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 Peterborough PE3 8DW United Kingdom +44 (0)1733 334455 Telephone 01733 333538 Fax [email protected] E-mail www.royalhaskoning.com Internet Document title North Northamptonshire Flood Risk Management Study Document short title Strategy Report Status Final Report Date June 2007 Project name North Northamptonshire 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 …………………. …………………. Strategy Report - i - 9S1244/R/302099/PBor Final Report June 2007 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 Kettering 8 3.3 Wellingborough 8 3.4 East Northamptonshire 9 3.5 Corby 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 Strategy Report - ii - 9S1244/R/302099/PBor Final Report June 2007 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 Strategy Report - iii - 9S1244/R/302099/PBor Final Report June 2007 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; Strategy Report 9S1244/R/302099/PBor Final Report - 1 - June 2007 • 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. Strategy Report 9S1244/R/302099/PBor Final Report - 2 - June 2007 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 River Nene 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. Strategy Report 9S1244/R/302099/PBor Final Report - 3 - June 2007 Strategy Report 9S1244/R/302099/PBor Final Report - 4 - June 2007 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 Rushden 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 (River Ise, Harpers Brook and Brook Willow); and • River Welland 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 Northampton 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 East Midlands 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. Strategy Report 9S1244/R/302099/PBor Final Report - 5 - June 2007 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.