Download - Darlington Borough Council Strategic Flood Risk Assessment ... · Volume I of the Darlington SFRA introduces the SFRA process. It is an excellent reference document for current flood

Darlington Borough Council

Strategic Flood Risk Assessment Level 1

Volume II- SFRA technical report

December 2009

Karen Johnson Spatial Planning Town Hall Feethams Darlington DL1 5QT

2009s0156 - DBC SFRA Vol II v2.0 i

Revision Ref / Date Issued Amendments Issued to

JBA Office JBA

Warrington

JBA Project Manager Sam Wingfield

Revision History

1 Digital Copy (as a pdf) to Draft report (V.1.0) Karen Johnson and

Cameron Sked

Final report (V.2.0) Updated following comments from EA and DBC.

1 Digital Copy (as a pdf) to Karen Johnson

Contract This report describes work commissioned by Karen Johnson, on behalf of Darlington Borough Council. Darlington Borough Council’s representative for the contract was Karen Johnson. Sam Wingfield of JBA Consulting carried out this work.

Prepared by ......................................Samuel Wingfield, BSc MRes Analyst

Reviewed by .....................................Christopher Isherwood, BSc DipWEM Analyst

Purpose This document has been prepared as a Draft Report for Darlington Borough Council. JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by the Client for the purposes for which it was originally commissioned and prepared.

JBA Consulting has no liability regarding the use of this report except to Darlington Borough Council. If the site is sold, the scope of the development changed or this report is provided to third parties then any liability or explicit or implied warranty is voided unless the consent of JBA Consulting is obtained.

This report may be assigned by the Client by way of absolute legal assignment once only to another company taking over the whole of their interest in connection with the carrying out of the Development without the consent of JBA Consulting being required and such assignment shall be effective upon written notice thereof being given to JBA. If further assignment is required please contact JBA Consulting.

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Acknowledgments JBA would like to thank all those who provided information and data for this report. From Darlington Borough Council: Karen Johnson. From the Environment Agency: Gemma Alecks.

Copyright © Jeremy Benn Associates 2009

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Executive Summary

Darlington Borough Council Level 1 SFRA

This report has been produced as a Level 1 Strategic Flood Risk Assessment (SFRA) for Darlington Borough Council, in accordance with PPS25 and its Practice Guide.

Development and Flood Risk

This report has been produced as a Level 1 Strategic Flood Risk Assessment (SFRA) for Darlington Borough Council, in accordance with PPS25 and its Practice Guide.

Development & Flood Risk

Local Planning Authorities (LPAs) have a raft of issues to consider when planning future development. These are dictated by Government Planning Policy Statements.

Planning Policy Statement 25 (PPS25) relates to development and the constraint of flood risk, with its overarching aim of avoiding development in flood risk areas. This is achieved through PPS25 by the sequential approach to land allocation, meaning that development should be firstly avoided in flood risk areas wherever possible before considering the vulnerability of development planned or possible mitigation measures. The sequential approach is governed by two tests; the Sequential and Exceptions Test. The consideration of flood risk to people and development must be considered by the LPA at the earliest stage of spatial planning decisions and these tests allows this process to be transparent and effective.

In order to carry out these tests a coherent understanding of flood risk is needed at a local level. High level policy and guidance documents such as Catchment Flood Management Plans (CFMPs), Shoreline Management Plans (SMPs) and Regional Flood Risk Appraisals (RFRA) have provided a good introduction in to flood risk; however they do not provide the level of detail required for the LPA to make informed spatial planning decisions.

Strategic Flood Risk Assessments (SFRAs) offer this local level of understanding. SFRAs provide the LPA with a central source of all relevant flood risk information and the evidence base to make planning decisions and develop focused local policies required for the Local Development Framework (LDF). The SFRA therefore becomes a key planning tool that enables the LPA to select and develop sustainable site allocations.

A Level 1 SFRA offers the foundation of this evidence base. It is based purely on the collation of existing flood risk information. The Environment Agency Flood Map is the main source of fluvial and tidal flood information across England and Wales and is the basis of PPS25 Flood Zones used in the Sequential and Exception Tests. The Level 1 SFRA must also consider flooding from all other sources (surface water, sewers, groundwater and artificial sources). This is only achievable through consulting with those stakeholders with specific interest or knowledge in other sources of flooding.

The Level 1 SFRA is assisted greatly by the use of Strategic Flood Risk Maps providing information on flood risk factors needed to be taken into account. The PPS25 Flood Zone Map enables the LPA to carry out the first sweep of Sequential Testing. The additional maps produced as part of the Level 1 SFRA should be used during the Sequential Test ‘sieving’ process to further identify inappropriate development.

Once the LPA has carried out the Sequential Test sieving process, they still may wish to allocate vulnerable development in high risk areas due to the wider need for economic growth and regeneration. In this case the allocations must pass the Exception Test. The evidence provided in the Level 1 SFRA is not detailed enough to justify development through the Exception Test. In order to achieve this Level 2 SFRA must be carried out.

A Level 2 SFRA provides the LPA with a detailed understanding of flood hazard, assessing flood depth, velocity and residual risks such as flood defence breaching or overtopping. This information provided in the Level 2 SFRA will give the LPA a much more detailed understanding of flood risk at potential development sites. Although it will not provide all the information needed to apply the Exception Test, it will include the appropriateness of the development and the likelihood of it remaining safe if flooded. If the LPA has justified the development by passing parts a) and b)

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of the Exception Test, it must be supported by a site specific Flood Risk Assessment (FRA) in order to pass part c).

The Three Level 1 SFRA Volumes

The Level 1 SFRA is presented in three volumes, each with their own purpose and intended audience.

VOLUME I: Understanding the SFRA Process

Volume I of the Darlington SFRA introduces the SFRA process. It is an excellent reference document for current flood risk management drivers, national regional and local planning policy and introduces Environment Agency policy such as the Tees CFMPs and SMPs.

The report also provides a brief understanding of the mechanisms of flooding and flood risk for those new to the subject. More importantly, it provides a comprehensive discussion on PPS25, the Sequential and Exception Tests and links regional and local flood risk assessments.

Volume I holds the main ‘Consultation & Data Management’ section, identifying key stakeholders and their involvement in the SFRA process.

This Volume should be read by:

� The general public or those new to flood risk � Those wanting to understanding current flood risk management drivers � Those wanting to understand the sequential approach to flood risk management;

and � Planners and Developers wanting to understand the wider constraints of

developing in flood risk areas. VOLUME II: SFRA Technical Report

Following on from the ‘Consultation & Data Management’ section in Volume I, Volume II provides the technical information and methods used in the assessment of flood risk across Darlington. It assesses six sources of flooding including; fluvial, tidal, surface water, sewers, groundwater and reservoirs and other artificial sources. The Volume also introduces the Environment Agency Flood Warning System and residual risks associated with flood defences.

As discussed, flood risk has many dimensions and as a result has been presented through a suite of maps. These extend the level of detail in the Environment Agency Flood Zone maps.

The SFRA maps include:

SET A: PPS25 Flood Zones

SET B: Flood Zone 3 Depths

SET C: Tidal Climate Change Sensitivity

SET D: Flood Risk Management Measures

SET E: Areas Naturally Susceptible to Surface Water Flooding

Volume II along with the suite of SFRA maps, should provide the evidence base of the Darlington Level 1 SFRA. It has been arranged in one volume to allow technical information to be easily updated when reviewed. It is only this Volume that can be updated with new flood risk information when available. Volume I and III would be difficult to update without completely revisiting the SFRA process.

Section 4 provides the results of the first pass of the Sequential Test against Darlington Council’s proposed strategic sites and potential future allocations.


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� Spatial Planners � Development Control � Planning consultants and agents � Developers � Emergency Planners � Key Stakeholders including the Environment Agency and Northumbrian Water

VOLUME III: SFRA Guidance for Spatial & Development Management

Volume III of the Darlington SFRA provides guidance and recommendations to planners, planning consultants and agents, developers and emergency planners, on how to use the flood risk information provided in Volume II and further plans which are required to improve the understanding of flood risk in Darlington.

Initially the Volume discusses further work required such as Level 2 SFRAs and Surface Water Management Plans which have been informed by the findings of Volume II. This extra work will provide Darlington Council with a strategic and coherent framework for managing flood risk in their area.


� Spatial Planners � Development Control � Planning consultants and agents � Developers � Emergency Planners � Key Stakeholders including the Environment Agency and Northumbrian Water

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Contents Executive Summary.......................................................................................................... iv

1 Data Sources .......................................................................................................1

1.1 Flood Zone Map...................................................................................................1 1.2 Flood Defences....................................................................................................2 1.3 Flood Risk Management and Hydraulic Modelling Studies .................................2 1.4 Topographic Data ................................................................................................4 1.5 Historical Flooding ...............................................................................................5

2 Flood Risk in the Borough of Darlington..............................................................7

2.1 Introduction ..........................................................................................................7 2.2 River Tees............................................................................................................8 2.3 River Skerne ........................................................................................................9 2.4 West Beck and Cocker Beck ...............................................................................11 2.5 Flooding from land ...............................................................................................13 2.6 Flooding from sewers ..........................................................................................17 2.7 Flooding from groundwater..................................................................................18 2.8 Flooding from reservoirs and other artificial sources...........................................18 2.9 Effects of Climate Change ...................................................................................18 2.10 Geology and Soils................................................................................................19 2.11 Flood Defences....................................................................................................19 2.12 Flood Warning .....................................................................................................20

3 Strategic Flood Risk Mapping..............................................................................22

3.1 Introduction ..........................................................................................................22 3.2 PPS25 Flood Zone Maps.....................................................................................22 3.3 Flood Zone 3 Depth Map .....................................................................................24 3.4 Climate Change Sensitivity Maps........................................................................24 3.5 Flood Risk Management Measures Map.............................................................24 3.6 Surface Water Flooding Maps .............................................................................25

4 Site Specific Allocations.......................................................................................26

4.1 Introduction ..........................................................................................................26 4.2 Current Development Site Sequential Test .........................................................26 4.3 Flood risk and the 2009 potential development sites ..........................................27 4.4 Preliminary Level 2 Assessment for Central Darlington ......................................34 4.5 Surface water flood risk .......................................................................................38 4.6 Individual planning applications...........................................................................39

Appendices ....................................................................................................................... I

A Figures ................................................................................................................. II

B Sequential Test Table.......................................................................................... III

List of Figures Figure 1: LiDAR Coverage in Darlington BC .................................................................... 5

Figure 2: Darlington Borough with the allocations and rivers ........................................... 8

Figure 3 - Possible critical drainage area in Pierremont................................................... 15

Figure 4 - Possible critical drainage area in the centre of Darlington next to the Skerne............................................................................................................................... 16

Figure 5 - Possible critical drainage area in Eastbourne.................................................. 17

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Figure 6 - Faverdale Strategic Reserve Employment site EP8 ........................................ 28

Figure 15 - SHLAA Site 56, Salters Lane West with a high vulnerability to surface

Figure 16 - SHLAA Site 20, Great Burdon and Yarm Road and Local Plan Employment Allocation EP2.6 areas with a high vulnerability to surface water

Figure 7 - Muscar House Farm residential site................................................................. 29

Figure 8 -Great Burdon residential site............................................................................. 30

Figure 9 - Blackett Road/Red Barnes Way Employment allocation EP2.4 ...................... 31

Figure 10 -Valley Street Employment allocation EP2.1 and Town Centre Fringe............ 32

Figure 11 -SHLAA 60 Feethams ...................................................................................... 33

Figure 12 -SHLAA 17 Roundhill Road, Hurworth ............................................................. 33

Figure 13 - Flood depth grids for the 1% and 0.1% a.p. events ....................................... 36

Figure 14 - Flood depth for the 1% and 0.1% a.p. events................................................ 37

water flooding ................................................................................................................... 39

flooding ............................................................................................................................. 39

List of Tables Table 1 - DEM availability ................................................................................................. 4

Table 2 - Recent flooding from the River Tees................................................................. 9

Table 3 - Recent flooding from West Beck and Cocker Beck .......................................... 13

Table 4 - Functional floodplain and candidate functional floodplain mapping.................. 23

Table 5 - Summary of development sites at risk of fluvial flooding .................................. 27

Table 6 - Summary of development sites at risk of surface water flooding...................... 27

Table 8 - Flood Hazard Thresholds .................................................................................. 35

Table 9 - Suggested screening criteria for mitigation measures ...................................... 35


Abbreviations ABD Areas Benefiting from Defences A.P. Annual Probability CFMP Catchment Flood Management Plans CLG Communities and Local Government COW Critical Ordinary Watercourse CS Core Strategy DPDs Development Plan Documents EA Environment Agency EU European Union FAS Flood Alleviation Schemes FEH Flood Estimation Handbook FCERM Flood and Coastal Erosion Risk Management FRA Flood Risk Assessment FRM Flood Risk Management IDB Internal Drainage Board IDD Internal Drainage District IFM Indicative Floodplain Map LDDs Local Development Documents LDF Local Development Framework LPAs Local Planning Authorities NEA North East Assemble NFCDD National Fluvial and Coastal Defence Database NPD National Property Dataset NWL Northumbrian Water Ltd PPG Planning Policy Guidance PPS Planning Policy Statement RBD River Basin District RBMP River Basin Management Plan RFRA Regional Flood Risk Assessment RPB Regional Planning Bodies RPG Regional Planning Guidance RSS Regional Spatial Strategy RVFD Receptors Vulnerable to Flooding Database SA Sustainability Appraisal SEA Strategic Environmental Assessment SFRA Strategic Flood Risk Assessment SFVI Social Flood Vulnerability Index SMP Shoreline Management Plans SoP Standard of Protection SPD Supplementary Planning Document SUDS Sustainable (Urban) Drainage Systems SWMP Surface Water Management Plan UDP Unitary Development Plan WCS Water Cycle Study


1 Data Sources

1.1 Flood Zone Map

The Environment Agency Flood Zone Maps provide an overview of areas considered susceptible to flood risk in the Borough as a result of fluvial and tidal flooding. These maps have been prepared in a consistent manner across England and Wales and provide an estimation of the extent of flooding for both the 1% and 0.1% annual probability (a.p.) events.

