North North amptonshire Flood Risk Management Study

Environment Agency

June 2007 Final Report 9S1244

A COMPANY OF

HASKONING UK LTD. COASTAL & RIVERS

Rightwell House Bretton PE3 8DW +44 (0)1733 334455 Telephone 01733 333538 Fax [email protected] E-mail www.royalhaskoning.com Internet

Document title North Flood Risk Management Study

Document short title Strategy Report Status Final Report Date June 2007 Project name Flood Risk Management Study Project number 9S1244 Client Environment Agency Reference 9S1244/R/302099/PBor

Drafted by R Gunasekara

Checked by Date/initials check …………………. …………………. Approved by Date/initials approval …………………. ………………….

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CONTENTS

Page

1 BACKGROUND 1 1.1 General Overview 1 1.2 Scope and Report Format 1 1.3 Objectives and Benefits 1

2 DATA COLLECTION 3

3 STUDY AREA AND DEVELOPMENT PROPOSALS 5 3.1 General 5 3.2 8 3.3 8 3.4 9 3.5 10

4 REVIEW OF SFRAS 11 4.1 Overview 11 4.2 Kettering and Wellingborough SFRA 13 4.2.1 Introduction 13 4.2.2 Data Assessment 13 4.2.3 Historic Flooding 13 4.2.4 Drainage and Hydrology 16 4.2.5 Strategic Assessment of Flood Risk 16 4.2.6 Compliance with PPG25/PPS25 17 4.2.7 Implications of recent studies and development proposals 19 4.3 East Northamptonshire SFRA 22 4.3.1 Introduction 22 4.3.2 Data Assessment 22 4.3.3 Historical Flooding 22 4.3.4 Drainage and Hydrology 23 4.3.5 Strategic Assessment of Flood Risk 24 4.3.6 Compliance with PPG25/PPS25 24 4.3.7 Implications of recent studies and development proposals 26 4.4 Corby SFRA 26 4.4.1 Introduction 26 4.4.2 Data assessment 27 4.4.3 Historical Flooding 27 4.4.4 Drainage and Hydrology 28 4.4.5 Strategic Assessment of Flood Risk 29 4.4.6 Compliance with PPG25/ PPS25 31 4.4.7 Implications of recent studies and development proposals 31

5 OUTLINE FLOOD RISK MANAGEMENT STRATEGY 35 5.1 Overview 35 5.2 Policies 36 5.3 Planning Conditions 41 5.4 Physical measures 41 5.5 Residual Risk Management 42

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5.5.1 General 42 5.5.2 Flood warning and emergency planning 42 5.6 Guidance 44

6 FUNDING AND PLANNING ISSUES 45

7 CONCLUSIONS 47

8 RECOMMENDATIONS 49

9 REFERENCES 51

FIGURES

1 Study Area 2 Flood Map for North Northamptonshire 3 Kettering Flood Map and Development Sites 4 Wellingborough Flood Map and Development Sites 5 East Northants Flood Map and Development Sites 6 Corby Flood Map and Development Sites 7 LiDAR coverage for North Northamptonshire 8 DG5 Sewer Flooding Records within North Northamptonshire

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1 BACKGROUND

1.1 General Overview

North Northamptonshire is within the Government’s growth plans for the Milton Keynes and South Midland Sub Region. Corby, Kettering, Wellingborough and East Northamptonshire Councils, together with Northamptonshire County Council, are working through a Joint Planning Unit (JPU) to create an overall town planning strategy for the area which then forms a key part of the Local Development Framework (LDF) for each Council. Each of the four Councils within North Northamptonshire has completed some form of a Strategic Flood Risk Assessment (SFRA) for their administrative areas within the last couple of years. However, an overall assessment for the whole of North Northamptonshire has not been undertaken to inform the emerging LDFs. In addition, the information contained in the completed SFRAs may be out of date due to new information on flood risk and development sites. Also, the recently enforced Planning Policy Statement (PPS) 25 is likely to affect some of the previous findings of the SFRAs.

Therefore, the Environment Agency appointed Royal Haskoning in September 2006 to carry out a study which will produce an overall flood risk management strategy for North Northamptonshire. This report presents the finding of the study.

1.2 Scope and Report Format

The four existing SFRAs have been analysed and information gleaned from them used to create an overall flood risk management strategy within North Northamptonshire. The key sections of the report include:

• Section 1 Background to the study; • Section 2 Data collection; • Section 3 General description of the study area and the development proposals within each Council area; • Section 4 Findings of the review of existing SFRAs; • Section 5 Details of the proposed outline flood risk management strategy; • Section 6 Funding and planning issues; • Section 7 Conclusions; and • Section 8 Recommendations.

1.3 Objectives and Benefits

The key objective of this desktop study is to ensure timely feeding of flood risk management needs of the growth proposals in North Northamptonshire into the Water Cycle Strategy (WCS) undertaken by the Environment Agency and the upcoming LDFs for each council.

The anticipated key benefits of the study will include:

• avoidance of damage to the environment; • avoidance of increasing flood risk to downstream areas from inappropriate major development proposals; • creation of safe and sustainable development that account for future climate change impacts;

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• compliance with high level national and regional planning policies; • avoidance of repeated ad-hoc extensions to the existing flood alleviation measures or new schemes at Government’s expenditure; and • enhancement of environmental opportunities through effective integration of Sustainable Drainage Systems (SUDS), green corridors and public amenity space.

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2 DATA COLLECTION

The study was carried out in close consultation with the Environment Agency, the Councils, Anglian Water and also Halcrow, who recently completed the Outline Water Cycle Strategy (WCS) for North Northamptonshire.

The relevant information was gathered from the above parties and the data sources are noted under the references at the end of this report. The key data sources include:

• Existing SFRAs; • Emerging LDF documents; o North Northamptonshire Core Spatial Strategy o Issues and Options for North Northamptonshire o Preferred options for North Northamptonshire Core Spatial Strategy • Information on committed and proposed development sites; • Recent Studies; o North Northamptonshire Outline WCS o Catchment Flood Management Plan o Hydrological Assessment of the Slade Brook Detention Reservoir o Corby Phase 2 WCS o Pre-feasibility Studies on Willow Brook and Harpers Brook • Historic sewer flooding information from Anglian Water; • Planning Policy Statement (PPS) 25: Development and Flood Risk; and • Development and Flood Risk: A Practice Guide Companion to PPS25 ‘Living Draft’.

The data gathered was reviewed as described in the following sections of the report to identify the key flooding issues and then to produce the proposed Flood Risk Management Study to accommodate the anticipated major growth plans in North Northamptonshire.

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3 STUDY AREA AND DEVELOPMENT PROPOSALS

3.1 General

North Northamptonshire is generally formed by the main towns of Corby, Kettering and Wellingborough, along with and a number of other smaller towns and many villages. Figure 1 shows the extent of the study area and the key locations.

The principal watercourses in the study area include:

• River Nene and its main tributaries (, Harpers Brook and Brook Willow); and • and its main tributaries (River Jordan).

As illustrated in Figure 1, the majority of the study area is within the River Nene catchment. However, the River Welland flows along the northwest boundary of the study area and therefore small parts of Corby, Kettering and East Northamptonshire Councils are within the River Welland Catchment.

The River Nene rises on the mainly clay soils of the uplands and crosses gently sloping rural country to the flat plains of Peterborough – see Figure 2. Upstream of Peterborough, the River Nene is joined by the principal tributaries of Wotton Brook, the Kislingbury Branch, the Brampton Branch, the River Ise, Harpers Brook and Willow Brook.

The River Nene catchment is largely rural and the major land use is agriculture. There are some key urban areas within the catchment including Kettering, Wellingborough, and Corby that fall within the study area.

The potential sources of flooding that may need further consideration include:

• overflowing of watercourses and existing flood defences including water retention facilities such as flood storage areas and storm water balancing ponds; • blockages of existing bridges, culverts and other structures in particular during large rainfall events; • mechanical, structural or other operational failure of existing hydraulic structures and pumps; • breaching of existing flood defences(including flood storage areas that hold water above surrounding ground levels); • localised surface water flooding (including sewer flooding and overland flooding); and • groundwater flooding.

The Regional Spatial Strategy (RSS) is currently under review and the existing Milton Keynes and South Midlands Regional Spatial Strategy (MKSM RSS) housing projections will be included within the revised overall RSS. Also, the RSS will now look up to 2026 whereas the MKSM RSS has set a target of 99,500 homes to be completed in Northamptonshire between 2001 and 2021. Of this figure 52,100 homes are within the study area as shown in Table 1 overleaf.

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Table 1: Homes constructed between 2001 and 2006 against MKSM targets Local Authority RSS Target 2001-21 Completed 2001-06 %of RSS completed Corby 16,800 2,500 15% Kettering 13,100 2,353 18% Wellingborough 12,800 1,521 12% East Northants 9,400 2,825 30% Total 52,100 9,199 18% (Source: North Northamptonshire Outline Water Cycle Strategy, January 2007 – Reference 1)

Committed or planned development within each of the Councils within North Northamptonshire is shown in Table 2. Committed development is that the ones granted with full planning permission but not yet fully completed.

Table 2: Homes currently committed or planned in order to meet the RSS targets Local Authority Committed Local Plan Windfall Total future Development allocation Estimate development (April 2006) without planning identified permission Corby 3,544 189 3,489 7,222 Kettering 2,880 519 2,138 5,537 Wellingborough 1,419 4,170 2,037 7,626 East Northants 1,991 541 2,731 5,263 Total 9,834 5,419 10,395 25,648 (Source: North Northamptonshire Outline Water Cycle Strategy, January 2007 – Reference 1)

In addition to the above, Table 3 and Table 4 show the preferred distribution for housing development and employment land between 2001 and 2021.

