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DRAFT

North WarwickshireSite Specific FloodRisk Technical Note

Project Number: 60589954

March 2019

DRAFT

Project number: PR-360400 DRAFT North Warwickshire Borough CouncilFlood Risk Techncial Note

Quality InformationDocument

VersionIssue Date Prepared by Checked by Verified by Approved by

DRAFT 29/03/2019 Jessica ClayGraduate

Consultant

Helen BurtonPrincipal

Consultant

Katie PearsonAssociate Director

Helen BurtonPrincipal

Consultant

Edgar FerreiraConsultant

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Prepared for:North Warwickshire Borough CouncilCouncil House, South Street, Atherstone CV9 1DE

Prepared by: AECOM Infrastructure & Environment UK LimitedRoyal Court, Basil CloseChesterfieldDerbyshire S41 7SLUnited Kingdom

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© 2019 AECOM Infrastructure & Environment UK Limited. All Rights Reserved.

This document has been prepared by AECOM Infrastructure & Environment UK Limited (“AECOM”) for sole use of our client North Warwickshire Borough Council (the “Client”) in accordance with generally accepted consultancy principles, the budget for fees and the terms of reference agreed between AECOM and the Client. Any information provided by third parties and referred to herein has not been checked or verified by AECOM, unless otherwise expressly stated in the document. No third party may rely upon this document without the prior and express written agreement of AECOM.

The conclusions and recommendations contained in this Report are based upon information provided by others and upon the assumption that all relevant information has been provided by those parties from whom it has been requested and that such information is accurate. Information obtained by AECOM has not been independently verified by AECOM, unless otherwise stated in the Report.

The methodology adopted, and the sources of information used by AECOM in providing its services are outlined in this Report. The work described in this Report was undertaken between November 2018 and March 2019 and is based on the conditions encountered and the information available during the said period of time. The scope of this Report and the services are accordingly factually limited by these circumstances.Where assessments of works identified in this Report are made, such assessments are based upon the information available at the time and where appropriate are subject to further investigations or information which may become available.

AECOM disclaim any undertaking or obligation to advise any person of any change in any matter affecting the Report, which may come or be brought to AECOM’s attention after the date of the Report.Certain statements made in the Report that are not historical facts may constitute estimates, projections or other forward-looking statements and even though they are based on reasonable assumptions as of the date of the Report, such forward-looking statements by their nature involve risks and uncertainties that could cause actual results to differ materially from the results predicted. AECOM specifically does not guarantee or warrant any estimate or projections contained in this Report.


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Table of Contents

Contents

1. Introduction.....................................................................................................11.1. Planning Context....................................................................................................................... 11.2. Commission.............................................................................................................................. 11.3. Study Area................................................................................................................................ 1

1.3.1. Hydrological Context.........................................................................................22. Methodology...................................................................................................52.1. Data Collection.......................................................................................................................... 52.2. Review of Flood Risks from All Sources...................................................................................5

2.2.1. Fluvial (River and Sea).....................................................................................52.2.2. Pluvial (Surface Water).....................................................................................82.2.3. Groundwater.....................................................................................................82.2.4. Sewers..............................................................................................................92.2.6. Man-made/Artificial Sources...........................................................................102.2.7. Records of Historical Flooding Incidents........................................................10

2.3. Flood Risk Mapping................................................................................................................112.3.1. Overview Maps...............................................................................................112.3.2. Comparison of Flood Extents and Water Levels with Ground Levels 11

2.4. Consideration of Climate Change...........................................................................................122.5. Development of Policies..........................................................................................................132.6. Application of the Sequential and Exception Tests.................................................................143. Assessment of Strategic Site H1.................................................................154. Assessment of Strategic Site H2.................................................................185. Assessment of Strategic Site H3.................................................................216. Assessment of Strategic Site E1.................................................................247. Assessment at Strategic Site H14...............................................................278. Summary.......................................................................................................29Appendix A – Hydrological & Hydraulic Analysis................................................30

Flow Estimation..........................................................................................................31Application of Flows in the Brookbanks 2015 InfoWorks ICM Model.........................34Fluvial Depth Mapping................................................................................................34Fluvial Hazard Mapping..............................................................................................36

Appendix B – Site Overview Flood Risk Mapping................................................38Appendix C – Assessment of Flood Zone Extents in respect of Climate Change.....................................................................................................................50Appendix D – Review of Ground Levels relative to Flood Water Levels in respect of Climate Change.....................................................................................58

Figures

Figure 1-1: Location Plan of the Strategic Allocation Sites– Atherstone (H1, H2, H3, E1).......................................3


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Figure 1-2: Location Plan of the Strategic Allocation Site – Wishaw (H14) (for definitions of Areas A & B, see Section X)................................................................................................................................................................. 4Figure A-1: 2015 Model Inflow Hydrographs and 2019 Model Inflow Hydrograph with corrected River Anker Timestep Interval..................................................................................................................................................... 35Figure B-1: Environment Agency Fluvial Flood Map for Planning (Flood Zones), Atherstone – Sites H1, H2, H3-& E1............................................................................................................................................................................ 40Figure B-2: Environment Agency Fluvial Flood Map for Planning (Flood Zones), Wishaw – H14..........................41Figure B-3: Environment Agency Pluvial Updated Flood Map for Surface Water (uFMfSW), Atherstone – Sites H1, H2, H3-& E1............................................................................................................................................................42Figure B-4: Environment Agency Pluvial Updated Flood Map for Surface Water (uFMfSW), Wishaw – H14........43Figure B-5: Environment Agency Areas Susceptible to Groundwater Flooding (AStGWF), Atherstone – Sites H1, H2, H3-& E1............................................................................................................................................................44Figure B-6: Environment Agency Areas Susceptible to Groundwater Flooding (AStGWF), Wishaw – H14...........45Figure B-7: Severn Trent Reported Incidents of Sewer Flooding (by postcode area), Atherstone – Sites H1, H2, H3-& E1.................................................................................................................................................................. 46Figure B-8: Severn Trent Reported Incidents of Sewer Flooding (by postcode area), Wishaw – H14...................47Figure B-9: Environment Agency Historical Flood Map, Atherstone – Sites H1, H2, H3-& E1...............................48

Tables

Table 1-1: Proposed Strategic Allocation Sites.........................................................................................................2Table 2-1: Fluvial Flood Zones (extracted from Table 1 of the NPPF PPG 20165)...................................................6Table 2-2: Flood Risk Mapping at Potential Strategic Allocation Sites by Source – Appendix B.............................11Table 2-3: Assessment of Flood Zone Extents relative to Ground Levels in respect of Climate Change at Potential Strategic Allocation Sites – Appendix C..................................................................................................................11Table 2-4: Review of Ground Levels relative to Flood Water Levels in respect of Climate Change at Potential Strategic Allocation Sites – Appendix D..................................................................................................................12Table 2-5: Peak River Flow Allowances for the Humber River Basin District (1961-1990 baseline).......................12Table 2-6: Peak Rainfall Intensity Allowances in Small and Urban Catchments (1961-1990 baseline)..................13Table 3-1: Assessment of Strategic Site H1.......................................................................................................15Table 4-1: Assessment of Strategic Site H2.......................................................................................................18Table 5-1: Assessment of Strategic Site H3.......................................................................................................21Table 6-1: Assessment of Strategic Site E1........................................................................................................24Table 7-1: Assessment of Strategic Site H14.....................................................................................................27Table A-1: Key to Maximum Depth Results.............................................................................................................36Table A-2: Danger to people relative to different combinations of flood flow depth and velocity............................36Table A-3: Debris factors (DF) for different flood depths, velocities and dominant land use...................................37Table A-4: Hazard to People as a Function of Velocity and Depth..........................................................................37


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1. Introduction 1.1. Planning Context

In March 2018, North Warwickshire Borough Council (NWBC) submitted their North Warwickshire Local Plan to the Secretary of State for independent examination. The evidence base for the Local Plan Submission included a review of flood risk at the proposed strategic development sites (sites required to meet North Warwickshire’s residential and business development needs for housing and employment opportunities). This review was informed by a Level 1 Strategic Flood Risk Assessment (SFRA)1 and a Level 1 SFRA Update2 that were completed for the site allocations as they emerged.

Through the consultation process, the Environment Agency has requested a more robust assessment of fluvial flood risks at five of the proposed strategic allocation sites (four in Atherstone, one in Wishaw) listed in Table 1-1 of this report. The assessment is required to provide confidence that these land allocations are likely to be deliverable in respect of future climate change , as there is currently a limited understanding on how the flood risk within these specified areas will change over the lifetime of the proposed development types.

1.2. Commission

AECOM were subsequently commissioned in October 2018 to produce a Site Specific Flood Risk Technical Note providing an assessment of all sources of flooding at these five proposed allocation sites within the 2018 Local Plan including an assessment of future risk based on Environment Agency climate change guidance3 (February 2016).

This assessment and Technical Note provides additional information to support the evidence base that will be used to inform the Examination of the North Warwickshire Local Plan by the Planning Inspector. The technical note provides best-practice policy guidance for the most sustainable way to develop the five sites in line with current recommendations for adapting to climate change in the National Planning Policy Framework4 (NPPF) and its accompanying Planning Practice Guidance: Flood Risk and Coastal Change5 (PPG).

1.3. Study Area

Four of the proposed strategic allocation sites (H1, H2, H3 and E1) are located to the north and north west of Atherstone, approximately 1 km north of the A5 as illustrated in Figure 1-1. The fifth site, H14, is located in the Wishaw area east of Sutton Coldfield and 1 km south west of the M6 Toll Station, (illustrated in Figure 1-2). Further site information is highlighted in Table 1-1.

1 Halcrow Group Ltd. (February 2008). Warwickshire County Council Strategic Flood Risk Assessment for Local Development Framework Level 1.2 URS. (September 2013) Stratford-on-Avon DC, Warwickshire CC, North Warwickshire BC & Rugby BC Level 1 SFRA.3 Environment Agency. (February 2016). Flood risk assessments: climate change allowances – Table 1 and Table 2. Available at: https://www.gov.uk/guidance/flood-risk-assessments-climate-change-allowances 4 Ministry of Housing, Communities and Local Government. (2012) National Planning Policy Framework. Available at:https://www.gov.uk/government/publications/national-planning-policy-framework--2 5 Ministry of Housing, Communities and Local Government (2016) Planning Practice Guidance: Flood Risk and Coastal Change. Available at: http://planningguidance.planningportal.gov.uk/blog/guidance/flood-risk-and-coastal-change/

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http://planningguidance.planningportal.gov.uk/blog/guidance/flood-risk-and-coastal-change/

https://www.gov.uk/government/publications/national-planning-policy-framework--2

https://www.gov.uk/guidance/flood-risk-assessments-climate-change-allowances


Table 1-1: Proposed Strategic Allocation SitesStrategic

Allocation Site ID Settlement Site Name Area (Ha) Proposed Land Use Table Number

H1 Atherstone Land at Old Holly Lane 32.7 Mixed Use Table 3-8

H2 Atherstone Land to the north-west of Atherstone off Whittington Lane

71.2 Mixed Use Table 4-9

H3 Atherstone Land at the Football Ground off Sheepy Road

2.2 Residential (reserve allocation)

Table 5-10

E1 Atherstone Land South of Rowlands Way 6.1 Employment Table 6-11

H14 Wishaw Land north of Lindridge Road 6.7 Residential Table 7-12

1.3.1. Hydrological Context

There are four key watercourses within the study area in Atherstone (see Figure 1-1) which potentially pose a fluvial flood risk to Sites H1, H2, H3 and E1.

River Anker; a Main River originating in Wolvey located to the north of the Atherstone study area. At its nearest point along the boundary, Site H1 is 200 m away from the left bank of the Anker, and Site H2 is 160 m from the left bank of the Anker. The Anker flows from the south east to north west with multiple tributaries contributing inflows throughout its course including Innage Brook and Merevale Brook (see below). At the downstream extent of Site H1 the catchment area of the River Anker is approximately 337 km2.

Merevale Tributary; an Ordinary Watercourse originating to the north east of Merevale flowing in a north easterly direction past the north western extent of Atherstone towards its confluence with the River Anker at OS NGR 430250, 299600. This tributary of the River Anker flows parallel to Holly Lane/ Old Holly Lane and forms the boundary between Sites H1 and H2. At the confluence, the catchment area of Merevale Brook is approximately 3.6 km2.

Innage Brook; an Ordinary Watercourse originating at Bentley and flowing in a north-easterly direction through Atherstone into the River Anker at OS NGR 430700, 299400. Innage Brook intersects Sites H2 and E1, and is located 0.1 km at its nearest point from the western edge of Site H3. At its confluence with the River Anker, the catchment area of Innage Brook is approximately 4.9 km2.

Coventry Canal; a 62 km long narrow canal (classified as an Ordinary Watercourse) linking Coventry to Lichfield. Within this study area, the canal stretches from north west to south east through the western region of Site H2, and is located to the south west of Sites H1 (510 m), H3 (590 m) and E1 (350 m).

Three un-named tributaries of the River Anker (Ordinary Watercourse land drains) also flow in a north westerly direction through the western and northern regions of Site H2 (see Figure 1-1).