The Flood Zone maps were prepared using a methodology based on the national digital terrain model (NextMap), derived river flows (Flood Estimation Handbook (FEH)) and two dimensional flood routing.

The derived Flood Zone extents have been adjusted in some locations where the results are inconsistent with historical flooding extents, where more detailed flood mapping studies have been completed, or where there are known errors in the digital terrain model used. In Darlington, the majority of fluvial and tidal Flood Zones have already been updated with the results of detailed flood mapping studies (see Section 1.3).

The Environment Agency Flood Zone Maps are precautionary in that they do not take account of flood defences and, therefore, represent a worst-case extent of flooding. They do not consider other forms of flooding and do not take account of climate change.

PPS25 divides the country into three basic flood zones, Flood Zones 1, 2 and 3, corresponding to areas of low, medium and high flood risk, respectively.

1.1.1 Delineation of Low Risk Zone 1

PPS25 considers areas within Flood Zone 1 to be at low risk to flooding. The annual probability of flooding within this zone is less than 0.1% or can be easily defined as areas within the Borough located outside either Flood Zone 2 or 3.

1.1.2 Delineation of Medium Risk Zone 2

PPS25 considers areas within Flood Zone 2 to be at medium risk of flooding. The annual probability of fluvial flooding within this zone is between 0.1% and 1% (or between 0.5% and 0.1% for tidal flooding). In general, Flood Zone 2 is considered suitable for most development except highly vulnerable land uses where the Exception Test is required, such as police stations, fire stations and ambulance stations.

1.1.3 Delineation of High Risk Zone 3

PPS25 considers areas within Flood Zone 3 to be at high risk of flooding. PPS25 splits Flood Zone 3 into two sub-zones, 3a and 3b, which correspond to high probability flooding and the functional floodplain.

� Flood Zone 3a: High Probability In accordance with Table D.1 of PPS25 “This zone comprises land assessed as having a 1% or greater annual probability of flooding or a 0.5% or greater annual probability of sea flooding in any year.”

� Flood Zone 3b: The Functional Floodplain In accordance with Table D.1 of PPS25 “This zone comprises land where water has to flow or be stored in times of flood”

1.1.4 Delineation of the Functional Floodplain

SFRAs are tasked with the responsibility of defining Flood Zone 3b. PPS25 suggests the 5% a.p. flood event for the baseline of a functional floodplain, however, a greater event can be used where appropriate, depending on catchment characteristics and on agreement between the LPA and the Environment Agency.

SFRAs can also identify where it might be appropriate to extend the 5% a.p. flood outline to areas within Flood Zone 2 and 3 to restore or expand the functional floodplain. The ability to identify and

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safeguard large enough areas against redevelopment and development in both urban and rural areas means that existing open space can potentially be used for flood storage, effectively reducing flood risk downstream. This process assists Flood Zone 3 policy aims, identified in table D.1 in PPS25, which include:

� “Reduce the overall level of flood risk in the area through the layout and form or the development and the appropriate application of sustainable drainage systems,”

� “Create space for flooding to occur by restoring functional floodplain and flood flow pathways and by identifying, allocation and safeguarding open space for flood storage.”

The SFRA should be fully integrated with CFMPs and other strategies that show, at catchment scale, the need to protect the floodplain and avoid inappropriate development in high flood risk areas.

1.2 Flood Defences

As discussed above the Environment Agency Flood Zone maps do not take account of the presence of flood defences (although defended areas and the location of raised defences are included in the suite of information provided with the maps). PPS251 states that defended areas (i.e. those areas that are protected to some degree against flooding by the presence of a formalised flood defence) are still at risk of flooding, and therefore sites within these areas must be assessed with respect to the adequacy of the defences.

The Environment Agency’s National Flooding and Coastal Defence Database (NFCDD) has been supplied and provides information on existing defences in the area, as well as categorising them by type and providing information on who owns and maintains them. Areas Benefiting from Defences (ABDs) have also been provided. ABDs are those areas which benefit from formal flood defences in the event of flooding from rivers with a 1% a.p. event or from the sea with a 0.5% a.p. event. If the defences were not there, these areas would be subject to increased flood risk.

1.3 Flood Risk Management and Hydraulic Modelling Studies

Many of the main rivers through Darlington have been represented using detailed hydraulic models and the Flood Zones in these locations give a good representation of reality. However, there is no single comprehensive hydraulic model for each of the river systems. Flood Zones outside of the modelled reaches are still represented with broad scale modelling techniques used in the original Flood Zone map definition and are therefore more prone to error.

The hydraulic models available in the area include:

� River Tees – 1D Hydrodynamic ISIS Model updated as part of the FRM Study (2008).

� River Skerne – Hydrodynamic model used produced for floodplain mapping (2001) and prefeasibility study (2003).

� West Beck – Hydrodynamic Model used for floodplain mapping study (2006).

1.3.1 Tees CFMP

The Tees CFMP will be used for evidence of flood history, flood risk locations and sources. This information is at a broad scale nature so will need to be supplemented with other detailed information. The proposed flood risk management policy for different areas within the Borough will be noted in order to help assess if future development proposals are likely to be sustainable.

Between June 2007 and January 2008 JBA Consulting undertook strategic catchment modelling work for the Environment Agency, primarily for the Environment Agency’s CFMPs in the North East (including the Tees CFMP). The modelling generated 19 new Flood Maps for approximately 10,000 km of watercourse, representing different flood events and assumptions about flood risk management measures.

1 Communities and Local Government (2006) Planning Policy Statement 25: Development and Flood Risk, Annex G para G2.


This catchment modelling was also developed in order to update the parts of the Environment Agency’s Flood Map for Flood Zone 3 where no detailed river modelling studies had been completed. This catchment modelling incorporates a number of improvements over the original Flood Maps, including the use of new LiDAR data in place of SAR (NextMap-Britain) data, where available. A number of different scenarios were modelled to represent when flood water would come out of bank e.g. for the 50% a.p. event. Included in these outputs are flood depth and flood hazard maps.

The current Flood Zone maps have not been updated with this new information and it is not known whether they will be updated in the future. It was initially thought that the SFRA could use the outputs to represent Flood Zone 3b, a climate change flood outline, flood depth and flood hazard maps (where there is no detailed modelling). However, it has not been possible to find a scenario that aligns with the current Environment Agency Flood Zone maps. For example, Flood Zone 3b would be greater than Flood Zone 3a in places. This is because different modelling techniques were used for the different extents. The SFRA will use a flood depth map from this study for a broad scale overview of the potential flood depths in Darlington.

The Environment Agency have stated that it is critical for the functional floodplain outline to be as accurate as possible. However, the Environment Agency state that as a precautionary principle, Flood Zone 3 should be used to represent Flood Zone 3b in undeveloped areas (until the functional floodplain can be accurately defined). See Section 3.2.1 for a detailed explanation of how the functional floodplain was derived.

1.3.2 North East Regional Flood Risk Appraisal

A scoping study for the North East Regional Flood Risk Appraisal (NE RFRA) was completed by JBA Consulting in January 2009. The primary objective of the NE RFRA is to provide an appraisal of strategically significant flood risk issues and guide strategic planning decisions. The findings of this work will form part of the Regional Spatial Strategy evidence base.

1.3.3 2007 Tees Valley SFRA

An SFRA was completed for the Tees Valley local authorities in 2007. This SFRA was a good example of an SFRA produced prior to the publication of the PPS25 Practice Guide, but it needs updating to reflect the new guidance.

The majority of the flood mapping that was used in the 2007 SFRA has now been updated. However, the 2007 SFRA will be used for additional flood history and flood risk location information.

1.3.4 River Tees Model Updates for Section 105 Mapping

In August 2004, Atkins produced a Phase 1 study (National Section 105 Framework Agreement Phase 1 River Tees, Environment Agency) which gave recommendations for further Section 105 modelling of the River Tees. This study looked at the existing modelling and modelling outputs as well as flood history. This flood history has been integrated into this report (see Chapter 2).

In June 2007 JBA undertook a study on the River Tees for the Environment Agency (River Tees Model Update Phase 1, Environment Agency). The aim of this study was to update the fluvial ISIS model of the River Tees originally constructed by HR Wallingford. This model extends from the A1 upstream of Darlington to the Tees barrage.

More specifically, the study aimed to improve in-river water levels for the main part of the Tees between the A1 Bridge and the Tees Barrage. In order to improve the water level predictions, the Phase 1 study updated and re-calibrated the existing ISIS model to incorporate recent data from Broken Scar gauging station and defence crest heights and washland topography.

In January 2008, JBA Consulting completed the project for the Environment Agency to update the existing ISIS model of the river Tees (River Tees Model Update Phase 2, Environment Agency). The existing ISIS model has a long history, as it has evolved from an original SALMON-F model developed by HR Wallingford and has undergone numerous updates (mostly by HR Wallingford and JBA Consulting.) for various projects.

The most recent update has incorporated information from LiDAR data in the floodplain spills and floodplain units. The model was re-calibrated using recent flood data and the hydrology was updated. Results from the updated model were used to produce revised outlines and NFCDD


data. It was also used to test embankment risk priorities, existing flood warning measures and to comment on implications for operations and maintenance.

1.3.5 River Skerne

In 1997, Section 105 modelling was undertaken on Skerne Beck in Darlington for the Environment Agency (Section 105 - 30/92 Survey, River Skerne, Environment Agency, 1999). The study area comprised 27.2km of the River Skerne, between the Woodham Burn confluence and the confluence with the River Tees. A HEC-RAS, 1D, steady state model of the River Skerne was produced for this study.

A prefeasibility report for the River Skerne was produced for the Environment Agency in September 2003 (River Skerne Pre-Feasibility Report, Version 2, Environment Agency). This updated the 1997 report, producing modelling of the River Skerne including the production of a 1% annual probability (a.p.) flood extent. A Skerne ISIS model was built by converting the above Section 105 model to ISIS and using new survey data to include the structures and weirs. LiDAR data provided by the Environment Agency was used to extend the channel sections into the floodplains. In June 2008 JBA Consulting updated this model to produce a 0.1% a.p. flood extent for the Environment Agency.

The outputs from the modelling (flood extents) and the flood risk information and history gathered will be used to inform this SFRA.

1.3.6 West Beck

In July 2001, the Environment Agency commissioned JBA Consulting to complete a detailed study of the West Beck as part of their Section 105 programme (West Beck S105 Study, Phase 2 Final Report, Volume 1 Main Report, Environment Agency). This study was recommended following the preliminary (Phase 1) studies undertaken in 1999. The Phase 1 study recommended a more detailed study, including computational hydraulic modelling in order to provide more representative flood risk maps for planning purposes. This update included a new hydrology and hydraulic study, to better understand flood risk on West Beck. The FEH rainfall runoff method was chosen as the preferred option for peak flow estimation within the West Beck Catchment. A HEC-RAS model of West Beck was also produced. This comprised of one reach extending from the confluence with the Cocker Beck upstream to Burtree Lane. The model geometry is based on the channel cross section survey carried out by Maltby Land Surveys for JBA in February 2001. Some flooding history was also included in this study.

In August 2006, the Environment Agency also commissioned JBA to produce a prefeasibility study for West Beck (West Beck, Darlington, Pre-Feasibility Study, Environment Agency). This study considered the existing and historic flood risk on West Beck. In addition, the steady state HECRAS model (see above) was updated and converted to an unsteady model with new flood extents produced. This study also provides a review of the flood risk management options considered, together with a technical assessment of their viability.

The outputs from the West Beck studies will be used for the understanding of flood risk on West Beck and potential future flood management options.

1.4 Topographic Data

The essential dataset required for flood modelling, mapping and general elevation information is a Digital Elevation Model (DEM). There are two main sources of DEM data for the Borough, as shown in Error! Reference source not found..

