36 Highbridge Street, Waltham Abbey
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36 HIGHBRIDGE STREET, WALTHAM ABBEY Flood Risk Assessment and Surface Water Drainage Statement Alcomax (Investments) Ltd SLR Ref: 408-07833-00001 Version No: 5 October 2018 36 Highbridge Street, Waltham Abbey : FRA and SWDS Filename: 181017_408-07833-00001_36HSWA_FRA_v5 SLR Ref No: 408-07833-00001 October 2018 BASIS OF REPORT This document has been prepared by SLR Consulting Limited with reasonable skill, care and diligence, and taking account of the manpower, timescales and resources devoted to it by agreement with Alcomax (Investments) Ltd. (the Client) as part or all of the services it has been appointed by the Client to carry out. It is subject to the terms and conditions of that appointment. SLR shall not be liable for the use of or reliance on any information, advice, recommendations and opinions in this document for any purpose by any person other than the Client. Reliance may be granted to a third party only in the event that SLR and the third party have executed a reliance agreement or collateral warranty. Information reported herein may be based on the interpretation of public domain data collected by SLR, and/or information supplied by the Client and/or its other advisors and associates. These data have been accepted in good faith as being accurate and valid. The copyright and intellectual property in all drawings, reports, specifications, bills of quantities, calculations and other information set out in this report remain vested in SLR unless the terms of appointment state otherwise. This document may contain information of a specialised and/or highly technical nature and the Client is advised to seek clarification on any elements which may be unclear to it. Information, advice, recommendations and opinions in this document should only be relied upon in the context of the whole document and any documents referenced explicitly herein and should then only be used within the context of the appointment. 36 Highbridge Street, Waltham Abbey : FRA and SWDS Filename: 181017_408-07833-00001_36HSWA_FRA_v5 SLR Ref No: 408-07833-00001 October 2018 CONTENTS INTRODUCTION.................................................................................................................... 1 1.1 Background ..................................................................................................................................... 1 1.2 Site Location .................................................................................................................................... 1 SITE DETAILS ........................................................................................................................ 2 2.1 Existing Site Features ...................................................................................................................... 2 2.2 Topography ..................................................................................................................................... 3 2.3 Hydrological Features ..................................................................................................................... 4 2.4 Sewerage and Drainage .................................................................................................................. 5 2.5 Geological and Hydrogeological ..................................................................................................... 5 2.5.1 Geology ............................................................................................................................................................................. 5 2.5.2 Hydrogeology .................................................................................................................................................................... 6 DEVELOPMENT PROPOSALS ................................................................................................. 7 3.1 Development Description ............................................................................................................... 7 3.2 Flood Zone Classification ................................................................................................................ 7 3.2.1 Environment Agency Classification.................................................................................................................................. 7 3.2.2 Strategic Flood Risk Assessment Classification ............................................................................................................... 8 3.3 Flood Risk Vulnerability .................................................................................................................. 8 3.4 Anticipated Lifetime of Development ............................................................................................ 8 3.5 Flood Zone Compatibility................................................................................................................ 9 3.6 Sequential Test ................................................................................................................................ 9 3.7 Exception Test ............................................................................................................................... 10 PLANNING POLICY AND GUIDANCE ................................................................................... 11 4.1.1 National Planning Policy ................................................................................................................................................. 11 4.1.2 Local Planning Policy ...................................................................................................................................................... 11 4.1.3 Other Local Planning Guidance ...................................................................................................................................... 12 4.1.4 National Planning Guidance on Climate Change .......................................................................................................... 12 POTENTIAL SOURCES OF FLOODING .................................................................................. 14 5.1 Screening Study ............................................................................................................................. 14 5.1.1 Flooding from Rivers and Sea ........................................................................................................................................ 14 5.1.2 Flooding from Surface Water and Overland Flow ........................................................................................................ 14 5.1.3 Flooding from Groundwater .......................................................................................................................................... 16 5.1.4 Flooding from Sewers and Water Mains ....................................................................................................................... 17 . 36 Highbridge Street, Waltham Abbey : FRA and SWDS Filename: 181017_408-07833-00001_36HSWA_FRA_v5 SLR Ref No: 408-07833-00001 October 2018 5.1.5 Flooding from Canals, Reservoirs and Artificial Sources .............................................................................................. 17 5.1.6 Flooding from Infrastructure Failure ............................................................................................................................. 18 5.1.7 Summary ......................................................................................................................................................................... 18 TECHNICAL ASSESSMENT OF FLUVIAL FLOOD RISK ............................................................ 19 6.1 Historic Flooding ........................................................................................................................... 19 6.2 Defended Flood Extents ............................................................................................................... 19 6.3 Defended Flood Levels & Flood Flows ......................................................................................... 20 6.4 Impact of Climate Change ............................................................................................................ 20 6.5 Residual Risk .................................................................................................................................. 21 6.5.1 Residual Hazard Assessment .......................................................................................................................................... 21 PROPOSED FLOOD MANAGEMENT MEASURES .................................................................. 23 7.1 Finished Floor Levels ..................................................................................................................... 23 7.2 Level Differentials ......................................................................................................................... 23 7.3 Flood Storage Compensation ....................................................................................................... 23 7.4 Flood Conveyance Compensation ................................................................................................ 23 7.5 Flood Warning & Evacuation Plan ................................................................................................ 23 7.6 Safe Refuge ...................................................................................................................................