Table 3: Distribution of Housing Development in North Northamptonshire 2001 - 2021 Settlement Preferred Option For Distributing Additional Growth Implied On Housing Growth Greenfield Extensions GROWTH TOWNS Corby Min 15,510 8,350 Kettering Min 7,300 4,120 Wellingborough Min 11,590 4,990 SMALLER TOWNS 900 520 1,940 700 Rothwell 1,320 700 1,020 190 1,700 660 Rushden 2,370 0 RURAL SERVICE CENTRES 610 140 1,100 850 1,140 200 NETWORK VILLAGES Corby rural Max 1,290 0

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Settlement Preferred Option For Distributing Additional Growth Implied On Housing Growth Greenfield Extensions Kettering rural Max 1,640 0 Wellingborough rural Max 1,210 0 East Northants rural Max 1,460 0 (Source: Preferred options for North Northamptonshire, November 2005, Reference 2)

Table 4: Distribution of Employment Land and Projected jobs Growth for North Northamptonshire to 2021 Location Total Land Required Indicative Existing Indicative Job Growth (Ha) Supply (Ha) Required Allocation (Ha) CORBY 14,400 General Industrial 16 33.3 -17.3 Strategic Distribution 83 58.4 24.6 Offices 67 22.7 44.3 EAST NORTHAMPTONSHIRE 3,000 General Industrial -9 32 -23 Strategic Distribution 19 39 -20 Offices 28 6 19 KETTERING 16,200 General Industrial 0 17 -17 Strategic Distribution 64 65 -1 Offices 64 5 59 WELLINGBOROUGH 13,800 General Industrial -4 102 -98 Strategic Distribution 78 38 40 Offices 82 10 72 NORTH NORTHAMPTONSHIRE 47,400 General Industrial 2 184.3 -182.3 Strategic Distribution 244 200.4 43.6 Offices 241 43.7 197.3 (Source: Preferred options for North Northamptonshire, November 2005, Reference 2)

Also, the preferred locations for the proposed sustainable urban extensions are East Kettering, Wellingborough East and Priors Hall on the northeast of Corby. Further potential extensions have been identified for development before 2021 at the western edge of Corby and the northwest edge of Wellingborough. It should be noted however that the recently submitted North Northamptonshire Core Spatial Strategy (Reference 3) may have some more up to date information on the distribution of housing and jobs than presented above and therefore it is recommended to make cross-reference with the Core Strategy for the latest information.

Figure 2 shows the Flood Map for the entire North Northamptonshire together with the locations of the committed and proposed developments. Sections 3.2 to 3.5 give further details of the study area, watercourses and proposed development in each council area.

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3.2 Kettering

Figure 3 illustrates the principal watercourses, flood extents and development sites within the . The watercourses within Kettering include:

• Tributaries of River Nene; and - River Ise - Slade Brook - Arm - Alledge Brook - Harpers Brook - East Brook

• River Welland and it’s main tributary, River Jordan (at northwest edge of the Borough).

Kettering is planned to accommodate 13,100 new homes by 2021. Only a limited amount of this growth can be accommodated within the existing urban areas and it is proposed that the town needs to grow eastwards, as indicated in Figure 3.

East Kettering development is currently planned in two phases as follows:

• Phase 1 (up to 2021) - 5,500 new homes - A district centre with shops, cafes, bars and restaurants, office and studio space, community facilities health clinic and park and ride. - Three housing neighbourhoods each with a primary school facility at their centre. - An extensive park system to support nature conservation and to create a network of open space for all types of recreation.

• Phase 2 (up to 2026) - Extending the site for the full capacity of 8,900 houses with a full range of appropriate supporting facilities.

3.3 Wellingborough

Figure 4 illustrates the principal watercourses, flood extents and development sites within the Borough of Wellingborough. The watercourses within Wellingborough include:

• River Nene; and • Tributaries of the River Nene - River Ise - Harrowden Brook - Swanspool Brook - Barton Brook - Denington Brook - Grendon Brooks - Wollaston Brook - Knuston Brook

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Wellingborough is planned to accommodate further 12,800 new homes by 2021. It is anticipated that the majority of this will be provided at Wellingborough East (WEAST) and at the Castleridge development of north west of Wellingborough.

The current development plans for Castleridge include health and education facilities, formal and informal public open space, leisure and district facilities, as well as up to 5,000 houses.

3.4 East Northamptonshire

Figure 5 illustrates the principal watercourses, flood extents and development sites within East Northamptonshire District. The watercourses within East Northamptonshire include:

• River Nene; • Tributaries of the River Nene; and - Harpers Brook - Willow Brook - Gretton Brook - Alledge Brook - Southwick Brook - Stonepit Brook - Skew Bridge Dyke - Chelveston Brook - Hog Dyke - Barnwell Brook - Polebrook Brook - Warmington Dyke

• River Welland (at the north western edge of East Northamptonshire).

East Northamptonshire is planned to accommodate 9,400 new homes by 2021. Table 5 summarises the distribution of housing according to the preferred options documents from the East Northamptonshire District Council.

Table 5: Preferred Housing Distribution within East Northants up to 2016 Settlement Total No. of Houses Rushden 2,433 Irthlingborough 1,541 Higham Ferrers 1,116 Oundle 238 Thrapston 490 King’s Cliffe 70 (Source: Preferred Options for Three Towns – Rushden, Higham Ferrers and Irthlingborough, September 2006 – Reference 4; Preferred Options for Rural North, Oundle and Thrapston, January 2006 – Reference 5)

The preferred options for Raunds Area were later published in January 2007. Table 6 demonstrates the Council’s intentions for providing the required 1,100 new houses within East Northamptonshire.

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Table 6: Preferred Housing Distribution for Raunds up to 2021 Settlement Completions Under Construction and Likely Large New Greenfield Total 2001 - 2006 Extant Planning Urban Allocations Permissions Potential Sites (Some to be allocated) Raunds 110 110 0 880 1,100 (Source: Raunds Area Preferred Options, January 2007 – Reference 6

3.5 Corby

Figure 6 illustrates the principal watercourses, flood extents and development sites within Corby Borough. The watercourses within Corby include:

• Tributaries of River Nene; and - Harpers Brook - Willow Brook - Gretton Brook • River Welland (at the north western edge of Corby).

An additional 28,000 houses and 30,000 new jobs will be required in Corby by 2031 to meet the Government’s growth plans. Out of this 16,800 new houses will be required by 2021. Figure 6 shows the locations of committed and proposed development sites in accordance with the information obtained from the Corby Phase 2 Water Cycle Strategy (Reference 7).

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4 REVIEW OF SFRAS

4.1 Overview

In July 2001 Central Government produced Planning Policy Guidance Note 25 (PPG25) “Development and Flood Risk” to give guidance to Local Planning Authorities (LPAs) how to consider flood risk in land-use planning process and development control decisions. This document gave the Government’s policy at that time to the management and reduction of flood risk in the planning process by acting on a “precautionary basis” and also by taking account of climate change. It also stated that “flood risk” is a material planning consideration. PPG25 was replaced by Planning Policy Statement 25 (PPS25) “Development and Flood Risk” in December 2006.

PPG25 stated that LPAs should “adopt a risk-based approach to proposals for development in or affecting flood risk areas (Paragraph 27) “and “apply a risk-based approach to the preparation of development plans and their decision on development control through a sequential test (Paragraph 30)”. Therefore, in drawing up or revising policies in development plans and in considering applications for development, LPAs should have given priority in allocation or permitting sites for development, in descending order to the Flood Zones set out in Table 1 of PPG25. In paragraph 31, it also stated that LPAs should “take account of the resulting level of actual risk”. This process typically redefined and subdivided the Flood Zones initially established by the Environment Agency’s high level Flood Map that ignores the effect of existing defences.

Allocating development sites without this information could have led to inappropriate decisions or to challenge by others, as the application of “sequential test” required by PPG25 may have been flawed. Some local authorities (including the ones in North Northamptonshire) have, with guidance from the Environment Agency, undertaken SFRAs to deal with this potential issue. Many of the authorities have taken the opportunity to investigate and assess specific strategic sites and make recommendations for measures that would be needed both on site and at strategic locations and also to provide general development control guidance.

The process of flood risk assessment is evolving both strategically (as national guidance is developed) and locally (as more detailed knowledge is gained about the location, nature and concept of the site proposals). Some types of development will be more vulnerable to flooding than others and therefore need special consideration in the assessment. The stronger emphasis on these issues is a particular aspect of the new Planning Policy Statement (PPS) 25: Development and Flood Risk, which was published in December 2006. This PPS sets out the Government’s latest national policy on dealing with development and flood risk within the land-use planning system. PPS25 replaced the PPG25, published in 2001.

Compared with PPG25, the new PPS25 imposes requirements for regional planning bodies and LPAs to prepare Regional Flood Risk Appraisals and SFRAs respectively. It strengthens the “risk-based approach” and guides new development away from the highest risk areas. However, it introduces the concept of an “exception test” that complements the sequential approach in exceptional circumstances where necessary to meet the wider aims of sustainable development for example where areas of high flood risk are extensive and there are no sites available in lower risk areas.

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The following sections of this report discuss the key findings of the review for the existing SFRAs within North Northamptonshire. Based on the currently available information to Royal Haskoning, this review is largely focussed on the suitability of the SFRAs in terms of their “Fitness for Purpose” for the inclusion within the emerging LDFs and Water Cycle Strategy (WCS) for North Northamptonshire. The findings are then fed into the development of proposal Flood Risk Management Strategy described in Section 5.0.

The key considerations to be reviewed are summarised in Box 1 below.

Figure 7 also shows the Environment Agency’s LiDAR coverage within the study area illustrating the current topographic survey availability for modelling and mapping purposes. The LiDAR spatial resolution in this area is 2m. Taken together with the generally accepted vertical accuracy of ±11cm to 25cm, this indicates that in the areas covered by the LiDAR data would provide a good representation of ground surface for the required flood risk mapping where further improvements to the existing SFRA outputs are required.

• Data assessment Quality of data used and rigor of review carried out in the strategic assessment

• Historic Flooding The record of past flood events and any factors that may have affected the risk of flooding, including development or land-use change within the catchment or implemented river flood management works

• Drainage and Strategic understanding of the hydrology and drainage Hydrology of river catchments

• Strategic Identification of land most likely to flood (from all Assessment of sources) whilst taking into account the effect of climate Flood Risk change and any existing defences. This will include the residual risk of flooding arising from any flood defences

• Compliance with Compliance of sequential test approach to flood risk PPG25/ PPS25 management within the planning process (For this purpose, the latest development proposals from the emerging LDF documents has been used) and impact of new information and legislation such as PPS25 which can challenge the conclusions of the SFRAs already completed

• Implications of Impact of major development proposals on flood risk recent studies and due to runoff issues including the use of strategic and development local SUDS measures proposals

Box 1: Key considerations for the SFRA review

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4.2 Kettering and Wellingborough SFRA

4.2.1 Introduction

Royal Haskoning completed this SFRA in May 2005 and the Environment Agency and the Councils subsequently approved the report (Reference 10). We have assessed the SFRA against the above criteria and our findings are summarized below.

4.2.2 Data Assessment

The SFRA uses the best available data following a sufficient level of quality check to satisfy the needs of a strategic assessment of this nature. Since the completion of the SFRA there is no valuable new data or studies in addition to the information discussed in Section 4.2.7.

4.2.3 Historic Flooding

Comprehensive analysis of fluvial flooding events is available in the SFRA, however it lacks records of possible sewer flooding. In particular, the SFRA highlights the potential flood risk on the following watercourses within each Council area:

Kettering Borough Council

• Slade Brook; • East Brook; • River Ise; and • River Jordon.