Table 1 - DEM availability

Type Source Grid Filtered Year

Nextmap SAR Environment Agency 5m Filtered -

LiDAR Environment Agency 2m Filtered & unfiltered 2000 to 2005

LiDAR Environment Agency 1m Filtered & unfiltered 2008 to 2009


LiDAR will be used in preference to Nextmap SAR data as it has a higher vertical accuracy. The coverage of the LiDAR datasets available is shown in Figure 1. The blue squares show where the high resolution 1m LiDAR data is. The red shows the extent of the lower resolution 2m LiDAR data. The white within the Darlinton BC boundary is LiDAR gaps.

Figure 1: LiDAR Coverage in Darlington BC

© Crown copyright. All Rights Reserved. 100023728. 2009.

1.5 Historical Flooding

There are a number of sources of historical flood information. The majority of historical data collected was received from key stakeholders during the SFRA consultation process or by reviewing past flood studies in the area. Studies which have provided details on flood history include:

� 2007 Tees Valley SFRA � Tees Catchment Flood Management Plan (CFMP) � West Beck Prefeasibility Study � River Skerne Section 105 Study

The British Hydrological Society’s Chronology of British Hydrological Events also provides some descriptive information of past flooding events in the Tees Valley. This goes back many centuries but is more consistent after 1700.

Key holders of historical flood data are identified below. All the data has been combined to provide a historical flooding GIS based dataset. This has been mapped for the SFRA and can be used by the LPA for future development planning and can be supplied to developers for site specific Flood Risk Assessments. The historic flood risk locations are shown with the PPS25 Flood Zone maps in Appendix A, Figures A1 to A8.

1.5.1 Environment Agency

The Environment Agency is a key source of all flood risk information in England and Wales. As part of the Flood Map, the Environment Agency provides a national historical flood map layer. This shows the extent of major flood incidents. Those identified include:


� January 1995 - overtopping of the defence on the east bank of the River Tees (just upstream of the barrage)

� January 1995 - flooding from the fluvial River Tees in Darlington, extensive but predominantly rural locations.

� Autumn 2000 - flooding from the River Skerne through parts of Darlington.

1.5.2 Darlington Borough Council

Local Authorities can be an important source of historical flood information. Unfortunately, the Council's drainage team were unable to provide any up to date flood risk data. However, during the 2007 SFRA, the Council provided a GIS list of drainage issues. This information had been archived by JBA but was made available for this study. This dataset includes 16 flood risk locations including incidents form surface water and fluvial flooding. This will be a useful data source to compare with the Environment Agency’s theoretical surface water flooding maps.

1.5.3 County Durham and Darlington Fire and Rescue Service

County Durham and Darlington Fire and Rescue Service have provided geo-referenced data in spreadsheet format of all water related call outs from 1995 to 2008. This has been edited down (excluding burst pipes etc) to around 290 flooding incidents and converted to GIS. These locations have also been mapped along with all other historical data collected. Again, as many of the flooding incidents are surface water related, this will be a useful data source to compare to the surface water flooding maps.

1.5.4 Cleveland Emergency Planning Unit

Cleveland Emergency Planning Unit (a consortium of emergency planners covering the Cleveland local authorities) provided a list of historic flooding locations. This Unit only responds to large scale events, where coordination of different emergency response organisations is required. As a result, information on only four incidents was provided.

1.5.5 Other sources

The Highways Agency and Northumbrian Water (NWL) were contacted for flood risk information. NWL has not been able to provide any information until recently; when it was agreed that they would send DG5 (sewer flooding data) at drainage area level. The drainage areas have also been highlighted according to the level of risk. The data is at quite a high level but NWL will provide the area and street level DG5 information at a Level 2 SFRA stage. A Level 2 SFRA should be able to identify those issues NWL have actually dealt with or those which will definitely need further work. Using this information, more precise recommendations for Surface Water Management Plans (SWMP) can be provided. These recommendations should then be use to start SWMP work. The initial DG5 data from NWL will be integrated into the final version of this SFRA.

A-One, the Highways Agency contactor for the A1 and A66, provided a large amount of data for the area. Unfortunately, much of this is not relevant to the SFRA.


2 Flood Risk in the Borough of Darlington

2.1 Introduction

There is a need to understand the risk of flooding from all sources in the Borough, consider where the highest risk locations are, and plan future development and regeneration accordingly.

This section assesses flood risk in the Borough from all sources, now and in the future. It makes use of all the data and information described in Chapter 1. It includes the fluvial Flood Zones and assesses flood risk from other sources, with the aim of providing enough information for the Council to perform the Sequential Test.

The major watercourse in the Borough is the River Tees which originates outside of the administrative boundary. The Tees flows along the southern boundary of the Borough, mainly placing agricultural land at flood risk. A more important watercourse in terms of flood risk is the River Skerne. This flows directly through the centre of Darlington. Other watercourses of interest within the urban area include West Beck and Cocker Beck (see Figure 2).

The historic flood risk information collated during this study also shows the distribution of other sources of flooding, the main being surface water flooding. Although the mapping shows a wide distribution of such locations (see Figures A1 to A8 in Appendix A), surface water flooding is not necessarily as significant as it may seem, due to the small scale and low hazard of the flood events. Many of the flood risk locations, for example, indicate only very localised pooling of shallow water after heavy rain.


Figure 2: Darlington Borough with the allocations and rivers

Cocker Beck

River Tees

River Skerne


2.2 River Tees

The River Tees rises in the Pennines where it passes through Cow Green Reservoir and High Force Waterfall. Further downstream, it flows through Middleton, Barnard Castle and Yarm, where it is joined by the River Leven. Ultimately, it flows through the heavily urbanised areas of Stockton-on-Tees and Middlesbrough before forming an estuary as it enters the North Sea.

Within Darlington, the River Tees meanders through predominantly rural land. The Tees has a wide floodplain here and flood flows from the Upper Tees and River Skerne are attenuated by significant overbank flood storage. Although much of this reach has flood defences, primarily built to protect agricultural land, they are overtopped or bypassed in major floods. Some sections of the Tees are protected to a higher level in order to protect settlements, such as Hurworth and Neasham.

2.2.1 History of flooding

There is a history of flooding on the River Tees within Darlington that goes as far back as records began. This is to be expected from a large river which will seasonally overtop its banks and fill the floodplain. Defences have been built along the Tees to protect agricultural land, but these private defences (i.e. non Environment Agency) are built to a low standard and therefore have a history of overtopping and breaching. In general, major development has not taken place along the Tees within Darlington and future development is not expected. However, there are some existing settlements that have a long history of flooding. This includes Neasham and Hurworth Place. Some flooding dates are below.


� Neasham - 1753, 1771 (15ft deep floods), 1852, 1886, 1890, 1892, 1918, 1923 (2 ft), 1924, 1927, 1928, 1963, 1967, 1968, 1995.

� Hurworth Place - 1967, 1995, 2000.

There is also history of flooding at the caravan park near Hurworth (1991 and 1995). There is a private embankment adjacent to the caravan park but the Environment Agency's flood defence dataset states that this offers no flood defence benefits. This caravan park is within Flood Zone 3 and the River Tees presents a significant hazard to the site.

Table 2.1 provides details on more recent flood events on the River Tees.

Table 2 - Recent flooding from the River Tees

Date Description

March 1968 30 properties were flooded at Hurworth Place. 12 properties flooded at Neasham.

1991 Caravan park flooded at Newbus Grange

1995 There was a flood event on the River Tees which lasted from 31 January to 1 February. At the onset of the event, the upland catchment was already saturated and further heavy rainfall together with mild weather conditions meant that snowmelt was also a significant factor. The average flow was estimated as having a 1.3% annual probability. Flooding of isolated properties in the upper and middle reaches occurred, and a total of 72 properties were reported as affected by flooding.

The banks of the River Tees were overtopped at Hurworth, the caravan park, Newbus Grange and Neasham causing significant flooding to properties.

2.2.2 Kent Beck

Kent Beck enters the River Tees just upstream of Neasham. During the January 1995 and June 2000 flood events, the Neasham flood defence scheme prevented flooding from the River Tees, but flooding still occurred to properties in Neasham. This flooding originated from Kent Beck, which backed up behind the flap/penstock at the Neasham defences. 55 properties were flooded during the 1995 event but since then, the defence at Willow Garth (Neasham) has been raised.

The 2000 event occurred due to seepage from through holes in the left flood defence bank, flooding 13 properties (steel piling has since been installed here and the bridge parapet strengthened). It was suggested in the Tees Model Update Report (Phase 2, Environment Agency, January 2008) that the flow in Kent Beck during the June 2000 event had a 1.6% annual probability.

2.3 River Skerne

The River Skerne catchment is divided into two distinct reaches. The upper reach is predominantly rural, consisting mostly of farmland. The lower reach comprises the urban conurbation of Darlington.

Compared to the River Tees, the Skerne is a dry lowland catchment and has extensive areas of very flat floodplains. The catchment is relatively dry because of the drier climate and the greater permeability of soils and bedrock. The volume of flow is also relatively low as the channel has artificially enlarged to convey the flood volume carried. However, when there is heavy rainfall or snowmelt, the channel has insufficient capacity and floodwater can spill out over a wide area. The areas around the upper (rural) floodplain are flooded nearly every winter and the land remains poorly drained throughout the year.

The Tees Valley CFMP states that the Skerne is affected by two conflicting influences in its flood generating characteristics:


1. Percentage storm runoff is generally less than 20 percent (Archer, 19842), due to low rainfall and high soil storage capacity and soil moisture deficits. These characteristics mean that summer floods are rare (Archer, 19813) despite the maximum storm rainfall occurring in summer. Instead, most floods occur towards the end of the winter when soils are approaching saturation.

2. The catchment has extensive areas of very flat land adjacent to the main channel and tributaries. These wetland ‘carrs’, notably at Mordon, Preston, Bradbury and Mainsforth, are the original floodplain of the natural river and were regularly flooded in winter. Drainage and embankment of the carrs for agricultural use means they are not flooded from the river by small events, although ponding occurs from incident rainfall. There is still substantial flooding in major events.

The main areas of flood risk from the 1% a.p. flood event, identified in the River Skerne Section 105 studies (1999) are:

� Skerne Park in Darlington, � the housing area at Riverside in Haughton-le-Skerne, � the agricultural land at Great Burdon Bridge in Darlington, � Ketton Lodge � Coatham Mundeville

The Skerne Prefeasibility Study (2003) concludes that the following locations are most at risk of flooding from the 1% a.p. event on the Skerne.

� Aycliffe Village � Coatham Munderville � Skerningham Plantation � Barmpton � Great Burdon � Haughton Road � Cleveland Industrial Estate � Victoria Embankment

From this flood event, there are only pockets of properties at risk from the Skerne and this most recent modelling (Skerne Prefeasibility, 2003) shows no serious flooding in Darlington town centre itself during the 1% a.p. flood. The Skerne Prefeasibility Study concludes that the floodplain storage upstream of Darlington, combined with the improvement works to the channel itself between 1952 and 1972, have succeeded in protecting Darlington town centre from widespread damage for all but very extreme fluvial flood events. The only history of flooding in Darlington town centre was in 1952 and 1967 (pre flood alleviation works).

The Skerne Prefeasibility Study also stated that through Darlington town centre, between John Street Bridge and South Park, the Skerne’s hinterland is significantly lower than the bank top levels. To protect the town, continual engineering of the channel over the past century has increased the river’s capacity and seemingly resolved much of the flooding problems. Although the standard of protection is now in excess of the 0.5% a.p. event through much of Darlington town centre, there remains a large defended area which, if breached or bypassed, could result in flooding of a significant number of properties. This can be seen in the difference between the Flood Zone 3 and 2 maps (see Figures A1 to A8 in Appendix A).

The Skerne Section 105 reports state that during more frequent flooding events (than the 1% a.p. event), water levels in the River Skerne may affect land and urban drainage networks. Backing up of discharges could result in surface water flooding from drains and manholes, leading to ponding in low lying areas. Historic flooding records have provided evidence for this, for example, in the north of the Borough there is evidence of storm drains overflowing around Coatham Mundeville.

2 Archer, D. (1984) The estimation of seasonal probable maximum flood. British National Committee on large dams Conference, Cardiff, Technical

Papers. 1-20

3 Archer, D. (1981) The seasonality of flooding and the assessment of seasonal flood risk. Proceedings Institution of Civil Engineers, Part 2, 1023

1035.


2.3.1 History of flooding

Historic flooding information reveals that the Skerne has flooded in the following years: 1771, 1852, 1856, 1875 (twice), 1876, 1878, 1880. 1886, 1892, 1895, 1900, 1903, 1924, 1928, 1948, 1967 (twice), 1979, 2000 and 2001.

The Skerne Prefeasibility Study (Environment Agency, September 2002) provides a review of recent flood history on the Skerne. Some of this is summarised below.

The first records of flooding along the Skerne are for an event in 1771, which caused widespread flooding to properties within the centre of Darlington. Flooding occurred twice in the same year in 1875 due to heavy rainfall. Flooding occurred from the gasworks at the upstream end of Darlington through to South Park.

In 1876 work to improve the capacity of the Skerne channel downstream from Victoria Road Bridge was undertaken. As a result of these works, flooding during the twentieth century seems to have been less frequent.

