West Northamptonshire Strategic Flood Risk Assessment Part 1 Northamptonshire County Council March 2019 REVISION SCHEDULE West Northamptonshire Level 1 Strategic Flood Risk Assessment. Revision Date Details Prepared by Reviewed by Approved by st 01 31 July Draft SFRA Josie Bateman Phil Jones Alison Parry 2017 Level 1 th 02 5 Interim Draft Josie Bateman Aiden Grist Alison Parry October SFRA Level 1 2017 th 03 14 Final Draft Josie Bateman Aiden Grist Alison Parry November SFRA Level 1 2017 th 04 5 Final SFRA Josie Bateman Aiden Grist Alison Parry December Level 1 SFRA 2017 th 05 19 March Updated Aiden Grist Phil Jones Alison Parry 2019 Groundwater Mapping Northamptonshire County Council Place Directorate Flood and water Management One Angel Square 4 Angel Street Northampton NN1 1ED CONTENTS EXECUTIVE SUMMARY ..................................................................................................... 7 STUDY AREA ............................................................................................................................. 7 OUTCOMES OF THE LEVEL 1 STRATEGIC FLOOD RISK ASSESSMENT ..................................................... 7 1. INTRODUCTION ..................................................................................................... 10 APPLYING THE SEQUENTIAL TEST FOR PLAN MAKING PURPOSES ...................................................... 10 APPLYING THE EXCEPTION TEST FOR PLAN MAKING PURPOSES ....................................................... 11 STUDY AREA ........................................................................................................................... 12 FLOOD RISK OBJECTIVES ........................................................................................................... 12 THE STRATEGIC FLOOD RISK ASSESSMENT STRUCTURE ................................................................... 13 2. METHODOLOGY ..................................................................................................... 14 OVERVIEW .............................................................................................................................. 14 TASKS .................................................................................................................................... 14 STAKEHOLDERS........................................................................................................................ 14 3. DATA COLLECTION AND REVIEW ............................................................................ 15 OVERVIEW .............................................................................................................................. 15 TOPOGRAPHY AND GEOLOGY ..................................................................................................... 15 GIS LAYERS ............................................................................................................................ 16 DATA GAPS AND ASSUMPTIONS ................................................................................................. 17 4. RELEVANT FLOOD RISK MANAGEMENT PLANS, STRATEGIES AND STUDIES .............. 18 NATIONAL FLOOD AND COASTAL EROSION MANAGEMENT STRATEGY FOR ENGLAND .......................... 18 PRELIMINARY FLOOD RISK ASSESSMENTS ..................................................................................... 18 FLOOD RISK MANAGEMENT PLANS AND RIVER BASIN MANAGEMENT PLANS .................................... 19 ANGLIAN FLOOD RISK MANAGEMENT PLAN ................................................................................. 19 THAMES FLOOD RISK MANAGEMENT PLAN .................................................................................. 20 SEVERN FLOOD RISK MANAGEMENT PLAN ................................................................................... 21 COUNTY-WIDE LOCAL FLOOD RISK MANAGEMENT STRATEGY ......................................................... 22 FLOOD AND WATER RELATED WORK .......................................................................................... 23 WEST NORTHAMPTONSHIRE STRATEGIC FLOOD RISK ASSESSMENT. FINAL LEVEL 1 REPORT – VOLUME 1 (FEBRUARY 2009) ................................................................................................................... 23 WEST NORTHAMPTONSHIRE (DAVENTRY AND SOUTH NORTHAMPTONSHIRE) LEVEL 2 STRATEGIC FLOOD RISK ASSESSMENT. “LIVING DOCUMENT” (JUNE 2009) ................................................................. 23 NORTHAMPTON LEVEL 2 STRATEGIC FLOOD RISK ASSESSMENT. LIVING DOCUMENT (FEBRUARY 2010) . 23 WEST NORTHAMPTONSHIRE DEVELOPMENT CORPORATION WATER CYCLE STRATEGY. PHASE 1. OUTLINE STUDY (MAY 2009) ................................................................................................................. 23 WEST NORTHAMPTONSHIRE WATER CYCLE STUDY. PRE-SUBMISSION JOINT CORE STRATEGY. DETAILED WATER CYCLE STUDY FINAL REPORT (AUGUST 2011) ................................................................... 24 NORTHAMPTON CENTRAL AREA ACTION PLAN DRAINAGE ASSESSMENT (AUGUST 2012).................... 24 SURFACE WATER MANAGEMENT PLAN ....................................................................................... 25 5. LOCAL PLANS ......................................................................................................... 26 WEST NORTHAMPTONSHIRE JOINT CORE STRATEGY (LOCAL PLAN PART 1) ....................................... 26 OBJECTIVE 1 - CLIMATE CHANGE ................................................................................................ 26 POLICY BN1 - GREEN INFRASTRUCTURE CONNECTIONS ..................................................... 27 POLICY BN7A - WATER SUPPLY, QUALITY AND WASTEWATER INFRASTRUCTURE .............. 27 POLICY BN7 - FLOOD RISK .................................................................................................... 27 NEIGHBOURHOOD PLANNING .................................................................................................... 29 6. FLOOD HISTORY ..................................................................................................... 30 MAIN RIVERS .......................................................................................................................... 32 RIVER NENE AND TRIBUTARIES ................................................................................................... 32 RIVER GREAT OUSE AND TRIBUTARIES ......................................................................................... 33 RIVER CHERWELL AND TRIBUTARIES ............................................................................................ 33 RIVER LEAM ............................................................................................................................ 33 RIVER AVON ........................................................................................................................... 33 FLOOD DEFENCE INFRASTRUCTURE ............................................................................................. 34 CANALS .................................................................................................................................. 34 LOCAL SOURCES OF FLOOD RISK ................................................................................................. 34 ORDINARY WATERCOURSES....................................................................................................... 34 SURFACE WATER FLOOD RISK .................................................................................................... 34 WATER AND SEWERAGE SYSTEMS .............................................................................................. 34 GROUNDWATER FLOODING ....................................................................................................... 35 RESERVOIR RISK ...................................................................................................................... 36 7. PREDICTED FLOOD RISK .......................................................................................... 39 SURFACE WATER FLOODING ...................................................................................................... 39 GENERAL DRAINAGE ISSUES....................................................................................................... 40 FLUVIAL FLOODING .................................................................................................................. 40 RESIDUAL FLOOD RISK .............................................................................................................. 41 GROUNDWATER FLOODING ....................................................................................................... 42 8. SITE-SPECIFIC INFORMATION.................................................................................. 44 TOWCESTER RACECOURSE, TOWCESTER ...................................................................................... 58 SITE DESCRIPTION .................................................................................................................... 58 EXISTING WATERCOURSES AND BODIES OF WATER ....................................................................... 59 GEOLOGY AND HYDROLOGY ...................................................................................................... 59 FLUVIAL FLOOD RISK ................................................................................................................ 59 COMPARISON OF GROUND LEVELS ............................................................................................