North London Strategic Flood Risk Assessment
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North London Strategic Flood Risk Assessment August 2008 Produced for North London Waste Plan Prepared by Ian Bakewell Knights House 2 Parade Sutton Coldfield West Midlands B72 1PH T 0121 355 8949 F 0121 355 8901 E [email protected] Strategic Flood Risk Assessment ii North London Final - August 2008 Document Control Sheet Report Title Strategic Flood Risk Assessment Revision 1 Status Final Control Date August 2008 Record of Issue Issue Status Authors Date Check Date Authorised Date Ian Bakewell Nov Nov Nov 01 Draft Sarah Luff Faruk Pekbeken Faruk Pekbeken 2007 2007 2007 Matthew Griffin Ian Bakewell Apr Apr Apr 02 Draft Faruk Pekbeken Faruk Pekbeken Sarah Luff 2008 2008 2008 Matthew Griffin August August August 03 Final Ian Bakewell Faruk Pekbeken Faruk Pekbeken Sarah Luff 2008 2008 2008 Distribution Organisation Contact Copies North London Waste Plan Archie Onslow 1 London Borough of Barnet Nick Lynch 1 London Borough of Camden Brian O’Donnell 1 London Borough of Enfield Tom Rumble 1 London Borough of Islington Sakiba Gurda 1 London Borough of Hackney Bob Dolata 1 London Borough of Haringey Jill Warren 1 London Borough of Waltham Forest Brian Whiteley 1 Environment Agency Vicky Boorman 1 Strategic Flood Risk Assessment iii North London Final - August 2008 Strategic Flood Risk Assessment iv North London Final - August 2008 Contents Document Control Sheet ...........................................................................................iii Contents ......................................................................................................................v Table of figures .........................................................................................................xv Tables........................................................................................................................xvi Glossary..................................................................................................................xviii Executive Summary ....................................................................................................1 1 Introduction ........................................................................................................4 1.1 Background..........................................................................................................4 1.2 Project Objectives ................................................................................................5 1.3 SFRA Scope ........................................................................................................6 1.4 Methodology ........................................................................................................6 1.5 Setting the Scene.................................................................................................7 1.5.1 London Borough of Barnet 8 1.5.2 London Borough of Camden 9 1.5.3 London Borough of Enfield 9 1.5.4 London Borough of Hackney 10 1.5.5 London Borough of Haringey 10 1.5.6 London Borough of Islington 11 1.5.7 London Borough of Waltham Forest 11 2 Planning Policy and Flood Risk ......................................................................14 Strategic Flood Risk Assessment v North London Final - August 2008 2.1 National Planning Policy and Guidance..............................................................14 2.1.1 Planning and Compulsory Purchase Act 2004 14 2.1.2 Planning Policy Statement 1 15 2.1.3 Planning Policy Statement: Planning and Climate Change: Supplement to PPS1 15 2.1.4 Planning Policy Statement 25 16 2.2 The Sequential Test and Exception Test............................................................16 2.2.1 The Sequential Test 16 2.2.2 The Exception Test 20 2.3 Planning Responsibilities ...................................................................................20 2.4 Other Planning Statements and Policies ............................................................22 2.5 The Thames Catchment Flood Management Plan (CFMP) ................................22 2.6 Making Space for Water.....................................................................................23 2.7 The Pitt Review – Final Report...........................................................................24 2.8 Flood Risk Management Key Stakeholders........................................................25 2.8.1 Environment Agency 25 2.8.2 Thames Water and Three Valleys Water 26 2.8.3 British Waterways 26 2.9 Flood Risk Responsibility ...................................................................................27 2.9.1 Main Rivers 27 2.9.2 Ordinary Watercourse 27 2.9.3 Riparian Owners 28 3 Review of Development Framework ...............................................................30 