By 1966, a flood alleviation scheme designed to improve the capacity of the Skerne was completed. The works included:

� Weir at outlet to South Park lake was remodelled as a gauging station � Russell Street weir lowered � Cocker Beck was diverted into the Tees via the Baydale Beck � Regrading of the Skerne channel

Since the completion of the scheme, flooding on the Skerne has greatly reduced, however, other events have occurred. For example, in November 1967, 54 properties along Valley Street, John Street, Oxford Street, Mount Street and Parkgate were all flooded. The severity of the flooding was attributed to the laying of a temporary sewer within the river channel which had obstructed the flow. This event prompted further improvement works between 1970 and 1972, which lowered the weir again at Russell Street and widened the channel between Chesnut Street and John Street from twenty-five to thirty-five feet.

In March 1979, the strength of the flood defences were tested. A heavy snowfall on the 17th March had begun to melt and swell the river, when on the 28th March 40-50 millimetres of rain fell on the saturated catchment. The peak flow at South Park for this event was 60m3/s, a flow rate probably not reached since the flood of 1875. Within the centre of Darlington the bridge at Priestgate was overtopped and the river came out of bank on to the Ring Road. However no properties were flooded. It therefore appeared that all the engineering works carried out over the previous 50 years had succeeded in preventing widespread flooding damage to domestic and commercial properties.

The most recent flood events were in November 2000 and February 2001 where a number of properties were flooded in Darlington. The Environment Agency's historic flood outlines show that in November 2000, the River Skerne overtopped its banks at: Barmpton, Great Burdon, HaughtonLe-Skerne and the land on the opposite side of the bank to Skerne Park.

2.4 West Beck and Cocker Beck

West Beck is a tributary of Cocker Beck, which in turn flows into the River Skerne (which is a tributary of the River Tees). West Beck originates north of Darlington, in the triangle of land between the A1 and the Darlington-Bishop Auckland railway line. The northern part of the West Beck catchment is almost entirely rural and is currently used for a mixture of arable and livestock farming. The remaining part of the catchment between Faverdale (north west Darlington) and Cockerton (further south in the urban area) is essentially urbanised. West Beck converges with Cocker Beck in Cockerton just upstream of the B6279.

Several small drains flow into West Beck. In addition, two un-named watercourses can be identified as tributaries of West Beck. These include a small watercourse which joins West Beck just upstream of the A68 Road Bridge and the second just upstream of High Faverdale Farm, both of which drain from the left bank. No further significant tributaries are present within the catchment.

West Beck was culverted in 1974-5, downstream of the former Faverdale Chemical works site (now West Park), by the Northumbrian Water Authority (NWA). Between Newton Road and the confluence with the Cocker Beck, West Beck remains open channel.


The current Flood Zone maps show widespread flooding of agricultural land at the upstream study extent. The flood risk maps also indicate that approximately 78 properties in the West Beck catchment are at flood risk from the 1% a.p. flood event. This includes 19 properties in the recent housing development in Faverdale, 50 properties in the vicinity of Spring Court, 7 properties in the Newton Lane and Cockerton Green area and 2 properties adjacent to the Cocker Beck confluence.

The prefeasibility study for West Beck (August 2006) summarised that for National Funding, 'Do Minimum' is the preferred flood risk management option to reduce flood risk. This would entail:

� Keeping all culverts and bridges clear of blockage � Maintaining vegetation in the channel and floodplain � Monitoring of silt levels at West Bridge

However, the study also stated that there is a viable locally funded scheme for West Beck which would provide a standard of protection (SoP) up to the 1.3% a.p. event. The preferred option for this locally funded scheme includes the following works:

� Construction of new flood wall along the right bank upstream of West Auckland Road

� Construction of a new flood wall along the right bank upstream of the rail embankment adjacent to West Auckland Road tying into natural high ground

� Construction of new flood walls either side of West Beck between West Bridge and Prior Street.

In addition, after an internet search, it was shown that Cocker Beck has recently been desilted, adjacent to Westbrook Terrace by the Environment Agency. It had been noted that the silt and debris which had built up in the beck prevents the drains from discharging effectively during heavy rain, which may lead to flooding on North Road.

2.4.1 History of Flooding

There are records of flood problems along West Beck and Cocker Beck dating back to 1975. These include 3 incidents of flooding recorded in the last 25 years in October 1976, March 1979, and June 1982 involving surcharging of the Newton Lane culvert and flooding of the road and a small number of residential properties. Flooding of fields at the Cocker Beck confluence was also recorded in October 1976. The watercourse has been identified as a problem watercourse by Darlington Borough Council and the Environment Agency as a result of the flooding at Newton Lane. The main cause has been attributed to a lack of capacity in the culvert and channel downstream, owing to inadequate size and siltation.


Table 3 - Recent flooding from West Beck and Cocker Beck

Date Description

1875 Cockerton Green, below the School House was submerged and several houses were flooded.

1903 The bridge at Cockerton washed away and houses on the south side of the village were flooded.

1976 Heavy localised rainfall resulted in flooding at West Beck and Cocker Beck confluence and of Newton Lane on West Beck.

1979 Flooding at Newton Lane.

1982 Severe storms over West Darlington caused overtopping of West Beck at Newton Lane culvert. Two residential properties were flooded (Numbers 90 and 111 The Green). Four others only saved by having raised door thresholds. The new developments of sheltered flats at Newton Court surrounded by water but not flooded.

2000 Despite widespread flooding in the Tees catchment in June and October 2000 there appears to be no record of flooding in the West Beck catchment.

2.5 Flooding from land

2.5.1 Historical flooding data

Many of the historical flooding locations collated from the Environment Agency, Darlington BC and Cleveland Fire Brigade are located outside of the fluvial and tidal Flood Zones. This indicates that these flooding locations are due to other sources, such as surface water flooding directly from the land or drainage system. The distribution of these locations can be seen in Figure A, Appendix A1 to A8.

The historic flooding locations data shows that overflowing of stormwater drains has occurred around Coatham Mundeville. This data also shows that Coatham Mundeville has a history of surface water flooding from land runoff after a heavy rainfall event. The surface water flooding maps also tie in with this location.

Other flooding incidents caused by surface water runoff have been recorded at:

� Redworth � Heighington � Burdon Hall � Petty's Nook � Souith of Bishopton � Skip Bridge � Low Middleton

These locations also tie in to some extent with the surface water maps but they are small-scale, isolated and predominantly outside the urban area.

The Tees CFMP states that surface water flooding is a particular problem in Darlington where surface water is unable to discharge to drains and rivers. The CFMP does not go into any detail as to why there is this surface water issue in Darlington.

2.5.2 Surface water maps

The Areas Naturally Susceptible to Surface Water Flooding Maps, based on the Environment Agency data, is discussed in Section 2.4.1 of this report. The surface water maps for Darlington are included in Appendix A (Figures E1 to E8). These maps show the surface water flood extent and variation in susceptibility due to an extreme rainfall event. These maps should be used to assist the strategic consideration of the impacts of surface water flooding but also the sequential approach, the production of Surface Water Management Plans (SWMPs), and detailed FRAs for specific development proposals.


The distribution of surface water flooding ties in with the fluvial flooding locations and other galleys and low areas. This is where surface water will flow after heavy rainfall. The built up locations with significant surface water flooding extents are:

� Middleton St George � Around the airport � Coatham Mundeville

Within the Darlington urban area: � Eastbourne area � Lingfield area � Pierremont area � Town Centre Fringe around the fire and police stations

Potential development sites with significant surface water flooding extents are:

� West Park � EP2.6 employment site - Lingfield

These locations, where surface water can pool due to topography, do not always present significant problems. This type of surface water flooding can be managed for new development and in developed areas through surface water drainage improvements and the application of SUDS.

However, pathways where surface water will naturally flow should be noted. These can potentially be hazardous and can damage property, but it should be possible to control this with surface water management techniques such a sequential approach to site layouts or adopting SUDS. These locations can be described as critical drainage areas (CDA) and are discussed below.

2.5.3 Screening of Critical Drainage Areas (CDA)

SFRAs provide the opportunity for local authorities to assess, at a strategic level, the risk from multiple sources of flooding, which can then feed into more detailed assessments where appropriate by both themselves and other operating authorities. This includes the identification of Critical Drainage Areas which are those areas identified from historical flood events and/or modelled data as having a significant risk from surface water flooding. Recommendations can then be made for the future provision of Surface Water Management Plans (SWMPs) in high risk locations or areas of significant development for which an integrated drainage solution is possible that can reduce flood risk to both the current community and new development (SWMPs guidance is discussed in Volume III).

Screening for CDAs within the Borough were undertaken using data from the following sources:

� Fire Brigade flood incident locations � The national Surface Water Map (SWM) � Local authority flood risk locations � Flooding records from previous studies

The area was assessed to try and identify any potential CDAs. This was done by finding any clusters of historical flooding locations. If incident clusters and mapped surface water flow pathways overlap, this would be an indication that there is a CDA.

It will be important to get feedback from Northumbrian Water (and the Council's drainage team) on whether the locations identified:

� are actual problems, � were existing problems but a scheme has been completed to deal with the

problem. � are existing problems but a scheme will be completed in the future

Pierremont

As highlighted in Section 2.5.2, the Pierremont area of Darlington has a particularly extensive surface water flooding area. Some parts of this include the intermediate and high susceptibility to


surface water flooding maps. The three areas circled in Figure 3, show where historic flooding locations overlap the SWM. The northwest area may be linked to Cocker Beck (which is to the north). This could be a natural flow pathway for surface water making its way to Cocker Beck. Backing up could occur which would increase risk to the Pierremont area. The other two locations appear to be low areas where surface water can pool. However, the whole area has a number of historic flooding locations (unrelated to fluvial flooding) and SWM extents.

In addition to this, Section 2.6 describes a scheme that Northumbrian Water is to undertake in the Pierremont area. Information on this scheme from Northumbrian Water's website states that during storms, rainfall entering the sewerage network has resulted in flooding to the properties on Pierremont Crescent. It is not known whether this scheme will rectify all the potential problems in the Pierremont area.

Figure 3 - Possible critical drainage area in Pierremont


Purple - high susceptibility to surface water flooding, orange = intermediate, green = low, green dots = historic flooding locations

Town Centre Fringe

In the centre of Darlington there is a cluster of historic flooding incidents (see Figure 4). However, not all of these locations tie in with the SWMs. Directly to the west of the River Skerne, there are around 10 historic flooding incidents. Also within this area, there are a number of outfalls into the Skerne. There is little descriptive data on the historic flooding locations but it may be that there is an issue with outfalls into the Skerne backing up. It was mentioned in Section 2.5.1 that the Tees CFMP recognises surface water flooding as a problem in Darlington, in particular, surface water being unable to discharge to drains and rivers. In addition, the Skerne Section 105 report state that during flooding events on the Skerne, water levels may affect land and urban drainage networks. Backing up of discharges could result in surface water flooding from drains and manholes, leading to ponding in low lying areas. Due to this evidence, this area has been highlight for surface water flooding issues, possibly due to backing up of culverts flowing into the Skerne.


Figure 4 - Possible critical drainage area in the centre of Darlington next to the Skerne

Crown copyright. All Rights Reserved. 100023728. 2009.


Eastbourne

Figure 5 shows significant intermediate (and some high) surface water susceptible locations. A number of historic flooding locations tie in with these areas. The topography seems to show this area as a shallow basin, where surface water flow from the north could flood the lower flatter area in the centre (see Figure 5). The area susceptible to surface water flooding generally covers Eastbourne Park, the play area to the south and the school playing fields further south. These fields should be kept undeveloped and, subject to more detailed studies, opportunities to open up areas further south could be sought.


Figure 5 - Possible critical drainage area in Eastbourne



2.6 Flooding from sewers

Northumbrian Water is currently unable to provide information on flooding from sewers and any planned improvement schemes. As a result, it has not been possible to consider the potential foul and surface water sewer risk to Darlington in any detail.

The River Skerne Prefeasibility study noted that within the centre of Darlington, there are a number of drainage outfall pipes discharging to the Skerne, which could convey flood waters and place properties within the centre of Darlington at risk. However, we do not have any flood history information on the backing up of sewers within Darlington.

The West Beck Prefeasibility Study states that considerable parts of the West Beck catchment are sewered, with all new developments in Faverdale and northwards being drained on a separate surface/foul system. Parts of Cockerton, however, remain on a combined system.

The older, combined sewer systems can be prone to flooding due to capacity issues. In addition, as the storm and foul sewers are combined, flooding would pose a human health and pollution hazard.

A search of Northumbrian Water's website has enabled this study to highlight some upcoming sewer improvement schemes. This identifies sewer flooding problem locations but also summarises works to reduce the risk. Northumbrian Water is to invest £3 million to reduce the risk of flooding to fourteen homes in Pierremont Crescent. In times of heavy rainfall the quantity of rainwater entering the sewerage network has resulted in flooding to the properties on Pierremont Crescent. To prevent this from happening, 650 metres of sewer pipe is to be upgraded, and


increased in size. A new combined sewer overflow will also be built in Brinkburn Dene Park. The work to build a screened, combined sewer overflow will also improve the water quality of Cocker Beck and the River Skerne.