Borough Council of Wellingborough

• Harrowden Brook; • Swanspool Brook; • Denington Brook; • River Ise; and • River Nene.

The lower reaches of Grendon, Wollaston and Knuston Brooks are also subject to flooding.

Therefore, the opportunities to alleviate the current flood risk at vulnerable locations (e.g. Venture Park and Pytchley Lodge Industrial areas in Kettering Borough and Road and Denington Industrial Estate areas within the Borough of Wellingborough) should be explored as part of the proposal Flood Risk Management Strategy (FRMS) for North Northamptonshire.

Table 7 and Table 8 summarize the records of known flooding within the Kettering Borough and the Borough of Wellingborough respectively.

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Table 7: Historic Flooding Records within Kettering Borough Town/Village/Location Watercourse and Dates Source Comments Cause Geddington River Ise – 1947, 1973, EA 1998 River Ise Improvement exceedance of 1980, 1981, Flood Investigation scheme channel and 1998 Preliminary Study implemented structure capacity. (Draft Report); EA since historical flood map for 1947/1998 Burton Mill River Ise – 1947, 1998 EA (AWA) 1985 Improvement Finedon Mill exceedance of detailed appraisal on scheme channel and alleviation of flooding implemented structure capacity. – River Ise since Northamptonshire; EA Kettering – d/s of Pytchley Slade Brook – 1998 EA historical flood Lane Exceedance of map for 1947/1998 channel and structure capacity Braybrooke River Jordan – 1968,1980 (2 EA (AWA) 1984 River Improvement -- 13 properties flooded exceedance of times), 1981, Jordan – Braybrooke scheme channel and 1983 Flood Alleviation implemented structure capacity, Scheme since flood duration is less than 12 hours Agricultural fields along River Welland – 1947, 1998 EA historical flood the River Welland. North Exceedance of map for 1947/1998 of Weston by – Welland channel and and Ashley and west of Structural capacity (Source: Kettering and Wellingborough SFRA Stage 2 Report, May 2005)

Note – This is not an exhaustive list of flooding records.

Table 8: Historic Flooding Records within Borough of Wellingborough Town/Village/Location Watercourse and Dates Source Comments Cause Wellingborough (mainly River Ise – 1998 EA 1998 River Ise agricultural fields at the Exceedance of Flood Investigation eastern parts). channel and Preliminary Study structure capacity Draft Report + EA historic flood Map for 1947/1998. Wilby – houses and Swanspool Brook 1981, 1980 EA (AWA) 1983 Improvement gardens on the south side – exceedance of letter entitled “Flood scheme of Brook Vale channel and Damage at Brook implemented structure capacity Vale, Wilby, since Northants.

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Town/Village/Location Watercourse and Dates Source Comments Cause Wellingborough Swanspool Brook 1981, 1978, 1980. EA (AWA) project Improvement • Swimming pool – exceedance of Serious Flooding appraisal report – scheme • Croyland Park channel and in 1978 (17 Swanspool Brook: implemented changing rooms structure capacity houses and a pub Wellingborough to since • Croyland Park flooded) and 1980 Wilby • Agricultural land (44 houses, a improvements; • Road and pub, a EA (AWA) 1981 Doddington Road supermarket, a Swanspool Brook with adjacent shoe factory and a Improvement properties veterinary surgery Scheme • Coryland Road flooded) • Kingsway pedestrian subway • Houses at Brook Vale, Wilby • Doddington Road, Wilby

Wellingborough – Section Harrowden Brook 1947 EA historic flood The 1947 flood of the Harrowden Brook – exceedance of map for 1947/1998 outline should be d/s of Kettering road to channel and considered very confluence with Ise. structure capacity carefully as the • Finedon Road flood outline Industrial Estate doesn’t include the river bed d/s of Finedon Road Industrial Estate. The floodplain also stops at the southern boundary OF sp875E OS map tile. Agricultural fields along Grendon Brook – 1947, 1981 EA (AWA) 1:2,500 The 1947 flood the lower and middle exceedance of map (Drawing outline should be reaches of Grendon Brook channel and 32/9/860/1079); considered very at north and east of structure capacity EA historic flood carefully as the Grendon map for 1947/1998 floodplain stops at the southern boundary of the SP865E OS Map tile. Agricultural land along Wollaston Brook – 1947 EA historic flood The 1947 flood lower and middle reaches exceedance of map for 1947/1998; outline should be of Wollaston Brook at channel and EA (AWA) 1984 considered very north west of Wollaston structure capacity Wollaston Brook carefully as the Improvement floodplain stops at Scheme the southern boundary of the

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Town/Village/Location Watercourse and Dates Source Comments Cause SP865E OS Map tile.

Agricultural land along the Knuston Brook – 1947 EA historic flood lower and middle reaches exceedance of map for 1947/1998 of Knuston Brook at north channel and east of structure capacity Wellingborough – lower Denington Brook – Not known BCW map reaches of Denington due to inlet (frequent Brook near Denington blockage occurrence) Industrial Estate Wellingborough – north of River Nene – 1947, 1998 EA historic flood A45 including Victoria Mills exceedance of map for 1947/1998 Area and the agricultural channel and fields along the river valley structure capacity. south of Wellingborough (Source: Kettering and Wellingborough SFRA Stage 2 Report, May 2005)

Note – This is not an exhaustive list of flooding records in particular note that the entire River Nene valley has been subjected to significant flooding during 1947 and 1998.

4.2.4 Drainage and Hydrology

FEH hydrology has been used for all studied major watercourses in the catchment but using limited model calibration due to the absence of gauged flow and water level data in the catchment. Therefore the model calibration has been limited to the Environment Agency’s River Nene Strategic Model, which also includes its principal tributaries of River Ise, Willow Brook, Harpers Brook and Slade Brook.

No further hydrological assessment has been undertaken for other watercourses as part of the SFRA although basic FEH hydrology using catchment descriptors has been used in the Environment Agency’s national Flood Zones for all watercourses that have a catchment area greater than 3km2. However, this assessment may not reflect the hydraulic effects imposed by existing flood defences and other structures on the water levels and river flows.

4.2.5 Strategic Assessment of Flood Risk

The SFRA covers the council areas of Kettering and Wellingborough. It gives particular attention to the locations where development sites are committed or proposed at that time and also to the places where known to have historic flooding problems. Therefore within these areas the results from various hydraulic models, which also consider the impact of any flood defences or storage reservoirs, have been used in the assessment.

The key flood defences the Boroughs include: • Kettering Town – Short sections of raised flood defences along Northfield Avenue along the Slade Brook; • Geddington Village – new flood relief channel implemented as part of the recent scheme; and

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• Wellingborough Town – Sections of raised flood defences along the Swanspool Brook.

Flood storage reservoirs / water retention facilities also present at: • Kettering leisure village (Slade Brook Flood Detention Reservoir); • West of Wilby village on the Swanspool Brook; • Northern part of Wellingborough along the Harrowden Brook; • and Thorpe Malsor Reservoirs on the tributaries of Slade Brook; • Sywell reservoir south of Sywell village on the upstream reach of the Barton Brook; and • Numerous storm water balancing ponds including at Kettering North Business Park and Prologies Business Park at Wellingborough.

In addition to the above, significant natural flood attenuation is available at some locations but most noticeably upstream of Glendon Railway culvert north of Kettering Town on the Slade Brook.

The modelled watercourses as part of the SFRA include: • River Nene; • River Ise; • Swanspool Brook; • Harrowden Brook; • Slade Brook; • East Brook; • Denington Brook; • Ecton Brook; and • Harpers Brook.

For other watercourses, the Environment Agency’s National Flood Zones that ignore the presence of existing flood defences have been used in the assessment and mapping.

Although the SFRA identified storm sewer flooding as a possible cause of flooding no modelling was undertaken to map the areas that may be at direct risk of such flooding.

4.2.6 Compliance with PPG25/PPS25

The SFRA provides a suitable reference document in order to satisfy the LPAs’ responsibilities expected by the Government through PPG25 at the time of publication of the SFRA in May 2005. The SFRA also provides brief details of the existing flood warning and emergency evacuation procedures in the area; these can be further developed as part of the proposed Flood Risk Management Study. It should generally satisfy the needs of the new PPS25 and has been noted as a case study within the recently published Living Draft Practice Guide (Reference 9) that accompanies the PPS25.

The SFRA recognises all sources of flooding and provides good quality flood mapping for the entire area (including for future climate change scenario). However, it does not provide detailed flood risk outlines neither for additional breach risk arising from flood storage areas nor for urban flood risk from urban storm sewers.

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The SFRA provides good guidance on managing the impact of runoff from new developments but no modelling has been carried out to assess the potential impact. It also highlights the importance of whole water cycle management.

The SFRA identifies the key flood risk issues associated with the committed and future growth sites and the sequential approach required by the PPG25/PPS25. It gives good guidance on the need for undertaking site specific Flood Risk Assessments (FRAs) and the importance of improving flood risk information including flood warning and emergency evacuation. The SFRA give clear guidance on how to carry out FRAs, the use of Sustainable Drainage Systems (SUDS) and details mechanisms for ensuring maintenance responsibilities for flood defence and SUDS. It identifies the need for further detailed studies in particular where watercourses are currently suffering from flooding problems or where sites are proposed within or closer to flood risk areas for all watercourses whether modelled or not modelled as part of the SFRA.

The SFRA finally highlights its limitations and gives recommendations to address them and also to promote integrated flood management and environmental enhancement (encompassing whole water cycle management) within the Boroughs.

The current SFRA will need updating when further flood risk information is available through the ongoing studies as described in Section 4.2.7 including from large development proposals such as Kettering East and Castlegate. An update of some of the terminology used in the SFRA outputs, a further review of the latest site allocations from the emerging Development Planning Documents and LDFs and the risk of flooding from sources other than main rivers will be required if a full compliance to PPS25 is to be achieved immediately. If these becomes a need for application of the Exception Test according to Table D.3 of PPS25 (see Table 9 below) then further detailed modelling will be required to consider the detailed nature of the flood hazard taking account of the presence of flood risk management measures such as flood defences. This should include the assessment of flood probability, flood depth, flood velocity and rate of onset of flooding within each flood zones.

Table 9: Flood Risk Vulnerability and Flood Zone ‘Compatibility’ (Source: Table D.3, PPS25, Communities and Local Government, December 2006)

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In addition, functional flood plain and climate change impacts will have to be further assessed and mapped in accordance with the PPS25 requirements.

Section 4.2.7 also discusses the likely impact of latest development proposals and the recent studies on the strategic flood risk within the boroughs based on the information gathered to date.

