. The Environment Agency’s hydraulic river model includes two structures under the Canal representing the culvert on the Wheelock and an orifice on Arclid Brook. These structures are extremely constricted and during the extreme flood events such as the 1 in 100-year event and the 1 in 1,000-year event water backs up behind these. The current model shows flood water flowing over the Canal contributing to the flood water downstream. It is however more likely that the water will first spill into the canal and flow downstream filling the canal down to the next lock and overtopping where canal bank levels are low. Due to the lack of data, this flood mechanism has not been included in the model, but it has been suggested that the Environment Agency should investigate the impact of overtopping into the canal.

There is also a potential risk from Small Brook to the north of Sandbach, which flows westerly towards Sanderson’s Brook and the River Croco. This watercourse has not been modelled by the Environment Agency and current Flood Zones are indicative based on broad scale modelling outputs. There is also a potential interaction with the Trent and Mersey Canal and the railway line, which form key obstructions to flood flow.

The Cheshire East SWMP has not identified any areas at high risk of surface water flooding within Sandbach.

Sandbach Development Strategy

The Development Strategy recognises the need for additional employment development in Sandbach including a new business park adjacent to Junction 17 of the M6. The Development Strategy identifies this area as a mixed use site, to include 20 hectares of employment land, a local centre, open space and about 700 new homes. The development of this site also reflects a key part of the overall Development Strategy which is to ensure that a range of new jobs are provided within the M6 corridor. The development of this site will also provide improvements to Junction 17 of the M6.

A further site is proposed at the former Albion Chemical Works, where the Council has previously resolved to grant planning permission for a mixed development including 375 dwellings and employment land.

Land adjacent to Junction 17 of M6, South East Congleton Road Strategic Site

The site is greenfield and is currently in agricultural use surrounded by agricultural land, residential properties and the M6 motorway. The site has been identified to deliver around 700 new homes and 20 hectares of employment land. Development of the site would be dependent on the prior delivery of improvements to Junction 17 of the M6 and demonstration to the Highways Agency and the Council that the impact of development traffic continues to allow the efficient and safe operation of the junction.

Arclid Book runs through the centre of the site splitting the area between north and south. The main river has been modelled in detail by the Environment Agency and the resulting Flood Zones are well defined due to local topography. Flood Zone 3 is limited to land directly adjacent to the river and includes a number of ponds. The extent of Flood Zone 2 increases closer to the A534, which forms a barrier to flood flow.

A site-specific FRA should be prepared for the site. However, it is unlikely that flood risk will pose a significant constraint to development in this area as fluvial Flood Zones could easily be avoided by placing all development on higher ground away from the main river. The functional floodplain should remain as is and form part of the wider blue / green infrastructure. Loss of functional floodplain could increase risk downstream and compensational storage will be required to offset any loss of storage. Condition and capacity of culverts underneath the A534 should be assessed.

As the site is currently greenfield, development has the potential to increase surface water runoff rates and flow entering Arclid Book. SuDS should be implemented to control runoff the greenfield rates or a reduction sought to reduce risk downstream.

Records show that there is potential for some areas of infill associated with former ponds, and there may be areas of localised contamination associated with a current farm on site. In


addition, there is a former waste tip on the south west of this area, which may pose a constraint to development and viable SuDS.

Former Albion Chemicals Strategic Site

The Albion Chemicals site covers an area of approximately 19 hectares and is situated 3.6km north west of Sandbach town centre, and 4.5km south east of Middlewich. The site comprises two distinct areas, an intensively developed chemical manufacturing facility (11.2 hectares), and a former sports ground affiliated to the chemicals factory (7.8 hectares). The former factory site has recently been cleared and now comprises a hardcore surface.

The site has been identified to provide up to 375 new homes by 2030, employment land and small scale retail development. The site currently has outline planning permission subject to a Section 106 agreement.

The site is at risk from a number of flood sources; however the level of detailed risk information available is poor. The site is located between the Trent and Mersey Canal to the west and Sandbach to Middlewich railway line to the east. Small Brook flows along the eastern side of the railway line. However, according to the Environment Agency’s current Flood Map, the northern corner of the site is within Flood Zones 2 and 3. These Flood Zones are indicative and based on broad scale modelling outputs.

In reality, the railway line is likely to form a defacto flood defence forming a barrier to flood water entering the site from Small Brook. There is a small drain that flows underneath the Canal and into the site from the west before flowing underneath the railway line and into Small Brook. The drain could pose a direct risk to the site. It also provides a flow route for flood water to enter the site from Small Brook.

A site-specific FRA should be prepared for the site. A detailed hydraulic model of Small Brook and its tributary must be developed in order to define the true nature of risk. As the A533 is the only route into the site, the FRA must consider Emergency Planning if a residual risk remains.