The fire brigade flooding incident dataset shows that this location also has a history of flooding. The fire brigade were needed to pump flood water out of a number of houses. The surface water flood maps also show this location at risk of surface water flooding. The scheme currently being completed should alleviate the surface water sewer flooding problems. However, the combined sewer overflow will enter Cocker Beck, which already has a history of flooding. This increased discharge could have the potential to increase flood risk on Cocker Beck.

A £4 million sewerage scheme is to be built at Middleton One Row, south east of Darlington. Northumbrian Water will lay 4km of pipes to transfer waste water to Stressholme treatment works on the outskirts of Darlington. The works include building a new pumping station and storm water tank at Middleton One Row. The work is needed due to an expansion in housing in the last few years, and the system is designed to cater for population growth. The work is in tandem with a £17m upgrade of the Stressholme treatment works to enable it to deal with 70m litres of waste water per day once it is complete.

2.7 Flooding from groundwater

The Draft Tees CFMP states that there is little documented evidence of groundwater flooding in the Tees catchment. However, with the cessation of minewater pumping and reductions in abstractions on the western edge of the Magnesian Limestone Escarpment, water table levels have risen and are thought to have caused flooding. Groundwater levels in the Skerne catchment are continuing to rise as a result of mine water rebound.

It is suspected that groundwater flooding occurs regularly in the Skerne catchment, but since the events often result in surface water flooding, they are recorded as such in the records. There is also the possibility that mine subsidence could cause flooding but there are no recorded instances in the catchment.

2.8 Flooding from reservoirs and other artificial sources

There are no major reservoirs or canals in Darlington.

2.9 Effects of Climate Change

UKCIP02 scenarios suggest that winters will become wetter over the whole of England, by as much as 20% by the 2050s. A shift in the seasonal pattern of rainfall is also expected, with summers and autumn becoming much drier than at present. Snowfall amounts will decrease significantly throughout the UK, the number of rain-days and the average intensity of rainfall is expected to increase. This could have significant implications for surface water flooding and should be considered when designing drainage systems for new developments. An increase in peak flow by around 20% over the next 50 years will translate into higher water levels.

Figures C1 to C8 in Appendix A shows the difference in extent between the 1% a.p. flood event with 1% a.p. event plus climate change. This shows an increase in flood extent from the River Tees in the Hurworth and Middleton St George areas. However, significant numbers of properties are not put at risk as a result (just isolated farm properties). The River Skerne to the north of South Park shows a small increase in extent, potentially putting more properties at risk. The flood extent of the River Skerne also increases by a small degree from Coatham Mundeville to the B6279 in Darlington (in mainly rural locations) The flood extent from Cocker Beck around Cockerton increases in this built up area, potentially putting more properties at risk.


Extracted from PPS25

2.10 Geology and Soils

The geology and soils of the Borough were investigated using a strategic scale (1:250,000) map available from the National Soil Research Institute and can be viewed at: http://www.landis.org.uk/soilscapes/

According to the soils map the majority of the Borough is covered by grass, arable land and some woodland. This is slowly permeable seasonally wet loam and clay soils. This will impede natural drainage. The area around the River Tees is composed of grassland and some arable land. This loamy soil is freely draining.

Unfortunately the scale of this data does not make it particularly relevant at a local level and should only be used as an indication of the potential for groundwater and surface water flooding and as a generalised dataset for the implementation of source control and infiltration sustainable drainage techniques (SUDS).

Therefore, geology and soils should also be investigated at a site level during a FRA. Their characteristics are not the only considerations when designing SUDS. It is recommended (refer to Volume III of this SFRA) that the application of SUDS should be explored at an early stage of new development projects and design requirements documented within any FRA produced. More detail on the application of SUDS and the SUDS “Management Train” is provided in Volume III.

2.11 Flood Defences

2.11.1 River Skerne

The River Skerne has had flood defences built in the past to reduce flood risk in Darlington. From 1952 to 1967 a comprehensive scheme was constructed to improve flood capacity. Further work was carried out in 1972 following the floods of 1967. As stated in section 2.3, since these defences were completed there have been no flooding incidents in Darlington.

In the Environment Agency's National Flood Defence Dataset (NFCDD), the only raised flood defence on the River Skerne are in the centre of Darlington, stretching from where the railway crosses the Skerne (south of Cleveland Street) to the Chesnut Street Bridge (although there is another small section adjacent to St Cuthberts Way). These consist of a mixture of private and Environment Agency owned concrete flood walls. NFCDD does not show the standard of protection (SoP) for these defences.

Current maintenance for the Skerne consists of twice yearly inspections of known hard defences, intermittent inspection of watercourse for tree removal and large urban debris and reactive inspection when required.

The River Skerne Prefeasibility Study (2003) assessed the economic viability of a flood alleviation scheme. The conclusion of the study was that there was no economic justification for a scheme. The recommended option was to 'do-minimum'; continuing with maintenance and accepting that there are pockets of properties at risk from flooding which should be integrated into the flood warning procedures.


2.11.2 River Tees

Much of the River Tees reach within Darlington has flood defences, primarily built to protect agricultural land. However these are overtopped or bypassed in major floods. Some sections of the Tees are protected to a higher level in order to protect settlements, such as Hurworth and in Neasham, where the defences protect the properties up to the 1% a.p. event but some flooding would occur from Kent Beck at this return period

The River Tees Model Update Phase 2 report (Environment Agency, January 2008) assessed the impact of removing defences on the River Tees. This study used the 1996 HR Wallingford report entitled ‘Lower River Tees: Impact of flood banks on flood water levels”. This used the ISIS model to identify the standard of the defences and to investigate effects of changing embankment levels on flood levels at Yarm. It was found that the existing standard of defence varied and in some cases was less than 5 years (rural defences). The minimum standard of protection was less than 100 years for about 75% of the washlands. The River Tees Model Update Phase 2 report built upon this and provided a risk category for each section of flood defence on the River Tees. Of the 43 sections of defences assessed, 20 (46%) are classified as low risk and maintenance could be safely withdrawn without impacting on flood risk at the 50-year return period.

2.12 Flood Warning

The Environment Agency has the lead role in providing the flood warning service in England and Wales. The aim of the flood warning service is to reduce risk to life, distress to people and damage to property caused by flooding by providing accurate, timely flood warnings to residents within the floodplain of rivers, estuaries and coasts; to the media and partner organisations.

It is crucial that people at risk receive appropriate flood warnings and take action to protect themselves and their property. Within the Environment Agency corporate plan “Creating a Better Place4” the Agency has highlight three main targets:

� To have 80% of properties at risk in the floodplain in England and Wales receiving an appropriate flood warning service;

� 75% of people who live in flood risk areas take appropriate action by 2011; and � To have major incident plans in place for high flood risk areas.

Currently the Environment Agency operates a flood warning service in specific locations known as “Flood Warning Areas” where “Flood Warning Codes” are assigned based on the overall impact of flooding within an area. These codes include:

“flooding of low-lying land and roads is Flood Watch expected”

“ flooding of homes and businesses is Flood Warning expected”

Severe Flood Warning “severe flooding is expected”

All Clear “all clear or receding floodwaters”

The Environment Agency’s Floodline Warnings Direct service provides flood warnings direct to people by telephone, mobile, email, SMS text message, fax or pager. There are a number of Flood Warning and Flood Watch areas that cover the Borough, some of which cross over administrative boundaries. Figure D in Appendix A show the Flood Warning Areas covered by Floodline Warnings Direct. They include:

4 Environment Agency (2006) Creating a Better Place: Corporate Strategy 2006-2011


Skerne Properties in Darlington Town Centre, and businesses on Valley Street North.

Tees Caravan Park at Newbus Grange Neasham village, from Kent Bridge, following Teesway, to Dibdale Road

2.12.1 Flood warning improvements

There are currently no flood warnings for West Beck and Cocker Beck. Recent studies on these two watercourses recommended that Darlington Borough Council and the Environment Agency take account of the identified flood risk areas and the findings of this report in their Emergency Planning.

For Cocker Beck it was highlighted that the installation of a telemetry rain gauge within the catchment to generate forecast for use in flood warning would be beneficial. Consideration should also be given to the modification of the model to run ‘real-time’ flood forecasting.

The flood warning procedures for the Skerne are based on trigger levels at Bradbury and Preston-le-Skerne Gauging Stations. Using the hydraulic model during the Skerne Prefeasibility Study, revised levels have been provided at Preston-le-Skerne and South Park Gauging Stations when flooding first commences at the four flood risk areas. This study recommended that that the current flood warning procedures be reviewed to consider these levels.

The River Tees Model Update Phase 2 report also recommended that the River Tees flood warning areas are updated to match the latest modelled outlines to eliminate inconsistencies and ensure that all people at risk are offered a warning.


3 Strategic Flood Risk Mapping

3.1 Introduction

The investigation and identification of the extent and level of flood risk to an area is assessed primarily geographically. Whilst the Environment Agency’s Flood Maps are very useful in this respect in showing indicative land use planning zones as required by PPS25, they are only a starting point in the consideration of flood risk in a particular area.

PPS25 Flood Zone Maps should be used primarily to enable the Sequential Test to be carried out, firstly in avoiding inappropriate development and then secondly, to seek compatibility between flood risk vulnerability and Flood Zones as required in Table D3 of PPS25.However, more detailed analysis is often needed to gain a greater understanding of the varying degree of flood risk at a district level.

At this SFRA level, it is not appropriate to look at flood risks in detail for individual development proposals, as this is a requirement of the site specific FRA and will be undertaken by developers in respect of a specific development proposal and prior to submitting a planning application. However, there is a need to undertake a broad assessment of flood risk issues to assist the LPA in making appropriate spatial planning decisions. This will enable a degree of certainty that the proposed strategic sites and allocations put forward in future DPDs, allow compliance with the Sequential and Exception Tests in PPS25 and importantly provide information to test whether the developments should be safe for occupants and users.

This broad assessment is assisted greatly by a suite of Borough wide flood risk information including the PPS25 Flood Zone Maps. No one map should be considered in isolation without reference to the others. The set of Strategic Flood Risk Maps provided in the Darlington BC Level 1 SFRA can be found in Appendix A and include:

SET A: PPS25 Flood Zones

SET B: Flood Zone 3 Depths

SET C: Climate Change Sensitivity

SET D: Flood Risk Management Measures

SET E: Areas Naturally Susceptible to Surface Water Flooding

After the PPS25 Flood Zone Map has been used to carry out the first sweep or Sequential Testing for various proposed development locations, all sets of maps need to be interpreted consistently in order to complete the second or third pass of the sequential approach sieving process. They can also be used “outside” of the development planning process to gain an understanding of various flood risk factors in other areas of interest across the Borough.

The detail provided in the Strategic Flood Risk Maps may also facilitate the application of the Exceptions Test where applicable. These maps should be used in sequence as shown in the Sequential Test sieving process as shown in Volume I of the SFRA.

3.2 PPS25 Flood Zone Maps

The PPS25 Flood Zones have been produced on a set of eight maps covering the Borough (see Appendix A Figures A1 to A8). The fluvial Flood Zone maps are based on information provided in the Environment Agency Flood Map. Version 3.14 of the Environment Agency Flood Zones issued in June 2009 has been used as the latest flood zones for the Borough. Flood Zones 2 and 3 were checked against all the most recent modelling outputs to see if they had all been integrated. Both Flood Zones 2 and 3 appear to have been updated with all the currently available hydraulic models.

As stated in PPS25, an aim of SFRAs is to define Flood Zone 3b: the functional floodplain. In this SFRA, this has been delineated using the method outlined in section 3.2.2.


These key maps should be used for facilitating the undertaking of the Sequential Test by planners and developers according to PPS25, as discussed previously in Volume I and illustrated within stage 1 of the Sequential Test sieving process.

3.2.1 Functional Floodplain

The Functional Floodplain (Flood Zone 3b) has been defined using modelled 4% a.p. outlines where available. The modelled outlines were then edited using the following methodology:

� Inclusion of land which provides a function for flood conveyance or flood storage (e.g. washlands)

� Removal of areas benefitting from defences (ABDs) � Removal of developed (Brownfield) land � Removal of major transport infrastructure (e.g. motorways and railways) � Removal of ‘dry islands’ defined using the ‘size standards’ within the Environment

Agency SFRM Specification for Flood Risk Mapping5

For those watercourses that have not been modelled or where a 4% a.p. outline is available, “Candidate Flood Zone 3b” areas have been identified based on the Environment Agency Flood Zone 3 outlines. Greenfield areas within Flood Zone 3 have been identified which should be safeguarded from future development. Storing flood water in these areas during an event could potentially reduce risk downstream in urban areas in the future.

However, as these areas have not been explicitly modelled (or have used a 1% a.p. modelled outline) and are partly based on professional judgement, it is important that they are assessed in more detail at a site-specific FRA level if development is planned in the future. Nevertheless it is recommended in this SFRA that they are left as open greenfield for future flood storage or as flood compensation needed to allow other development.

The data used to define the functional floodplain and “Candidate Flood Zone 3b” for each watercourse is summarised in Error! Reference source not found..