There is one key watercourse within the study area in Wishaw (see Figure 1-2) which poses a potential fluvial flood risk to Site H14:

Lindridge Brook; an Ordinary Watercourse tributary of Langley Brook originating in the central and eastern areas of Reddicap Heath, Sutton Coldfield. At its confluence with Langley Brook, located 165 m downstream of Site H14, the catchment area is approximately 4.1 km2.

Langley Brook; an Ordinary Watercourse located approximately 140 m to the north of Site H14 at its closest point flowing eastwards that flows into the River Tame at Kingsbury.


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© Crown copyright and database rights 2019 Ordnance Survey 100024198

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Figure 1-1: Location Plan of the Strategic Allocation Sites– Atherstone (H1, H2, H3, E1)



Figure 1-2: Location Plan of the Strategic Allocation Site – Wishaw (H14) (for definitions of Areas A & B, see Section X)



2. Methodology 2.1. Data Collection

The data reviewed to support this Flood Risk Technical Note comprised:

Site redline boundaries provided by NWBC;

national flood risk datasets obtained from the Environment Agency’s website6;

LiDAR data from Defra’s website7

additional national flood risk datasets provided by key stakeholders for the Level 1 SFRA Update (September 2013); and

the InfoWorks ICM hydraulic model provided by Brookbanks Consulting Ltd as part of a Level 3 FRA supporting planning application ref. PAP/2014/0540 for Site H1 (December 2015).

2.2. Review of Flood Risks from All Sources

The method adopted to produce this Flood Risk Technical Note enabled determination of the flood risk issues relative to the following sources of flooding and with regard to the vulnerability classification of the proposed land uses at the sites:

River (Fluvial)

Land (Pluvial surface water and overland flow)

Groundwater

Sewers (surface water sewers)

Other artificial sources (Canals and Reservoirs)

These sources of potential flood risk were reviewed and each assessed as defined further below in comparison to each of the five Sites in Table 3-8 to Table 7-12 in Sections 3 to 7 of this report.

A review was also undertaken of the residual risks of flooding from these sources (where/if applicable). A review of the flood defence infrastructure was also undertaken, however this review concluded that there are no formal flood defences providing any protection to the Sites of interest, so no further investigation of the potential failure of these was necessary.

Recommendations were made for site specific strategic policies to be applied, and requirements for site-specific FRAs where more information will be needed to satisfy planning application approvals.

This Flood Risk Technical Note should be read in parallel to the Level 1 SFRA Update (September 2013) as this provides supplementary information for NWBC and developers.

2.2.1. Fluvial (River and Sea)

Flood Zone Definitions

The NPPF (2018) classifies land according to the probability of flooding from fluvial and tidal sources as defined in the Environment Agency’s ‘Flood Map for Planning (Rivers and Sea)’8. The definitions for each Flood Zone with respect to fluvial flooding, which are of relevance to the NWBC study area, are shown in Table 2-2.

Table 2-2: Fluvial Flood Zones (extracted from Table 1 of the NPPF PPG 20165)Flood Zone Fluvial Flood Zone Definition Probability of

Flooding

Flood Zone 1 At risk from flood event less than the 1 in 1000 year event (less than Low

6Defra. (2019). Defra Data services Platform. Available at: https://environment.data.gov.uk/ 7 Light Detection and Ranging digital terrain model (DTM) data (1m and 2m resolution) – Defra. 2019. Defra Survey Data Download. Available at: https://environment.data.gov.uk/DefraDataDownload/?Mode=survey 8 Environment Agency (2017) Flood Map for Planning (Rivers and the Sea). Available at:https://flood-map-for-planning.service.gov.uk/


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https://flood-map-for-planning.service.gov.uk/

https://environment.data.gov.uk/DefraDataDownload/?Mode=survey

https://environment.data.gov.uk/


Flood Zone Fluvial Flood Zone Definition Probability of Flooding

0.1% annual probability (AP) of flooding each year)

Flood Zone 2 At risk from flood event between the 1 in 100 and 1 in 1000 year event (between 1% and 0.1% annual probability of flooding each year) Medium

Flood Zone 3a At risk from flood event less than or equal to the 1 in 100 year event (greater than 1% annual probability of flooding each year) High

Flood Zone 3bLand where water has to flow or be stored in times of flood, or land purposely designed to be flooded in an extreme flood event (0.1% annual probability). The 1 in 20 year event (5% annual probability) floodplain is the starting point for consideration.

High(Functional Floodplain)

As of October 2018 at project inception, the available Flood Zones defined for the watercourses identified in Section 1.3 in the vicinity of the Sites had been produced from three hydraulic modelling techniques:

Low resolution broadscale modelling (1D only, JFLOW, circa 2006) along Lindridge Brook, Langley Brook, Innage Brook upstream of Rowland Way/Holly Lane, and Merevale Brook upstream of Whittington Lane).

Medium resolution modelling along the River Anker (1D only) from the Environment Agency’s 2006 River Anker SFRM model; and

High resolution detailed modelling along the River Anker, Innage Brook downstream of Rowland Way/Holly Lane, and Merevale Brook downstream of Whittington Lane) (1D-2D, generated by Brookbanks Consulting Ltd 2015 in InfoWorks ICM to inform planning application ref. PAP/2014/0540 for Site H1, adapted from the Environment Agency’s 2006 River Anker SFRM model).

The flood extents from the Low and Medium resolution modelling techniques above are included within the current ‘Flood Map for Planning’ and are illustrated in Figure B-1A for Atherstone and Figure B-2A for Wishaw at Appendix B.

The low resolution broadscale modelling (JFLOW) outlines are only indicative and are not usually considered suitable by the Environment Agency for site-specific assessment of flood risk. The higher resolution modelling techniques provide more confidence in the results to determine the risk of fluvial flooding in relation to specific sites.

However, due to the time constraints of the Local Plan programme, production of a full Level 2 SFRA defined in the NPPF (2018) and the accompanying PPG (2016) which would require further detailed hydraulic modelling for Sites E1, H3 and H14 was not feasible. In order to assess the fluvial flood risk, an alternative proportionately detailed methodology relative to the scale of and potential flood risks at the Sites was developed by AECOM through consultation with NWBC and the Environment Agency and undertaken between October 2018 and March 2019.

The aim was to pursue a more pragmatic approach for these Sites to demonstrate a higher level of confidence in the indicative JFLOW modelling outputs in the absence of more detailed hydraulic modelling at this time. This provides more confidence for the Environment Agency, in their consultation role, that the number/density of residential or commercial/employment land uses would likely be accommodated on the five proposed strategic allocation Sites.


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This approach entailed the following scope of services:

Collection of FEH Web Service Catchment Descriptors at six key flow estimation points along the local watercourses to provide the basis of new flow estimation calculations, undertaken within the latest industry standard Revitalised Flood Hydrograph (ReFH2) model (see further details of the hydrological modelling in Appendix A). This provided flow estimates for two purposes:

─ Sites H1 and H2; to enable sensibility checks of the existing inflows applied within the 2015 Brookbanks ICM model to determine if these were still considered appropriate (as the ReFH2 method now supersedes the ReFH1 method used in that study), and to update the model with inflows inclusive of the +30%/+50% climate change allowances on the 1% AP event9; and

─ Sites H3, E1 and H14; to establish the difference between the 1% AP +30%/+50% allowances for climate change flows and the 0.1% AP flows to assess if the 1% AP+CC scenario events would be likely to extend further across the site than the current Flood Zone 2 outlines (0.1% AP event) if they were to be modelled in detail.

At Sites H1 and H2, analysis was then made of the outputs of re-runs of the existing Brookbanks ICM model with +30% and +50% flow allowances for climate change on the 1% AP event, (see details of the hydraulic modelling in Appendix A and Figures C4 at Appendix C). The flood extents were compared to the existing outlines for the present day 1% AP and 0.1% AP scenarios (equivalent to Flood Zones 3 and 2 respectively). Depth and hazard data within the floodplain during a 1% AP event with a +50% climate change allowance were also reviewed to determine the risks within the flood extents at these two Sites (see Figures C5 and C6 at Appendix C) to satisfy the requirements of an Exception Test; and

For Sites E1, H3 and H14, a comparison was made of the broadscale modelling (JFLOW) derived Flood Zones with LiDAR topographic ground level data across the Sites and wider floodplain using reasonable engineering judgement to estimate the potential floodwater routing mechanisms from increases in water levels and flood extents resulting from climate change. See the Site topographies illustrated in Figures C1 to C3 at Appendix C, and cross sections comparing the approximate JFLOW water levels to these in Figures D1 to D6 at Appendix D. Comparison of these fluvial outlines was also made against the Environment Agency’s Risk of Flooding from Surface Water (RoFfSW) maps on the Environment Agency’s website10 (see further details in Section 2.2.2 and Figures B-2A and B-2B at Appendix B).

Definition of Functional Floodplain

The Level 1 SFRA Update (September 2013) identified Flood Zone 3b (>=5% AP, 1 in 20 year event) for the River Anker alongside Sites H1 and H2 as derived by the Environment Agency’s SFRM study. This extent however is larger than that defined by Flood Zone 3a in the more detailed Brookbanks ICM model outputs, and the >=5% AP event was not remodelled as part of the FRA study. Therefore, as the extent of modelled Flood Zone 3a (>= 1% AP event) from the Brookbanks ICM model supersedes the extent of Flood Zone 3b illustrated in the Level 1 SFRA Update, it should be used as a proxy for Flood Zone 3b until more detailed modelling for this magnitude event becomes available.

There is no designated Functional Floodplain along Lindridge Brook or Langley Brook in the vicinity of Site H14, along Innage Brook alongside Sites E1 and H3, or along Merevale Brook alongside H2 as no detailed hydraulic modelling studies have been completed and/or approved by the Environment Agency in these areas. Therefore, the extent of modelled Flood Zone 3a (>= 1% AP event) from the Environment Agency’s Flood Map for Planning will be used as a proxy for the purposes of this Flood Risk Technical Note at these Sites. Further detailed modelling would therefore be required to define outlines for the 5% annual probability Functional Floodplain.

The results of this analysis above are summarised in the ‘Sources of Flood Risk – Rivers (Fluvial)’ rows in the Site Summary Tables in Sections 3, 4, 5, 6 and 7.

2.2.2. Pluvial (Surface Water)

Overland flow and surface water flooding typically arise following periods of intense rainfall, often of short duration, when the rainfall is unable to soak into the ground or enter drainage systems. It can run quickly off land as overland flow and result in localised flooding.

9 See Section 2.4 of this Technical Note for more information about climate change guidance applicable in this area.10 Environment Agency. (2019). Long term flood risk assessment for locations in England, ‘Risk of Flooding from Surface Water’ maps; see Detailed View \ High Risk Extents, Depth and Velocities. Available at: https://flood-warning-information.service.gov.uk/long-term-flood-risk/map


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https://flood-warning-information.service.gov.uk/long-term-flood-risk/map



One of the key issues with pluvial flooding is that even in areas with no history of surface water flooding, relatively small increases in impermeable hard surfacing and surface gradients can cause flooding (garden loss and reuse of brownfield sites for example). As a result, continuing development could mean that the probability or consequences of pluvial flooding could increase, and, although not on the same scale as fluvial flooding, it can still cause significant disruption.

The Environment Agency undertook modelling of surface water flood risk at a national scale and produced Risk of Flooding from Surface Water maps10 identifying those areas at risk of surface water flooding during the following three magnitude rainfall events:

High Probability – 3.3% AP (1 in 30 chance of flooding in any one year),

Medium Probability – 1% AP (1 in 100 chance of flooding in any one year), and

Low Probability – 0.1% AP (1 in 1000 chance of flooding in any one year)

The latest version of the mapping, published in 2013 (uFMfSW), is available to Local Planning Authorities either as GIS layers or via the Environment Agency’s online viewer. This dataset now provides the Environment Agency, NWBC and the public access to information on surface water flood risk that is consistent across England and Wales.

As such, they are considered the most appropriate dataset available to inform the assessment of surface water flood risk at the five strategic sites as part of this Flood Risk Technical Note to assist NWBC in their duties relating to management of surface water flood risk.

However, it should be noted that this national mapping has the following limitations:

Use of an assumed single drainage rate for all urban areas;

It does not show the susceptibility of individual properties to surface water flooding;

The mapping has significant limitations for use in flat catchments;

No explicit modelling of the interaction between the surface water network, the sewer systems and watercourses;

In a number of areas, modelling has not been validated due to a lack of surface water flood records;

As with all models, the uFMfSW is affected by a lack of, or inaccuracies, in available data.

Maps illustrating the uFMfSW in the vicinity of the strategic allocation Sites have been provided in Figures B-2A in Atherstone and B-2B in Wishaw in Appendix B.

2.2.3. Groundwater

The Environment Agency released a dataset entitled Areas Susceptible to Groundwater Flooding (AStGWF) in March 2011. This data has used the top two susceptibility bands of the British Geological Society (BGS) 1:50,000 Groundwater Flooding Susceptibility Map and thus covers consolidated aquifers (sandstone etc., termed 'clearwater' in the data attributes) and superficial deposits. It does not take account of the chance of flooding from groundwater rebound. It shows the proportion of each 1 km grid square where geological and hydrogeological conditions show that groundwater might emerge.

The susceptible areas are represented by one of four categories (listed below) showing the percentage of each 1 km2

grid that is susceptible to groundwater emergence.