4.2.7 Implications of recent studies and development proposals

The only key recent study that may have some impact on the findings of the SFRA is the hydrological assessment of the Slade Brook Detention Reservoir at the Leisure Village, commissioned by Kettering Borough Council. The draft report was produced in July 2006 by W A Fairhurst and Partners (Reference 11) but no further work has taken place since. It provides the necessary background information to the Council for addressing the concerns of the Environment Agency (and the Reservoir Panel Engineer) regarding the public safety of the balancing reservoir under the terms of the Reservoir Act 1971.

The Slade Brook Detention Reservoir is an online storage reservoir and is formally maintained by Kettering Borough Council. It has three spillway sections (central spillway is 300mm lower than the other two). Downstream of the spillway and the embankment of this reservoir, the golf course access road provides a secondary flood embankment where the Slade Brook flows through two 1500mmX 1500mm concrete box culvert sections. Also, potential overtopping of the reservoir can lead to a breach of the embankments of the reservoir and the golf course access road causing significant flooding downstream where several residential developments, commercial and industrial units are located (including the Pytchley Lodge Industrial Estate and the Kettering Venture Park). Therefore, it is essential to review this recent study and incorporate its findings into the proposed Flood Risk Management Strategy (FRMS) for North Northamptonshire.

The hydrological study confirms that the golf course access road will be overtopped during 1 in 10,000 year flood event which can lead into a possible breach of the road embankment causing major flooding downstream. It also confirms that the Detention Reservoir is providing only very limited attenuation of the inflows from the Slade Brook even for 1 in 5 year event. This is mainly due to the high outflows over the three spillway sections at this online reservoir. For 1 in 50 year event there is hardly any flow attenuation within the Detention Reservoir. The report also clearly indicates the benefit of natural flood attenuation upstream of the reservoir (e.g. at Glendon Railway, Brooklands Farm, Rothwell Cemetry, Kettering Golf Club and Nunnery Farm) and the inevitable flood threat to Kettering Town if this storage is lost in the future. The inability of the Slade Brook Detention Reservoir to act as a flood mitigation feature up to 100 year event now is a significant drawback. This reservoir was originally constructed in 1990s under the constraints of the overall development plan and design standards at that time.

Despite the above findings, the SFRA mapping and the reports are still valid as they consider the current state of the Slade Brook and River Ise Catchment using an ISIS hydraulic model - compared to the recent study by the Council which uses an ISIS hydrological routine model. The SFRA has already highlighted potential issues with the Slade Brook Detention Reservoir and the recent hydrological study by the Council

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further confirms them. Therefore, the flood risk impact of new development in Kettering Borough upstream of the Detention Reservoir (e.g. Desborough, Rothwell and northern and western parts of Kettering) and the possible changes to the natural flood attenuation on the Slade Brook and the River Ise catchments should be carefully considered when making future development planning decisions. Future developments will need a robust approach to surface water management using source control SUDS and strategic flow attenuation. Opportunities should be explored to enhance flow attenuation at the existing Detention Reservoir and at the places where natural attenuation is already available although these opportunities are currently overlooked by the emerging LDF documents.

In addition, it should be noted that the emerging LDF documents suggest that Kettering East development is much more extensive than originally planned at the time of SFRA preparation. It now extends considerably into the hydrological catchment of the Alledge Brook which was not studied in detail during the SFRA as there was no development proposal or flood risk concerns on this watercourse at that time. The upper parts of the Alledge Brook are within Kettering Borough but the lower parts (i.e. downstream of A14) are within East Northamptonshire District. The middle and lower reaches of the Alledge Brook were improved in early 1990s during the construction of A14 but it now needs a detailed hydrological and hydraulic review due to the major development proposals of Kettering East Development. In particular, the ability of this watercourse to take additional flows from the proposed development upstream of A14 crossing should be sufficiently investigated. Note that Cranford St John Village is located in this stretch of Alledge Brook which may limit further improvements to this watercourse but the flood risk to the existing community may be increased unless surface water from the Kettering East development is not adequately managed.

Castlegate development at North West of Wellingborough is also more extensive than originally thought at the time of SFRA. Additional runoff from this large development into the Harrowden Brook needs careful consideration as this watercourse has a history of flooding. Two flood storage reservoirs have already been built to alleviate the flooding problems on this constrained watercourse that almost runs through the built up areas along its entire length. The limited hydraulic capacity of the railway culvert at the downstream limit of the Harrowden Brook is a key constraint to flood risk management on this urban watercourse.

Sewer flooding information presented in the North Northamptonshire Outline Water Cycle Strategy (WCS) report (Reference 1) has been reviewed to identify any important issues that SFRA might have overlooked. The Outline WCS also reports about some sewer capacity problems at Severn Way in Kettering where the sewer carries flow from Rothwell and Desborough and on the Swanspool Brook sewer serving the west of Wellingborough.

During this Flood Risk Management Study we have consulted Anglian Water to obtain the sewer flooding records from the DG5 register so that this information can be assessed within the review of SFRAs. The DG5 register is updated annually and it lists the areas and properties which have previously experienced an internal or external sewer flooding incident caused by lack of capacity of a sewer (i.e. from a public sewer, whether foul, combined or surface water). Temporary problems such as blockages, siltation, sewer collapses, and equipment or operational failures are excluded from the register. An entry upon this register will not be removed until the problem has been solved.

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Anglian Water's position on the use of sewer flooding records within the SFRAs is outlined below:

• Occurrences of sewer flooding within the study area are recorded by Anglian Water under its license obligations. All flooding instances will be prioritized within their capital investment process, and solutions implemented through the regulatory funding mechanism. Sewer flooding is an indication of localized under-capacity, not as a constraint to development. It should be recognized that reporting is not necessarily complete as some property owners do not report sewer flooding events. In addition, spillages from sewerage systems in remote areas are unlikely to be reported.

Nevertheless, Anglian Water has subsequently supplied postcodes of places that have been subject to sewer flooding. The listing gives the number of properties which suffered internal flooding, and the number of places subject to external flooding. External flooding therefore includes highways, public open space, open land, parkland, as well as private gardens.

Table 10 lists all of the postcodes where sewer flooding has occurred within the Boroughs of Kettering and Wellingborough. These locations are also shown in Figure 8.

Table 10: DG5 Sewer Flooding Records within the Boroughs of Kettering and Wellingborough

Council Total flooding External flooding Internal Flooding Both internal and Postcode areas by only only external flooding postcode Kettering NN142LF 0 2 0 2 NN146AR 0 1 0 1 NN146DN 0 2 0 2 NN146JJ 0 3 0 3 NN156NY 1 0 0 1 NN168EF 0 1 0 1 NN168QL 1 0 0 1 NN168LD 0 9 0 9 NN169HN 0 5 0 5 Wellingborough NN8 1DJ 0 2 0 2 NN8 INB 0 1 0 1 NN8 2BY 0 1 0 1 NN8 2DP 1 0 0 1 NN8 3PN 1 0 0 1 NN8 4HH 1 0 0 1 NN297AB 1 0 0 1 NN297LY 1 0 0 1

Finally, it can be concluded that the SFRA together with the additional information presented in this FRMS report should be considered when assessing flood risk needs within the Boroughs. These should form the basis for preparing flood risk management policies for the area and provide sufficient information to carry out a Sustainability

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Appraisal of the Local Development Documents and the Sequential Test of development sites.

4.3 East Northamptonshire SFRA

4.3.1 Introduction

Faber Maunsell completed this SFRA in September 2006 (Reference 12) and formal approval of the Environment Agency was given in November 2006. We have assessed the SFRA against the criteria described in Section 4.1 and our findings are summarized below.

4.3.2 Data Assessment

The SFRA uses the best available data following a sufficient level of quality check to satisfy the needs of a strategic assessment of this nature. Since the completion of the SFRA there is no valuable new data or studies in addition to the information discussed in Section 4.3.7.

4.3.3 Historical Flooding

Details of fluvial flooding events are available including some incidents of sewer flooding. In particular, the SFRA highlights the potential flood risk on the following watercourses: • River Nene; • Skew Bridge Dyke; • Harpers Brook; • Hog Dyke; and • Unnamed stream at Polopit near Titchmarsh.

It also highlights some sewer and overland flood risk at Rushden, Irthlingborough, Glapthorn and Oundle. Table 11 summarises the records of known flooding within the East Northamptonshire District.

Table 11: Historic Flooding Records within East Northamptonshire District Town/Village/Location Watercourse and Dates Source Cause Rushden – Duck Street Skew Bridge Dyke – Oct 02 ENDC/Parish Blocked culvert in Council Hall Park Oundle – Glapthorn Road Runoff from new Mar 98 and Aug ENDC/Parish development and 04 Council adjoining fields Oundle – Glapthorn Road Sewer flooding but 27-29 Nov 2000 Anglian Water not clear whether due to surface water or foul water Oundle – Prince William Sewer flooding and Frequent Environment School at Hern Road runoff from adjacent Agency fields (blocked drains and

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Town/Village/Location Watercourse and Dates Source Cause inadequate drainage) Titchmarsh – Polopit Flooding from 1992, 1998 and ENDC/Parish stream others Council Nassington Not given 1998 and others ENDC/Parish Council Elmington – Main Road Aug 04 ENDC/Parish (A605) Council Glapthorn Surface water runoff Aug 04 ENDC/Parish from fields Council Sudborough Harpers Brook Regular ENDC/Parish Council Thorpe Waterville Local drainage Not known ENDC/Parish problems Council Fotheringhay – Tansor Not given – 1998 and others ENDC/Parish Road probably River Council Nene Raunds – Brook Street Hog Dyke – lack of 1952, 1998 and Raunds Drainage (1952 and 1998), Midland capacity in lengthy others Study, July 2001 by Road culverts and short Bullen Consultants lengths of open Ltd. channel (1 in 10 yr standard) Brigstock – Not given – as Not given except for 1998 Typed report map is not attached to the stating the RP of the without its SFRA report event is 1 in 25 provenance years – possibly Harpers Brook Rushden – Paddocks Road Sewer flooding but 27-29 Nov 2000 Anglian Water not clear whether due to surface water or foul water Irthlingborough – Portland Sewer flooding but 27-29 Nov 2000 Anglian Water Road not clear whether due to surface water or foul water Barnwell Barnwell Brook 1980s Not known.

(Source: East Northamptonshire SFRA Stage 2 Report, September 2006 and Environment Agency)

Note – This is not an exhaustive list of flooding records in particular note that the entire River Nene valley has been subjected to significant flooding during 1947 and 1198.

4.3.4 Drainage and Hydrology

FEH hydrology has been used for River Nene and its two principal tributaries within East Northamptonshire District (i.e. Willow Brook and Harpers Brook). This was done by the Environment Agency at the time of development of River Nene Strategic Model.

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No further hydrological assessment has not been undertaken for other watercourses as part of the SFRA although basic FEH hydrology using catchment descriptors has been used in the Environment Agency’s national Flood Zones for all watercourses that have a catchment area greater than 3km2.