3.1 Regional Planning Policy – The London Plan.....................................................30 Strategic Flood Risk Assessment vi North London Final - August 2008 3.2 Lower Lee Valley Opportunity Area Planning Framework...................................33 3.3 Water Matters, Draft Water Strategy ..................................................................34 3.4 Local Planning Policy – The UDP and LDF Core Strategies...............................34 4 Data Collection and Validation........................................................................38 4.1 Mapping and Topographic Data .........................................................................38 4.2 Flood Defences..................................................................................................39 4.3 Thames Water Data ...........................................................................................39 4.4 Clean Water Supply Data...................................................................................39 4.5 River Lee and Brent Data...................................................................................39 4.5.1 Historic Flood Records 39 4.5.2 Flood Modelling Results 40 4.6 Regional Flood Risk Appraisal ...........................................................................40 4.7 Lower Lee Flood Risk Management Strategy.....................................................43 4.8 Other Drainage Studies......................................................................................43 4.8.1 The Drain London Project 43 4.8.2 Central London Forward 44 4.8.3 North London Strategic Alliance 44 4.9 Strategic Flood Risk Assessments .....................................................................45 4.9.1 East London SFRA 45 4.9.2 Lower Lee SFRA 45 4.9.3 Enfield SFRA 46 4.9.4 Islington SFRA 47 4.9.5 Olympic FRA 47 Strategic Flood Risk Assessment vii North London Final - August 2008 4.10 Community Risk Registers .................................................................................48 4.11 Groundwater Data..............................................................................................48 4.12 Flood Records....................................................................................................48 4.12.1 Individual Boroughs 48 4.12.2 Transport for London 48 4.12.3 London Underground 49 4.12.4 The London Fire Brigade 49 4.13 Public Reservoirs ...............................................................................................49 4.14 British Waterways ..............................................................................................49 4.15 Low Confidence Data.........................................................................................50 4.15.1 EA Asset Data 50 4.15.2 Barnet Flooding Records 50 4.16 Data Gaps..........................................................................................................50 4.16.1 Thames Water 50 4.16.2 London Underground Flood Records 51 5 Sources of Flooding.........................................................................................52 5.1 Introduction ........................................................................................................52 5.2 Key Watercourses..............................................................................................52 5.2.1 Lower River Lee (Lee) 54 5.2.2 River Lee Tributaries 55 5.2.3 River Brent and Tributaries Upstream of the Brent Reservoir 56 5.2.4 Subterranean and Culverted Rivers 57 5.3 Fluvial Flooding..................................................................................................57 Strategic Flood Risk Assessment viii North London Final - August 2008 5.3.1 Historic Fluvial Flood Events 58 5.3.1.1 March 1947 floods 58 5.3.1.2 December 2000 Floods 58 5.3.1.3 Silk Stream Floods 58 5.3.1.4 Other Localised Fluvial Flooding 58 5.3.1.5 Haringey Council Flood Management Strategy Report Review 59 5.3.2 Tidal Flooding 59 5.3.3 Flood Risk Modelling and Mapping 60 5.3.3.1 Flood Mapping Overview 60 5.3.3.2 Review of Modelling Techniques 60 5.3.3.3 River Lee Modelling and Mapping 61 5.3.3.4 River Brent Modelling and Mapping 61 5.3.4 Flood Zone 3b - Functional Floodplain 61 5.3.4.1 Lower Lee Valley Functional Floodplain 61 5.3.4.2 Upper Brent Valley Functional Floodplain 62 5.3.5 Flood Defences and Inline Structures 62 5.3.5.1 Silk Stream Flood Alleviation Scheme 66 5.3.5.2 Salmons Brook Flood Alleviation Scheme 66 5.3.6 Overtopping 66 5.3.7 Breach 67 5.4 Groundwater Flooding........................................................................................67 5.4.1 Geology 68 Strategic Flood Risk Assessment ix North London Final - August 2008 5.4.2 Groundwater Flooding 69 5.4.3 Borehole Data and Groundwater Contour Data 69 5.4.4 GARDIT