East Cambridgeshire District Council Strategic Flood Risk Assessment
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East Cambridgeshire District Council Strategic Flood Risk Assessment Level 1 SFRA February 2011 Prepared for East Cambridgeshire District Council Level 1 Strategic Flood Risk Assessment Revision Schedule Level 1 Strategic Flood Risk Assessment Rev Date Details Prepared by Reviewed by Approved by 01 May 2010 Draft Level 1 for Helen Judd Elizabeth Gent Jon Robinson comments Assistant Hydrologist Principal Consultant Associate Director Gemma Hoad Assistant Hydrologist 02 September Level 1 Elizabeth Gent Jon Robinson Jon Robinson 2010 Principal Consultant Technical Director Technical Director 03 February Level 1 - FINAL Elizabeth Gent Carl Pelling Jon Robinson 2011 Principal Consultant Principal Consultant Technical Director Gemma Hoad Assistant Water Scientist Scott Wilson Scott House Alençon Link Basingstoke 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 do not provide legal or tax advice or opinion. © Scott Wilson Ltd 2011 www.scottwilson.com East Cambridgeshire District Council Level 1 Strategic Flood Risk Assessment Acronyms and Abbreviations Abbreviation Description AONB Area of Outstanding Natural Beauty BAR Broad Areas for Regeneration BGS British Geological Society CFMP Catchment Flood Management Plan CLG Communities and Local Government Defra Department for Environment, Food and Rural Affairs DPD Development Plan Document DTM Digital Terrain Model FRA Flood Risk Assessment GIS Geographical Information System 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 PCPS 2004 Planning and Compulsory Purchase Act 2004 PPS Planning Policy Statement RBMP River Basin Management Plan RFRA Regional Flood Risk Appraisal RPG Regional Planning Guidance RSS Regional Spatial Strategy (East of England Plan) SA Sustainability Appraisal SFRA Strategic Flood Risk Assessment SPA Special Protection Area SPD Supplementary Planning Document SPZ Source Protection Zone SUDS Sustainable Drainage Systems WCS Water Cycle Study WFD Water Framework Directive Level 1 Strategic Flood Risk Assessment February 2011 East Cambridgeshire District Council Level 1 Strategic Flood Risk Assessment Glossary Term Definition Event that on average will occur once every 100 years. Also expressed as an event, 1 in 100 year event which has a 1% probability of occurring in any one year. Flood defence that is designed for an event, which has an annual probability of 1%. 1 in 100 year design In events more severe than this the defence would be expected to fail or to allow standard flooding. Layers of rock sufficiently porous to hold water and permeable enough to allow water Aquifer to flow through them in quantities that are suitable for water supply. The Environment Agency has defined 'primary' (previously major) and 'secondary' (previously minor) aquifers. Formations that permit water to move through them, but at much lower rates than Aquitard through the adjoining aquifers. Formations that may be sufficiently porous to hold water, but do not allow water to Aquicludes move through them. A high-level planning strategy through which the Environment Agency works with Catchment Flood their key decision makers within a river catchment to identify and agree policies to Management Plan secure the long-term sustainable management of flood risk. Culvert A channel or pipe that carries water below the level of the ground. 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. Freeboard Height of flood defence crest level (or building level) above designed water level Water that is in the ground, this is usually referring to water in the saturated zone Groundwater below the water table. Inundation Flooding The core of the updated planning system (introduced by the Planning and Compulsory Purchase Act 2004). The LDF comprises the Local Development Local Development Documents, including the development plan documents that expand on policies and Framework (LDF) provide greater detail. The development plan includes a core strategy, site allocations and a proposals map. An element of development design which may be used to manage flood risk or avoid Mitigation measure an increase in flood risk elsewhere. Risk The probability or likelihood of an event occurring. Sewer flooding Flooding caused by a blockage or overflowing in a sewer or urban drainage system. Flooding caused when intense rainfall exceeds the capacity of the drainage systems Surface Water flooding or when, during prolonged periods of wet weather, the soil is so saturated such that it cannot accept any more water. Sustainable drainage Methods of management practices and control structures that are designed to drain system surface water in a more sustainable manner than some conventional techniques. Level 1 Strategic Flood Risk Assessment February 2011 East Cambridgeshire District Council Level 1 Strategic Flood Risk Assessment Table of Contents Acronyms and Abbreviations .................................................................... 3 Glossary ....................................................................................................... 4 1 Non-Technical Summary ................................................................. 8 1.1 SFRA Background ............................................................................................................ 8 1.2 SFRA Planning Objectives ............................................................................................... 8 1.3 SFRA Report Layout ........................................................................................................ 8 1.4 East Cambridgeshire District Council Considerations ...................................................... 8 1.5 Way Forward .................................................................................................................. 10 1.6 A Living Document ......................................................................................................... 10 2 Introduction .................................................................................... 11 2.1 Overview ........................................................................................................................ 11 2.2 Growth in East Cambridgeshire ..................................................................................... 11 2.3 The Aim of East Cambridgeshire DC SFRA ................................................................... 12 2.4 Level 1 SFRA Objectives ............................................................................................... 12 2.5 SFRA Structure .............................................................................................................. 12 3 East Cambridgeshire DC SFRA Study Area ................................. 13 3.1 East Cambridgeshire SFRA Boundary ........................................................................... 13 3.2 East Cambridgeshire Study Area Characteristics .......................................................... 13 3.3 History of Flooding in East Cambridgeshire ................................................................... 13 3.4 Sources of Flooding ....................................................................................................... 14 4 Policy Context ................................................................................ 23 4.1 Role and Responsibilities ............................................................................................... 23 4.2 Flood Risk Policy ............................................................................................................ 25 4.3 Cambridgeshire Flood & Water Management Studies ................................................... 27 4.4 Studies Progress ............................................................................................................ 28 4.5 Regional Policies ............................................................................................................ 29 4.6 Local Policies ................................................................................................................. 29 5 Data Collection and Review ........................................................... 31 5.1 Project Approach ............................................................................................................ 31 5.2 Data Review ................................................................................................................... 32 6 Level 1 Assessment ......................................................................