4.3.5 Strategic Assessment of Flood Risk

The SFRA covers entire East Northamptonshire District mainly using a combination of modelled flood levels from the Environment Agency’s River Nene model (including Willow Brook and Harpers Brook), national Flood Zones and Section 105 mapping. Other information such as historic flooding, flood defence information and topographic data has been used in the assessment.

Within East Northamptonshire District, the flood defences or flood storage structures are present at: • Thrapston – upstream of Thapston (Nine Arch) Bridge; • Sudburough – upstream of Slipton Road Bridge; • Brigstock – upstream of Grafton Road Bridge; • Titchmarsh – a private flood defence near No.27 Polopit; • Barnwell Flood Storage Reservoir; and • Several small balancing facilities.

It gives particular attention to the locations where development sites are proposed at that time and therefore providing a slightly more detailed flood risk assessment for each study area than for the remainder of the District.

Although the SFRA identified storm sewer flooding as a significant issue in the District (especially where large development sites are proposed in urban areas without sufficient capacity in existing sewers – e.g. Rushden, Raunds and Irthlingborough) no modeling was undertaken to map the areas that at direct risk of such flooding.

Where modelled information is not available from the River Nene Strategic Model the Flood Zones have been generally used in the assessment although at places they have been amended according to the SFRA report. However, it is not very clear the detail of the exact locations where the Flood Zones have been changed due to their anomalies. The lack of documentation within the maps and the report where Flood Zones have been amended leads some difficulty in following the audit trail.

4.3.6 Compliance with PPG25/PPS25

The SFRA provides a suitable reference document in order to satisfy the LPA’s responsibilities expected by the Government through the PPG25 at the time of publication of the SFRA in September 2006. It provides useful information (including the existing arrangements for operational and emergency planning) for the proposed flood risk management strategy but further work to clarify its contents may be needed to fully comply with the new PPS25. Especially, it is not clear how the assessment has addressed the impact of climate change now this is a key objective of the PPS25.

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The SFRA considers all sources of flooding and provides flood mapping for the entire area using five 1:25,000 scale strategic flood risk maps. It states that the principal flood risk source for most of East Northamptonshire is the River Nene.

SFRA include flood risk policy and guidance statements on: • The Need for Flood Risk Assessment; • Development in areas within various flood risk categories (i.e.” Little or No Risk”, “Low to Medium Risk” and “ High Risk”) that relate to actual flood risk by considering the presence of flood defences; • Development in areas identified as Washland or Functional Floodplain; • Sustainable Drainage Systems; and • Culverting of Open Watercourses.

The SFRA identifies the hydrology and the flood risk issues associated with twelve specific development sites based on the available information and the sequential approach required by the PPG25/PPS25. It provides general guidance to manage the impact of runoff from new developments but no modelling has been carried out to assess the potential impact. The SFRA concluded that at number of locations (e.g. Kings Cliffe, Raunds South, Raunds North East and Highham Ferrers East) surface water runoff from the proposed sites is likely to be discharged into watercourses which already pose some flood risk to the built up areas. One limitation of the individual study area detailed plans supplied in the SFRA is the absence of flood risk extents, which makes it difficult to identify the possible areas of the site that may be within risk areas.

The East Northamptonshire SFRA maps lack some detail (e.g. locations of flood defences, defended areas, flood outlines for climate change, differentiation of modelled watercourses from the watercourses not modelled). Also, the maps do not provide flood outlines for climate change. In common with Kettering and Wellingborough SFRA, this SFRA does not provide detailed flood risk outlines for additional breach risk arising from flood storage areas or urban flood risk from storm sewers.

The SFRA recommends applying the sequential test in accordance with PPG25 when deciding most appropriate areas for development based on its findings. Amongst its other recommendations the following is worth noting:

• Encouragement of 200 year standard of flood protection across the District for all future flood defence schemes; • Extension of the Environment Agency’s River Nene Strategic Model to include Raunds Hog Dyke and Skew Bridge Dyke; • Modelling of surface water sewers in Rushden and Raunds to determine their hydraulic capacity and the degree flood risk to properties; and • Application of flood risk policies and guidance included in the SFRA.

Finally, the Council should consider updating the current SFRA to at least demonstrate how the Council has addressed the impact of climate change in the assessment in order to satisfy the new PPS25 requirements in relation to development and flood risk. In addition, functional floodplain will have to be further assessed and mapped as part of this update.

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4.3.7 Implications of recent studies and development proposals

The SFRA has received the formal acceptance of the Environment Agency in November 2006. We consider that there are no major further studies or development proposals that would change the current findings of the SFRA although there are additional requirements to the Councils imposed by PPS25 when undertaking SFRAs.

We have reviewed the sewer flooding information presented in North Northamptonshire Outline WCS report (February 2007). It reports about localised sewerage issues at Oundle and notes that Anglian Water currently monitors the situation. There are no other issues mentioned in this report but it recommends further study to assess the capacity of sewer system and pumping stations. We also recommend this as the SFRA highlights some sewer flooding incidents at Rushden, Raunds and Irthlingborough. Therefore it is essential that developers should directly consult Anglian Water and the Council’s drainage department during the pre-application consultation process in order to establish the ability of existing sewers to receive additional flows from new developments.

We have also consulted Anglian Water to obtain the DG5 flooding register information during this study and Table 12 summarises the sewer records within the East Northamptonshire District Council. These locations are also shown in Figure 8.

Table 12: DG5 Sewer Flooding Records within the East Northamptonshire District

External Internal Flooding Both internal and Total flooding areas Postcode flooding only only external flooding by postcode

NN14 3JP 1 0 0 1 NN14 4DL 0 1 0 1 NN14 4EQ 0 1 0 1

As for Kettering and Wellingborough SFRA, an update of some of the terminology used in the SFRA outputs, a further review of the latest site allocations from the emerging Development Planning Documents and LDFs and the risk of flooding from sources other than main rivers will be required if a full compliance to PPS25 is to be achieved immediately. If there becomes a need for application of the Exception Test according to Table D.3 of PPS25 then further detailed modelling will be required to consider the detailed nature of the flood hazard taking account of the presence of flood risk management measures such as flood defences. This should include the assessment of flood probability, flood depth, flood velocity and rate of onset of flooding within each flood zones.

4.4 Corby SFRA

4.4.1 Introduction

Bullens (now Faber Maunsell) produced the draft Stage 2 report in April 2004 (Reference 13) following the Stage 1 assessment in March 2004. Subsequently, sections of the draft report and the related figures have been reissued. However, the Environment Agency is yet to approve the Stage 2 report.

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4.4.2 Data assessment

The latest data available to consultants has been used following a sufficient level of quality check to satisfy the needs of the strategic assessment. However, since the completion of the draft report in April 2004 there has been a considerable amount of additional studies in the study area. Therefore, the information presented in SFRA is now largely out dated and needs revising.

4.4.3 Historical Flooding

The SFRA provides details of flooding based on staff knowledge of the Corby Borough Council and the Environment Agency together with the incidents mentioned in flood study reports (most noticeably the report produced by John Taylor and Sons in 1984). Although Corby is prone to have sewer flooding risk no information has been obtained from Anglian Water as part of the SFRA.

Table 13 summarises the records of known flooding based on the SFRA findings.

Table 13: Historic Flooding Records within Corby Borough Town/Village/Location Watercourse and Dates Source Comments Cause Corby – Gretton Brook Gretton Brook – Not known CBC A large diameter pipe has been Road (near Gretton cause not known installed since under the road Reservoir) linking the reservoir and the open channel section of the Gretton Brook but the effect is not known. Corby – Cottingham Road Willow Brook Not known CBC Reshaping of the channel in Central Arm – conjunction with installation of cause not known weirs in Thoroughsale Woods was undertaken in 1980 to provide an online buffer zone upstream of Studfall Avenue Corby – Studfall Avenue Willow Brook Not known CBC Flooding seems to occur due to Central Arm – lack of maintenance of the blockage of the grille grilles on the inlet to the culverted section of the Willow Brook Weldon – Bridge Street Willow Brook Not known CBC Central Arm – cause not known Corby – Oakley Road Willow Brook South Not known CBC Arm – cause not known Weldon – Hillside Crescent Willow Brook Not known CBC (garages and gardens) Central Arm – cause not known Corby – Cecil Close Not known Not known CBC

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Town/Village/Location Watercourse and Dates Source Comments Cause Corby – west of the Not known Not known CBC A427/A6003 Corby – Gainsborough Not known Flooding CBC Road downstream of occurs Sower Leys Road approximately once in every two years Corby – Near the Hazel Willow Brook South Not known CBC Leys school at Oakley Arm – surcharged Road/ Westcott Way manhole or Junction overtopping of open channel (Source: Corby SFRA Stage 2 Report, April 2004)

Note – This is not an exhaustive list of flooding records as further records are available within Corby including the incident in 1982 described below.

In addition to the above records, the SFRA presents a table detailing the properties affected by the July 1982 according to 1984 drainage study report produced by John Taylor and Sons on behalf of the Corby Borough Council. This table has been reproduced as Table 14 overleaf.

The 1982 storm was regarded to be a 1 in 72 year, 2-hour duration event. The report also concluded that more frequent short storms than this event can produce flooding within Corby due to its limited and significantly urbanized catchment.

In addition to the above locations, two areas in Cottingham are known to have flooding problems.

4.4.4 Drainage and Hydrology

The Corby Borough is generally situated on the Lower Limestone with a capping of Boulder Clay. The Borough straddles the watershed between the River Welland and Nene catchments. The River Welland forms the northern boundary. The majority of the Borough is, however, situated within the headwaters of Willow Brook, Harpers Brook and Gretton Brook, which are the tributaries of the River Nene.

FEH hydrology has been used for all studied major watercourses in the catchment but using limited model calibration due to the absence of gauged flow and water level data in the catchment. Therefore the model calibration has been limited to the Environment Agency’s River Nene Strategic Model, which also includes its principal tributaries of the River Ise, Willow Brook, Harpers Brook and Slade Brook.

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Table 14: Properties flooded by storm of 30th July 1982 Willow Brook – North Arm Number of properties Flooded Location 5 123 to 131 Shire Road 6 74 to 84 Studfield Avenue 2 1 & 2 Kane Walk 10 232 to 250 Stephenson Way Total 23

Willow Brook – Central Arm Number of properties Flooded Location 6 110 to 20 Kingsthorpe Avenue 1 292 Studfield Avenue 1 22 Rosedale Avenue 8 175 to 181 Cottingham Road 20 Boon Walk 4 1,8,11, & 15 Chapel Lane Total 40

Willow Brook – Central Arm Number of properties Flooded Location 1 39 Tower Hill Road 3 482, 492 & 494 Gainsborough Road 2 47 & 49 Gainsborough Road 5 1, 3, 5, 7 & 9 Brayford Avenue 6 1, 3, 5, 7 & 9 Burghley Drive 2 Danesholme Total 19 (Source: Corby SFRA Stage 2 Report, April 2004)

4.4.5 Strategic Assessment of Flood Risk

The SFRA covers the entire Corby Borough. In addition, specific flood risk assessments have been carried out for five areas identified for potential residential development and five areas identified for potential industrial development within the Borough. These areas correspond with those identified in the Catalyst Corby Regeneration Framework, which incorporates large areas identified for development in addition to the current Local Plan proposals.