Table 4 - Functional floodplain and candidate functional floodplain mapping

Watercourse Extent Data source

River Tees (east of A1) 4% a.p. River Tees ISIS model (2008)

River Skerne 4% a.p. River Skerne floodplain mapping "001 and 2003)

West Beck 4% a.p. West Beck floodplain mapping (2006)

River Tees (west of A1) 1% a.p. Candidate Flood Zone 3b Flood Zone 3 Version 3.14

Cocker Beck 1% a.p. Candidate Flood Zone 3b

Flood Zone 3 Version 3.14

Cree Beck (north of Hurworth) 1% a.p. Candidate Flood Zone 3b Flood Zone 3 Version 3.14

Neasham Stell (north of Neasham)

1% a.p. Candidate Flood Zone 3b


Coatham Beck 1% a.p. Candidate Flood Zone 3b Flood Zone 3 Version 3.14

Carcut Beck 1% a.p. Candidate Flood Zone 3b


Billingham Beck 1% a.p. Candidate Flood Zone 3b Flood Zone 3 Version 3.14

5 Environment Agency (2006) Strategic Flood Risk Management Specification for Flood Risk Mapping release 1.2


Halliwell Beck 1% a.p. Candidate Flood Zone 3b


Corner Beck 1% a.p. Candidate Flood Zone 3b Flood Zone 3 Version 3.14

Dyance Beck 1% a.p. Candidate Flood Zone 3b


Summerhouse Beck 1% a.p. Candidate Flood Zone 3b Flood Zone 3 Version 3.14

3.3 Flood Zone 3 Depth Map

An indicative depth map of the 1% a.p. fluvial event has been provided for Darlington BC (see Figure B1 in Appendix A). This fluvial depth grid was obtained from the Environment Agency North East broad scale modelling work for CFMPs undertaken by JBA Consulting in 2008. The methodology is based on the original methodology used in creating the original Environment Agency Flood Map using an overland routing model JFLOW. However, the map was improved by:

� Updating the hydrology of inflows into the model, and � Updating the topographical data from NEXTMAP to LiDAR data. Flow paths

under structures were also included to provide a more realistic result. Whilst the extent of the depth grid cannot be directly compared to the current Flood Zones (as Flood Zones are based on detailed hydraulic models in some locations and NEXTMAP extents in others) they do provide a useful indication of potential scale of flood inundation during a 1% a.p. event.

The depth map has been categorised in depth ranges using the scaling below:

Max Depth (m) 0.1 - 0.6

0.6 - 1.5

1.5 - 3

>3

3.4 Climate Change Sensitivity Maps

Where there is modelling available, climate change sensitivity maps have been provided (see Figures C2 to C8 in Appendix A). These maps show fluvial flood extents for an undefended floodplain with a 1% a.p. flood flow plus a 20% increase in flood flows. This is representative of a plus 100 years climate change extent. For un-modelled watercourses the presumption is to take Flood Zone 2 as a precautionary extent of Flood Zone 3a in the future.

The sequential approach requires early consideration of the effects of climate change on flood risk and these maps help greatly in this respect. PPS25 requires the consideration of the sensitivity of new developments to climate change to be considered as part of an appropriate FRA and these maps provide an indication of this sensitivity. In addition, emergency evacuation routes can be identified and planning put in place to ensure they are outside of the flood extent.

The sensitivity of a particular location and land use to climate change can be factored into decisions regarding floor levels, building uses and safe access and egress etc. Greater changes in depth or extents can be associated with greater increases in flood risk and in these areas, where this risk cannot be avoided, or substituted, mitigation measures are likely to be extensive. For some developments, the FRA may not be able to demonstrate continued safety for occupants as required by the Exception Test in PPS25.

3.5 Flood Risk Management Measures Map

Residual risks are the risks that remain after all risk avoidance, substitution and mitigation measures have been taken. The residual risks in the Borough are therefore related to the occurrence of events of low probability, such as extreme flood events greater than the design


capacity of the constrained river/coastal system or where the design standard of flood defences is exceeded.

A map of flood risk management measures has been produced (see Figure D in Appendix A). The map includes the:

� location of Environment Agency river flood defences � coverage of Environment Agency Flood Warning Areas

This map is very important when considering the residual risks associated with flood. These residual risks must be investigated within any Level 2 SFRA or site specific FRA as relevant.

3.6 Surface Water Flooding Maps

The Areas Susceptible to Surface Water Flooding Maps show actual surface water flood extent and variation in depths for particular geographical areas of interest, assuming a 0.5% rainfall event and a “hard surface” ground model.

The areas susceptible to surface water flooding zones have been provided on a set of eight maps, and are largely based on information provided in the Environment Agency national Surface Water Map (see Figures E1 to E8 in Appendix A).

The vulnerability zones are split between three zones:

More Susceptible

Susceptible

Less Susceptible

These maps are extremely helpful in supplementing the PPS25 Flood Zone Maps as they show where localised, flash flooding can cause problems, even if the Main Rivers are not overflowing.

More information on surface water flooding and the surface water flood maps can be found in section 3.2.3 of Volume I.


4 Site Specific Allocations

4.1 Introduction

A Level 1 SFRA should enable Darlington BC to carry out the Sequential Test as outlined in Annex D of PPS25. This evidence is required to support the Core Strategy strategic sites and the future allocation of land in DPDs at examination to show that the LPA has considered sites outside flood risk areas before allocating them in areas at risk of flooding.

This Level 1 SFRA has provided Darlington BC with PPS25 Flood Zone classifications for all locations identified for development provided within this assessment. The Council will be required to prioritise the allocation of land for development in ascending order from Flood Risk Zone 1 to 3, including the subdivisions of Flood Risk Zone 3, if necessary.

The Environment Agency has statutory responsibility and must be consulted on all development applications allocated with medium and high risk zones, including those in areas with critical drainage problems and for any development on land exceeding 1 hectare outside flood risk areas. In these circumstances, the Environment Agency will require the Council to demonstrate that there are no reasonable alternatives, in lower flood risk categories, available for development. Where appropriate, the Exception Test is to be applied.

A Sequential Test spreadsheet has been produced showing the results of all potential development sites (as at June 2009) provided by Darlington BC against PPS25 Flood Zones and as an extra layer of information against the surface water vulnerability zones. Area (ha) and percentage cover of each Flood Zone is provided. In addition, two columns have been provided, one indicating whether the site is affected by the climate change extent (Flood Zone 3 in 2100) and which identifies whether the site is at risk from any other sources of flooding. The spreadsheet is included in Appendix B.

Darlington BC should use this information to carry out the first sieve of the Sequential Test, by identifying and removing those sites at greatest risk. Once a decision has been made by Darlington BC on whether to remove or keep those sites at higher risk due to wider social and/or economic circumstances, they should then carry out a second or third pass of the Sequential Test against the wider suite of flood risk maps produced within this SFRA. This should ensure that there is an evidence base for replacing sites at a high risk of flooding with those that are at a lower risk or for keeping the sites and bringing them forward for the Exception Test.

Once the sequential sieving process has been carried out, the Environment Agency will require the Council to demonstrate that there are no reasonable alternatives in lower flood risk categories available for development. The vulnerability of the remaining sites at risk should be considered and substituted with lower risk development (if possible) before any mitigation measures are considered.

The next part of this chapter summarises flood risk to the potential development sites that Darlington BC have provided for this study. This includes recommendations for changing the proposed sites (before the Sequential Test is undertaken) and whether certain sites are likely to pass the Exception Test.

4.2 Current Development Site Sequential Test

Development sites identified by Darlington BC include:

� Indicative residential sites � Strategic Housing Land Availability Assessment (SHLAA) sites over 1ha � Employment sites

Including the above sites, the total developable area is around 950 ha. Tables 5 and 6 provide a summary of sites at risk of fluvial and surface water flooding that are included in the Sequential Test spreadsheet.


4.2.1 Summary of sites at risk of fluvial flooding Table 5 - Summary of development sites at risk of fluvial flooding

Flood Zone Coverage

Flood Zone 2 Flood Zone 3a Flood Zone 3b

No. Sites

Total Area (ha)

Area (ha) No. Area

(ha) No. Area (ha) No.

Total 46 949.2 48.8 13 3.3 8 25.9 9

� 29 ha of sites are at risk of flooding in the 1% a.p. outline (Flood Zone 3a+3b). � 78 ha of sites are at risk of flooding in the 0.1% a.p. event (Flood Zone 2+3a+3b) � 9 employment / housing sites are situated in the functional floodplain and under

PPS25 these will not be permitted. However, some of the areas considered functional floodplain are relatively small. It should be possible to redefine some of these site boundaries to make development acceptable. More details will be provided later in this chapter.

Table 6 - Summary of development sites at risk of surface water flooding

Surface Water Flood Zone Coverage

Low Vulnerability

Intermediate Vulnerability

High Vulnerability

No. Sites

Total Area (ha)

Area (ha) % Area

(ha) % Area (ha) %

Total 46 949.2 173.8 8.4 82.6 3.7 11.0 0.4

The risk of surface water flooding to Dalrington BC’s potential development sites is shown to be more widespread than fluvial flooding.

� 43 of the 46 sites are at some risk of surface water flooding. � A total of 16 sites have a high vulnerability of flooding which must be considered

within the Sequential Test sieving process (depending on the extent of surface water flooding). If these sites go forward and are developed, a FRA must consider surface water mitigation techniques such as Sustainable Urban Drainage or a more open site layout.

4.3 Flood risk and the 2009 potential development sites

4.3.1 Introduction

The previous section combines Flood Zone and surface water map information with the potential development sites to allow the application of the Sequential Test. This section summarises where specific, generally larger, sites are at flood risk and includes recommendations for development planning.

Following this section is a more detailed assessment of the sites in central Darlington which are at risk from the River Skerne and Cocker Beck. This provides an indication as to whether these sites will pass the Exception Test (if no alternative sites can be found) and which areas have a lower flood hazard. This will be sufficient for development planning but a more detailed study may be required before the Core Strategy and DPDs go to examination.


Faverdale Strategic Reserve (Local Plan employment allocation EP8)

This greenfield site has a watercourse running through the centre of it. The floodplain affecting this site includes Flood Zone 2 (blue) and 3b (purple). Under PPS25, development should not be permitted in Flood Zone 3b. The employment site could be developed with Flood Zone 2 but a flood risk assessment would be required to show that the risk could be safely managed.

As the proposed development area lies directly over a watercourse, this area would need to be open to make space for this watercourse. Due to current policy such as Making Space for Water, it is unlikely that culverting of this watercourse would be approved. It is recommended that if development goes ahead, the area at risk of flooding is left open as greenspace to allow the watercourse to use the floodplain rather than putting new development at risk.

It will also be important to manage surface water runoff effectively. Otherwise, developing on greenfield will increase flood risk to the existing development downstream in Faverdale. Faverdale is already shown to be at risk of flooding so upstream surface water runoff to this watercourse should be reduced not increased. As open space is already proposed in the Flood Zones, SUDS could be incorporated into this area, using the natural topography to direct surface water into, for example, attenuation ponds. However, as the area to be developed is large, it is likely that other surface water management areas will be required around the site.

Figure 6 - Faverdale Strategic Reserve Employment site EP8


SHLAA 59: Muscar House Farm

This greenfield site has a watercourse running adjacent to it. The floodplain for this watercourse includes Flood Zone 2 (dark blue), 3a (light blue) 3b (purple). Under PPS25, development should not be permitted in Flood Zone 3b. Residential development could be developed with Flood Zone 3a but the Exception Test would need to be passed. As the site is greenfield, it is unlikely that development in Flood Zone 3a would be approved. Residential development could be approved in Flood Zone 2 if the Sequential Test shows that there are no alternative sites of lower flood risk available.


It is recommended that the area shown to be at risk of flooding is retained for green space to allow the River Skerne to flood in extreme conditions. Downstream, the Skerne puts parts of Darlington at risk of flooding. As with site EP8 above surface water runoff into the Skerne should be reduced, not increased, in order to reduce the risk of flooding from the River Skerne downstream.

Figure 7 - Muscar House Farm residential site


SHLAA 20: Great Burdon

A large part of this site is shown to be within Flood Zones 2 (dark blue), 3a (light blue) and 3b (purple). There is also historic evidence of the River Skerne overtopping its banks and flooding the land here. According to PPS25, residential development should not be approved in 3b and would need to pass the Exception Test to be approved in Flood Zone 3a. Being on greenfield land, it is unlikely that the site would pass the Exception Test. Development could be approved in Flood Zone 2 if a detailed Flood Risk Assessment showed that the risk could be safely managed.

It is recommended that the area at risk of flooding is removed from the proposed development area. The LPA may have to decide not to include the site in future DPDs if the change in developable area prevents development of the site being viable.


Figure 8 -Great Burdon residential site


Blackett Road/Red Barenes Way (Local Plan employment allocation EP2.4)

This developed employment area is shown to be within Flood Zones 2 and 3a. There is also historic evidence of flooding from the Skerne due to overtopping. According to PPS25, employment use could be appropriate here, subject to a Flood Risk Assessment. However, the aim of the Sequential Test is to try and move all new development outside of the areas at risk of flooding. As there is historic flooding here, this is especially important.

