Haringey Council Strategic Flood Risk Assessment
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Haringey Council Strategic Flood Risk Assessment DRAFT REPORT February 2015 Haringey Council Civic Centre High Road Wood Green LONDON N22 8LE Haringey Council - Strategic Flood Risk Assessment - February 2015 This page is intentionally blank. ii Haringey Council - Strategic Flood Risk Assessment - February 2015 JBA Office 35 Perrymount Road HAYWARDS HEATH West Sussex RH16 3BW JBA Project Manager Jack Southon BSc MSc FRGS MCIWEM C.WEM CSci CEnv Revision History Revision Ref / Amendments Issued to Date Issued Draft v1 Jane Mulcahey, London Borough of Haringey Chapters 1 & 2 Draft v2 Chapters 1,2,3, Jane Mulcahey, London Borough of Haringey 6& 7 Full Report with initial V3 Draft Jane Mulcahey, London Borough of Haringey comments V4 Final Full Report Jane Mulcahey, London Borough of Haringey Additional site and V5 revised (Feb new flood risk Gavin Ball, London Borough of Haringey 2015) Draft mapping Contract This Level 2 Strategic Flood Risk Assessment (SFRA) is commissioned by Haringey Council. This document has been prepared by JBA Consulting in response to the Level 2 SFRA commission awarded by Haringey Council, in August 2012. It was updated in 2015 to included additional development sites and updated flood risk information. Prepared by .................................................. Jack Southon Charted Senior Analyst | Team Leader Reviewed by ................................................. Alastair Dale Director Purpose This document has been prepared as a report for Haringey Council. JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by LB of Haringey for the purposes for which it was originally commissioned and prepared. iii Haringey Council - Strategic Flood Risk Assessment - February 2015 Copyright © Jeremy Benn Associates Limited 2015 Carbon Footprint A printed copy of the main text in this document will result in a carbon footprint of 462g if 100% post-consumer recycled paper is used and 588g if primary-source paper is used. These figures assume the report is printed in black and white on A4 paper and in duplex. JBA is aiming towards becoming a carbon neutral company and the carbon emissions from our activities are offset. iv Haringey Council - Strategic Flood Risk Assessment - February 2015 Executive Summary Context This SFRA updates and enhances the previously commissioned North London Level 1 SFRA and replaces the SFRA issued by the London Borough of Harringey in March 2013. The assessment looks exclusively at flood risk within the London Borough of Haringey. The mapping in this SFRA replaces the mapping contained in the Level 1 SFRA. The Preliminary Flood Risk Assessment (PFRA) commissioned for Haringey by the Greater London Authority (GLA) identifies the borough (along with the other 32 London Boroughs) as an area of significant flood risk, in accordance with the Flood Risk Regulations, 2009. The outcome of a high level Surface Water Management Plan (SWMP), also commissioned by the GLA identified nine Critical Drainage Areas (CDAs) across the borough. Flood Risk in Haringey Surface water runoff is the source of flood risk that potentially has the greatest effect in Haringey and is the flooding most likely to be experienced. There is also significant residual risk as a result of reservoir breach effecting large areas of the borough which is much less likely to be experienced, but the consequences would be significant. Climate change effects increase the severity and frequency of the flood risk. The extent and frequency of surface water flooding would be increased across the borough. The standard of protection from river flooding is also reduced by climate change effects in some parts of the borough adjacent to the River Lea. Planned Development in Haringey A total of 133 development sites have now been assessed as part of this SFRA (only 77 were assessed in the March 2013 version). The planned new development consists of approximately three and a half square kilometres of new infrastructure distributed across the borough covering nearly 12% of the total borough area. Impact of Development in Haringey Haringey is a densely developed area of London. The impact of development without accompanying mitigation measures is negative. However, with careful planning supported by effective local policy the planned development presents a significant opportunity to introduce measures that will contribute to betterment of the existing situation. Mitigation Options A range of mitigation options are outlined - chiefly focusing on surface water schemes including those highlighted in the recent high level Surface Water Management Plan as well as identifying other local solutions that can contribute to strategic benefits. v Haringey Council - Strategic Flood Risk Assessment - February 2015 This page is intentionally blank. vi Haringey Council - Strategic Flood Risk Assessment - February 2015 Contents Executive Summary .......................................................................................................... v Abbreviations and Glossary of Terms .................................................................................................................... xii i 1. Introduction .......................................................................................................... 1 1.1 About Haringey ...................................................................................................... 1 1.2 About this Report ................................................................................................... 1 1.3 SFRA Objectives ................................................................................................... 2 1.4 How to Find What You Need in the SFRA............................................................. 3 1.5 Approach ............................................................................................................... 6 1.6 Consultation ........................................................................................................... 10 2. Understanding Flood Risk in Haringey Council ............................................... 11 2.1 Historic Flooding .................................................................................................... 11 2.2 Topography, Geology, Soils and Hydrology .......................................................... 11 2.3 How Flood Risk is Assessed ................................................................................. 19 2.4 Understanding Flooding in Haringey Council ........................................................ 23 2.5 Possible Responses to Flooding ........................................................................... 28 2.6 Thames Catchment Flood Management Plan (CFMP) ......................................... 29 3. Policy Context ...................................................................................................... 31 3.1 National Planning Policy Framework (NPPF) ........................................................ 31 3.2 Applying the Sequential Test and Exception Test to individual planning applications ............................................................................................................ 35 3.3 Localism Act .......................................................................................................... 36 3.4 The London Plan ................................................................................................... 37 3.5 London Regional Flood Risk Appraisal (RFRA) .................................................... 37 3.6 River Basin Management Plan Thames River Basin District ................................ 37 3.7 Association of British Insurers (ABI): Guidelines on Planning and Insurance in Flood Risk Areas for Local Authorities in England. ........................................... 38 3.8 Climate Change and Adaptation and Mitigation .................................................... 38 4. Mapping and Risk Based Approach .................................................................. 41 4.1 Summary of Mapping for All Sources of Flood Risk .............................................. 41 4.2 Other Relevant Flood Risk Information ................................................................. 43 5. Overview of Future Development ...................................................................... 45 5.1 Introduction ............................................................................................................ 45 5.2 Part 1A - Extent and type of development ............................................................. 45 5.3 Part 1B - Review of Future Development .............................................................. 49 5.4 Part 1C - Programme of Future development ....................................................... 52 5.5 Part 2 - Defining the Baseline ................................................................................ 53 5.6 Part 3A - Development over the next 5 Years (up to 2020) .................................. 66 5.7 Part 3B - Longer Term Development ..................................................................... 68 5.8 Part 4 - Impacts of Climate Change on Runoff ...................................................... 70 6. Subterranean Development ................................................................................ 75 6.1 Introduction ............................................................................................................ 75 6.2 Basement Development and