5.5.9 Wilmslow Community Review

Wilmslow Flood Risk Overview

There are four main rivers running through Wilmslow, the River Dean, River Bollin, Handforth Brook and Whitehall Brook.

The River Bollin is the largest watercourse in the area, however, this mainly occupies a strip of green space through the town and the risk to property is at present limited to a small area near the town centre.

There is a risk of surface water flooding identified by the Environment Agency’s national surface water maps, which indicate the potential for extensive ponding surrounding Wilmslow Business


Park, residential properties off Gravel Lane and the area of Handforth. These surface water flow paths help identify a number of culverted Ordinary Watercourses that run through the area. No flood risk information is available on these watercourses.

Wilmslow Development Strategy

The Development Strategy proposes to deliver in the order of 400 new homes by 2030 with an appropriate level of employment land to encourage new and retain existing employers.

Adlington Road Strategic Site

This site is located to the east of Wilmslow to the north of Adlington Road. The site is a mix of greenfield and existing residential properties and has been identified as a residential development area proving 225 new homes.

According to the flood risk data collected in the SFRA, the level of risk to the site is low and should not pose a significant constraint to development. The site is situated in Flood Zone 1 with no major watercourses nearby. There is a risk of surface water flooding in the area identified by the Environment Agency’s national surface water maps, which indicate the potential for extensive ponding around Brick Yard Farm.

A site-specific FRA should be prepared for the site focusing on surface water management. As the site is currently greenfield, development has the potential to increase surface water runoff rates. SuDS should be implemented to control runoff the greenfield rates or a reduction sought to reduce risk downstream.

Land at Royal London Strategic Site

Land at Royal London is a greenfield site, with a currently developable area of around 12.5 hectares to the east of Royal London's office campus. The site is bounded to the east by the West Coast mainline and the A34 bypass.

The site has been identified as a mixed use employment and housing site with the provision of provide 75 new homes and around 2 hectares of employment land. Approximately 4 hectares of land to the west of Royal London across Alderley Road is safeguarded for future development.

The site is at risk of fluvial flooding from Mobberley Brook, which runs along the south western corner of the site. According the OS mapping, part of the brook is diverted along the southern edge of the A34 before flowing underneath the bypass and into the site. Both paths of the brook converge within the site before flowing underneath the B5359 (Alderley Road). Although a main river, the brook has not been modelled in detail by the Environment Agency and current Flood Zones are indicative based on broad scale modelling outputs.

This site is also at risk of flooding from a small field drain to the north. The drain originates on land off Prestbury Road, flowing west underneath the A34 and the West Coast mainline before entering the site near Harefield Farm. Part of the drain is in culvert before it discharges into a series of ponds in front of the Royal London House. If and where these ponds discharge to cannot be identified from OS mapping or United Utilities sewer network.

A detailed site-specific FRA should be prepared for this site. This is likely to require the development of a new fully hydrodynamic model of Mobberley Brook. Prior to developing a model, a site investigation should be carried to assess likely flood mechanisms and capacity and condition of culverts underneath the West Coast mainline and the A34 bypass. The site investigation must also be used to identify the route of the drain to the north and discharge points.

Land North of Beech Road, Alderley Edge

Land north of Beech Road in Alderley Edge has been identified as a possible additional site proposed by developer and land interests. The site is over 10ha in size and has the potential to provide 200 to 250 new homes. Currently the land is grassed and is surrounded by residential to the south and open countryside to the north and east. The railway forms the western boundary of the site.

The site is directly at risk from Whitehall Brook, which runs north directly through the centre of site before flowing underneath the railway line. 45% of the site is within Flood Zone 3. Most of


this area has been designated as functional floodplain as part the SFRA and it is recommended that this site is avoided as any loss of floodplain could have a significant negative impact on surrounding properties.

However, if development is sough, it is recommended that a site-specific FRA is carried out. This will require the development of a hydraulic river model to better define the level of risk, as the current flood zones are based on broad scale modelling outputs. Regardless of the outcome of the modelling, compensational flood storage will be required to offset any impacts of development.

The site is also at risk from surface water flooding which pools on the low lying floodplain. The railway line and A34 form critical obstructions to overland flow. There are also a number of field drains on site which convey water towards the brook.

5.5.10 New Settlement Community Review

New Settlement Development Strategy

Three new settlements are proposed at Stowford (near Crewe Hall), Barthomley and Handforth East, which together could accommodate in the region of 120 hectares of new employment land and 3,800 new homes with new transport infrastructure, community facilities, open space and new local centres.