There is only a small part of the site shown within Flood Zone 3, so it may be possible to leave this area undeveloped or used for an amenity or SUDS area.

The Flood Zone 2 area is probably too large to be left undeveloped and as the proposed land use is 'less susceptible ' employment land, substitution (as described in PPS25) would not be possible. Residential development could be approved here if the Sequential Test is completed showing there are no alternative sites in Flood Zone 1 for residential development.

Again, as this development is upstream of flood risk locations on the River Skerne and surface water runoff is likely to go into the river, surface water management will be a key issue to be considered in a Flood Risk Assessment.


Figure 9 - Blackett Road/Red Barnes Way Employment allocation EP2.4


Valley Street (Local Plan employment allocation EP2.1) and SHLAA Town Centre Fringe

Large proportions of these proposed employment and residential sites are within Flood Zone 2 (dark blue) of the River Skerne. One of the sites is within Flood Zone 3a (light blue) of Cocker Beck. The site at risk from Cocker Beck will need to undergo the Exception Test if it were to be allocated. A more detailed assessment of the risk from Cocker Beck would also be required. Some parts of the sites to the north are protected by flood defences. There is therefore a residual risk of flooding if the defences breach, creating a potentially high flood hazard. This area is considered in more detail in Section 4.4.

Again, surface water management should be a key element of any Flood Risk Assessment as surface water runoff is likely to enter the Skerne and could increase flood risk downstream.


Figure 10 -Valley Street Employment allocation EP2.1 and Town Centre Fringe


SHLAA 60: Feethams

This proposed residential site is within Flood Zone 2 of the River Skerne. Although PPS25 allows for residential development in this zone (subject to a flood risk assessment), the Sequential Test requires that efforts are made to place any new development outside of areas at risk of flooding. If this is not possible, the allocation could be substituted with development of a lower vulnerability. As this is residential development, it would be more appropriate for less vulnerable land to be allocated here. If this is not possible, a detailed Flood Risk Assessment will be required taking into account access and egress routes and reducing surface water runoff into the River Skerne.


Figure 11 -SHLAA 60 Feethams


SHLAA 17 Roundhill Road, Hurworth

The northeast corner of this potential residential site is shown to be within Flood Zone 3b. PPS25 states that residential development should not be allowed here. However, there is low confidence in this 3b definition due to the lack of a modelled flood outline. A detailed Flood Risk Assessment, which would include modelling the watercourse, may show that the site is within the lower risk Flood Zones (3a or 2) or not at risk at all. This allocation could therefore be retained or the area at risk of flooding kept free from development.

Figure 12 -SHLAA 17 Roundhill Road, Hurworth



4.3.2 Strategic housing site summary

The Council provided information on a range of potential future housing sites identified through the Strategic Housing Land Availability Assessment (SHLAA) process. All sites have been assessed in this SFRA to help ensure that the Council identifies the best general locations for new housing, taking into account many variables, including flood risk.

However, this SFRA cannot identify the best housing sites on flood risk grounds because, at this stage, the Council only has indicative sites and housing numbers available rather than different housing layouts for each site. Based on the information provided these SHLAA sites have no land in flood zones; SHLAA sites 45, 48, 53, 29, 58, 55, 8, 29, 34, 39, 49, 55, 56, 13, 42, 32, 43, 73, 22, 54 and 40.

Although the following sites do have part of their land within flood zones, this does not always mean that the site cannot be developed. Detailed site layout plans will help inform the selection of strategic sites and future allocations to show whether it is feasible for a site to be included in the Core Strategy and other DPDs. If there are overriding social and economic reasons for development to go ahead in these areas, the Exception Test may be able to show that the site can proceed. In summary, the following sites could be developed if the issues next to them can be fulfilled.

� Town Centre Fringe – The ST would need to be completed for the part of the site in Flood Zone 2 and the Exception Test for section in FZ3.

� SHLAA site 60 - The ST would need to be completed for the part of the site in Flood Zone 2.

� SHLAA site 17 – The development layout would need to be adjusted so that future development is not at risk of flooding.

� SHLAA sites 59 – The development layout would need to be adjusted so that future development is not at risk of flooding.

� SHLAA sites 20 – Development within the Flood Zone 3a and 3b area is not possible under PPS25, but development of the remainder of the site is possible.

4.4 Preliminary Level 2 Assessment for Central Darlington

This section of the SFRA focuses on the proposed development sites in the area where Cocker Beck converges with the River Skerne. As shown in section 4.3.1, large parts of these potential development sites are within Flood Zone 2 while a small part is within Flood Zone 3.

For this Level 1 SFRA, a preliminary assessment has been completed in order to indicate whether the sites could be developed safely and therefore pass the Exception Test. This should be sufficient for spatial planning purposes but not for submission for examination.

More detail is needed in this area, as flood risk is complicated by the convergence of Cocker Beck with the River Skerne, along with the presence of raised defences on sections of the Skerne. Cocker Beck does not have a hydraulic model and it is likely that a detailed modelling assessment of Cocker Beck and the impact of a defence breach on the Skerne will be required before the Core Strategy and future DPDs go to examination.

Flood depth and flood hazard grids were obtained from the Environment Agency North East Broad Scale modelling work for CFMPs undertaken by JBA Consulting in 2008. Flood hazard is a function of depth and velocity and the scale of risk represents hazard to people.

The methodology used to produce this broad scale modelling is based on that used in creating the original Environment Agency Flood Map using an overland routing model called JFLOW. However, the map was improved by:

� Updating the hydrology of inflows into the model, and � Updating the topographical data from NEXTMAP to LiDAR data. � Flow paths under structures were also included to provide a more realist result.

The depths and hazard grids do not directly correspond to the SFRA Flood Zones as the River Skerne Flood Zone is based on a detailed hydraulic model while the Cocker Beck Flood Zone is base on the original JFLOW modelling. As a result, this broad scale modelling more accurately defines the Cocker Beck flood outline for the 1% and 0.1% events (Flood Zone 3 and 2). However the 0.1% extent on the Skerne is less accurate than the current Flood Zone 2.


A number of different flooding scenarios exist for the broad scale modelling work. It was decided to choose the flood depth and hazard grid (scenario) that most accurately represents the current Flood Zone maps.

Figures showing the 1% and 0.1% a.p. flood depth and hazard grids can be seen in Appendix A, Figures G1 to G4. Smaller scale extracts are included in Figures 12 and 13 below. Included in these plans is the location of the flood defences on sections of the River Skerne. Tables 8 and 9 below (taken from Volume III of this SFRA) show how flood depth and hazard data can be used to indicate whether development can be developed safely.

Table 7 - Flood Hazard Thresholds

Table 8 - Suggested screening criteria for mitigation measures

Flood Hazard d(v+0.5)+DF Description Alternative Name / Hazard Class

0 Safe (dry) None

0 to 0.75 Caution Low

0.75 to 1.5 Dangerous for some Moderate

1.5 to 2.5 Dangerous for most Significant

Over 2.5 Dangerous for all Extreme

Flood Hazard d(v+0.5)+DF Description Alternative Name / Hazard Class

Depth of Inundation*

Comments

0 to 1.0 m Sustainable mitigation and flood risk management may be feasible for both housing and employment purposes. There is a greater likelihood that the Exception Test can be passed.

1.0 to 1.5 m Mitigation is likely to be costly and may not be economically justifiable for low value land uses. Housing allocations are considered appropriate, provided flood risk can be managed or mitigated (e.g. by using lower levels for car parks or public areas). Floor level raising for employment purposes is unlikely to be economically viable and employment allocations should be reconsidered in favour of alternative lower risk sites. The likelihood of passing the Exception Test is lower.

Above 1.5 m Flood risk mitigation measures are unlikely to be economically justifiable and both housing and employment allocations should be reconsidered in favour of alternative lower risk sites. Development is unlikely to be sustainable and the likelihood of passing the Exception Test is low.

Notes: * Based on predicted depth of inundation for the 1% (Fluvial) event + 20% additional flow for Climate Change as per PPS25. Environment Agency flood zone data.

For the 1% a.p. flood depth grid, a small section of the development site is shown to be at risk from Cocker Beck. This depth grid shows a better representation of Cocker Beck than the current Flood Zone map, which is misaligned due to inaccurate DTM data. The flood depths here are half in the 0.1 to 0.6m and half in the 0.6 to 1.5m categories. The depths are greatest closer to the River Skerne. It is expected that this is due to flood water from Cocker Beck flowing against the raised defences on the Skerne and pooling there.

For the 0.1% a.p. depth grid, flood risk comes from Cocker Beck and the River Skerne. This is because at events greater than the 1% a.p., flood levels reach bank top on the Skerne. This does not mean that the defences on the right bank are overtopped, but that they have the potential to breach. The 0.1% depth grid below therefore shows indicative flood depths if the right bank defences breach and flood water overtops on the left bank.


The 0.1% depth map shows the greatest depths (1.5 to 3m) either side of the River Skerne. The northwest section of one of the development sites is also affected by these higher depths. The majority of the remaining area is at risk of flooding from depths in the 0.6 to 1.5m category with some shallower areas on the periphery. The deeper areas indicate topographically lower locations where flood water is more likely to pool.

Figure 13 - Flood depth grids for the 1% and 0.1% a.p. events

1% a.p. Event Flood Depth 0.1% a.p. Event Flood Depth


The hazard grid for the 1% a.p. flood shows the greatest flood hazard (depth multiplied by velocity) where Cocker Beck meets the River Skerne. This could be a result of Cocker Beck overtopping, pooling against the defence and flowing south adjacent to the Skerne. The remaining area is of the lowest hazard category.

For the 0.1% a.p. hazard grid, the greatest hazard is again either side of the River Skerne. As the river overtops, depths and velocities will be greatest in this corridor. The northwest section of the potential development site also shows a higher hazard rating than the other sections. For this flooding to occur on the Skerne, the flood defences would need to be breached and the undefended banks overtopped. If the west bank defences breached, the areas to the west of the


flood defences will be at the greatest flood hazard. This is because flood waters could rapidly flow through the breach at high velocities and depth, carrying debris and putting people at risk. However, this event would only occur between the 1% and 0.1% a.p. event and with a breach in the defences (combined probability).

Figure 14 - Flood depth for the 1% and 0.1% a.p. events

1% a.p. Event Flood Hazard 0.1% a.p. Event Flood Hazard


4.4.1 Recommendations

The areas of lowest flood depth and hazard will generally be to the east and southwest of the River Skerne. These areas do not flood until the 0.1% a.p. event (Flood Zone 2). They are not at risk from Cocker Beck and will not be at risk from the potential flood hazard of a flood defence breach. The further away from the River Skerne, the lower the flood risk. Depths here are less than 1.5m so mitigation should be possible (although costly). Flood hazard is 'danger to most' and 'danger to some'. Mitigation measures should be able to reduce this hazard to people allowing residential development to go ahead. For development planning purposes, it should be possible to allocate this area for residential development, as long as no other sites can be found (Sequential


Test), the Exception Test is passed and subject to a Flood Risk Assessment. Future development should be set back from the Skerne to avoid the highest flood depth and hazard indicated in the figures.

The far northwest section of the development site does not flood until the 0.1% a.p. event but the flood depth and hazard is high (over 1.5m deep flooding). This is probably due to low lying land directly to the west of the Skerne. This means mitigation measures are unlikely to be economically justifiable and the likelihood of passing the Exception Test is low. This area is also defended. At the 0.1% a.p. event, there is the possibility of the defences breaching and creating a high flood hazard for anybody within the area at risk. This would present a 'danger for most' and 'danger for all' flood hazard suggesting that residential development is not appropriate. This is a residual risk, and the conclusions are subject to more detailed modelling. If it were essential that residential development were to be approved, a more detailed strategic study of the area would need to be undertaken to assess the risk of a breach here. However, the conclusions may still be that residential development is not appropriate.

The area perceived to be at greatest risk is the land to the west of the Skerne and next to Cocker Beck. The area floods at the 1% a.p. event from Cocker Beck. This flood water could pool at the Skerne defences, creating a flow pathway adjacent to the Skerne. In addition, at the 0.1% a.p. event, the flood defences have the potential to breach creating a high flood hazard in this area. As this part of the site is within Flood Zone 3, the Exception Test would need to show that residential development could be developed safely here. This would include breach modelling of the Skerne and modelling Cocker Beck to better understand the risk that this watercourse poses. It is not known at this stage whether this part of the site would pass the Exception Test. The depths shown in the broad scale modelling do not rule out mitigation measures and the hazard rating does not rule out residential development. However, the priority should be to avoid development in this area or substitute it with a less vulnerable land use (e.g. employment land). If this is not possible, then the detailed assessment described above would be required.

4.5 Surface water flood risk

The surface water flood maps show that a number of proposed development sites are at risk from surface water flooding. These maps show three different scales of surface water flooding (low, intermediate and high susceptibility). For all developments, surface water management will be an issue that will have to be dealt with. Large dense development could have significant implications on current risk in the area and further downstream if runoff is not controlled. Some surface water management recommendations are included in Section 4.3.