< 25%,

>= 25% <50%,

>= 50% <75%, and

>= 75%.

It does not show the likelihood of groundwater flooding occurring. Absence of values for any grid square means that no part of that square is identified as being susceptible to groundwater emergence.

Maps illustrating the AStGWF in the vicinity of the five proposed strategic allocation Sites are provided in Figure B-3A for Atherstone and Figure B-3B for Wishaw at Appendix B.

2.2.4. Sewers

In urban areas, rainwater is frequently drained into surface water sewers or sewers containing both surface and waste water known as ‘combined sewers’. Flooding can result when the sewer is overwhelmed by heavy rainfall, becomes blocked or is of inadequate capacity.


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Areas affected by sewer flooding have been determined using historical data provided by Severn Trent Water (ST) in 2013 from their Director General 5 (DG5) register for the 10 year time period 2003-2013. All water companies are obliged to keep such a register of those properties that have been affected by sewer flooding and indicate the location, cause and the extent of historical flood events (internal or external to properties). The DG5 register simply indicates areas reported to ST that have experienced flooding as a result of insufficient hydraulic capacity in the sewer network but does not indicate areas or properties at risk of future flooding.

This data was provided for the Level 1 SFRA Update (September 2013) by four digit post code areas showing the internal, external and total number of sewer flooding incidents from public foul, combined or surface water sewers covering the period 2003-2013. A map illustrating the ST DG5 data (total number of incidents) in the vicinity of the strategic allocation sites has been provided in Figure B-4A for Atherstone and B-4B for Wishaw at Appendix B.

It is important to note that maintenance work may have been undertaken by ST since the flooding incident(s) occurred. More detailed ST sewer flooding models provide a much more detailed and useful appreciation of the risk posed. More detailed information should be requested from ST for site specific FRAs. Furthermore, it should be noted that these are flooding incidents that have been reported to ST by the home owners. There are obviously incidents that do not get reported and therefore will not show on the register.

Until more detailed and suitable data becomes available, the Local Planning Authorities, the Environment Agency and the utility companies should continue to liaise to determine how sewer flooding data can best be used to inform strategic planning. Early consultation by the developer with these agencies/authorities is recommended as part of a site specific FRA at the start of any master-planning phases of a new development.

2.2.5.


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2.2.6. Man-made/Artificial Sources

Man-made/artificial sources of flooding include canals, reservoirs and lakes where water is retained above natural ground level, operational and redundant industrial processes including mining, quarrying and sand and gravel extraction, or result from the failure of engineering installations such as flood defence, land drainage pumping stations, sluice gates, floodgates and weirs. There is a potential residual risk to the proposed strategic allocation Sites in North Warwickshire from overtopping or breach failure of the Coventry Canal and several reservoirs located further upstream in the River Anker catchment.

The risk of reservoir or canal flooding is deemed to be minimal and residual, but may occur as a result of the facility being overwhelmed and/or as a result of dam or bank failure. Failure may occur through the slow deterioration of structural components which is often difficult to detect, and when it occurs, is often sudden and unexpected. Failure is more likely when the structure is under maximum stress, such as extreme fluvial events when pressures on the structure are at its most extreme resulting in rapidly flowing, deep water that can cause significant threat to life and major property damage. Canal embankment failure has been known to happen occasionally but the impact is not considered to be as extensive as a failure of a reservoir dam as studies have shown that maximum discharges are limited to the volume held within the canal cross section between two locks.

This residual risk is managed by the Canal and River Trust (CRT) who perform monthly towpath side inspections and offside inspections at regular intervals and manage some critical flood defence structures including flood gates. Canals generally work at relatively stable water levels with the various lock by-passes, and waste weirs passing and controlling excess feeds without leading to overtopping of the banks. In general, the canal system is therefore hydraulically closed down at relatively low river levels prior to the issuing of a flood alert from the Environment Agency. The most likely cause of overtopping in canals is vandalism, incorrect use of lock gate sluices and if the weirs have also been blocked by debris.

Councils presume as a principle that canals are maintained effectively but will consider for each of them the effect of a catastrophic structural failure resulting in rapid inundation of protected areas. It is considered that overtopping of such structures during conditions more severe than for which they have been designed would not itself lead to rapid inundation. Although the probability of breach failure is small, the potential for a large volume of water to be released quickly means that the hazard resulting from rapid inundation adjacent to these structures is high.

The locations of recorded canal breach failures are illustrated in the historical flooding map in the Level 1 SFRA Update (September 2013) (see Figure A6 of the document); however none of these incidents were located in the vicinity of any of the strategic allocation Sites of interest in this Flood Risk Technical Note.

Published in 2010, the Environment Agency’s ‘Risk of Flooding from Reservoirs’ dataset available on their website11 provides an indication of the areas that could be affected by reservoir flooding in the event of breach or dam failure. These extents, are also illustrated in Figure A6 of the Level 1 SFRA Update have been reviewed as part of the assessments made in Sections 3 to 7 of this report.

2.2.7. Records of Historical Flooding Incidents

The Environment Agency’s Historical Flood Map (HFM) and locations of other historical flooding incidents reported to Warwickshire County Council (WCC) (the Lead Local Flood Authority (LLFA)) in the vicinity of the proposed strategic allocation sites in Atherstone have been illustrated in Figures B-5A at Appendix B. There are no records of historical flooding incidents in the vicinity of Site H14 in Wishaw, so no map has been provided.

2.3. Flood Risk Mapping

Using the Site red line boundary layers provided by NWBC, overview maps provided in Appendix B, Appendix C and Appendix D were produced for this Flood Risk Technical Note to visually assist the consideration of flood risks at the five proposed strategic allocation Sites.

11 Environment Agency. (2019). Long term flood risk assessment for locations in England, Flood risk from Reservoirs map. Available at: https://flood-warning-information.service.gov.uk/long-term-flood-risk/map


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2.3.1. Overview Maps

Table 2-3: Flood Risk Mapping at Potential Strategic Allocation Sites by Source – Appendix BDescription Settlement

NameSite IDs Figure

Environment Agency Fluvial Flood Map for Planning(Flood Zones)

Atherstone H1, H2, H3, E1 Figure B.1A

Wishaw H14 Figure B.1B

Environment Agency Risk of Flooding from Surface Water Map (uFMfSW)



Environment Agency Area Susceptible to Groundwater Flooding (AStGWF)



Historical Total Reported Sewer Flooding Incidents (Severn Trent Water DG5 2006-2016)



Reported Historical Flooding Incidents


Wishaw H14 (No reported incidents in vicinity to map)

2.3.2. Comparison of Flood Extents and Water Levels with Ground Levels

Table 2-4: Assessment of Flood Zone Extents relative to Ground Levels in respect of Climate Change at Potential Strategic Allocation Sites – Appendix C

Description Settlement Name

Site IDs Figure

High Level Comparison of Existing Environment Agency Flood Zones (JFLOW outputs) to Ground Levels Atherstone E1 Figure C1

High Level Comparison of Existing Environment Agency Flood Zones (JFLOW outputs) to Ground Levels Atherstone H3 Figure C2

High Level Comparison of Existing Environment Agency Flood Zones (JFLOW outputs) to Ground Levels Wishaw H14 Figure C3

ICM Modelled Flood Extents with Environment Agency February 2016 Climate Change Allowances in Comparison with Existing Flood Zones Atherstone H1, H2 Figure C4

ICM Modelled Flood Depths for a 1% Annual Probability Event+50% Climate Change Allowance Atherstone H1, H2 Figure C5

ICM Modelled Flood Hazard Classifications for a 1% Annual Probability Event+50% Climate Change Allowance Atherstone H1, H2 Figure C6


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Table 2-5: Review of Ground Levels relative to Flood Water Levels in respect of Climate Change at Potential Strategic Allocation Sites – Appendix D


Site IDs Figure

Cross Section of Ground Levels and Flood Water Levels Atherstone E1Figure D1Figure D2

Cross Section of Ground Levels and Flood Water Levels Atherstone H3 Figure D3

Cross Section of Ground Levels and Flood Water Levels Wishaw H14Figure D4Figure D5Figure D6

2.4. Consideration of Climate Change

It is predicted that increases in peak rainfall intensity and river flow could result in more frequent and severe flood events and, for planning purposes, flood risk assessment should consider the potential impacts of climate change.

Mapping of Flood Zone 3 with the Environment Agency’s pre-February 2016 recommended climate change allowances was undertaken for the purposes of the Level 1 SFRA Update (where available from detailed modelling) using a +20% increase in flows (1% AP+20%CC event). The existing Brookbanks ICM model 1% AP (Flood Zone 3) outline for the River Anker and the downstream reaches of its tributaries Innage Brook and Merevale Brook were also inclusive of a +20% allowance for climate change (1% AP+CC). NWBC’s NPPF PPG Sequential Test has been based upon the present day Flood Zones however.

Developers now need to demonstrate consideration of the Environment Agency’s February 2016 national climate change guidance and policies3 and consider the potential impacts of the latest climate change allowances for North Warwickshire in their planning submissions.

Where there is no 1% AP plus 30% climate change detailed modelled outline available, then the 0.1% AEP (1 in 1000 year) outline (Flood Zone 2) can be used as an indicative proxy until a developer can prove otherwise through further modelling as part of a detailed FRA.

The uFMfSW does not include a specific scenario to determine the impact of climate change on the risk of surface water flooding. However, a range of three annual probability events have been undertaken; 3.3%, 1% and 0.1% and therefore it is possible to use with caution the 0.1% AP outline as a substitute dataset to provide an indication of the implications of climate change on a 1% AP event.

The February 2016 climate change guidance is provided on the Environment Agency website3. The anticipated changes in peak river flow allowances by river basin district are listed in Table 1 and Table 2 of the 2016 guidance, and those for the Humber river basin (the River Anker is within the Humber River Basin District) are replicated in Table 2-6 and Table 2-7 below respectively.

Table 2-6: Peak River Flow Allowances for the Humber River Basin District (1961-1990 baseline)Total potential change

anticipated for the 2020s (2015-2039)

Total potential change anticipated for the 2050s

(2040-2069)


(2070-2115)

Humber River Basin

Upper End Estimate 20% 30% 50%

Higher Central 15% 20% 30%

Central 10% 15% 20%

Table 2-7: Peak Rainfall Intensity Allowances in Small and Urban Catchments (1961-1990 baseline)Applies across all of

EnglandTotal potential change

anticipated for the 2020s (2015-2039)


(2040-2069)


(2070-2115)

Upper End Estimate 10% 20% 40%

Central 5% 10% 20%

The nature of any proposed development and the level of flood risk will determine which climate change scenario should be applied as part of FRAs undertaken for proposed developments within the strategic allocation Sites.


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Guidance is provided on the Environment Agency website3 for which allowance to use for peak river flows as part of a FRA relative to which Flood Zone a development is proposed to be located within, the NPPF PPG vulnerability classification of the development and the likely lifespan of such development. For FRAs, both the Central and Upper End peak rainfall intensity allowances should be assessed to understand the potential range of impact.

For example:

Residential development is classified in Table 2 of the NPPF PPG as ‘More Vulnerable’ and therefore, if it is proposed to be located in Flood Zone 3, the risk posed by the ‘Higher Central’ allowance of 2070 to 2115 time epoch (+30% in river flow) should be used, and the ‘Upper End’ allowance of 2070 to 2115 time epoch (+50% in river flow) should be used to assess the range/sensitivity of flood risk at the Sites.

Employment land uses (including warehousing, offices and car parking) are classified by Table 2 of the NPPF PPG as ‘Less Vulnerable’ development and therefore, if it is proposed to be located in Flood Zone 3, the risk posed by the ‘Central’ allowance of the 2070 to 2115 time epoch (+20% in river flow) should be used, and the ‘Higher Central’ allowance of 2070 to 2115 time epoch (+30% in river flow) should be used to assess the range/sensitivity of flood risk at the Sites.

Access roads and footpath infrastructure associated with these residential and employment land uses are classified as ‘Essential Infrastructure’ in Table 2 of the NPPF PPG and therefore, if it is proposed to be located in Flood Zone 3, the risk posed by the ‘Upper End’ allowance of 2070 to 2115 time epoch (+50% in river flow) should be used.

Open space for recreation, natural and flood storage uses are classified in Table 2 of the NPPF PPG as ‘Water-Compatible’ development and therefore, if it is proposed to be located in Flood Zone 3, the risk posed by the ‘Central’ allowance of 2070 to 2115 time epoch (+20% in river flow) should be used.

It is therefore possible that these new climate change predictions may infer an increase in the risk of fluvial flooding in certain areas of the sites further than the modelled flood outlines presented in the Level 1 SFRA Update have accounted for.

It is highlighted throughout this report that further hydraulic modelling will be required as part of a detailed FRA to support planning applications on any of these five sites. The modelling will need to demonstrate the impacts of these climate change predictions and suitability of any proposed mitigation measures, especially on sites where a small increase in flood risk could have a significant impact (i.e. any site with relatively flat topography where only a slight increase in depth could lead to major increase in extent).

2.5. Development of Policies

A series of additional flood risk policies were developed for NWBC as part of a sequential approach to either further trim the site red-line boundaries outside of the floodplain or to direct allocation of the most vulnerable land uses to the areas of the sites at lowest risk in accordance with the principles of the NPPF (July 2018) and the PPG (March 2016).