Handforth East Sustainable Community

The Handforth East Settlement is a Greenfield site, located to the east of Handforth and to the south of the A555 and a short distance south of Cheadle Hulme and Bramhall. The area has been identified to provide a new sustainable community delivering around 2,300 new homes, a mixed-use local centre and 5 hectares of employment land.

The area is located along Handforth Brook, a tributary to the River Dean. The Environment Agency has developed a detailed hydraulic model of the main river, but it does not extend upstream of the A34 into the site.

The Environment Agency’s national surface water maps indicate the potential for extensive ponding surrounding the north western corner of the site. Due to the local topography this area is also likely to be at risk of fluvial flooding from Handforth Brook.

A site-specific FRA should be prepared for the site. The FRA must extend the Handforth Brook model upstream of the A555, in order to assess fluvial risks. However, it is unlikely that flood risk will pose a significant constraint to development in this area as fluvial risk could easily be avoided by placing all development on higher ground away from the main river.

The area between the A555, A34 and Handforth Brook should remain as functional floodplain. As the site is currently greenfield, development has the potential to increase surface water runoff rates and flow entering the Book. SuDS should be implemented to control runoff the greenfield rates or a reduction sought to reduce risk downstream.

Records show that there is potential for some areas of infill associated with former ponds, and there may be areas of localised contamination associated with a current farm on site. In addition, there is a former waste tip on the south west of this area, which may pose a constraint to development and viable SuDS.

Stowford Village A

The Stowford Village A is located to the south east of Crewe adjacent to the Basford East site and Crewe Hall. The site has been identified as a possible new sustainable settlement delivering 1,000 new homes and a mixed-use local centre.

The site is located in the River Weaver catchment. Englesea Brook, a tributary to Valley Brook and the Weaver lies to the east and a small field drain to the north.

The Stoke-on-Trent / Nottingham rail line runs through the centre of site, splitting the area in two. The northern area will drain towards the small field drain, which then flows towards the Basford East site, joining Basford Brook and into Valley Brook before reaching the Weaver. It is difficult


to ascertain how the southern area will drain unless there are connections underneath the railway line.

It is unlikely that flood risk will pose a significant constraint to development in this area as it is within Flood Zone 1. As the site is currently greenfield, development has the potential to increase surface water runoff rates and flow entering Arclid Book. SuDS should be implemented to control runoff at greenfield rates or a reduction sought to reduce risk downstream. A site investigation should be carried out as part of a site specific FRA to establish drainage routes.

Barthomley Village B

Village B is currently an Area of Search to the east of Crewe and west of the M6 motorway. The site has been identified as a possible new sustainable settlement delivering 1,000 new homes and a mixed-use local centre.

The Area of Search for the settlement covers a considerable area and includes Barthomley Brook a tributary to Englesea Brook and Valley Brook to the north. Currently the entire area is undeveloped and risk is low. The main rivers have not been modelled by the Environment Agency and Flood Zones are indicated based on broad scale modelling outputs. Flood Zones are however narrow and are well defined and could be avoided through careful master planning.

The Stoke-on-Trent / Nottingham rail line runs through the north of the site and will form a barrier to flood flows along Valley Brook.

Whilst located in Flood Zone 1, development in the area has the potential to increase surface water runoff rates and flow entering local watercourses. SuDS should be implemented to control runoff at greenfield rates or a reduction sought to reduce risk downstream.

Employment Areas 1, 2 and 3

Employment Areas 1, 2 and 3 are located along the M6 and lie within the Valley Brook catchment. Currently the entire area is undeveloped and risk is low.

The main rivers have not been modelled by the Environment Agency and Flood Zones are indicated based on broad scale modelling outputs. Flood Zones are, however, narrow and are well defined and could be avoided through careful master planning.

Whilst located in Flood Zone 1, development in the area has the potential to increase surface water runoff rates and flow entering local watercourses. SuDS should be implemented to control runoff at greenfield rates or a reduction sought to reduce risk downstream.


5.6 Development Management Sequential & Exception Test This section of the SFRA has been developed to provide a useful tool to inform the development management process about the potential risk of flooding associated with future planning applications and the basis for requiring specific FRAs where necessary.

According to the NPPF

“When determining planning applications, local planning authorities should ensure flood risk is not increased elsewhere and only consider development appropriate in areas at risk of flooding where, informed by a site-specific flood risk assessment following the Sequential Test, and if required the Exception Test, it can be demonstrated that:

Within the site, the most vulnerable development is located in areas of lowest flood risk unless there are overriding reasons to prefer a different location; and

Development is appropriately flood resilient and resistant, including safe access and escape routes where required, and that any residual risk can be safely managed, including by emergency planning; and it gives priority to the use of sustainable drainage systems.” (Para 103)

The NPPF re-affirms that planning applications “must be determined in accordance with the development plan unless material considerations indicate otherwise” (Para 11). Development proposals that are in line with Local Plan policies should be approved. Those that conflict should be refused unless material considerations indicate otherwise.