The intermediate and low surface water flooding areas can, in general, be managed relatively easily. However, sites should be identified that are at risk from high susceptibility surface water flooding and those situated directly on surface water flow paths.

Figures 14 and 15 show the development sites that are at risk from high susceptibility surface water flooding (area at risk is in blue). If these areas are to be developed, the risk from surface water flooding should be taken into account at an early stage. The risk in Figure 14 could also come from a minor watercourse which may require modelling in a Flood Risk Assessment.


Figure 15 - SHLAA Site 56, Salters Lane West with a high vulnerability to surface water flooding


Figure 16 - SHLAA Site 20, Great Burdon and Yarm Road and Local Plan Employment Allocation EP2.6 areas with a high vulnerability to surface water flooding


4.6 Individual planning applications


The Sequential Test ‘sieving’ process discussed above has focused on those potential development sites which have been identified by the LPA in the SHLAA process. However there will be circumstances where the Sequential Test will have to be applied to individual planning applications and some where it will be difficult to apply. In every case it must been seen as best practice to search for alternative sites for development in lower flood risk areas before considering the vulnerability of the proposed development site and applying the Exception Test. There are two types of development in which the Sequential Test must be applied:

� Windfall sites � Areas requiring redevelopment or regeneration

Where sites have not been sequentially tested by the LPA, the Sequential Test will need to be applied at the individual site level. The developer will be expected to provide evidence to the LPA that there are no other reasonable available sites where the development could be located and the LPA will carry out the Sequential Test. According to PPS25, as part of this evidence the planning application must include:

� The geographical area in which the search is to applied � Flood risk to the site � Availability of ‘reasonably available’ sites � The vulnerability classification of the development � If it is likely that the Exceptions Test will need to be applied � That the development is safe and residual flood risks can be overcome to the

satisfaction of the Environment Agency and other stakeholders Once individual sites have been identified, a comparison of flood risk needs to be undertaken. This should be carried out against the suite of Strategic Flood Risk Maps provided with this SFRA. Sites should also be compared against:

� Development plan status � Capacity � Constraints (availability, policy restrictions, physical problems or limitations,

potential impacts of development and future environmental conditions) Following on from this SFRA, the LPA should develop policies in their DPDs on how windfall sites should be treated in flood risk terms. Through the Sequential Test, LPAs should identify where specific types of windfall development would be constituted as appropriate development in certain flood risk areas and what the broad criteria should be for submitting a planning application under these circumstances.

Whilst all development on previously developed land still requires the application of the Sequential Test, where redevelopment is ongoing as part of an existing regeneration strategy in Flood Zones 2 or 3, it has to be accepted that the redevelopment cannot always go outside a Flood Zone butI it is likely that the site will pass parts a) and b) of the Exception Test. In this case flood risk must be considered at the earliest stage of the regeneration strategy promoting opportunities to reduce flood risk for the community. This still may mean locating higher/more vulnerable parts of the development in lower flood risk areas within the site or removing some aspects of the redevelopment in order to increase flood storage or flow routes, as part of the wider regeneration strategy.

PPS25 recognises in exceptional cases, for the redevelopment of an existing single property that it will be difficult to consider alternative sites and apply the Sequential Test. In these cases, although the site will not be subject to the Sequential Test, the planning application must state why this is the case. Redevelopment sites will still need to pass the Exception Test and the sequential approach to site layout should also be considered. Importantly, the site will still need to deliver the recommendations of its site-specific Flood Risk Assessment, aiming to keep the development and its residents or users safe.


Appendices

2009s0156 - DBC SFRA Vol II v2.0 I

A Figures (Provided separately)

2009s0156 - DBC SFRA Vol II v2.0 II

B Sequential Test Table

2009s0156 - DBC SFRA Vol II v2.0 III

(ha) (ha) (ha) (ha) (ha) (ha) (ha) (ha)

Indicative FB - 6 separate25 Residential Sites 2.50 2.50 80.67 0.48 19.33 0.00 0.00 0.00 0.00 0.40 15.88 0.16 6.24 0.00 0.00

Darlington Strategic Flood Risk Assessment Darlington Borough Council Sequential Test

Summary Table

Number of Sites Area Area # Area # Area # Area # Area % at risk Area % at risk Area % at risk Total 46 949.2 949.2 46 48.8 13 3.3 8 25.9 9 173.8 837.2 82.6 366.8 11.0 37.0

Main Table

Surface Water Vulnerability

High Vulnerability Flood Zone 1 Flood Zone 2 Flood Zone 3a Flood Zone 3b Low Vulnerability Intermediate Vulnerability

Flood Zone Coverage

Flood Zone Coverage Surface Water Vulnerability

Site ID Name Ref Land Use Area (ha)

Area (ha)

% Area (ha)

% Area (ha)

% Area (ha)

% Area (ha)

% Area (ha)

% Area (ha)

% FZ3 +CC?

Other sources

1 42 SHLAA 32.10 32.10 98.45 0.16 0.50 0.00 0.00 0.34 1.05 3.45 10.75 1.38 4.31 0.11 0.34 2 Skerningham 40A SHLAA 6.18 6.18 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.35 5.70 0.17 2.75 0.00 0.00 3 Neasham Rd/Snaipe Lane Other SHLAA 13.97 13.97 100.00 0.00 0.00 0.00 0.00 0.00 0.00 5.05 36.15 2.25 16.12 0.00 0.00

4 Memorial Hospital 45a SHLAA 1.87 1.87 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.29 15.37 0.12 6.17 0.00 0.00 FB - pumping out flood incident

5 Mowden Hall 13 SHLAA 3.42 3.42 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 6 Stag House Farm 54 SHLAA 21.78 21.78 100.00 0.00 0.00 0.00 0.00 0.00 0.00 5.40 24.79 2.83 13.00 0.26 1.19 7 West park 22 SHLAA 62.22 62.22 100.00 0.00 0.00 0.00 0.00 0.00 0.00 18.87 30.33 13.78 22.15 0.04 0.06 8 Firth Moor Open Space 67 SHLAA 7.37 7.37 100.00 0.00 0.00 0.00 0.00 0.00 0.00 1.31 17.77 0.05 0.62 0.00 0.00 9 Glebe Road 56 SHLAA 7.66 7.66 100.00 0.00 0.00 0.00 0.00 0.00 0.00 2.89 37.67 2.29 29.91 1.36 17.73

10 Dean & Chapter Land 20

SHLAA 105.72 105.72 73.51 7.83 7.40 1.61 0.02 18.57 17.57 24.34 23.02 17.14 16.22 6.30 5.96 YES

Historic overtopping of River Skerne defences

Flood Zone 1

Flood Zone Coverage Surface Water Vulnerability

Flood Zone 2 Flood Zone 3a Flood Zone 3b Low Vulnerability Intermediate Vulnerability

High Vulnerability

10 Dean & Chapter Land SHLAA 105.72 105.72 73.51 7.83 7.40 1.61 0.02 18.57 17.57 24.34 23.02 17.14 16.22 6.30 5.96 YES defences 11 Easbourne School & access 65 & 66 SHLAA 6.56 6.56 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.83 12.74 0.14 2.06 0.00 0.00 12 Mayfair Road Open Space 55 SHLAA 2.36 2.36 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.30 12.62 0.03 1.27 0.00 0.00 13 Harrowgate Hill 34 SHLAA 0.50 0.50 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.04 7.81 0.00 0.00 0.00 0.00 14 Muscar House Farm 59 SHLAA 21.98 21.98 83.23 1.97 8.97 0.27 0.01 1.45 6.58 2.61 11.89 1.61 7.34 0.33 1.50 YES 15 Berrymead Farm 49 SHLAA 36.93 36.93 100.00 0.00 0.00 0.00 0.00 0.00 0.00 4.08 11.05 2.29 6.20 0.00 0.00 16 Burtree Lane 8 SHLAA 2.34 2.34 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.42 18.06 0.08 3.39 0.00 0.00

17 Whessoe Road North 39 SHLAA 9.21 9.21 100.00 0.00 0.00 0.00 0.00 0.00 0.00 1.93 20.92 1.20 13.04 0.03 0.30 FB - pumping out flood incident

18 Ward Bros, Cleveland St 12 SHLAA 6.59 6.59 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.83 12.63 0.25 3.80 0.00 0.00 19 Hunters Green, MStG 73 SHLAA 3.03 3.03 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.28 9.33 0.18 5.89 0.00 0.00 20 Neasham Road MStG 18 SHLAA 2.13 2.13 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.13 6.31 0.00 0.00 0.00 0.00 21 Hurworth 17 SHLAA 4.15 4.15 95.14 0.05 1.18 0.00 0.00 0.15 3.68 1.60 38.56 0.35 8.32 0.00 0.00 22 Hopelands, Heighington 23 SHLAA 3.91 3.91 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 23 Neasham Rd/Snaipe Lane 32 SHLAA 1.62 1.62 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.28 17.33 0.04 2.60 0.00 0.00 24 Neasham Rd/Snaipe Lane 43 SHLAA 4.80 4.80 100.00 0.00 0.00 0.00 0.00 0.00 0.00 1.26 26.22 0.63 13.11 0.00 0.00

25 A Indicative

Residential Sites 2.50 2.50 80.67 0.48 19.33 0.00 0.00 0.00 0.00 0.40 15.88 0.16 6.24 0.00 0.00

26 B Indicative

Residential Sites 3.60 3.60 10.77 3.22 89.23 0.00 0.00 0.00 0.00 3.27 90.67 3.14 87.02 0.21 5.83 FB - 6 separate incidents

27 C Indicative


28 D Indicative

Residential Sites 1.89 1.89 4.71 1.80 95.29 0.00 0.00 0.00 0.00 0.91 48.26 0.40 21.07 0.00 0.00 YES

29 F Indicative

Residential Sites 14.27 14.27 15.81 11.21 78.53 0.17 0.01 0.64 4.50 4.14 29.04 1.42 9.98 0.08 0.58 YES FB - pumping out flood incident

30 G Indicative


31 H Indicative

Residential Sites 4.22 4.22 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.19 4.59 0.00 0.00 0.00 0.00 32 EP2.10 Employment 4.70 4.70 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.59 12.46 0.18 3.73 0.00 0.00 33 EP2.9 Employment 15.46 15.46 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.98 6.35 0.01 0.05 0.00 0.00

en ra ar . . . . . . . . . . . . . . . oo nc en

34 EP2.6 Employment 34.69 34.69 100.00 0.00 0.00 0.00 0.00 0.00 0.00 7.84 22.60 1.28 3.69 0.00 0.00 35 EP2.6 Employment 173.35 173.35 100.00 0.00 0.00 0.00 0.00 0.00 0.00 34.74 20.04 13.32 7.68 0.83 0.48 36 EP2.5 Employment 10.50 10.50 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.89 8.52 0.05 0.50 0.00 0.00

37 EP2.4 Employment 11.94 11.94 62.19 4.45 37.25 0.07 0.01 0.00 0.00 1.51 12.67 0.08 0.63 0.00 0.00 YES Historic flooding of Skerne overtopping

38 EP2.4 Employment 2.79 2.79 68.97 0.74 26.74 0.12 0.04 0.00 0.00 0.50 17.98 0.06 2.04 0.00 0.00 YES Historic flooding of Skerne overtopping

39 EP2.3 Employment 16.42 16.42 100.00 0.00 0.00 0.00 0.00 0.00 0.00 2.20 13.41 0.32 1.95 0.00 0.00 40 EP2.2 Employment 18.18 18.18 99.98 0.00 0.00 0.00 0.00 0.00 0.02 2.55 14.04 0.78 4.32 0.01 0.08 YES

41 EP2.8 Employment 24.94 24.94 100.00 0.00 0.00 0.00 0.00 0.00 0.00 2.55 10.23 0.63 2.54 0.03 0.11 FB - flood incident here.

42 EP2.8 Employment 7.35 7.35 100.00 0.00 0.00 0.00 0.00 0.00 0.00 1.37 18.62 0.14 1.87 0.00 0.00 43 EP2.7 Employment 55.38 55.38 99.99 0.00 0.01 0.00 0.00 0.00 0.00 8.56 15.45 3.26 5.89 0.13 0.23 YES

44 EP2.1 Employment 21.79 21.79 28.30 14.13 64.86 0.60 0.03 0.89 4.09 5.28 24.22 2.11 9.67 0.09 0.41 YES FB - pumping out flood incident

45 EP8 Employment 121.17 121.17 94.15 2.80 2.31 0.45 0.00 3.83 3.16 12.12 10.01 6.12 5.05 0.66 0.54 YES

46 46 C t l P kCentral Park 31 25 31.25 31 25 31.25 100 00 100.00 0 00 0.00 0 00 0.00 0 00 0.00 0 00 0.00 0 00 0.00 0 00 0.00 6 28 6.28 20 10 20.10 2 14 2.14 6 85 6.85 0 50 0.50 1 61 1.61 FB - pumping out fl d i id tflood incident

Download - Darlington Borough Council Strategic Flood Risk Assessment ... · Volume I of the Darlington SFRA introduces the SFRA process. It is an excellent reference document for current flood

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