The ten specific flood risk assessments undertaken as part of the SFRA are:

• Western Extension – executive residential development; • Southern Extension – medium to high priced residential development; • Northern Extension – executive residential development; • Oakley/ Stanion Extension – medium to high priced residential development; • Priors Hall and Weldon Extensions – mixture of executive, medium and lower priced residential development; • Great Oakley – light industrial development (Motor Business Cluster); • St James Industrial Estate – town centre mixed use development;

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• Corby East – mix of high quality business, processing parks and logistics uses; and • Weldon South Industrial Estate and Max Park – mix of high quality business, processing parks and logistics uses.

The SFRA outputs are based on various hydraulic models, which consider the impact of any flood defences or storage areas. Corby was subjected to major development during early 1930s when a steel industry was established and the open stream channels were progressively entrained and culverted as the development was progressed. Flood alleviation measures in Corby consist principally of several flood storage reservoirs to manage additional flood risk from significant town expansion. However, following the July 1982 floods the deficiencies of flood defence standards in Corby were noticed which then led to several studies and flood mitigation measures.

The details of strategically planned and site specific water retention features include:

Strategically Planned: Gretton Brook Flood storage Reservoir Penn Green Lane Balancing Pond Penn Green Flood Storage Reservoir Phoenix Parkway Flood Storage Reservoir Hazel Leys, Studfall Avenue and The Jamb Weldon Lagoon Snatchill Flood Storage Reservoir Weldon Reservoir Great Oakley Flood Storage Reservoir

Site Specific: Car Yard Reservoir Stanier Road Flood Storage Reservoir Crucible Road Flood Storage Reservoir Eurohub Balancing Pond Soot Banks Flood Storage Reservoir Quarry Road Flood Storage Reservoir CTC Pond and Oakley Vale Ponds Longcroft Road Balancing Pond Rockingham Motor Speedway Balancing Pond

The watercourses assessed by the SFRA include:

• Willow Brook; and • Harpers Brook.

For other watercourses, the Environment Agency’s Circular 30/92 Maps and Indicative Floodplain Maps together with the engineering judgment have been used in the assessment and mapping. Although storm sewers are a significant contributor to flooding in Corby this risk has not been mapped as part of the SFRA, which can be seen as a major drawback to fully comply with the PPS25. This issue is further discussed in Sections 4.4.6 and 4.4.7.

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4.4.6 Compliance with PPG25/ PPS25

The SFRA provides useful information for the proposed flood risk management strategy (including existing operational and emergency planning) but further work to clarify its contents may be needed to fully comply with the new PPS25. Especially, it lacks clarity on how the assessment has addressed the impact of climate change, a key objective of the PPS25. Also, more information on sewer flooding risk should have been included in the SFRA as this is known to be a significant “catchment-wide” flooding issue within the Corby Borough. However, the Phase 2 Water Cycle Strategy (WCS) by Halcrow on behalf of the Environment Agency plans to address this sewer flooding risk through flood risk mitigation work as explained in Section 4.4.7 below.

Functional floodplain will have to be further assessed and mapped as needed through any future update of the existing SFRA as PPS25 now requires this.

In summary, the existing SFRA needs updating urgently to incorporate the latest information on flood risk and development proposals whilst satisfying the new requirements imposed by PPS25.

4.4.7 Implications of recent studies and development proposals

Since the completion of this SFRA a considerable amount of additional studies has been undertaken as part of the Corby WCS and individual development proposals. The Corby WCS Phase 2 report produced by Halcrow in November 2006 (Reference 7) provides the latest comprehensive information on the current and future flood risk issues in Corby. This report also includes a number of strategic and local specific measures required to accommodate the proposed growth sites so that they do not increase existing flood risk in Corby and in downstream areas. However, the proposed works alone will not result in a uniform standard of protection of 1 in 100 years across Corby as it is already extensively urbanised limiting the available options.

As part of the WCS a Developer Checklist was developed. This checklist will be used by within the normal planning process by the Council and the Environment Agency in order to assess the compliance of developer proposals against the recommendations of the Water Cycle Strategy.

The key recommendations of the published WCS in relation to the sewer and fluvial flood risk mitigation measures include:

• Improvement of the existing sewer network to provide additional storage and replacement of approximately 1.5km of under-sized pipework subject to the outcome of further modelling by Anglian Water;

• Provision of several flood risk mitigation measures to prevent additional runoff entering the west of Corby, store flood flows in Central Corby and to release it more quickly in the east of the town. The key elements of the work include flood storage ponds and general channel improvements throughout the catchment; and

• Maintenance of the existing system until the new works are implemented.

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According to the WCS report the most urgent measure is construction of a second culvert downstream of the Corby Sewerage Treatment Works along with improvements to the Weldon Flood Storage Reservoir and the downstream channel. These works will be required to accommodate the increased volume of sewerage affluent in order to agree a revised consent for the Sewerage Treatment Works in 2008.

Phase 2 WCS report also gives additional information about the flood history within the Corby Borough (see Table 15) and this information supplements the SFRA historic flooding information described in Section 4.4.3 above.

Table 15: Additional Flooding Records from Corby Water Cycle Strategy Site Name OS Coordinate Current Status Comment Tunwell Lane SP897891 Sold for Buildings allowed to encroach in the development floodplain, backwater effect from undersized downstream culvert Sewage Works SP906888 Restrictive railway culvert Stephenson Way1 SP894902 Sold for Inadequate flood storage, aqueduct, development constrictive culvert under parkway Edison Courtyard SP888911 Depot, Brookfield, Power SP896913 Planning Station Rockingham Road SP885902 Listed for Inadequate flood storage, aqueduct, development constrictive culvert under parkway Kingsthorpe Avenue1 SP870891 Gainsborough Road1 SP875878 Cottingham Road1 SP880890 Town Hill Road SP862877 Kingswood School SP863885 Sold for development St Marks Road SP893883 Sold for Minor historical flooding, sold for development development Sedborough Road SP870870 Hillside Crescent, Weldon SP923894 Church Street, Weldon Willow Brook Central East Entire length Residents etc. have built obstructions in the channel and the floodplain Oakley Road1 SP881876 Courts Farm Road SP885881 The Grove SP902886 Great Oakley SP872856 Factory, Great Oakley SP866855 Little Oakley SP894856 Village flooding Mill House Stanion SP921868 (Source: Phase 2 Corby WCS Report, January 2007)

1 Already reported in Section 4.4.3

During this Flood Risk Management Study, we have also consulted Anglian Water to obtain the DG5 flooding register information during this study and Table 16 summarises the obtained sewer records. These locations are also shown in Figure 8.

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Table 16: DG5 Sewer Flooding Records within the Corby Borough

External Internal Flooding Both internal and Total flooding areas Postcode flooding only only external flooding by postcode

NN17 1LB 0 1 0 1

It is essential that developers should consult Anglian Water and the Councils’ drainage department during the pre-application consultation process in order to establish the ability of existing sewers to receive additional flows from new developments.

Royal Haskoning is also currently undertaking a study, Weldon Flood Storage Probable Maximum Flood Assessment, on behalf of the Environment Agency. Depending on the final conclusions of this study some flood risk implications for the downstream areas may be highlighted.

It should be noted that Halcrow completed pre-feasibility studies on both Willow Brook and Harpers Brook in February 2006 and the modelling outputs from these should be formally incorporated into the final Corby SFRA outputs.

Finally although the SFRA gives useful information on the flood risk issues in the Corby Borough its outputs must be used in conjunction with the latest information from the other recent studies. Otherwise, it is clear that the existing SFRA (yet to be formally approved by the Environment Agency) does not meet the key requirements of PPS25. The absence of an approved current SFRA may prevent the achievement of key objectives of PPS25, in particular as Corby is currently undergoing major expansion.

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5 OUTLINE FLOOD RISK MANAGEMENT STRATEGY

5.1 Overview

The findings of the review of the SFRAs and the information obtained from the Environment Agency’s Water Cycle Strategies and River Nene Catchment Flood Management Plan (CFMP) have been used to develop the proposed outline strategy. It also includes recommendations for the next steps of the Flood Risk Management Strategy (FRMS).

The strategy explores the opportunities to reduce the existing flood risk in North Northamptonshire through a combination of the above elements and suitable planning interventions achieved by collaborative working with all parties involved (e.g. planners, developers, regulators and community groups).

Positive planning and working in constructive partnerships to reduce flood risk will be a key to the successful implementation of PPS25 and will be essential to accommodate the major growth proposals in this area (e.g. 52,100 new homes and 47,400 new jobs between 2001 and 2021).

North Northamptonshire is expected to accommodate more housing growth than any other part of the Milton Keynes and South Midlands growth area. Another challenge is to address the additional flood risk posed by climate change which exacerbates current flood risk from the already overloaded urban watercourse and sewers.

The proposed Flood Risk Management Strategy is comprised of the following key components:

• Policies; • Planning conditions; • Physical measures (including their operation and maintenance); • Flood warning and emergency planning; and • Guidance.

Alongside with other considerations above, physical measures will be needed both at local and strategic levels to manage flood risk within the Districts in a sustainable fashion over the next 50 to 100 years.

The FRMS will be examined at the public inquiry for the North Northamtonshire Core Strategy that has been submitted to the Secretary of State in February 2007. Once agreed with all key parties, it is expected that the FRMS will be implemented through the emerging Local Development Documents involving Supplementary Planning Guidance.

The lessons learned from the Corby WCS and other examples in the UK and abroad have been incorporated into the development of outline strategy.

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5.2 Policies

The River Nene CFMP Summary of Draft Plan July 2006 identifies the following flood risk management polices and actions for the watercourses (i.e. policy units) within North Northamptonshire.

Table 17: Actions for implementing sustainable flood risk management in policy units within North Northamptonshire

Policy Policy Actions Lead organisation unit In line with the overall strategy and in a planned sequence:

P4: Action to sustain 1. Consider controlling the contributions to Environment flood flow made by tributary catchments. current level of Agency

flood risk

Note 1 2. Implement local protection if necessary

e P5: Action to reduce

n

e flood risk

N

r e 3. Reduce flood risk where prominent, e.g. v i P6: Action to increase commercial/industrial areas of Note 1 R

n Northampton and Wellingborough

i

a frequency of

M Environment 4. Consider the reinstatement of floodplain flooding. Agency/English and develop floodplain storage, exploiting opportunities, where presented, in planned Nature sequence.