5.6.1 Demonstrating the Sequential Test for Planning Applications

The Environment Agency recommends the approach15 below is used by LPAs to apply the Sequential Test to planning applications located in Flood Zones 2 or 3. The approach provides an open demonstration of the Sequential Test being applied in line with the NPPF and the flood risk Practice Guide. Close working between LPA Development Management and Spatial Planning departments will be required to implement the Sequential Test effectively.

The Sequential Test for planning applications can be carried out over three main stages described below and illustrated in Figure 5-3.

Stage 1 – Strategic application & development vulnerability

The Sequential Test does not apply to change of use applications unless it is for change of use of land to a caravan, camping or chalet site, or to a mobile home site or park home site. The Sequential Test can also be considered adequately demonstrated if both of the following criteria are met:

The Sequential Test has already been carried out for the site (for the same development type) at the strategic level (Local Plan); and

The development vulnerability is appropriate to the Flood Zone (see table 3 of technical guidance to the NPPF).

If both these criteria are met, reference should be provided for the site allocation and Local Plan document in question and the vulnerability of the development should be clearly stated. If neither criteria is met, then the applicant should move onto Stage 2.

Stage 2 – Defining the evidence base

Stage 2 considers the parameters in which the Sequential Test is to be applied, including:

The geographic area in which the test is to be applied, The source of reasonable available sites in which the application site will be tested

against; and The evidence and method used to compare flood risk between sites.

15 http://www.environment-agency.gov.uk/research/planning/82587.aspx


Stage 3 – Applying the Sequential Test

Stage 3 focuses on applying the Sequential Test by comparing the reasonably available sites identified under stage 2 with the application site.

Sites should be compared in relation to flood risk; Local Plan status; capacity; and constraints to delivery including availability, policy restrictions, physical problems or limitations, potential impacts of the development, and future environmental conditions that would be experienced by the inhabitants of the development.

The Test should concluded if there are any reasonably available sites in areas with a lower probability of flooding, which would be appropriate to the type of development or land use proposed.

From the information provided in these three stages, the LPA should be able to assess whether or not the applicant site has passed the Sequential Test. If the Test has been passed the applicant should apply the Exception Test in the circumstances set out by tables 1 and 3 of the technical guidance to the NPPF.

In all circumstances, where the site is within areas at risk of flooding and where one has not already been carried out, a site-specific FRA should be completed in line with the NPPF. Further guidance is provided in Section 5.7.

In addition to the formal Sequential Test, the NPPF sets out the requirement for developers to apply the sequential approach to locating development within the site. As part of their application and master planning discussions with applicants, LPAs should seek whether or not:

Flood risk can be avoided by substituting less vulnerable uses or by amending the site lay-out;

Less vulnerable uses for the site have been considered; or Density can be varied to reduce the number or vulnerability of units located in higher risk

parts of the site.


Figure 5-3: Development Management Sequential Test Process

5.7 Site-Specific Flood Risk Assessment According to the NPPF Technical Guide, a site-specific FRA should:

“Identify and assess the risks of all forms of flooding to and from the development and demonstrate how these flood risks will be managed so that the development remains safe throughout its lifetime, taking climate change into account. Those proposing developments should take advice from the emergency services when producing an evacuation plan for the development as part of the flood risk assessment.” (Para 9)

In line with the current government NPPF guidance, development proposals should:

Show development is not at risk of flooding or is compatible with the residual risk; Not increase flood risk elsewhere, taking into account the impacts of climate change; Not increase surface water peak flow rates or runoff volumes above greenfield levels

including an allowance for climate change , as this would result in an increased flood risk to the receiving catchments;

Not increase the risk of groundwater flooding elsewhere or change the hydrogeological regime of the area;


Wherever possible use the opportunities offered by new development to reduce flood risk within the site and elsewhere; and

Ensure that where new development is, exceptionally, necessary in areas of flood risk, it is made safe from flooding for the lifetime of the development, taking into account the impacts of climate change.

The NPPF Technical Guide doesn’t contain any further detail on the minimum requirements for FRAs. It is therefore important that Chapter 3 of the PPS25 Practice Guide and the Environment Agency’s Flood Risk Standing Advice is still referred to. CIRIA’s report C624 Development and Flood Risk also provide useful guidance.

When is a FRA Required?

