North Kesteven Strategic Flood Risk Assessment 2008 Revision Report North Kesteven District Council November 2009 AECOM North Kesteven Strategic Flood Risk Assessment Table of Contents Executive Summary ..................................................................................................................... i 1 Introduction ..................................................................................................................... 1 2 Development Planning ................................................................................................... 3 East Midlands Regional Spatial Strategy .......................................................................... 3 North Kesteven Adopted Local Plan ................................................................................. 3 3 Level 1 SFRA - Introduction ......................................................................................... 5 Planning Policy Statement 25 ........................................................................................... 5 Sequential Test ................................................................................................................. 5 Flood Zones ...................................................................................................................... 5 Functional Floodplains and Washlands ............................................................................ 6 4 Sources of Flooding in North Kesteven ....................................................................... 7 Introduction to the North Kesteven District ....................................................................... 7 Major Sources of Flooding ................................................................................................ 7 Tidal Flooding .................................................................................................................... 7 Fluvial Flooding ................................................................................................................. 7 Internal Drainage Board Arterial Drains ............................................................................ 9 Minor Sources of Flooding ................................................................................................ 9 Critical Ordinary Watercourses ....................................................................................... 10 Groundwater Flooding ..................................................................................................... 10 Surface Water Flooding .................................................................................................. 11 Areas Susceptible to Surface Water Flooding ................................................................ 11 Sewer Flooding ............................................................................................................... 12 River Witham Catchment Flood Management Plan ........................................................ 14 5 Flood Risk Management ............................................................................................... 17 Inappropriate Development in the Floodplain ................................................................. 17 Flood Storage Areas ....................................................................................................... 17 Raised Defences ............................................................................................................. 19 Waddington Low Fields ................................................................................................... 21 Operational and Emergency Planning ............................................................................ 22 Flood warning .................................................................................................................. 23 6 Climate Change ............................................................................................................. 25 7 Local Plan Sustainability Appraisal ............................................................................ 27 8 Sequential Test .............................................................................................................. 29 Development Planning Sequential Test .......................................................................... 29 Development Control Sequential Test ............................................................................ 31 9 Exception Test ............................................................................................................... 33 Application of the Exception Test .................................................................................... 33 10 Level 2 SFRA - Introduction ......................................................................................... 35 Planning Policy Statement 25 ......................................................................................... 35 11 Actual Flood Risk .......................................................................................................... 36 Introduction...................................................................................................................... 36 Causes of Flooding ......................................................................................................... 36 Historical Flooding ........................................................................................................... 36 Man Made Flood Risk Sources ....................................................................................... 40 Residual Flood Risk ........................................................................................................ 45 AECOM North Kesteven Strategic Flood Risk Assessment 12 Flood Hazard ................................................................................................................. 47 Flood Hazard Zones ........................................................................................................ 47 Impact of Climate Change ............................................................................................... 48 13 Study Areas ................................................................................................................... 51 Flood Risk Assessment for Study Areas ......................................................................... 52 Flood Hazard ................................................................................................................... 52 14 Sleaford Town Study Area ........................................................................................... 53 General Description of the Study Area ........................................................................... 53 Hydrology of the Study Area ........................................................................................... 54 Flood Risk within the Study Area .................................................................................... 57 Actual Flood Risk ............................................................................................................ 59 Impact of Climate Change ............................................................................................... 59 Flood Hazard ................................................................................................................... 59 Flood Risk to Downstream Areas ................................................................................... 59 Conclusion....................................................................................................................... 60 15 Lower Witham Fens Study Area .................................................................................. 61 General Description of the Study Area ........................................................................... 61 Hydrology of the Study Area ........................................................................................... 64 Flood Risk within the Study Area .................................................................................... 67 Actual Flood Risk ............................................................................................................ 68 Impact of Climate Change ............................................................................................... 69 Flood Hazard ................................................................................................................... 69 Flood Hazard Maps ......................................................................................................... 69 Flood Risk to Downstream Areas ................................................................................... 69 Conclusion....................................................................................................................... 70 16 Sequential Approach .................................................................................................... 71 Sequential Test ............................................................................................................... 71 Exception Test ................................................................................................................ 71 17 Guidance For Planners and Developers ..................................................................... 73 Development Sites .......................................................................................................... 73 Flood Avoidance