Should developers later decide to submit new or further updated proposals to occupy land within the floodplain within the redline boundaries, these policies will also require them to undertake hydraulic modelling as part of a detailed Level 3 FRA to better define the Flood Zones for the required events inclusive of the necessary climate change allowances and prove to a greater level of detail and confidence that their proposals are safe and follow the sequential approach (and if needed, pass the Exception Test).

2.6. Application of the Sequential and Exception Tests

NWBC have utilised the information from within the Level 1 Updated SFRA (September 2013) and this Flood Risk Technical Note to apply the Sequential Test to potential development sites within the district, and where necessary, will apply the Exception Test to the five potential strategic allocation Sites in the future.

As specified in detail in the Level 1 Updated SFRA (September 2013), in order to determine the suitability of land for development in flood risk areas, the vulnerability of the proposed development must first be established (see Table 2-2). Flood risk vulnerability classifications are summarised in Table 2 of the NPPF PPG 20165. The need to apply the Exception Test is then determined based on the Flood Zone in which the proposed development is located and the development vulnerability (defined by Table 3 ‘Flood Risk Vulnerability and Flood Zone Compatibility’ of the NPPF PPG 2016).


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3. Assessment of Strategic Site H1These following tables detail the outcomes of the assessments undertaken as per the methodology referred to in Section 2 for the five potential strategic allocation Sites highlighted in the Local Plan Submission. Details of the Hydrological and Hydraulic Modelling assessments are provided in Appendix A. Flood risk mapping in the vicinity of the Sites from all sources is provided to complement the information provided in Appendices B and C.

Table 3-8: Assessment of Strategic Site H1

Site H1

Site Area 32.7Ha

Existing Land Use and

Topography

Site H1 is located 1 km north west of Atherstone Town Centre. It is bound by the existing urban fringe of Atherstone which borders the Holly Lane Industrial Estate located to the south west. To the west of the site, there are several agricultural fields and Whittington Farm. Aldermill Business Park is located to the north east.

The current land use is rural, agricultural and gardening nurseries. The site topography slopes from the southern extent at a peak of approximately 82.0 mAOD gently

downhill towards the centre of the site then graduates on a shallower gradient into the northern region of the site down to ground levels of 67.0m AOD along the northern boundary.

Proposed Use and

Vulnerability Classification

Site H1 is proposed for mixed land use including 651 residential dwellings classified as ‘More Vulnerable’ in Table 2 of the NPPF PPG.

Access roads and footpath infrastructure associated with these dwellings are classified as ‘Essential Infrastructure’ in Table 2 of the NPPF PPG.

The remaining area of the Site is proposed for open space/recreation, natural and flood storage uses which are classified in Table 2 of the NPPF PPG as ‘Water-Compatible’ development.

The appropriateness of the development was considered prior to this assessment and it was concluded that the site should be separated into Area A and Area B based on its risk of flooding. This is explored further in ‘Sources of Flood Risk’ below.

Sources of Flood Risk

Rivers (Fluvial)

The River Anker has the potential to impact of the proposed development due to the close proximity; 0.4 km away from north western extent of the site. Innage Brook flows through a culvert under Holly Lane/Rowland Way into the Site and proceeds in a northerly direction within the eastern region of the site towards the River Anker. Merevale Brook flows in a north-easterly direction along the western boundary of the Site towards the River Anker

The Environment Agency’s Historical Flood Map (see Figure B5A at Appendix B) illustrates a small area within the northern region of Site H1 to have flooded from the River Anker, west of Old Holly Lane. It does not however include any records of flooding from Innage Brook.

The Environment Agency’s’ Flood Map for Planning’ (see Appendix B, Figure B1A) illustrates that approximately half of the Site spread across the central, southern and eastern regions is at a low risk (<0.1% AP event) of fluvial flooding. Approximately one third of the Site is at ‘medium risk’ (>=0.1% AP event) of fluvial flooding along the corridors of Innage Brook and Merevale Brook and from the River Anker in the northern region of the Site.

As part of the Brookbanks Consulting Ltd FRA (2015), the River Anker, and the Innage Brook and Merevale Brook tributaries were modelled in further detail within an InfoWorks ICM hydraulic model for the 1% AP and 0.1% AP events. These models were re-run for this Technical Note in 2019 with allowances for climate change (+30% flow and +50% flow) on the 1% AP event (Flood Zone 3+CC). The resultant modelled flood extents are illustrated in Appendix C, Figure C-4. These illustrate that approximately 80% of the Site is located outside of the 1% AP (Flood Zone 3) +50% CC event flood extent (<0.1% AP event, ‘low risk’), except for alongside the Innage Brook and Merevale Brook corridors in the eastern and north-western corner respectively that are located within the ‘medium risk’ (>=0.1% AP event, Flood Zone 2) flood extent. The modelling illustrates very limited flooding along Innage Brook and the southern extent of Merevale Book.

Flood depths within the extent of Flood Zone 3 +50%CC (see Appendix C, Figure C-5) range up to 0.8 m; the deepest along the northern boundary. The flood hazard classifications within this flood extent range from ‘Danger for Some’ to ‘Danger to All’ (see Appendix C, Figure C-6).

Land (Pluvial) The Environment Agency’s updated ‘Flood Map for Surface Water’ (uFMfSW) (see Appendix B, Figure

B2A) illustrates that the majority of the land throughout the site is at a very low risk (<0.1% AP event) of surface water flooding.

There are however areas of low risk (<1% to 0.1% AP event) of surface water flooding across the central


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and northern areas to the west of Old Holly Lane, and in the northern area east of Old Holly Lane. This risk increases across a broader area from medium risk (>=1% AP to 3.3% AP event) to high risk (>3.33% AP event) to the south of Alder Mill Business Park and Old Holly Lane, ponding at lower ground levels. Areas of high risk also follow the watercourse centrelines of Innage Brook and Merevale Brook.

The Brookbanks Consulting Ltd FRA also highlights a low risk of surface water flooding resulting from overland flow associated with poor infiltration of precipitation and/or inadequate drainage system capacity during intense rainfall events, but concludes that there is no substantial risk of an overland mechanism affecting the Site as it is elevated at higher ground levels in comparison to the surrounding land use.

Groundwater Figure B3A illustrates the Environment Agency’s Areas Susceptible to Groundwater Flooding (AStGWF)

map (identifying the percentage of each 1 km grid square that may be susceptible to groundwater emergence, but not the probability of it occurring or by what magnitude).

The region of the Site north of the nurseries is located within a 1 km grid square of which >=75% of its area is considered susceptible to groundwater emergence. Within and south of the nurseries, and towards the south-eastern extent of Whittington Lane, the Site is located within a 1 km grid square of which >+50% <75% of its area is considered susceptible to groundwater emergence. However, the Brookbanks Consulting Ltd FRA stated that there is a low risk of groundwater flooding at the Site due to the underlying geology comprising low permeability.

Sewers (Pluvial)

Historical total reported sewer flooding incident records from Severn Trent Water (DG5 2003-2013) were reviewed and are presented in Figure B4A in Appendix B. The DG5 register simply indicates areas reported to ST that have experienced flooding as a result of insufficient hydraulic capacity in the sewer network. but does not indicate areas or properties at risk of future flooding.

This illustrates that there have been no reported incidents of flooding from sewers within the postcode within which Site H1 is located.

Artificial Sources

Site H1 is not considered to be at risk of flooding from overtopping of the Coventry Canal as it is located a considerable distance to the south (510 m) and is not elevated at significantly lower ground levels than the canal.

The Environment Agency’s ‘Risk of Flooding from Reservoirs’ map illustrates that a large proportion of the eastern and northern Site H1 alongside the Innage Brook corridor, and a smaller area within the south western region of the Site are inundated by the maximum modelled flood extents resulting from a reservoir breach failure. The nearest reservoirs are Merevale Lake located 2 km upstream, and Hartshill Hays Lake located 4 km upstream.

Flood Defence Infrastructure

There are no formal fluvial flood defences alongside or in the near vicinity of Site H1.

Residual Flood Risk

There are no flood defences within close proximity to Site H1, so there is not considered to be any residual risk of flooding from defence breach failure at Site H1.

The Coventry Canal is not elevated on any embankment at higher levels than the ground within Site H1, so it is not considered to pose a residual risk of flooding to the Site resulting from canal breach failure.

Reservoir breach failure is considered to pose a considerable residual risk of flooding to Site H1.

Recommendations and Policies

Area A of Site H3 has been designated as the area of the Site located entirely within Flood Zone 1. The remaining area of the Site, designated Area B is the area of the Site located within modelled Flood Zone 2 (<1% AP to >=0.1% AP event, ‘medium risk’) and Flood Zone 3+CC (>=1% AP +30% CC, ‘high risk’). No land raising or built development is permitted inside the modelled Flood Zone 3+CC flood extent.

The proposed open and green space is classified by the NPPF PPG as a ‘water-compatible’ development, and retaining this open space/recreation area will enable a ‘blue corridor’ alongside the Innage Brook that will prevent a net loss of floodplain storage, will not impede water flows and will not increase flood risk elsewhere. It is considered to be operational and safe for users in times of flood however it is therefore advised that any property construction within Area A should be a reasonable distance away from the perimeter of Area B.

As the area is primarily agricultural land, any development within the area will increase surface water runoff (unless attenuated). A surface water management framework should be adopted by the developer as part of a masterplan to reduce surface water runoff to runoff rates and volumes as required by the Environment Agency and the LLFA (WCC), and as such prevent any resultant increase in flood risk posed to downstream. When the site is developed, as per NPPF guidance, SuDS should mimic the natural drainage mechanism in the local area particularly due to the associated high surface water flood risk at the northern region of the Site. The Environment Agency advice indicates a presumption in favour of infiltration SuDS techniques being used wherever possible.

It is recommended that development does not encroach within a minimum of 8 m of the watercourse banks (the by-law distance for maintenance access along Ordinary Watercourses at the discretion of the LLFA (WCC)). It is recommended that WCC and NWBC stakeholders should be contacted during the undertaking of an FRA to determine their requirements for any margin for maintenance either side of the local Ordinary Watercourses. This would be beneficial in terms of flood risk, wildlife habitat and amenity potential.

Site Specific FRA Guidance


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The developer should take into account the impact of the latest climate change allowances on all possible sources of flooding as part of a detailed Level 3 FRA for development proposals at the Site.

Appropriate mitigation measures would then need to be agreed with the Environment Agency and incorporated to protect ‘More Vulnerable’ residential development, for example minimum floor levels above the local 1% AP +30% CC maximum modelled flood level.

Within the modelled extents of modelled Flood Zone 3 +30% CC (1% AP), any proposed building or landscaping earthworks should not increase the risk of flooding to surrounding areas (i.e. if land is to be raised, flood volume compensation on a ‘level for level’ and ‘volume for volume’ basis will be required elsewhere within the site boundary within a lower risk Flood Zone).

A site-specific FRA will be required to address surface water management for any development which exceeds 1 Ha applying consideration of surface water management options. It will be necessary as part of a site-specific FRA to quantify the volumes of surface water runoff to be discharged (subject to consultation with the LLFA (WCC) and the Environment Agency), and the suitability of the SuDS techniques taking into account the site geology and soils to be incorporated to reduce the risk posed should be demonstrated if deemed appropriate.

A site-specific FRA should also demonstrate suitable provision for dry site access and egress, taking into account any requirements of the North Warwickshire emergency plan.

An agreement in principle from ST that foul drainage from the site will be accepted into their network should be obtained as part of any planning application for the site.

A site-specific FRA should consider the likelihood and impact of groundwater emergence. To investigate this and further understand SuDS suitability, the FRA should be informed by a suitable site GI.


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4. Assessment of Strategic Site H2 Table 4-9: Assessment of Strategic Site H2

Site Information

Site Area 71.2 Ha


Topography

The existing land use at Site H2 is rural, agricultural open space. Whittingham Farm and Whitley Farm are located within the central eastern region of the site.

The site topography is varied; the lowest ground levels of 69 mAOD are located along the northern boundary. The highest ground levels within the Site are located is towards the eastern boundary at 82.0 mAOD.

Proposed Use and Vulnerability

Classification

Land use proposals for Site H2 include a residential development (1280 new homes) which is classified in Table 2 of the NPPF PPG as ‘More Vulnerable’ development.





Rivers (Fluvial) The River Anker flows in a westerly direction alongside the northern boundary of the site, located

approximately 0.3 km away at its nearest point as illustrated in Figure 1-1. Merevale Brook, a tributary of the River Anker flows northwards towards its confluence with the Anker, along the north-eastern boundary of the Site. Three un-named Ordinary Watercourse (land drains) tributaries of the River Anker flow north-westwards through the northern region of site.

The Environment Agency’s Historical Flood Map (see Figure B5A at Appendix B) illustrates no records of Site H2 to have flooded from the River Anker. It does not however include any records of flooding from Merevale Brook or the three un-named Ordinary Watercourse (land drain) tributaries of the River Anker.

The Environment Agency’s’ Flood Map for Planning’ (see Appendix B, Figure B1A) illustrates that the majority of the Site is at ‘low risk’ (<0.1% AP event) of fluvial flooding, and approximately one fifth of the Site in the north-eastern region is at ‘medium risk’ (>=0.1% AP event) of fluvial flooding along the corridors of Merevale Brook and from the River Anker.