A site-specific FRA should be prepared when the application site is:

Situated in Flood Zone 2 and 3 Greater than 1ha in size and located in Flood Zone 1 Greater than 0.5ha in size and located a Critical Drainage Area (CDA) At risk of flooding from other sources of flooding as identified in this SFRA Situated in an area currently benefitting from defences Situated within 20m of the bank top of a Main River Situated over a culverted watercourse or where development will require controlling the

flow or any river or stream or the development could potentially change structures known to influence flood flow

5.7.1 Taking Climate Change into Account

Climate change will increase flood risks over the lifetime of a development. In making an assessment of the impacts of climate change on flooding from the land and rivers as part of a FRA, the sensitivity ranges shown below may provide an appropriate precautionary response to the uncertainty about climate change impacts on rainfall intensities and river flow.

Considering the impacts of climate change during a FRA will have implications for both the type of development that is appropriate according to its vulnerability to flooding and design standards for any SuDS or mitigation scheme proposed.

For example very flat floodplains, using the 20 per cent from 2025 to 2115 allowance for peak flows, could see an area currently within lower risk zones (Flood Zone 2), in future be re-classified as lying within a higher risk zone (e.g. Zone 3a). Therefore residential development may not be appropriate without appropriate flood mitigation measures or flood resilient or resistant houses. In well-defined floodplains the same climate change allowance could have significant impacts on flood depths influencing building type and design (e.g. finished floor levels) Table 5-3: Recommended National Precautionary Sensitivity Ranges

Parameter 1990 to 2025 2025 to 2055 2055 to 2085 2085 to 2115 Peak rainfall intensity +5% +10% +20% +30% Peak river flow +10% +20%

The sensitivity ranges shown in Table 5-3 and in the NPPF Technical Guidance, originate from Defra’s FCDPAG3 Economic Appraisal Supplementary Note to Operating Authorities – Climate Change Impacts (October 2006) and are based on UK Climate Projections 2002 (UKCIP02) scenarios.

The Environment Agency has updated this advice note, with the Adapting to Climate Change: Advice for Flood and Coastal Erosion Risk Management Authorities16, which uses the latest science from UKCP09. This advice is based on Government’s policy for climate change adaptation, and is specifically intended for projects or strategies seeking Government Flood Defence Grant in Aid (FDGiA). However, RMAs in England, such as CEC, may also find it useful in developing plans and making FCERM investment decisions even if there is no intention of

16 Environment Agency Adapting to Climate Change: Advice for Flood and Coastal Erosion Risk Management Authorities


applying for central Government funding. This is important for any future large scale infrastructure used to support the delivery of Strategic Sites such as flood defence schemes.

This is necessary to ensure that a fair comparison can be made between investment in sites in different locations that compete for central Government grants, as well as ensuring that the most appropriate means of reducing risk is investigated in any one place.

The note offers a range of climate change sensitivities called change factors which are different depending on the region of England and are based on UKCP09 information. Upper and lower end estimates of change are also provided to help represent the range of the future risks.

Although, it is anticipated that the eventual change in river flows will lie somewhere within the range of lower to upper end estimates, more extreme change cannot be discounted. To help represent this extreme change “H++ scenarios” have been included in line with the UKCP09 approach. These can be used to represent more severe climate change impacts and help identify the options that would be required. The “H++ scenarios” should be considered in sensitive areas or for contingency planning to understand what might be required if climate change were to happen much more rapidly than expected. The UKCP09 change factors are presented below for North West England. Table 5-4: UKCP09 Change Factors

Parameter Estimates 2020s 2050s 2080s Peak rainfall intensity H++ No H++ scenario is provided for changes to

extreme rainfall Upper end estimate +10% +20% +40% Change factor +5% +10% +20% Lower end estimate +0% +5% +10%

Peak river flow H++ +40% +60% +105% Upper end estimate +25% +35% +65% Change factor +15% +20% +30% Lower end estimate +5% +10% +10%

In order to help Local Authorities better understand current best estimates of climate change and associated uncertainty ranges across the River Basin (North West), the Environment Agency has carefully selected UKCP09 outputs and displayed them spatially on a map. This map can be found at: http://www.environment-agency.gov.uk/research/planning/135749.aspx

5.8 Sustainable Drainage Systems Development has the potential to cause an increase in impermeable area, an associated increase in surface water runoff rates and volumes, and a consequent potential increase in downstream flood risk due to overloading of sewers, watercourses, culverts and other drainage infrastructure.

Managing surface water discharges from new development is therefore crucial in managing and reducing flood risk to new and existing development downstream. Carefully planned development can also play a role in reducing the amount of properties that are directly at risk from surface water flooding.

The FWMA 2010 requires new developments and redevelopments in England and Wales to have drainage plans for surface runoff approved by the Sustainable Drainage Systems Approval Body17 (SAB) where the construction work would have drainage implications. The SAB is responsible for adopting and maintaining new SuDS that serve more than one property and have been constructed as approved and function as designed.