P4: Action to sustain 1. Implement measures to prevent increase in Environment flood risk along the River Ise and to current level of Agency contribute to reduction through Kettering flood risk and Wellingborough

P5: Action to reduce 2. Reduce flood risk, if economically viable, to Note 1

e Kettering and Wellingborough s flood risk I

r

e v

i 3. Consider measures, in conjunction with P6: Action to increase R other tributaries, to prevent increase in Environment frequency of flood risk through Wellingborough and to contribute to flood control along the River Agency/English flooding. Nene. Nature

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Policy Policy Actions Lead organisation unit In line with the overall strategy and in a planned sequence:

P4: Action to sustain 1. Implement measures to prevent increase in Environment flood risk along the Harper’s Brook. current level of Agency

k flood risk

o o r

B P6: Action to increase Environment s

’ 2. Consider measures to contribute to flood r

e Agency/English frequency of control along the River Nene. p r Nature a

H flooding.

P4: Action to sustain 1. Implement measures to prevent increase in Environment flood risk along the Willow Brook. current level of Agency

flood risk

k o o

r B

P6: Action to increase w 2. Consider measures to contribute to flood o l

l Environment i frequency of control along the River Nene.

W Agency/English flooding. Nature

(Source: River Nene Catchment Flood Consultation Draft Plan, July 2006 – Environment Agency)

Notes 1. The draft consultation document does not define the lead organisation for carrying this action.

We have reviewed the above policies and suggested actions and then developed an overall flood risk management policy which will need to be incorporated within the emerging LDFs and related Local Development Documents (LDDs) for North Northamptonshire.

The suggested overall flood risk management policy is presented overleaf.

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T he overall Flood Risk Management Policy:

C ouncils will produce an overall Flood Risk Management Strategy for North N orthamptonshire for compliance when producing Local Development Documents a nd in submitting planning applications by developers.

T he strategy will be comprised of the following key components: a) Policies; b) Planning conditions; c) Physical measures (including their operation and maintenance); d) Residual risk management; and e) Guidance.

T he key requirements to be addressed by the strategy will include: 1. Implementation of strategic flood risk management measures in advance or in parallel with the proposed developments with the intent of obtaining appropriate financial contributions from the prospective developers through Section 106 Agreements including for long-term management;

2. Continuing to seek opportunities using a partnership approach to reduce

flood risk within North Northamptonshire, avoiding the temptation just to manage flood risk within individual administrative areas; 3. Provision of a combination of source control and strategic SUDS measures within individual development sites where the opportunities for catchment- wide strategic measures are limited; 4. Incorporation of sufficient capacity in strategic flood management measures allowing for planned growth and future climate change; 5. Rejection of a piecemeal approach to manage runoff from smaller individual sites whilst providing strategic and local green corridors to incorporate SUDS for managing surface water runoff from developments; 6. Restoration of the river floodplains as the land becomes available for redevelopment through set back options and creation of green space; 7. Identification of the locations that are known to have surface water flooding

problems from sewers and overland flow routes and exploring possible solutions for them through new development proposals.

The key requirements of the proposed strategy are further illustrated below with the use of example applications as needed.

K ey requirement 1 L ocal Authorities will implement strategic flood risk management measures in advance or in parallel with the proposed developments with the intent of obtaining appropriate fi nancial contributions from the prospective developers through Section 106 Agreements. T he Local Authorities will ensure the long-term management and routine operation of s uch strategic measures.

E xample Application In vestigate opportunities for strategic flow balancing measures on the Slade Brook in c onjunction with the developments in Rothwell and East Kettering Development to reduce c urrent flood risk through the urbanised part of Kettering whilst not increasing the net fl ood risk on the River Ise in downstream areas. This will involve direct discharge or r elaxed on-site flow attenuation from the individual developments in return for the d evelopers’ financial contributions to the strategic schemes implemented in advance of th e developments by the Local Authorities.

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Key requirement 2 Local Authorities will continue to work together in seeking opportunities to reduce flood risk within North Northamptonshire avoiding the temptation just to manage flood risk within their individual administrative areas. This will include the consideration of maximising the use of natural floodplains of large rivers such as River Nene and River Ise for flood storage where possible.

Example Application Kettering Borough Council and Borough Council of Wellingborough will jointly work to reduce flood risk within the Slade Brook and River Ise Catchments. Consider minimum on-site attenuation at WEAST as it is located at the downstream reach of the River Ise but instead consider strategic flow balancing on the Slade Brook and River Ise at their upstream reaches; this will reduce the existing flood risk in urbanised areas of Kettering but still will not increase the net flood risk on the River Ise or River Nene in downstream areas. Similar opportunities maybe available within East Northamptonshire where the runoff from the proposed developments can be discharged directly to the broad floodplain of the middle reaches of the River Nene or other watercourses without capacity problems.

The financial contributions of the developers, who would benefit from the relaxed onsite surface water attenuation, will be secured through Section 106 agreements or similar arrangements for implementing the strategic flow balancing schemes elsewhere under this requirement or Requirement 1 above.

Key requirement 3

Developers will provide a combination of source control and strategic SUDS measures

within their development sites in accordance with the constraints, design parameters

and maintenance arrangements agreed with the Local Authorities, Environment Agency

and Anglian Water. This will be appropriate at a large sub-catchment scale where

developers are committed to develop the entire site and where the opportunities for

other catchment-wide strategic measures are limited. Local Authorities will ensure the

long-term management and routine operation of such measures.

Example Application Source control and strategic on-site SUDS measures will be used where appropriate, including:

• Part of the East Kettering development that drains to the Alledge Brook • Castlegate development that drains to Harrowden Brook • Development sites in Raunds that drain to Hog Dyke • Development sites that drain to Skew Bridge Brook in Rushden.

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Key requirement 4 Strategic flood management measures must have sufficient capacity allowing for planned growth and future climate change in order to minimise the need for further site specific measures at individual developments other than for source control SUDS.

Example Application Strategic measures upstream of Kettering and through the town (e.g. improved Slade Brook Flood Detention Reservoir) should have sufficient capacity to minimise further measures at individual sites unless they clearly offer source control and bio diversity enhancements in addition to or as part of the overall strategy.

Key requirement 5

For small scale developments where strategic measures are not feasible then

developers take a local approach to manage runoff from the individual sites using

SUDS where possible. However, it should be noted that this is not the preferred

strategic approach by this Flood Risk Management Strategy and therefore should be

seen only as the fall back position. Developers will be responsible for the

implementation and long-term management of any site-specific measures.

Notwithstanding, the Local Authorities will ensure that strategic and local green

corridors are provided to incorporate SUDS for managing surface water runoff from

individual developments where possible.

Example Application

A local approach can be used at proposed smaller scale sites within East

Northamptonshire District (e.g. Higham Ferrers, Rushden and Oundle) and also

currently committed or potential windfall sites within North Northamptonshire where the

opportunities for strategic options are currently limited.

Key requirement 6 Local Authorities will take the opportunity to restore the currently developed land within river floodplains or high flood risk areas identified in the SFRAs as the land become available for redevelopment. This should be extended to searching for opportunities when they make long term land use policy document to make North Northamptonshire sustainable for future generations.

Example Application Opportunities should be available for restoring currently constrained floodplain in Corby, Kettering and Wellingborough especially where commercial and industrial areas are due for redevelopment.

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Key requirement 7 Local Authorities in conjunction with Anglian Water and Environment Agency will identify the locations that are known to have surface water flooding problems from sewers and overland flow routes. The identified problems will be resolved as and when the opportunities arise through new development proposals.

Example Application A number of existing surface water flooding issues are expected to be resolved in Corby through the Phase 2 Water Cycle Strategy. Similarly, known surface water problems can be addressed in other parts of North Northamptonshire through the emerging Water Cycle Strategy for the entire area. For example, at Severn Way in Kettering where a sewer carries flow from Rothwell and on the Swanspool Brook Sewer serving the west of Wellingborough.

5.3 Planning Conditions

Suitable planning conditions will need to be enforced through the normal planning application process for individual development sites in order to implement the overall flood risk management policy explained under Section 5.2. Standard conditions should be drafted by the Councils and agreed with the Environment Agency where possible prior to granting planning consents for the applicants.

5.4 Physical measures

The options considered include: • Localised source control and site control SUDS measures; • Strategic Flood storage areas and washlands; • Localised flood defences; and • Localised channel improvement works.

All of the above measures will be dependent on management works which include long term as well as routine maintenance, monitoring and operation. Therefore it is very important to ensure such needs are well addressed through the proposed strategy to prevent flooding problems later on.

Possible locations for the strategic measures, which fulfil the key requirements of the suggested overall Flood Risk Management Policy in Section 5.2, have been identified during this study. However, further consultation will be needed with the key parties during the next phase of the study to agree such locations. We have currently assumed that no additional physical measures are needed for the future flood risk management in Corby to accommodate the anticipated growth once the recommendations of the Phase 2 Corby Water cycle Strategy are fully implemented. However, this view needs a further review as part of future studies.

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5.5 Residual Risk Management

5.5.1 General

The risks after applying the sequential approach to development planning (where developments are first directed to areas at least risk from flooding) and taking mitigating actions are known as residual risks.

PPS25 states that it is the responsibility of those planning development to fully assess flood risk, propose measures to mitigate it and demonstrate that any residual risks can be safely managed. This is very important as flooding is unpredictable and flood prediction has several interrelated uncertainties.

Residual risk management should typically include: • assessment of breach and overtopping risk of existing defences; • assessment of blockage risk of existing structures; • arrangements for remedial actions and ongoing maintenance of flood risk management infrastructure; • provision of overland flow paths to manage exceedance flows; • incorporation of flood resilience and resistance measures; and • flood warning and evacuation plans.

5.5.2 Flood warning and emergency planning

The receipt of and response to warning of floods is an essential element in the management of the residual risk of flooding.

Currently placed arrangements

General flood warnings are currently disseminated by the Environment Agency, via a system known as Floodline Warnings Direct, for the all main river reaches within North Northamptonshire.

The service is a free flood warning service that provides warnings direct to customers 24 hours a day by telephone, mobile, fax or pager. It replaces the older Automatic Voice Messaging System which was used to send out flood warnings direct to the public since 1996. The message details the level of warning issued and the area for which the warning is in force and advises on what action to take. As flood events develop the public is encouraged to phone Floodline for updates. This system requires residents of “at risk property” to register their telephone numbers with the Environment Agency. Concerned parties are able to obtain current flood warning information according to a particular river or Flood Warning Risk Area.