Area A of Site H2 has been designated as the area of the Site located entirely within Flood Zone 1. Area B of Site H2 has been designated as the area of the Site located within Flood Zone 2 (<1% AP to >=0.1% AP event, ‘medium risk’) and Flood Zone 3+CC (>=1% AP +30% CC, ‘high risk’).

As part of the Brookbanks Consulting Ltd FRA (2015), the River Anker and Merevale Brook tributary were modelled in further detail within an InfoWorks ICM hydraulic model for the 1% AP and 0.1% AP events. These models were re-run for this Technical Note in 2019 with allowances for climate change (+30% flow and +50% flow) on the 1% AP event (Flood Zone 3+CC). The resultant modelled flood extents are illustrated in Appendix C, Figure C-5. These illustrate that the entire Site is located outside of the 1% AP (Flood Zone 3) +50% CC event flood extent (within Flood Zone 1, <0.1% AP event, ‘low risk’), except for only a small area in the north-eastern corner is located within the ‘medium risk’ (>=0.1% AP event, Flood Zone 2 flood extent. The modelling illustrates very limited flooding along the southern extent of Merevale Book.

It is noted however that modelling has not yet been undertaken for the three un-named Ordinary Watercourse (land drain) tributaries of the River Anker. There may be a risk of flooding from these sources and planning policies have been developed below to address this.

Land (Pluvial) The Environment Agency’s updated ‘Flood Map for Surface Water’ (uFMfSW) (see Appendix B,

Figure B2A) illustrates that the majority of the land throughout the site is at a very low risk (<0.1% AP event) of surface water flooding.

There are however areas of low risk (<1% to 0.1% AP event), medium risk (>=1% AP to 3.3% AP event) and high risk (>3.33% AP event) of surface water flooding following the watercourse centrelines of Merevale Brook and the floodplain of the largest un-named Ordinary Watercourse (land drain) tributary of the River Anker flowing northwards in the central and south-western regions of the Site. The risk of surface water flooding is considered the most extensive along this tributary to the south-west of the Coventry Canal.

Additional minor areas of low-medium risk are located along the other two un-named Ordinary Watercourses (land drains) tributaries of the River Anker flowing northwards in the central-northern


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region of the Site, and along the access road through and within eastern fields of Whitley Farm.

Groundwater Figure B2A illustrates the Environment Agency’s Areas Susceptible to Groundwater Flooding

(AStGWF) map (identifying the percentage of each 1 km grid square that may be susceptible to groundwater emergence, but not the probability of it occurring or by what magnitude).

This illustrates that the majority of the land throughout the Site are located within 1 km grid squares of which >=25%<50% of its area is considered susceptibility to groundwater emergence. The eastern region of the Site north east of Whitley Farm is located within a 1 km grid square of which >=75% of its area is considered susceptible to groundwater emergence.

Sewers (Pluvial) Historical total reported sewer flooding incident records from Severn Trent Water (DG5 2003-2013)

were reviewed and are presented in Figure B4A in Appendix B. The DG5 register simply indicates areas reported to ST that have experienced flooding as a result of insufficient hydraulic capacity in the sewer network. but does not indicate areas or properties at risk of future flooding.

This illustrates that the south-eastern extent of Site H2 is located within a postcode area that has had 15-20 reports of historical sewer flooding incidents.

Artificial Sources Site H2 is considered to be potentially at risk of flooding from overtopping of the Coventry Canal as it

stretches from north west to south east through the western region of the Site. The Environment Agency’s ‘Risk of Flooding from Reservoirs’ map illustrates that the majority of the

site is not located within the maximum modelled flood extent of reservoir flooding that could result from breach failure. However, a small area in the southern region of the Site, to the west of Whittington Lane and Merevale Brook is located within the maximum extent of flooding from reservoirs due to breach failure. The nearest reservoirs are Merevale Lake located 1.5 km upstream of the Site.


There are no formal fluvial flood defences alongside or in the near vicinity of Site H2.

Residual Flood Risk


The Coventry Canal is not elevated on any embankment at higher levels than the ground immediately adjacent within Site H2, so it is not considered to pose a residual risk of flooding to the Site resulting from canal breach failure.

A small area in the southern region of Site H2 is considered to potentially be at a residual risk of flooding resulting from reservoir breach failure.


Area A of Site H3 has been designated as the area of the Site located entirely within Flood Zone 1. The remaining area of the Site, designated Area B is the area of the Site located within the modelled Flood Zone 2 (<1% AP to >=0.1% AP event, ‘medium risk’) and Flood Zone 3+CC (>=1% AP +30% CC, ‘high risk’). No land raising or built development is permitted inside the modelled Flood Zone 3+CC flood extent.

The proposed open and green space is classified by the NPPF PPG as a ‘water-compatible’ development, and retaining this open space/recreation area will enable a ‘blue corridor’ alongside the Innage Brook that will prevent a net loss of floodplain storage, will not impede water flows and will not increase flood risk elsewhere. It is considered to be operational and safe for users in times of flood however it is therefore advised that any property construction within Area A should be a reasonable distance away from the perimeter of Area B.

As the area is primarily agricultural land, any development within the area will increase surface water runoff (unless attenuated). A surface water management framework should be adopted by the developer as part of a masterplan to reduce surface water runoff rates and volumes from the developed site as required by the Environment Agency and the LLFA (WCC), and as such prevent any resultant increase in flood risk posed to downstream. When the site is developed, as per NPPF guidance, SuDS should mimic the natural drainage mechanism in the local area particularly due to the associated high surface water flood risk at the northern region of the Site. Infiltration is part of the natural drainage process. The Environment Agency advice indicates a presumption in favour of infiltration SuDS techniques being used wherever possible.

It is recommended that development does not encroach within a minimum of 8 m of the watercourse banks (the by-law distance for maintenance access along Ordinary Watercourses at the discretion of the LLFA (WCC)). It is recommended that WCC and NWBC stakeholders should be contacted during the undertaking of an FRA to determine their requirements for any margin for maintenance either side of the local Ordinary Watercourses. This would be beneficial in terms of flood risk, wildlife habitat and amenity potential. This by-law should also be applied to Coventry Canal (although this is not a Main River, it is recommended that developers contact the Canal and River Trust).



A site-specific FRA will be required to address surface water management for any development which exceeds 1 Ha applying consideration of surface water management options. It will be necessary as part of a site-specific FRA to quantify the volumes of surface water runoff to be discharged (subject to consultation with the LLFA (WCC) and the Environment


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Agency), and the suitability of the SuDS techniques taking into account the site geology and soils to be incorporated to reduce the risk posed should be demonstrated if deemed appropriate.





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5. Assessment of Strategic Site H3 Table 5-10: Assessment of Strategic Site H3

Site Information

Site Area 2.2 Ha


Topography

The site topography has gentle slope westwards from its highest elevation of 77.5 mAOD in the southern region towards the eastern/right bank of Innage Brook at 74.5 m AOD, Higher ground level of 76.5 are located in the norther region of the Site.

The site is owned by NWBC and is currently leased as a football pitch.


Classification

Land use proposals for Site H3 reserve allocation include a residential development (potentially 53 new homes) which is classified in Table 2 of the NPPF PPG as ‘More Vulnerable’ development.





Rivers (Fluvial) Innage Brook flows in a north-easterly direction approximately 100 m to the west of the western

boundary of Site H3 towards the River Anker. The Environment Agency’s Historical Flood Map (see Figure B5A at Appendix B) illustrates no

records of Site H3 to have flooded from the River Anker. It does not however include any records of flooding from Innage Brook.

The Environment Agency’s ‘Flood Map for Planning’ (see Appendix B, Figure B1A) illustrates that the central and north-western areas of the site are located within Flood Zone 3 (>=1% AP event,’ high risk’ of fluvial flooding). Flood Zone 2 (<1% AP to >=0.1% AP event, ‘medium risk’ of fluvial flooding) extends slightly further out around the outer edges of Flood Zone 3. Approximately 65% of the Site is in Flood Zone 1 (<0.1% AP event, ‘low risk’ of fluvial flooding).

A review of the Site topography (see Figure C2 at Appendix C and Figure D3 at Appendix D) concluded that if more detailed modelling was undertaken, and it was to demonstrate water levels increases of, for example only 0.5 m during a <1%AP to >=0.1% AP event, there is the potential for floodwater to spread further out across the central region of the Site due to the shallow gradient here. Areas in the far northern, southern and eastern regions of the Site would be less susceptible to any increases in flooding. The hydrological modelling exercise (Appendix A) determined that the 1% AP event +30%/50% CC flows would not exceed the 0.1% AP event flows however.

The low resolution JFLOW derived Flood Zone 2 outlines in the current ‘Flood Map for Planning’ along this reach of Innage Brook are therefore to be used by NWBC as a proxy for the latest climate change allowance at this Site in the absence of this more detailed modelling until it becomes available as part of a Level 3 FRA undertaken to support planning applications within the Site.

Land (Pluvial) The Environment Agency’s updated 'Flood Map for Surface Water’ (see Appendix B, Figure B2A)

illustrates that approximately half of the Site has a very low risk (<0.1% AP event) of surface water flooding coinciding with higher ground levels around the southern, eastern and northern extents.

The central and north-western areas, small pockets alongside Gypsy Lane at the southern boundary and along Sheepy Road to the east, are illustrated as having a low risk (<1% AP to 0.1% AP event) of surface water flooding.

An area in the central northern region of the Site coinciding with the lowest ground levels is illustrated as being at medium risk (>=1% AP event) increasing to a high risk (>3.3% AP event) of surface water flooding.



The entire Site is located within a 1 km grid square of which >=50% to <75% of its area is considered susceptible to groundwater emergence.


were reviewed and are presented in Figure B4A in Appendix B. The DG5 register simply indicates areas reported to ST that have experienced flooding as a result of insufficient hydraulic capacity in


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the sewer network. but does not indicate areas or properties at risk of future flooding. This illustrates that there have been no reported incidents of flooding from sewers within the

postcode within which Site H3 is located.

Artificial Sources Site H3 is not considered to be at risk of flooding from overtopping of the Coventry Canal as it is

located a considerable distance away (590 m) and is not elevated at lower ground levels than the canal.

The Environment Agency’s ‘Risk of Flooding from Reservoirs’ map illustrates that Site H3 is almost entirely inundated by the maximum modelled flood extents resulting from a reservoir breach failure. The nearest reservoir is Merevale Lake located 1.8 km upstream of the Site.


There are no formal fluvial flood defences alongside or in the vicinity of Site H3.

Residual Flood Risk

There are no flood defences within close proximity to the site. Therefore, there is not considered to be any residual risk of flooding from defence breach failure at Site H3.

The Coventry Canal is not elevated on any embankment at higher levels than the ground within Site H3, so it is not considered to pose a residual risk of flooding to the Site resulting from canal breach failure.

Reservoir breach failure is considered to pose a considerable residual risk of flooding to the majority of Site H3.


Area A of Site H3 has been designated as the area of the Site located entirely within Flood Zone 1. Area B of Site H3 has been designated as the area of the Site located within Flood Zone 2 (<1% AP to >=0.1% AP event, ‘medium risk’) and Flood Zone 3+CC (>=1% AP +30% CC, ‘high risk’). No land raising or built development is permitted inside the modelled Flood Zone 3+CC flood extent. As the proposed number and density of residential land use (as part of the reserve allocation) is expected to be small, the Site is still considered suitable for investigating further for development of this as part of a detailed planning application.

These Flood Zones however, should be refined/determined in more detail with more accuracy by higher resolution hydraulic modelling as part of a site specific Level 3 FRA to support any future planning applications within the Site, and the extents of Area A and Area B should be refined with results of such modelling.

No land raising or built development is permitted inside the extent of modelled Flood Zone 3+CC region of the Site without provision of compensatory floodplain storage volume being accommodated elsewhere in the site on a ‘level for level’, ‘volume for volume’ basis as required by the NPPF PPG. This could maintain a ‘blue corridor’ providing public open space/recreation area alongside Merevale Brook that will prevent a net loss of floodplain storage, will not impede water flows and will not increase flood risk elsewhere.

There is the potential for redistribution of ground levels within this Site and possibilities for safe access and egress to/from the Site via Sheepy Road to the east and Gypsy Lane to the south. A detailed FRA should consider these routes in relation to emergency evacuation from the Site in case of a major flood event.

As the area is primarily green space for a football pitch, any development within the area will increase surface water runoff (unless attenuated). A surface water management framework should be adopted as part of a masterplan to reduce surface water runoff to greenfield runoff rates and volumes from the developed site as required by the Environment Agency, and as such prevent any resultant increase in flood risk posed to downstream. The NPPF states that SuDS should, where possible, mimic the natural drainage mechanism of an area. Infiltration is part of the natural drainage process. The Environment Agency advice indicates a presumption in favour of infiltration SuDS techniques being used wherever possible.




Once detailed modelling as part of a detailed Level 3 FRA is completed, should future development pressure and other sustainability objectives create the need to develop within the modelled Flood Zone 3 +50% CC (1% AP) envelope, then in accordance with the requirements of the NPPF PPG, evidence from the hydraulic modelling will be required to demonstrate to NWBC, the LLFA (Warwickshire County Council) and the Environment Agency its suitability on the basis of fluvial flood risk (i.e. consideration of maximum depths, velocities and hazard) to satisfy the requirements of the Exception Test.