17 SAB requirement of the FWMA is expected to be implemented in April 2014

http://www.environment-agency.gov.uk/research/planning/135749.aspx


The current Draft National Standards for Sustainable Drainage Systems18 (2011) require all new developments, where practicable (excluding single dwellings), to implement SuDS.

The standards set out appropriate design criteria based on four main parameters:

1. Runoff Destination (in order of preference) a. To ground; b. To surface water body;c. To road drain or surface water sewer; d. To combined sewer

2. Peak flow rate and volume (pre and post development) 3. Water Quality (based on potential hazards arising from development and sensitivity of

the runoff destination) 4. Function (design; flood risk; operation and maintenance)

In addition, the Local Planning Authority may set local requirements for planning permission that have the effect of more stringent requirements than these National Standards. More stringent requirement should be considered in CDAs identified in this SFRA or where current greenfield site lie upstream of high risk area. This could include improvements on greenfield runoff rates.

Many different SuDS techniques can be implemented. As a result, there is no one correct drainage solution for a site. In most cases, a combination of techniques, using the Management Train principle, will be required, where source control is the primary aim. Figure 5-4: SuDS Management Train Principle19

The effectiveness of a flow management scheme within a single site is heavily limited by land use and site characteristics including (but not limited to) topography, geology (soil permeability), and available area. In addition to potential ground contamination associated with urban and formerly industrial sites with concern being placed on the depth of the local water table and potential contamination risks. The design, construction and ongoing maintenance regime of such a scheme must be carefully defined as part of a site-specific FRA, and a clear and comprehensive understanding of the catchment hydrological processes (i.e. nature and capacity of the existing drainage system) is essential.

5.9 Emergency Planning Along with the Environment Agency Flood Warning systems, there is a range of Flood Plans at a sub-regional and local level, outlining the major risk of flooding and the strategic and tactical response framework for key responders.

18 Defra (2010) National Standards for Sustainable Drainage Systems 19 CIRIA (2008) Sustainable Drainage Systems: promoting good practice – a CIRIA initiative


This SFRA contains useful data to allow emergency planning processes to be tailored to the needs of the area and be specific to the flood risks faced. The detailed maps and GIS layers provided should be made available for consultation by emergency planners during an event and in the planning process.

5.9.1 Civil Contingencies Act

Under the Civil Contingencies Act (CCA, 2004)20, CEC is classified as a Category 1 responder holding a statutory duty to provide civil protection to their communities to ensure human welfare, environmental stability and UK security are not affected. Under the Act, risk assessments and emergency planning are arranged through Local and Regional Resilience Forums (LRF/RRF).

During an emergency such as a flood event, the Local Authority must also co-operate with other Category 1 responders (such as the emergency services and the Environment Agency) to provide the core response.

CEC is part of the Cheshire Local Resilience Forum (LRF)21. The role of the LRF is to ensure that there is an appropriate level of preparedness to enable an effective multi-agency response to emergency incidents that may have a significant impact on the communities of Cheshire. The LRF consists of representatives from the Emergency Services, Local Authorities, Health, Environment Agency and other professional and voluntary agencies. As a strategic decision-making organisation, the LRF has prepared a Community Risk Register (CCR)22, which considers the likelihood and consequences of the most significant risks the area faces including tidal fluvial and urban flooding. The CCR also identifies the number of controls in place one of which is the Cheshire East Local Flood Response Plan.

5.9.2 Local Flood Plans

The SFRA provides a number of flood risk data sources that should be used when producing or updating flood plans. Plans currently in place or under preparation that affect CEC include the:

Environment Agency Flood Warning Plan Multi-Agency Flood Response Plan

The SFRA data can be used to:

Update these Flood Plans if appropriate. Inform Emergency Planners in understanding the possibility, likelihood and spatial

distribution of all sources of flooding (Emergency Planners may, however, have access to more detailed information, such as for Reservoirs Inundation Maps, which have not been made available for this SFRA).

Identify safe evacuation routes and access routes for emergency services. Identify key strategic locations to be protected in flooding emergencies, and the locations

of refuge areas that are capable of remaining operational during flood events. Engage local communities. Support emergency responders in planning for and delivering a proportionate, scalable

and flexible response to the level of risk. Provide flood risk evidence for further studies such as SWMPs.

5.9.3 Flood Warning and Evacuation Plans

Developments that include areas that are designed to flood (e.g. ground floor car parking and amenity areas) or have a residual risk associated with them, will need to provide appropriate flood warning and instructions so users and residents are safe in a flood. This will include both physical warning signs and written flood warning and evacuation plans.