Other current methods of warning dissemination include:

• The media – warnings are issued through the media; they are broadcast on TV weather bulletins and on radio weather and travel reports. Flood warnings are also displayed on ITV Teletext regional weather pages (page 154) and on the BBC Ceefax (page 419).

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• Floodline 0845 988 1188 – offers callers the option to listen to recorded flood warning information 24 hours a day and speak to a trained operator for more advice. • Internet – The Environment Agency’s website www.environment- agency.gov.uk/flood contains live warning information.

If anyone has not currently registered their phone number but is at risk of flooding, they should consider contacting the Environment Agency.

The Environment Agency issues flood warnings using a set of four easily recognisable codes which include:

• Flood Watch, where flooding of low-lying land and roads is possible; • Flood Warning, where flooding of homes, businesses and main roads is expected; • Severe Flood Warning, where severe flooding is expected. Extreme danger to life and property; and • All Clear, where flood watches or warnings are no longer in force.

A Flood Watch would be issued when water levels along the river are forecast to cause out-of-bank flooding of low-lying land and roads.

A Flood Warning is issued when the Environment Agency anticipate flooding to property. The trigger levels currently set for this are based on the levels of permanent dwellings.

The trigger for issue of a Severe Flood Warning is dependent on a number of factors, but is essentially used when there is thought to be extreme danger to life.

The Environment Agency generally aims to give a two-hour lead time for all of the above levels of warning. However in certain cases of severe or “flash flooding” this may not always be possible. Certain areas may be at additional risk due to their location downstream of heavily urbanised areas and urban areas that have the potential for “flash flooding”, surcharging the capacity of existing sewers and watercourses. This aspect needs further investigation by the Councils in conjunction with the Environment Agency to ensure that adequate telemetry, flood warnings etc. are provided.

Recommendations

As part of the proposed strategy it should consider the following:

a) Local Authorities should draw up emergency planning and evacuation procedures for North Northamptonshire.

b) In exceptional circumstances, having undertaken the Sequential Test and the Exception Test by the Councils, if development is allowed in high risk and medium risk areas then emergency plans are to be prepared by the developers. Evacuation plans should be in place in those areas known to be at risk of flooding and should make provision for:

i. How flood warning is to be provided; ° Availability of existing flood warning systems;

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° Rate of onset of flooding and available flood warning time, including contingency for possible failure (e.g. breach) of defences or infrastructure; and ° Method of dissemination of flood warning.

ii. What will be done to protect the infrastructure of the development and contents, such as: ° How more easily damaged items (including parked cars) will be relocated; ° The potential availability of staff/occupants/users to respond to a flood warning; and ° The potential time taken to respond to a flood warning.

iii. Ensuring safe occupancy and access to and from the development, such as: ° Occupant awareness of the potential frequency and duration of flood events; ° Provision of safe access to and from the development; ° Ability to maintain key services during an event; ° Vulnerability of occupants, and whether rescue by emergency services will be necessary and feasible; and ° Expected time taken to re-establish normal practices following a flood event (clean-up times, time to re-establish services etc.).

Where such evacuation plans are required they need to consider the lifetime of the development by fully taking into account the prospective climate change impacts.

Development of proposals will need to include early liaison with the Environment Agency so that flood warning infrastructure requirements can be determined.

5.6 Guidance

Councils should produce general guidance on how developers should comply with the Flood Risk Management Strategy proposed in Section 5. Sustainable Urban Extensions proposed by the emerging North Northamptonshire Core Strategy will need clear direction from the Councils through this guidance.

This guidance should clarify the following key aspects:

• preparation of Flood Risk Assessments; • management of surface water; • consideration of climate change impacts and the broad criteria for design life depending on land-use of proposed development; • management of residual flood risk; • recovery of financial costs for implementing the required strategic mitigation measures; and • maintenance and adoption needs of any site specific mitigation measures.

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6 FUNDING AND PLANNING ISSUES

The success of the proposed Flood Risk Management Strategy will be dependent on securing funds from the central government and prospective developers and other crucial factors such as coordination, planning, phasing, monitoring and long-term management of the required physical measures. However, the Business Investment Plan prepared by the North Northants Development Company has already recognised the need for significant investment on strategic flood risk management.

To address the funding and planning issues associated with the implementation of the strategic measures will need a coordinated approach during the next phase of this study.

We have not carried out detailed cost estimates for the required works as the scope of the required works is yet to be identified and agreed. Also costs will be dependent on the detailed design, site investigation and environmental scoping. However, based on the preliminary cost estimates for Corby flood risk mitigation measures we have estimated that the implementation of the remaining works in North Northamptonshire will cost some £50M at current prices without discounting. The estimates also exclude any land purchase costs and design fees.

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7 CONCLUSIONS

The four existing SFRAs and the information gleaned from the recent studies have been used in developing the proposed Flood Risk Management Strategy for North Northamptonshire.

The key findings of this review are: • Surface water management is a key issue in all four Council Districts; • SFRAs provide a useful framework for development planning and flood risk management but further update and clarification is needed to fully comply with PPS25, for example, to address the latest guidance on climate change, to assess all sources of flooding in more detail and to map functional foodplain; • The emerging Core Spatial Strategy for North Northamptonshire and related information shows that the Councils have generally taken a sequential approach when identifying broad locations for the proposed Sustainable Urban Extensions; • Evidence of the Sequential Test undertaken by the Councils when identifying and allocating development sites will be required. Also, further clarification and information on individual developments will be needed from the Councils to confirm the need for application of Exception Test and any further modelling work; and • A robust flood risk management strategy for North Northamptonshire will be needed (even if the development sites are located in low risk areas) in order to address extra runoff and residual risk issues resulting from planned growth proposals and the existing flooding problems on the receiving watercourses.

North Northamptonshire is expected to accommodate more housing growth than any other part of the Milton Keynes and South Midlands growth area. Another challenge is to address the additional flood risk posed by climate change which exacerbates current flood risk from the already overloaded urban watercourse and sewers.

The proposed strategy should explore the opportunities to reduce the existing flood risk in North Northamptonshire through a range of measures and suitable planning interventions together with collaborative working with all parties involved (e.g. planners, developers, regulators and community groups). It is also very important that the strategy should address residual flood risk management needs of the proposed developments as well as the rest of North Northamptonshire.

Positive planning and working in constructive partnerships to reduce flood risk is needed for successful implementation of PPS25 and will be essential to accommodate the major growth proposals in this area (e.g. 52,100 new homes and 47,400 new jobs between 2001 and 2021).

The success of the proposed Flood Risk Management Strategy will be dependent on securing funds from the central government and prospective developers and other crucial factors such as coordination, planning, phasing, monitoring and long-term management of the required physical measures. However, the Business Investment Plan prepared by the North Northants Development Company has already recognised the need for significant investment on strategic flood risk management.

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8 RECOMMENDATIONS

A Flood Risk Management Strategy for North Northamptonshire is required comprising the following key components:

• Policies; • Planning conditions; • Physical measures (including their operation and maintenance); • Residual risk management; and • Guidance.

Alongside other considerations above, physical measures will be needed both at local and strategic levels to manage flood risk within the Districts in a sustainable fashion over the next 50 to 100 years.

The key requirements to be addressed by the strategy should include:

• Implementation of strategic flood risk management measures in advance or in parallel with the proposed developments with the intent of obtaining appropriate financial contributions from the prospective developers through Section 106 Agreements including for long-term management; • Continuing to seek opportunities using a partnership approach to reduce flood risk within North Northamptonshire, avoiding the temptation just to manage flood risk within individual administrative areas; • Provision of a combination of source control and strategic SUDS measures within individual development sites where the opportunities for catchment-wide strategic measures are limited; • Incorporation of sufficient capacity in strategic flood management measures allowing for planned growth and future climate change; • Avoidance of a piecemeal approach to manage runoff from smaller individual sites whilst providing strategic and local green corridors to incorporate SUDS for managing surface water runoff from developments; • Restoration of the river floodplains as the land becomes available for redevelopment through set back options and creation of green space; • Identification of the locations that are known to have surface water flooding problems from sewers and overland flow routes and exploring possible solutions for them through new development proposals; and • Recognition of accommodating imminent development currently planned in North Northamptonshire ahead of the final Core Strategy.

To address the funding and planning issues associated with the implementation of the strategic measures will need a coordinated approach during the development of the proposed Flood Risk Management Strategy.

=o=o=o=

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9 REFERENCES

1. North Northamptonshire Outline Water Cycle Strategy, Technical Report (Environment Agency, January 2007)

2. Preferred Options for North Northamptonshire – Towards a Joint Core Spatial Strategy (North Northamptonshire Joint Planning Unit, November 2005)

3. North Northamptonshire Core Spatial Strategy (North Northamptonshire Joint Planning Unit, February 2007)

4. Preferred Options for Three Towns – Rusden, Higham Ferrers and Irthlingborough (East Northamptonshire Council, September 2006)

5. Preferred Options for Rural North, Oundle and Thrapston (East Northamptonshire Council, January 2006)

6. Preferred Options for Raunds Area (East Northamptonshire Council, January 2007)

7. Corby Phase 2 Water Cycle Strategy, Technical Report (Environment Agency, November 2006)

8. Planning Policy Statement 25 (Communities and Local Government, December 2006)

9. Development and Flood Risk: A practice guide to PPS25 ‘Living Draft’ (Communities and Local Government, February 2007)

10. Kettering and Wellingborough SFRA – Stage 2 Report (Kettering Borough Council, May 2005)

11. Hydrological Assessment for Slade Brook Flood Detention Reservoir Draft Report (Kettering Borough Council, July 2006)

12. East Northamptonshire SFRA – Stage 2 Report (East Northamptonshire Council, November 2005)

13. Corby SFRA – Stage 2 Draft Report (Corby Borough Council, April 2004)

14. Sustainable Drainage Systems for New Homes – Best Practice Guidance ( County Council, June 2006)

15. National Standing Advice to Local Planning Authorities for Planning Applications, Development and Flood Risk – , User Guidance Note (EA, June 2004)

16. Making Space for Water, First government response to the autumn Making Space for Water Consultation exercise, Department for Environment, Food and Rural Affairs (Defra), March 2005

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17. Foresight future flooding, volumes 1 and 2 (Office of Science and Technology, 2004)

18. C624 Development and flood risk – guidance for the construction industry (CIRIA, September 2004)

19. C697 The SUDS Manual (CIRIA, 2007)

20. C625 Model agreement for sustainable water management systems (CIRIA, 2004)

21. Interim Code of Practice for Sustainable Drainage Systems (National SUDS Working Group, 2004)

22. River Nene Catchment Flood Management Plan – Summary of Draft Plan and Consultation Draft Plan (Environment Agency, July 2006)

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