West Northamptonshire Strategic Flood Risk Assessment Final Level 1 Report – Volume 1 February 2009 Prepared for: West Northamptonshire Strategic Flood Risk Assessment Level 1 Report Revision Schedule West Northamptonshire Strategic Flood Risk Assessment Final Level 1 Report January 2009 Rev Date Details Prepared by Reviewed by Approved by D01 18/05/07 DDC, SNC & Fay Tivey Michael Timmins NBC SFRA Assistant Flood Risk Principal Consultant Specialist Andrew Woodliffe Senior Flood Risk Specialist F01 21/08/07 Amendments Fay Tivey Michael Timmins Damon O’Brien requested by Assistant Flood Risk Principal Consultant Technical Director DDC, SNC, Specialist NBC and EA Andrew Woodliffe Senior Flood Risk Specialist F02 06/01/09 Amendments Andrew Woodliffe Michael Timmins Damon O’Brien requested by EA Senior Flood Risk Principal Consultant Technical Director Specialist F03 19/02/09 Amendments Gemma Costin Andrew Woodliffe Damon O’Brien requested by EA Assistant Flood Risk Senior Flood Risk Technical Director Specialist Specialist Scott Wilson Mansfield i-Centre Oakham Business Park Hamilton Way Mansfield This document has been prepared in accordance with the scope of Scott Wilson's appointment with its client and is subject to the terms of that appointment. 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The contents of this document are not to be construed as providing legal, business or tax advice or opinion. © Scott Wilson Group PLC 2009 West Northamptonshire Strategic Flood Risk Assessment Level 1 Report Table of Contents Abbreviations ................................................................................................ i Glossary....................................................................................................... ii 1 Introduction ....................................................................................... 1 1.1 The West Northamptonshire SFRA................................................................................. 1 1.2 The SFRA Objectives ..................................................................................................... 2 1.3 The SFRA Structure ....................................................................................................... 2 2 Level 1 SFRA – Methodology............................................................ 4 2.1 Objective ........................................................................................................................ 4 2.2 Tasks.............................................................................................................................. 4 2.3 Stakeholders................................................................................................................... 4 2.4 Data / Information Collected ........................................................................................... 5 2.5 GIS Layers ..................................................................................................................... 6 3 Study Area ...................................................................................... 10 3.1 Flood Sources .............................................................................................................. 10 3.2 Administrative Areas..................................................................................................... 15 3.3 Specific Local Information............................................................................................. 15 3.4 Flood Defence Infrastructure ........................................................................................ 20 4 Northampton Borough Council SFRA Review ................................. 22 4.1 Overview ...................................................................................................................... 22 4.2 Causes and Classes of Flooding within Borough .......................................................... 22 5 Flood Risk Overview ....................................................................... 38 5.1 Flood Risk Review........................................................................................................ 38 5.2 Implications of PPS25................................................................................................... 41 6 Sequential Testing........................................................................... 42 6.1 Background .................................................................................................................. 42 6.2 Using the SFRA to Apply Sequential Testing................................................................ 45 7 Policy Review.................................................................................. 50 7.1 Catchment Flood Management Plans........................................................................... 50 7.2 Water Cycle Strategies ................................................................................................. 53 7.3 Flood Risk .................................................................................................................... 53 7.4 Sustainable Drainage Systems..................................................................................... 54 7.5 Water Environment....................................................................................................... 55 West Northamptonshire Strategic Flood Risk Assessment Level 1 Report 8 Flood Risk Assessment Guidance................................................... 57 8.1 Site Specific Flood Risk Assessment Guidance............................................................ 57 8.2 Additional Requirements............................................................................................... 59 9 Development Targets ...................................................................... 61 9.1 Joint Core Strategy....................................................................................................... 61 9.2 Potential Development Sites......................................................................................... 61 10 Recommendations .......................................................................... 63 West Northamptonshire Strategic Flood Risk Assessment Level 1 Report Abbreviations ACRONYM DEFINITION AONB Area of Outstanding Natural Beauty AW Anglian Water BW British Waterways CFMP Catchment Flood Management Plan DDC Daventry District Council DEM Digital Elevation Model DPD Development Plan Documents EA Environment Agency EP English Partnerships FRA Flood Risk Assessment GIS Geographical Information Systems IDB Internal Drainage Board LDDs Local Development Documents LDF Local Development Framework LDS Local Development Scheme LiDAR Light Detection and Ranging LPA Local Planning Authority MKSM SRS Milton Keynes South Midlands Sub-Regional Strategy NBC Northampton Borough Council ODPM Office of the Deputy Prime Minister PCPA Planning and Compulsory Purchase Act 2004 PPG25 Planning Policy Guidance Note 25: Development and Flood Risk PPS25 Planning Policy Statement 25: Development and Flood Risk RFRA Regional Flood Risk Assessment RPG Regional Planning Guidance RSS Regional Spatial Strategy SW Scott Wilson SAR Synthetic Aperture Radar SA Sustainability Assessment SFRA Strategic Flood Risk Assessment SNC South Northants Council SPG Supplementary Planning Guidance SSSI Site of Special Scientific Interest SuDS Sustainable Drainage Systems TW Thames Water Final i February 2009 West Northamptonshire Strategic Flood Risk Assessment Level 1 Report Glossary TERM DEFINITION A source of groundwater comprising water-bearing rock, sand or gravel capable Aquifer of yielding significant quantities of water. Catchment A high-level planning strategy through which the Environment Agency works with Flood their key decision makers within a river catchment to identify and agree policies to Management secure the long-term sustainable management of flood risk. Plan Both natural and human actions causing long term variations in global Climate Change temperature and weather patterns. Culvert A channel or pipe that carries water below the level of the ground. Infrastructure used to protect an area against floods as floodwalls and Flood defence embankments; they are designed to a specific standard of protection (design standard). A map that delineates the areas that have been predicted to be at risk of being Flood Map flooded during an event of specified probability. Floodplain Area adjacent to river, coast or estuary that is naturally susceptible to flooding. Flood storage A temporary area that stores excess runoff or river flow often ponds or reservoirs. Fluvial flooding Flooding by a river or a watercourse. This comprises land where water has to flow or be stored in times of flood. SFRAs Functional should identify the functional floodplain, i.e. land which would flood with an annual Floodplain probability of 1 in 20 (5%) or greater in