CEC will be unable to write specific flood plans for new developments at flood risk. Developers should write their own. Guidance can be found in both PPS25 and on the Environment Agency

20 http://www.cabinetoffice.gov.uk/ukresilience/preparedness/ccact.aspx 21 http://www.cheshireresilience.org.uk/ 22 http://www.cheshireresilience.org.uk/your_community/risk_register.aspx


website23. Alternatively, CEC should recommend Emergency Management Consultants who will design flood plans for new and existing developments. Generally, owners with individual properties at risk should write their own individual flood plans, however larger developments or regeneration areas, such as retail parks, hotels and leisure complexes, should consider writing one collective plan for the assets within an area.

Whilst there is no statutory requirement on the Environment Agency or the emergency services to approve evacuation plans. CEC is accountable via planning condition or agreement to ensure that plans are suitable. This should be done in consultation with Development Management Officers. Given the cross cutting nature of flooding, it is recommended that further discussions are held internally to CEC between emergency planners and policy planners/development management officers and drainage engineers and to external stakeholders such as the emergency services, the Environment Agency, United Utilities and the Canal and Rivers Trust.

It may be useful for both Emergency and Spatial Planners to consider whether, as a condition of planning approval, flood evacuation plans should be provided by the developer that aim to safely evacuate people out of flood risk areas, using as few emergency service resources as possible. The application of such a condition is likely to require policy support in the Local Plan, and discussions with the Cheshire LRF are essential to establish the feasibility/ effectiveness of such an approach, prior to it being progressed. It may also be useful to consider how key parts of agreed flood evacuation plans could be incorporated within local development documents, including in terms of protecting evacuation routes and assembly areas from inappropriate development.

Once the development goes ahead, it will be the requirement of the Plan owner (developer) to make sure the plan is put into place, and liaise with the Council regarding maintenance and updating of the plan.

5.9.4 What should the Plan Include?

Flood Warning and Evacuation Plans should include the information highlighted in Table 5-5. Table 5-5: Flood Warning and Evacuation Plans

Consideration Purpose Availability of existing flood warning system

The Environment Agency offer a flood warning service that currently covers designated Flood Warning Areas in England and Wales. In these areas they are able to provide a full Flood Warning Service.

Rate of onset of flooding The rate of onset is how quickly the water arrives and the speed at which it rises that, in turn will govern the opportunity for people to prepare and respond effectively for a flood. This is an important factor within Emergency Planning in assessing the response time available to the emergency services.

How flood warning is given and occupants awareness of the likely frequency and duration of flood events

Everyone eligible to receive flood warnings should be signed up to the Environment Agency service. Where applicable, the display of flood warning signs should be considered. In particular sites that will be visited by members of the public on a daily basis; sports complexes, car parks, retail stores. It is envisaged that the responsibility should fall upon the developers and should be a condition of the planning permission. Information should be provided to new occupants of houses on the level or risk and procedures if flood occurs.

The availability of staff/occupants/users to respond to a flood warning and the time taken to respond to a flood warning.

The Plan should identify roles and responsibilities of all responders. The use of Community Flood Wardens should also be considered.

Designing and locating safe access routes, prepare

Dry routes will be critical for people to evacuate as well as emergency services entering the site. The extent, depth and

23 http://www.environment-agency.gov.uk/homeandleisure/floods/38329.aspx

http://www.environment-agency.gov.uk/homeandleisure/floods/38329.aspx


Consideration Purpose evacuation routes and the identification of safe locations for evacuees

flood hazard rating should be considered when identifying these routes.

Vulnerability of occupants Vulnerability classifications associated with development as outlined in the NNPF. This is closely linked to its occupiers.

How easily damaged items will be relocated and expected time taken to re-establish normal use following an event

The impact of flooding can be long lasting well after the event has taken place affecting both the property, which has been flooded, and the lives that have been disrupted. The resilience of the community to get back to normal will be important, including time taken to repair/replace damages.

5.9.5 Flood Awareness

Emergency planners should also use the outputs from SFRA to raise awareness within local communities. This should include raising awareness of measures that people can take to make their homes more resilient to flooding from all sources and encouraging all those at fluvial flood risk to sign up to the Environment Agency’s Floodline Warnings Direct service. It is also recommended that Category 1 responders are provided with appropriate flood response training to help prepare them for the possibility of a major flood with an increased number of people living within flood risk areas.


6 Conclusions and Recommendations

6.1 Conclusions This SFRA provides a single planning tool relating to flood risk and development in Cheshire East. It has consulted key flood risk stakeholders such as the Environment Agency and United Utilities and collated all available and relevant flood risk information on all sources in one comprehensive assessment.

The flood risk information, assessment, guidance and conclusions of the SFRA will provide Strategic Planners with the evidence base required to apply the Sequential and Exception Tests, as required under the NPPF, and demonstrate that a risk based, sequential approach has been applied in the preparation of their development plans and documents. This will allow for a sustainable and robust Core Strategy.