Appropriate mitigation measures would then need to be agreed with the Environment Agency and incorporated to protect ‘More Vulnerable’ residential development, for example minimum floor levels to adopt above the local 1% AP +50% CC maximum modelled flood level.

Within the modelled extents of Flood Zone 3 +50% CC (1% AP event), any proposed building or landscaping earthworks should not increase the risk of flooding to surrounding areas (i.e. if land is to be raised, flood volume compensation on a


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‘level for level’ and ‘volume for volume’ basis will be required elsewhere within the site boundary within a lower risk Flood Zone).


A site-specific FRA will be required to address surface water management for any development which exceeds 1 Ha applying consideration of surface water management options. It will be necessary as part of a site-specific FRA to quantify the volumes of surface water runoff to be discharged (subject to consultation with the LLFA (WCC) and/or Environment Agency), and the suitability of the SuDS techniques to be incorporated to reduce the risk posed should be demonstrated.




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6. Assessment of Strategic Site E1 Table 6-11: Assessment of Strategic Site E1

Site Information

Site Area 6.1 Ha


Topography

The site topography slopes in an easterly direction gently towards the south- eastern extents. The highest ground level is 83.5 AOD located in the north-west corner, and the lowest level is alongside the banks of Innage Brook at a level of 74.5 mAOD.

The Site land use currently comprises an industrial estate.

Proposed Use and

Vulnerability Classification

Employment land uses proposed within Site E1 include warehousing and offices and car parking which are classified by Table 2 of the NPPF PPG as ‘Less Vulnerable’ development.





Rivers (Fluvial) The Environment Agency’s Historical Flood Map (see Figure B5A at Appendix B) illustrates no records

of Site E1 to have flooded from the River Anker. It does not however include any records of flooding from Innage Brook.

The Environment Agency’s ‘Flood Map for Planning’ (see Appendix B, Figure B1A) illustrates that the central and north-western areas of the Site are located within Flood Zone 1 (<0.1% AP event, ‘low risk’). The eastern region of the Site, approximately 25% is located within Flood Zone 3 (>=1% AP event,’ high risk’ of fluvial flooding). Flood Zone 2 (<1% AP to >=0.1% AP event, ‘medium risk’ of fluvial flooding) extends slightly further out around the outer edges of Flood Zone 3; further on the eastern side.

A review of the Site topography (see Figure C1 at Appendix C and Figure D1 and D2 at Appendix D) concluded that if more detailed modelling was undertaken, and it was to demonstrate water levels increases of, for example only 0.5 m during a <1%AP to >=0.1% AP event, there is the potential for floodwater to spread slightly further out eastwards across the far eastern region of the Site due to the shallow gradient here, but the higher elevated areas in the western regions of the Site would be much less susceptible to any increases in flooding. Predominantly lower ground levels across the opposite bank of Innage Brook would encourage such floodwater north-eastwards away from the site in preference.

The hydrological modelling exercise (Appendix A) determined that the 1% AP event +30%/50% CC flows would not exceed the 0.1% AP event flows however.

The low resolution JFLOW derived Flood Zone 2 outlines in the current ‘Flood Map for Planning’ along this reach of Innage Brook are therefore to be used by NWBC as a proxy for the latest climate change allowance at this Site in the absence of this more detailed modelling until it becomes available as part of a Level 3 FRA undertaken to support planning applications within the Site.

Land (Pluvial) The Environment Agency’s updated 'Flood Map for Surface Water’ on their website (see Appendix B,

Figure B2A) illustrates that the majority of the Site has a very low risk (<0.1% AP event) of surface water flooding.

The eastern and northern areas of the Site are illustrated as having a low risk (<1% AP to 0.1% AP event) of surface water flooding, increasing to medium risk (>=1% AP to 3.3% AP event) proceeding closer to the banks of Innage Brook, and high risk (>3.3% AP event) along the centreline Innage Brook.



The entire Site is located within a 1 km grid square of which >=50% to <75% of its area is considered susceptible to groundwater emergence.

Sewers (Pluvial)

Historical total reported sewer flooding incident records from Severn Trent Water (DG5 2003-2013) were reviewed and are presented in Figure B4A in Appendix B. The DG5 register simply indicates areas reported to ST that have experienced flooding as a result of insufficient hydraulic capacity in the sewer network. but does not indicate areas or properties at risk of future flooding.


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This illustrates that the majority of Site E1 is located within a postcode area that has had 15-20 historical sewer flooding incidents reported, with the exception of the north-eastern extent which is located within a postcode area that has no reported incidents of sewer flooding.

Artificial Sources

Site E1 is not considered to be at risk of flooding from overtopping of the Coventry Canal as it is located a considerable distance away (350 m) and is not elevated at significantly lower ground levels than the canal.

The Environment Agency’s ‘Risk of Flooding from Reservoirs’ map illustrates that the lower elevated eastern region of Site E1 in is inundated by the maximum modelled flood extents resulting from a reservoir breach failure. The nearest reservoir is Merevale Lake located 1.5 km upstream of the Site.


There are no formal fluvial flood defences alongside or in the vicinity of Site E1.

Residual Flood Risk

There are no flood defences within close proximity to Site E1, so there is not considered to be any residual risk of flooding from defence breach failure at Site E1.

The Coventry Canal is not elevated on any embankment at higher levels than the ground within Site E1, so it is not considered to pose a residual risk of flooding to the Site resulting from canal breach failure.

Reservoir breach failure is considered to pose a residual risk of flooding to a small area in eastern region of Site E1.


Area A of Site H3 has been designated as the area of the Site located entirely within Flood Zone 1. Area B of Site H3 has been designated as the area of the Site located within Flood Zone 2 (<1% AP to >=0.1% AP event, ‘medium risk’) and Flood Zone 3+CC (>=1% AP +30% CC, ‘high risk’). No land raising or built development is permitted inside the modelled Flood Zone 3+CC flood extent.

These Flood Zones however, should be refined/determined in more detail with more accuracy by higher resolution hydraulic modelling as part of a site specific Level 3 FRA to support any future planning applications within the Site, and the extents of Area A and Area B should be refined with results of such modelling.

No land raising or built development is permitted inside the extent of modelled Flood Zone 3+CC region of the Site without provision of compensatory floodplain storage volume being accommodated elsewhere in the site on a ‘level for level’, ‘volume for volume’ basis as required by the NPPF PPG.

There are possibilities for safe access and egress to/from the Site via Rowalnds Way to the north, Holly Lane to the west and Abeles Way to the south. A detailed FRA should consider these routes in relation to emergency evacuation from the Site in case of a major flood event.

The Site is primarily an industrial estate. Any development within the area will potentially increase surface water runoff (unless attenuated). A surface water management framework should be adopted as part of a masterplan to reduce surface water runoff to greenfield runoff rates and volumes from the developed site as required by the Environment Agency, and LLFA (WCC) and as such prevent any resultant increase in flood risk posed to downstream. The NPPF states that SuDS should, where possible, mimic the natural drainage mechanism of an area. Infiltration is part of the natural drainage process. The Environment Agency advice indicates a presumption in favour of infiltration SuDS techniques being used wherever possible.




Once detailed modelling as part of a detailed Level 3 FRA is completed, should future development pressure and other sustainability objectives create the need to develop within the modelled Flood Zone 3 +30% CC (1% AP) envelope, then in accordance with the requirements of the NPPF PPG, evidence from the hydraulic modelling will be required to demonstrate to NWBC, the LLFA (Warwickshire County Council) and the Environment Agency its suitability on the basis of fluvial flood risk (i.e. consideration of maximum depths, velocities and hazard) to satisfy the requirements of the Exception Test.

Appropriate mitigation measures would then need to be agreed with the Environment Agency and incorporated to protect ‘More Vulnerable’ residential development, for example minimum floor levels above the local 1% AP +30% CC maximum modelled flood level.

Within the modelled extents of Flood Zone 3 +30% CC (1% AP), any proposed building or landscaping earthworks should not increase the risk of flooding to surrounding areas (i.e. if land is to be raised, flood volume compensation on a ‘level for level’ and ‘volume for volume’ basis will be required elsewhere within the site boundary within a lower risk Flood Zone).

A site-specific FRA will be required to address surface water management for any development which exceeds 1 Ha applying consideration of surface water management options. It will be necessary as part of a site-specific FRA to quantify the volumes of surface water runoff to be discharged (subject to consultation with the LLFA (WCC) and the


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Environment Agency), and the suitability of the SuDS techniques taking into account the site geology and soils to be incorporated to reduce the risk posed should be demonstrated if deemed appropriate.





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7. Assessment at Strategic Site H14 Table 7-12: Assessment of Strategic Site H14

Site Information

Site Area 6.7 Ha


Topography

The site topography slopes from the highest ground level of 113.25 m AOD at the southern extent of the Site towards Lindridge Brook alongside the north-western boundary at 91.75 m AOD. The gradient of the Site rises sharply from 96 mAOD away from the watercourse towards the south east.

The Site is existing green open space and is enclosed by Lindridge Road to the south, Lindridge Brook to the west and the A38 to the east.


Classification

Land use proposals for Site H14 include a residential development (141 new homes) which is classified in Table 2 of the NPPF PPG as ‘More Vulnerable’ development.





Rivers (Fluvial) The Environment Agency’s Historical Flood Map illustrates no records of flooding at the site (see

Appendix B, Figure B.5). The Environment Agency’s ‘Flood Map for Planning’ (see Appendix B, Figure B1B) illustrates that

western boundary of the Site is bordered by Flood Zone 2 (<1% AP to >=0.1% AP event, ‘medium risk’ of fluvial flooding) and Flood Zone 3 (>=1% AP event,’ high risk’ of fluvial flooding. The entire Site however is located within Flood Zone 1 (<0.1% AP event, ‘low risk’).

A review of the Site topography (see Figure C2 at Appendix C and Figure D4, D5 and D6 at Appendix D) concluded that if more detailed modelling was undertaken, and it was to demonstrate water levels increases of, for example only 0.5 m during a <1%AP to >=0.1% AP event, there is the potential for floodwater to spread slightly further out south-eastwards across the far northern region of the Site due to the shallow gradient here. The higher elevated areas in the central and southern regions of the Site would be much less susceptible to any increases in flooding, and even lower ground levels across the opposite bank of Innage Brook would encourage such floodwater north-eastwards away from the site in preference.

The hydrological modelling exercise (Appendix A) determined that the 1% AP event +30%/50% CC flows would not exceed the 0.1% AP event flows however.

The low resolution JFLOW Flood Zone 2 outlines in the current Flood Map for Planning are therefore to be used by NWBC as a proxy for the latest climate change allowance at this Site in the absence of this more detailed modelling until it becomes available as part of a Level 3 FRA undertaken to support planning applications within the Site.

Land (Pluvial) The Environment Agency’s updated 'Flood Map for Surface Water’ on their website (see Appendix B,

Figure B2B) illustrates that a the majority of the Site has a very low risk (<0.1% AP event) of surface water flooding coinciding with the highest ground levels in the central and southern extents.

The northern and north-western areas of the Site are illustrated as having a low risk (<1% AP to 0.1% AP event) of surface water flooding, increasing to medium risk (>=1% AP to 3.3% AP event) and high risk (>3.3% AP event) proceeding closer to the right bank of Lindridge Brook.

Groundwater Figure B3B illustrates the Environment Agency’s ‘Areas Susceptible to Groundwater Flooding’


The entire Site is located within a 1 km grid square of which <25% of its area is considered susceptible to groundwater emergence.


were reviewed and are presented in Figure B4B in Appendix B. The DG5 register simply indicates areas reported to ST that have experienced flooding as a result of insufficient hydraulic capacity in the sewer network. but does not indicate areas or properties at risk of future flooding.

This illustrates that there have been no reported incidents of flooding from sewers within the postcode within which Site H14 is located.


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Artificial Sources Site H14 is not located in near vicinity of any canal, so is therefore not considered to be at risk of

flooding from overtopping of any canals. The Environment Agency’s ‘Risk of Flooding from Reservoirs’ map illustrates that Site H14 is not

located within the maximum modelled flood extent of a reservoir breach, however,


There are no formal fluvial flood defences alongside or in the vicinity of Site H14.

Residual Flood Risk


Site H14 is not located in near vicinity of any canal, so is therefore not considered to be at risk of flooding from breach failure of any canals. not considered at risk from reservoir flooding.

Langley Pool and Lindridge Pool are impounded bodies of water located 270 m and 560 m to the north west respectively along Lindridge Brook. These waterbodies were not included within the scope of the Environment Agency’s ‘Risk of Flooding from Reservoirs’ breach modelling study (it is assumed due to being <10,000 m3 in capacity), but if these dams were to experience breach failure, it is considered possible that due to their close proximity, the flood extents would follow the local topography and proceed towards Site H14 and inundate the lower ground levels within in the northern region of the Site boundary.


