East Northamptonshire Council Strategic Flood Risk Assessment - Stage 2 East Northamptonshire Council September 2006 Table of Contents Contents ................................................................................................................................. i List of Tables and Figures ................................................................................................... v Executive Summary ........................................................................................................... vii 1 Introduction .............................................................................................................. 1 2 Flood Risk ................................................................................................................. 3 Planning Policy Guidance Note 25 ............................................................................ 3 Indicative Floodplain Maps......................................................................................... 4 Flood Zone Maps ....................................................................................................... 5 Flood Maps.................................................................................................................5 3 Causes of Flooding.................................................................................................. 7 Overflowing of Watercourses ..................................................................................... 7 Breaching of Embankments ....................................................................................... 8 Mechanical, Structural or Operational Failure............................................................9 Localised Flooding ..................................................................................................... 9 Functional Floodplains and Washlands ................................................................... 11 4 Flooding in East Northamptonshire ..................................................................... 13 Classes of Flooding.................................................................................................. 13 Records of Flooding ................................................................................................. 14 Flood Alleviation Measures ...................................................................................... 16 Operational and Emergency Planning ..................................................................... 17 5 Strategic Assessment of Flood Risk.................................................................... 19 General Methodology............................................................................................... 19 Topographic Divisions.............................................................................................. 21 Anthropogenic Influences......................................................................................... 22 The River Nene Model ............................................................................................. 30 Flood Risk Mapping ................................................................................................. 31 6 Assessment of Flood Risk In Study Areas.......................................................... 35 7 Study Areas in East Northamptonshire ............................................................... 39 KINGS CLIFFE......................................................................................................... 41 OUNDLE EAST ........................................................................................................ 45 THRAPSTON SOUTH ............................................................................................. 49 RAUNDS SOUTH .................................................................................................... 53 RAUNDS NORTH EAST.......................................................................................... 57 RAUNDS WEST....................................................................................................... 63 IRTHLINGBOROUGH NORTH ................................................................................ 67 IRTHLINGBOROUGH WEST ..................................................................................71 IRTHLINGBOROUGH SOUTH WEST..................................................................... 75 HIGHAM FERRERS EAST ...................................................................................... 79 RUSHDEN SHIRLEY ROAD.................................................................................... 83 RUSHDEN WEST .................................................................................................... 83 Continued over …. Continued …. 8 Planning Policy And Flood Risk ........................................................................... 83 Milton Keynes & South Midlands Sub Regional Strategy ........................................ 83 Recommended Policy and Guidance Statements ................................................... 83 Sustainable Urban Drainage Systems ..................................................................... 83 9 Conclusions............................................................................................................ 83 10 Recommendations ................................................................................................. 83 References .......................................................................................................................... 83 FIGURES PHOTOGRAPHS APPENDICES APPENDIX A1 RECOMMENDED FLOOD RISK POLICY AND GUIDANCE STATEMENTS FOR INCLUSION IN THE LOCAL DEVELOPMENT FRAMEWORK APPENDIX A2 FLOOD RISK STANDING ADVICE MATRIX (and Explanatory Notes) Faber Maunsell East Northamptonshire Strategic Flood Risk Assessment – Stage 2 v List of Tables and Figures LIST OF TABLES Table 1.1 Study Areas in East Northamptonshire Table 2.1 PPG 25 Flood Risk Zones Table 3.1 Critical Ordinary Watercourses in East Northamptonshire Table 4.1 Local Flooding Problems in East Northamptonshire Table 4.2 Flood Storage Facilities in East Northamptonshire Table 5.1 Impounding Reservoirs in the Nene and Welland Catchments Table 5.2 Navigation Locks along the River Nene in East Northamptonshire Table 5.3 Flood Hazard Zone Widths Table 6.1 Indicative Standards for Fluvial Flood Defence Table 6.2 High Risk Category – Flood Risk Sub-Divisions Table 8.1 Future Housing Development in Northamptonshire LIST OF FIGURES Figure 1.1 General Location Plan Figure 1.2.1 Study Area Location Plan - Kings Cliffe & Oundle Figure 1.2.2 Study Area Location Plan - Thrapston & Raunds Figure 1.2.3 Study Area Location Plan - Rushden, Higham & Irthlingborough Figure 4.1 River Nene - Recorded Flood Levels, 1947 & 1998 Figure 5.1 Strategic Flood Risk Maps of East Northamptonshire (Five Sheets) Study Area Site Plans Figure 7.1 Kings Cliffe Figure 7.2 Oundle East Figure 7.3 Thrapston South Figure 7.4 Raunds South Figure 7.5 Raunds North East Figure 7.6 Raunds West Figure 7.7 Irthlingborough North Figure 7.8 Irthlingborough South West Figure 7.9 Higham Ferrers East Figure 7.10 Rushden Shirley Road Figure 7.11 Rushden West Figure 7.12 Irthlingborough West Faber Maunsell East Northamptonshire Strategic Flood Risk Assessment – Stage 2 vi - This page intentionally left blank - Faber Maunsell East Northamptonshire Strategic Flood Risk Assessment – Stage 2 vii Executive Summary The Department of Transport, Local Government and the Regions' Planning Policy Guidance Note 25 entitled "Development and Flood Risk" outlines how flood risk issues should be addressed in regional planning guidance and Local Authorities' development plans. Bullen Consultants Ltd, now part of Faber Maunsell, were commissioned by East Northamptonshire District Council in March 2004 to undertake a Strategic Flood Risk Assessment of East Northamptonshire based on a Brief issued by the District Council. The Brief, prepared by the District Council in partnership with the Environment Agency, divided the study into two phases. Phase 1 involved the collation and evaluation of data and information relating to the hydrological and hydraulic aspects of flooding in East Northamptonshire. Phase 2 of the study, based on the findings and conclusions of Phase 1, was to include the following main topics, including agreed work supplementary to the Brief: • Identifying and mapping the areas of flood risk over the whole of the District within the categories defined in Planning Policy Guidance Note 25 (PPG25). • Flood risk assessments of a number of study areas within the District. (Eleven specific study areas were originally defined and notified by the Council and a twelfth was added later.) • Assessment of the potential effect on flood risk in East Northamptonshire of large scale urban development in the Nene catchment resulting from the implementation of the sub regional development strategy proposals contained in the Milton Keynes & South Midlands (MKSM) Sub Regional Strategy Report. • Preparation of guidance notes for developers, recommending procedures to be followed by prospective developers for the assessment of flood risk and measures to be adopted to minimise that risk and mitigate the effects of increased runoff from the development on flood risk elsewhere. The purpose of the Study was to provide a reference and policy document to inform the East Northamptonshire Local Development Framework and to ensure that the District Council meets its obligations