Whilst the aim of the sequential approach is the avoidance of high flood risk areas, in locations such as Crewe, Macclesfield, Congleton and Nantwich where the Council strives for continued growth and regeneration, this will not always be possible. The SFRA therefore provides the necessary links between spatial developments, wider flood risk management policies, local strategies and on the ground works by bringing flood risk information into one location.

6.2 Recommendations for Further Work The SFRA process has however, developed into more than just a planning tool. Sitting alongside the Cheshire East PFRA and SWMP, it can be used to provide a much broader and inclusive vehicle for integrated, strategic and local flood risk management and delivery.

This said there are a number of plans and assessments listed in Table 6-1 that would be of benefit to CEC in developing their flood risk evidence base to support the delivery of their Local Plan or help fill critical gaps in flood risk information. Table 6-1: Recommended Further Work

Type Study Reason Timeframe Strategy LFRMS CEC should prepare a LFRMS as required

under the FWMA. Short Term

Data Collection

Flood Incident Data

CEC have a duty to investigate and record details of significant flood events within their area. General data collected for each incident, should include date, location, weather, flood source (if apparent without an investigation), impacts (properties flooded or number of people affected) and response by any RMA.

Short Term / Ongoing

Data Collection

Asset Register CEC should maintain a register of structures and features that are considered to have an effect on flood risk.


Risk Assessment

Asset Register Risk Assessment

CEC should carry out a strategic flood risk assessment of structures and features on Asset Register to inform capital programming and prioritise maintenance programming.


Risk Assessment

Critical Drainage Areas

CEC should carry out a desktop study to identify the actual extent of Critical Drainage Areas recommended in this SFRA. CDAs should be used to formulate policies within the LFRMS and used by Development Management to identify the need for site-specific FRAs for windfall

Medium Term


Type Study Reason Timeframe sites at risk of surface water flooding.

Risk Assessment

Local SWMPs CEC should take forward recommendations of the Cheshire East SWMP and carry out local detailed assessment in high risk area.

Medium Term

Capacity SAB Under the FWMA, CEC as LLFA are required to establish a SAB. This is expected to be enacted in April 2014. CEC should identify internal capacity required to deal with SuDS applications, set local specifications and set policy for adoption and maintenance of SuDS.

Short Term

Partnership United Utilities CEC should continue to work with United Utilities on sewer and surface water projects, especially those which have been identified through the SWMP.

Ongoing

Partnership Environment Agency

CEC should continue to work with the Environment Agency on fluvial flood risk management projects. This should include future strategies planned along the Bollin and in Congleton. CEC should also identify potential opportunities for joint schemes to tackle flooding from all sources.

Ongoing

Partnership Canal and Rivers Trust

CEC should continue to work with the Canal and Rivers Trust to understanding the residual risks associated with the canal network. Focus should be given to those networks or assets in poor condition.

Ongoing

Cheshire East Council SFRA - Final Report - v4.0.doc I

Appendices

A SFRA Flood Risk Maps A.1 Level 1 SFRA Maps

001 CEC_Potential_Development_Sites_001b.pdf 002 CEC_NPPF_Flood_Zones_002b.pdf 003 CEC_AStSWF_003b.pdf 004 CEC_FMfSW_30yr_004b.pdf 005 CEC_FMfSW_200yr_005b.pdf 006 CEC_AStGWF_006b.pdf 007 CEC_Historicial_Flood_Incidents_007b.pdf

A.2 Level 2 SFRA Community Flood Risk Review Maps 001 CEC_Community_Review_ALSAGER_001a.pdf 002 CEC_Community_Review_CONGLETON_002a.pdf 003 CEC_Community_Review_CREWE_003a.pdf 004 CEC_Community_Review_KNUTSFORD_004a.pdf 005 CEC_Community_Review_MACCLESFIELD_005a.pdf 006 CEC_Community_Review_MIDDLEWICH_006a.pdf 007 CEC_Community_Review_NANTWICH_007a.pdf 008 CEC_Community_Review_SANDBACH_008a.pdf 009 CEC_Community_Review_WILMSLOW_009a.pdf

Cheshire East Council SFRA - Final Report - v4.0.doc II

B Historical Flood Events

Cheshire East Council SFRA - Final Report - v4.0.doc III

C Critical Drainage Areas

Cheshire East Council SFRA - Final Report - v4.0.doc IV

D Development Site Assessment Spreadsheet

Cheshire East Council SFRA - Final Report - v4.0.doc V

E NPPF Flood Zone and Vulnerability Classifications and Compatibility

Cheshire East Council SFRA - Final Report - v4.0.doc VI

F Glossary of Terms

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