The Site is currently located entirely within Flood Zone 1. Once detailed modelling as part of a detailed Level 3 FRA is completed, should the Flood Zones be found to extend further into the Site than currently mapped, then any future development pressure and other sustainability objectives create the need to develop within the modelled Flood Zone 3 +30% CC (1% AP) envelope, then in accordance with the requirements of the NPPF PPG, evidence from the hydraulic modelling will be required to demonstrate to NWBC, the LLFA (Warwickshire County Council) and the Environment Agency its suitability on the basis of fluvial flood risk (i.e. consideration of maximum depths, velocities and hazard) to satisfy the requirements of the Exception Test.

No land raising or built development is permitted inside the combined modelled Flood Zone 2 (applied as a proxy for Flood Zone 3 +CC) which extends into the northern region of the Site. This could maintain a ‘blue corridor’ providing public open space/recreation area alongside Lindridge Brook that will prevent a net loss of floodplain storage, will not impede water flows and will not increase flood risk elsewhere.

As the area is primarily agricultural land, any development within the area will increase surface water runoff (unless attenuated). A surface water management framework should be adopted by the developer as part of a masterplan to reduce surface water runoff to rates and volumes as required by the Environment Agency and the LLFA (WCC), and as such prevent any resultant increase in flood risk posed to downstream. When the site is developed, as per NPPF guidance, SuDS should mimic the natural drainage mechanism in the local area particularly due to the associated high surface water flood risk at the northern region of the Site. Infiltration is part of the natural drainage process. The Environment Agency advice indicates a presumption in favour of infiltration SuDS techniques being used wherever possible.




A site-specific FRA will be required to address surface water management for any development which exceeds 1 Ha applying consideration of surface water management options. It will be necessary as part of a site-specific FRA to quantify the volumes of surface water runoff to be discharged (subject to consultation with the LLFA (WCC) and the Environment Agency), and the suitability of the SuDS techniques taking into account the site geology and soils to be incorporated to reduce the risk posed should be demonstrated if deemed appropriate.



A site-specific FRA should consider the likelihood and impact of groundwater emergence. To investigate this and further understand SuDS suitability, the FRA should be informed by a suitable site GI


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8. Summary The Environment Agency has requested a more robust assessment of all sources of flood risk at the sites to provide confidence that the proposed land uses at the five Site Specific Flood Risk Technical Note sites are likely to be deliverable, in respect to climate change. The aim of this Site Specific Flood Risk Technical Note, therefore, is to provide a clarification of the flood risk posed to the five potential allocation sites, resulting from potential climate change. The Environment Agency’s 2015 climate change allowances have been taken into account in the current modelled flood extents of adjacent watercourses.

The findings of this assessment are presented in flood maps(Appendix B) and in site specific assessment tables (above). Recommendations and policies have been presented in the above tables for each of the five sites put forward for allocation from NWBC.

It is recommended that this Site Specific Flood Risk Technical Note should be read in parallel with the NWBC’s Local Plan (AECOM, March 2018)). These reports accompany each other and give supplementary information for site developers.


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Appendix A – Hydrological & Hydraulic AnalysisTo inform this Flood Risk technical Note, a new InfoWorks ICM modelling exercise was conducted for the River Anker, Innage Brook and Merevale Brook in the vicinity of Sites H1 and H2 based upon an existing hydraulic model produced by Brookbanks Consulting Ltd to support a site specific FRA to support a planning application (ref. PAP/2014/0540) for development within Site H1.

The following key documentation was reviewed:

Land at Atherstone – Flood Study Report (produced by Brookbanks Consulting Ltd. in 2015); and

River Anker InfoWorks ICM Updated Hydraulic Model Review, Final Report (produced by AECOM as part of a peer review in January 2016).

The model geometry network (“River Anker”) and the hydrological inflow file (“JBA Inflow 100yr”) within the ICM transportable database provided by Brookbanks Consulting Ltd to AECOM in 2016 for peer review (“River Anker_update.icmt”) has been used as the basis of this Flood Risk Technical Note.

The outcome of AECOM’s peer review concluded that the network model was appropriate for the purpose of a site specific FRA to support a planning application, but AECOM provided several additional recommendations to improve the quality of the model. It is understood however that no further updates have been made to the model since January 2016, and the model was accepted by the Environment Agency following consultation as part of the planning application process.

Due to NWBC’s programme for the Local Plan independent examination, following discussions with NWBC and the Environment Agency, it was agreed that none of AECOM’s 2016 recommended model updates would be implemented for the purposes of informing this Flood Risk Technical Note.

However, considering the publication of the Environment Agency’s more recent Flow Estimation Guidelines (May 2017)12 which states that whenever possible, the Revitalised Flood Hydrograph (ReFH1) method should be compared with the updated ReFH2 method, it was agreed that sensibility checks be undertaken to determine if the hydrological inflows applied in the 2015 ICM model (ReFH1 hydrographs scaled to peaks derived by the FEH Statistical method) remained appropriate in comparison with estimates from the newer ReFH2 model (version 2.213). This model also uses newer FEH2013 rainfall depth duration frequency (DDF) model profiles. The model was also to be updated with inflows inclusive of the +30%/+50% climate change allowances on the 1% AP event.

For Sites H3, E1 and H14; in the absence of models, ReFH2 flow estimates were also calculated for Innage Brook and Lindridge Brook to establish the difference between the 1% AP +30%/+50% allowances for climate change flows, and the 0.1% AP flows. This enabled assessment of whether the 1% AP+CC scenario events would be likely to extend further across the site than the JFLOW derived Flood Zone 2 outlines (0.1% AP event) if they were to be modelled in detail.

Flow EstimationHydrological analysis was undertaken to determine peak flow estimates at six locations relative to the fluvial sources of flood risk to the five Sites. These locations were as follows:

1. the downstream extent of Site H14 along Lindridge Brook at the junction of the A38 with the M6 Toll (OSNGR 415600, 296650);

2. the upstream extent of the Brookbanks ICM model along Innage Brook (OSNGR 430600, 298800) at Rowlands Way/Holly Lane;

3. the downstream extent of Innage Brook at is confluence with the River Anker (OSNGR 430700, 299400) (applied to the upstream extent of Innage Brook in the Brookbanks ICM model);

12 Environment Agency. (May 2017). Flood Estimation Guidelines - Technical Guidance 197_0813 Wallingford HydroSolutions. 2017. Revitalised Flood Hydrograph 2 (ReFH2) version 2.2. https://www.hydrosolutions.co.uk/software/refh-2/refh2_download/


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https://www.hydrosolutions.co.uk/software/refh-2/refh2_download/


4. the downstream extent of Merevale Brook at is confluence with the River Anker (OSNGR 430250, 299600) (applied at the upstream extent of Merevale Brook in the Brookbanks ICM model at Old Holly Lane);

5. at Atherstone Bridge along the River Anker (OSNGR 430800, 299400) (applied to the upstream extent of the Brookbanks ICM model located shortly downstream of Ratcliffe Road); and

6. the downstream extent of the Brookbanks ICM model along the River Anker (OSNGR 429000, 299900) in line with Atherstone Lock on the Coventry Canal.

The catchment boundaries and catchment descriptors were exported from the FEH Web Service14. No changes were made to the catchment descriptors. The critical rainfall storm durations that produced the largest peak flows were established for each flow estimation point within the ReFH2 software for key design events with allowances for climate change. These varied from the critical durations of the ReFH1 model, however the shape of the ReFH2 hydrographs compare well with the ReFH1 hydrographs.

The ReFH2 software enables the estimation of design flood hydrographs for both rural and urbanised catchments, using the latest methods which draw on the FEH 2013 rainfall DDF model profiles. The URBEXT2000

values for all catchments were less than 0.25 and therefore, there was no need to apply the ‘urban adjustment’ method in the ReFH2. Winter storm profiles were also used instead of Summer profiles.

In the 2015 model, the ReFH1 hydrographs produced were scaled to the peak flows produced by the FEH Statistical method (hybrid approach common in hydrological modelling studies in the UK). Although the peak flows from the FEH Statistical method havenot been re-evaluated as part of this Flood Risk Technical Note, the peak flow values derived by this method would not be expected to change significantly as no major events have occurred in the River Anker since 2015, and there are no gauges on Merevale Brook or Innage Brook to provide any increased confidence in the outputs from this method.

Tables A.1 to A.3 details the results of this ReFH2 hydrological analysis for Innage Brook, Merevale Brook and the River Anker at Sites H1 and H2 in comparison with the 2015 ReFH1 flow estimates and FEH Statistical flow estimates where used, considered sufficient for comparison in light of the above to those used in the 2015 ICM model. Those calculated for the upstream extent of Innage Brook pertain to Sites E1, H3.

Table A.4 details the results of this ReFH2 hydrological analysis for Lindridge Brook at Site H14.

14 Centre for Ecology & Hydrology. (2017). Flood Estimation Handbook Web Service. https://fehweb.ceh.ac.uk/


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https://fehweb.ceh.ac.uk/


Table A.1: Hydrological Analysis – Peak Flow Estimates for Innage Brook Annual Probability (%)(1 in X Years)

Upstream Extent of Model at Holly Lane

Downstream Extent at River Anker

2019 ReFH2 2015 FEH Statistical 2015 ReFH1 2019 ReFH2

Estimated Peak Flow (m3/s)

1% (1 in 100 Year) (Flood Zone 3) 3.28 2.64 4.4

(*4.36)

3.90

1%+30% for Climate Change 4.26 3.43 5.67 5.07

1%+50% for Climate Change 4.92 3.96 6.54 5.85

0.1% (1 in 1000 Year) (Flood Zone 2) 5.81 (Not Available) 4

(*7.98)

6.83

*Calculation checked using parameters given in 2015 FEH Calculation Record

These demonstrate that the newer ReFH2 flow estimates are smaller than the ReFH1 flow estimates. Therefore, it is not considered necessary to revise the model inflows for the purposes of this Flood Risk Technical Note as they are conservative.These also demonstrate that the 1% annual probability (1 in 100 year) flow estimates including a 30%/50% allowance for climate change do not exceed the 0.1% annual probability (1 in 1000 year) flows.

Table A.2: Hydrological Analysis – Peak Flow Estimates for Merevale Brook Annual Probability (%)(1 in X Years)

Downstream Extent at River Anker

2015 FEH Statistical 2015 ReFH1 2019 ReFH2


1% (1 in 100 Year) (Flood Zone 3) 2.16 3.2

(*3.23)

3.48

1%+30% for Climate Change 2.81 4.20 4.59

1%+50% for Climate Change 3.24 4.85 5.23

0.1% (1 in 1000 Year) (Flood Zone 2) 3.14 5.9

(*5.91)

6.14

*Calculation checked using parameters given in 2015 FEH Calculation Record

These demonstrate that the newer ReFH2 flow estimates are only marginally larger than the ReFH1 flow estimates. Therefore, it is not considered necessary to revise the model inflows for the purposes of this Flood Risk Technical Note as they are closely comparable.These also demonstrate that the 1% annual probability (1 in 100 year) flow estimates including a 30%/50% allowance for climate change do not exceed the 0.1% annual probability (1 in 1000 year) flows.


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5


Table A.3: Hydrological Analysis – Peak Flow Estimates for the River Anker Annual Probability (%)(1 in X Years)

at Atherstone Road (applied at Upstream Extent of Model) Downstream Model Extent (in line with Atherstone Lock)

2015 ReFH1 2015 FEH Statistical 2019 ReFH2 2019 ReFH2


1% (1 in 100 Year) (Flood Zone 3) 113.7

(*113.51)

102.97 102.07 102.73

1%+30% for Climate Change 147.81

(*147.56)

133.87 131.69 133.56


(*170.27)

154.46 153.11 154.10

0.1% (1 in 1000 Year) (Flood Zone 2) 190.7

(*189.63)

149.80 170.34 170.97

* Calculations checked using parameters given in 2015 FEH Calculation Record

These demonstrate that the newer ReFH2 flow estimates are less than the ReFH1 and FEH Statistical flow estimates. Therefore, it is not considered necessary to revise the model inflows for the purposes of this Flood Risk Technical Note as they are more conservative.Although the inflows for 3 un-named tributaries do not appear to have been included within the ICM model inflows, the flow estimate at the model downstream extent is only marginally larger than the inflows derived at Atherstone Bridge, and are very close to the FEH Statistical derived values. An updated 1% AP peak of 124.5 m3/s was actually applied in the model, which is larger than the FEH Statistical value of 102.97 m3/s and is therefore more conservative.These also demonstrate that the 1% annual probability (1 in 100 year) flow estimates including a 30%/50% allowance for climate change do not exceed the 0.1% annual probability (1 in 1000 year) flows.

Table A.4: ReFH2 Hydrological Analysis – Peak Flow Estimates for Lindridge Brook Annual Probability (%)(1 in X Years)

Downstream Extent of Site at A38/M6 Toll Junction


1% (1 in 100 Year) (Flood Zone 3) 4.75



0.1% (1 in 1000 Year) (Flood Zone 2) 8.27

These demonstrate that the 1% annual probability (1 in 100 year) flow estimates including a 30% allowance for climate change do not exceed the 0.1% annual probability (1 in 1000 year) flows.


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In summary, all of the flow estimates demonstrated that the 1% AP (1 in 100 year) flow estimate including a 30% and 50% allowance for climate change does not exceed the 0.1% AP (1 in 1000 year) flows. This provides reasonable confidence that if the latter event was modelled in more detail, the flood extent would unlikely extend further across Sites H3, E1 and H14 than the Flood Zone 2 extents.


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Application of Flows in the Brookbanks 2015 InfoWorks ICM Model

The “JBA Inflow 100yr” inflow file in the Brookbanks 2015 ICM model contains three inflow points (named “Anker Inflow” for the River Anker, “Innage Inflow” for Innage Brook, and “Merevale Inflow” for Merevale Brook). The Brookbanks 2015 Flood Study Report states that inflows from 3 additional un-named tributaries contributing to the River Anker between the upstream and downstream extents of the modelled reach were also included as constant peak flows into the model. This was concluded to be a reasonable approach by AECOM in their 2016 peer review. However, these are not contained within the “JBA Inflow 100yr” inflow file, so it is not clear at this stage, how/if these additional inflows were actually accounted for in the model.

It was also identified that the ‘Anker inflow’ hydrograph applied in the “JBA Inflow 100yr” inflow file was set with a 0.5 hour timestep instead of a 1 hour timestep defined by ReFH1, thus reducing the overall volume of water applied to the model. It is assumed this was incurred in error as within the ICM inflows interface, all hydrographs require the same timestep and the 2 other inflows (“Innage inflow” and “Merevale inflow”) comprise 0.5 hour timesteps. This was corrected in the 2019 model re-runs, and the other two inflows were converted accordingly to a relative 1 hour timestep. A comparison of the resultant final 2015 and 2019 hydrographs is provided in Figure A-8-3.

The corrected “JBA Inflow 100yr” inflow file was run through the model for the 1%AP event, and this provided almost identical flood extents to those presented in the 2015 FRA. This was then retained and uplifted by 30% and 50% within this Flood Risk Technical Note to determine the potential impacts of climate change at Sites H1 and H2.

Model re-runs have been conducted using Infoworks ICM 8.0.6; a more recent version than was used in 2015 (5.0). Initial conditions have been generated from a ‘hot start’ file created with the “JBA Inflow 100yr” inflow file.

To assess backwater impacts upon flood risk within the study area of interest, model predictions using an ICM ‘free outfall’ unit have been sensitivity tested with a constant downstream water level (mAOD) boundary condition. As per the Brookbanks 2015 model, this water level of 66.14 mAOD was retained (equivalent to the approximate top bank level at the furthest downstream cross section of the River Anker in the model in line with Atherstone Lock).

It should be noted that model predictions using a constant downstream boundary condition are likely to be conservative as peak water levels in the River Anker will be transient; however, it is standard practice to apply this simplified approach to have a first indication whether backwater effects are relevant or not. The results of this sensitivity test produced flood outlines comparable to the free draining scenario in the vicinity of Sites H1 and H2, but with slightly greater flood depths downstream of the sites. No further sensitivity tests have subsequently been conducted for the purpose of this Flood Risk Technical Note.

Fluvial Depth Mapping

The modelled maximum depth results grids within the maximum flood extents were thematically mapped in GIS according to the following maximum depth classifications (Table A-13) and were provided in Figure C5 at Appendix C.


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0 5 10 15 20 25 30 35 40 45 50 550

102030405060708090

100110120130

0.5 hour intervals (All Inflows)

Innage Brook (0.5 hr Interval Timestep)

Merevale Brook (0.5 hr Interval Timestep)

Anker Inflow (0.5hr Interval Timestep - INCORRECT)

0 5 10 15 20 25 30 35 40 45 50 550

0.5

1

1.5

2

2.5

30.5 hour intervals (Tr ibutary Inflows Only )

Innage Brook (0.5 hr In-terval Timestep)

Merevale Brook (0.5 hr Interval Timestep)

0 5 10 15 20 25 30 35 40 45 50 550

102030405060708090

100110120130

1 hour intervals (All Inflows )

Innage Inflow (1hr Interval Timestep)

Merevale Inflow (1hr Interval Timestep)

Anker Revised (1hr Interval Timestep - RECTIFIED)

0 5 10 15 20 25 30 35 40 45 50 550

0.5

1

1.5

2

2.5

3 1 hour intervals (Tr ibutary Inflows Only )

Innage Inflow (1hr Interval Timestep)

Merevale Inflow (1hr Interval Timestep)

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Longer duration

and greater

volume

resulting from

corrected

timestep

interval


Figure A-8-3: 2015 Model Inflow Hydrographs and 2019 Model Inflow Hydrograph with corrected River Anker Timestep Interval


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Table A-13: Key to Maximum Depth ResultsMaximum Depth of Flooding (m)

Fluvial Hazard Mapping

Where detailed modelling has been undertaken (Sites H1 and H2) the following information details how the model results were represented in Figure C6 at Appendix C. Guidance set out by Defra (2005)15 categorises the danger to people for different combinations of depth and velocity as shown in Table A-14.

Table A-14: Danger to people relative to different combinations of flood flow depth and velocity

*Taken from Table 13.1 of the Defra/EA FD2320/TR2 report15.

The flood hazard rating (HR) is calculated as a function of depth, velocity and debris factor based on Defra (2006)16 using the following equation:

HR = ((v + 0.5) * D) + DF

Where: v = velocity (ms-1) d = depth (m)

DF = debris factor (probability that debris will lead to a hazard, defined in the model)

InfoWorks ICM software calculates the flood hazard rating throughout a model simulation using varying debris factors with depth and velocity, dependent on the land use category as specified in Table 3.1 of DEFRA 2006 16 and replicated in Table A-15 below. A conservative land use category was applied in the ICM model output for this study.

15 Defra and Environment Agency. October 2005. ‘Framework and Guidance for Assessing and Managing Flood Risk for New Development’, Flood Risk Assessment Guidance for New Development. FD2320 R&D Technical Report 2. Defra London. Table 13.1, Pg. 118.16 Defra and Environment Agency. March 2006. ‘Flood Risks to People – Methodology’. Flood Risks to People Phase 2. FD2321 R&D Technical Report 1. Defra London. Table 3.2 Pg. 8.


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Table A-15: Debris factors (DF) for different flood depths, velocities and dominant land use

Depths Conservative

0 to 0.25 m 0.5

0.25 to 0.75 m 1

d>0.75 m and/or v>2 ms-1 1

V > 2ms-1 criteria in the last row is applied at all depths greater than 0.1m.

A guide to the different groups/vulnerabilities of people that should be considered as falling into each of the danger classifications based on this HR16 is provided below in Table A-16.

Table A-16: Hazard to People as a Function of Velocity and Depth(Adapted from Table 2 of EA/HR Wallingford 2008 Supplementary Note17)

HR Threshold(d x (v + 0.5)) + DF) =

Degree of Flood Hazard Danger Classification

<0.75 LowCaution“Shallow flowing water or deep standing water”

0.75 – 1.25 ModerateDanger for Some (i.e. children, the elderly and the infirm)“Deep or fast flowing water”

1.25 – 2.0 SignificantDanger for Most people (includes the general public)“Deep fast flowing water”

>2.0 ExtremeDanger for All (includes emergency services)“Deep fast flowing water”

Using the above information, the varying surface water flood risk within and across the areas identified as being at risk can be determined to inform an Exception Test.

17 Environment Agency and HR Wallingford. May 2008. ‘Supplementary Note on Flood Hazard Ratings and Thresholds for Development and Planning and Control Purpose’. Table 2, Pg. 4.


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Appendix B – Site Overview Flood Risk Mapping

Table B.1: Flood Risk Mapping at Potential Strategic Allocation Sites by SourceDescription Settlement

NameSite IDs Figure

Environment Agency Fluvial Flood Map for Planning(Flood Zones)



Environment Agency Risk of Flooding from Surface Water Map (uFMfSW)



Environment Agency Area Susceptible to Groundwater Flooding (AStGWF)



Historical Total Reported Sewer Flooding Incidents (Severn Trent Water DG5 2006-2016)



Reported Historical Flooding IncidentsAtherstone H1, H2, H3, E1 Figure B.5A

Wishaw H14 (No reported incidents in vicinity to map)


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Figure B-1A: Environment Agency Fluvial Flood Map for Planning (Flood Zones), Atherstone – Sites H1, H2, H3-& E1



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Figure B-1B: Environment Agency Fluvial Flood Map for Planning (Flood Zones), Wishaw – H14



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Figure B-2A: Environment Agency Pluvial Updated Flood Map for Surface Water (uFMfSW), Atherstone – Sites H1, H2, H3-& E1



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Figure B-2B: Environment Agency Pluvial Updated Flood Map for Surface Water (uFMfSW), Wishaw – H14



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Figure B-3A: Environment Agency Areas Susceptible to Groundwater Flooding (AStGWF), Atherstone – Sites H1, H2, H3-& E1



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Figure B-3B: Environment Agency Areas Susceptible to Groundwater Flooding (AStGWF), Wishaw – H14



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Figure B-4A: Severn Trent Reported Incidents of Sewer Flooding (by postcode area), Atherstone – Sites H1, H2, H3-& E1



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Figure B-4B: Severn Trent Reported Incidents of Sewer Flooding (by postcode area), Wishaw – H14



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Figure B-5A: Environment Agency Historical Flood Map, Atherstone – Sites H1, H2, H3-& E1



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Appendix C – Assessment of Flood Zone Extents in respect of Climate Change

Table C.1: Assessment of Flood Zone Extents relative to Ground Levels in respect of Climate Change at Potential Strategic Allocation Sites


Site IDs Figure

High Level Comparison of Existing Environment Agency Flood Zones (JFLOW outputs) to Ground Levels Atherstone E1 Figure C1

High Level Comparison of Existing Environment Agency Flood Zones (JFLOW outputs) to Ground Levels Atherstone H3 Figure C2

High Level Comparison of Existing Environment Agency Flood Zones (JFLOW outputs) to Ground Levels Wishaw H14 Figure C3

ICM Modelled Flood Extents with Environment Agency February 2016 Climate Change Allowances in Comparison with Existing Flood

ZonesAtherstone H1, H2 Figure C4

ICM Modelled Flood Depths for a 1% Annual Probability Event+50% Climate Change Allowance Atherstone H1, H2 Figure C5

ICM Modelled Flood Hazard Classifications for a 1% Annual Probability Event+50% Climate Change Allowance Atherstone H1, H2 Figure C6


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Figure C-1: High Level Comparison of Existing Environment Agency Flood Zones to Ground Levels, Atherstone – Site E1


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66




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Figure C-2: High Level Comparison of Existing Environment Agency Flood Zones to Ground Levels , Atherstone – Site H3


68



69




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Figure C-3: High Level Comparison of Existing Environment Agency Flood Zones to Ground Levels, Wishaw – Site H14


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72




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Figure C-4: Modelled Flood Extents with Environment Agency February 2016 Climate Change Allowances in Comparison with Existing Flood Zones, Atherstone – Sites H1 & H2


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Figure C-5: Modelled Flood Depths for the 1% Annual Probability Event with a +50% Climate Change Allowances, Atherstone – Sites H1 & H2


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Figure C-6: Modelled Flood Hazard Classification for the 1% Annual Probability Event with a +50% Climate Change Allowances, Atherstone – Sites H1 & H2


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Appendix D – Review of Ground Levels relative to Flood Water Levels in respect of Climate Change

Table D.1: Review of Ground Levels relative to Flood Water Levels in respect of Climate Change at Potential Strategic Allocation Sites


Site IDs Figure

Cross Section of Ground Levels and Flood Water Levels Atherstone E1Figure D1Figure D2

Cross Section of Ground Levels and Flood Water Levels Atherstone H3 Figure D3

Cross Section of Ground Levels and Flood Water Levels Wishaw H14Figure D4Figure D5Figure D6


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0 50 100 150 200 250 300 350 400 45069.5

7070.5

7171.5

7272.5

7373.5

7474.5

7575.5

7676.5

7777.5

7878.5

7979.5

8080.5

8181.5

8282.5

8383.5

84

Ground

FZ2 (0.1% AP Event) Approx. Water Level

Distance from B1-B2 (m)

Elev

atio

n (m

AOD)



80

0 50 100 150 200 250 300 350 400 45069.5

7070.5

7171.5

7272.5

7373.5

7474.5

7575.5

7676.5

7777.5

7878.5

7979.5

8080.5

8181.5

8282.5

8383.5

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Ground



Elev

atio

n (m

AOD)


Figure D-1: Cross Section of Ground Levels and Flood Levels at E1, Atherstone – Cross Section A1-A2


Figure D-2: Cross Section of Ground Levels and Flood Levels at E1, Atherstone – Cross Section B1-B2



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0 50 100 150 200 250 300 350 400 450 500 55094

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

Ground


Distance from A1-A2 (m)

Elev

atio

n (m

AOD)


Figure D-3: Cross Section of Ground Levels and Flood Levels at H3, Atherstone - Cross Section A1-A2

0 50 100 150 200 250 300 350 400 450 50085

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

Ground



Elev

atio

n (m

AOD)


Figure D-4: Cross Section of Ground Levels and Flood Levels at H14, Wishaw – Cross Section A1-A2

Object 9


Figure D-5: Cross Section of Ground Levels and Flood Levels at H14, Wishaw – Cross Section B1-B2

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 40086

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

Ground


Distance from C1-C2 (m)

Elev

atio

n (m

AOD)


Figure D-6: Cross Section of Ground Levels and Flood Levels at H14, Wishaw – Cross Section C1-C2


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