Swindon Borough Council Strategic Flood Risk Assessment Level I Swindon Borough Council May 2019 Level 1 Strategic Flood Risk Assessment Update Swindon Borough Council Quality information Prepared by Checked by Approved by Adam Lewis Matt Tandy Fida Choudhury Graduate Engineer Principal Engineer Project Director Revision History Revision Revision date Details Authorised Name Position 1 04/01/2019 Draft FC Fida Choudhury Project Director 2 23/05/2019 Post consultation FC Fida Choudhury Project Director Distribution List # Hard Copies PDF Required Association / Company Name - 1 Swindon Borough Council, Environment Agency, Thames Water 1 Swindon Borough Council, Environment Agency, Thames Water Prepared for: Swindon Borough Council AECOM Level 1 Strategic Flood Risk Assessment Update Swindon Borough Council Prepared for: Swindon Borough Council Civic Offices, Clarence House, Euclid Street, Swindon, Wiltshire SN1 2JH Prepared by: Adam Lewis Graduate Engineer AECOM Limited AECOM House 63-77 Victoria Street St Albans Hertfordshire AL1 3ER UK T: +44(0)1727 535000 aecom.com © 2019 AECOM Limited. 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Prepared for: Swindon Borough Council AECOM Level 1 Strategic Flood Risk Assessment Update Swindon Borough Council Contents 1 Introduction and Background ...................................................................................................................... 1 1.1 Terms of Reference .......................................................................................................................... 1 1.2 Project Background .......................................................................................................................... 1 1.3 Approach to Flood Risk Management............................................................................................... 1 1.4 Partner Organisations ....................................................................................................................... 2 1.5 Level 1 SFRA Approach .................................................................................................................... 4 2 Legislative and Planning Policy Context ..................................................................................................... 5 2.1 Introduction ....................................................................................................................................... 5 2.2 Flood and Water Management Act ................................................................................................... 5 2.3 Flood Risk Regulations ..................................................................................................................... 6 2.4 Thames Catchment Flood Management Plan .................................................................................. 7 2.5 National Planning Policy Framework ................................................................................................ 8 2.6 Local Planning Policy........................................................................................................................ 8 2.7 Water Cycle Strategy ........................................................................................................................ 9 2.8 National Receptor Dataset .............................................................................................................. 10 2.9 Summary ........................................................................................................................................ 10 3 Assessing Flood Risk ................................................................................................................................ 12 3.1 Introduction ..................................................................................................................................... 12 3.2 Study Area ...................................................................................................................................... 12 3.3 Flooding from Rivers....................................................................................................................... 13 3.4 Flooding from Surface Water .......................................................................................................... 16 3.5 Flooding from Groundwater ............................................................................................................ 17 3.6 Flooding from Sewers ..................................................................................................................... 18 3.7 Reservoirs, Canals and Other Artificial Sources ............................................................................. 18 3.8 Historic Flooding ............................................................................................................................. 19 3.9 Climate Change .............................................................................................................................. 20 4 Avoiding Flood Risk – Applying the Sequential Test .................................................................................. 22 4.1 Sequential Approach....................................................................................................................... 22 4.2 Applying the Sequential Test – Plan-Making ................................................................................... 22 4.3 Applying the Sequential Test – Individual Applications ................................................................... 26 4.4 Exception Test ................................................................................................................................ 27 5 Managing and Mitigating Flood Risk ......................................................................................................... 28 5.1 Overview ......................................................................................................................................... 28 5.2 Development Layout and Sequential Approach .............................................................................. 28 5.3 Riverside Development (Main Rivers and Ordinary Watercourses) ................................................ 28 5.4 Floodplain Compensation Storage ................................................................................................. 29 5.5 Finished Floor Levels...................................................................................................................... 30 5.6 Flood Resistance ‘Water Exclusion Strategy’ ................................................................................. 30 5.7 Flood Resilience ‘Water Entry Strategy’ ......................................................................................... 31 5.8 Structures ....................................................................................................................................... 32 5.9 Safe Access and Egress ................................................................................................................. 32 5.10 Safe Refuge .................................................................................................................................... 33 5.11 Car Parks ........................................................................................................................................ 33 5.12 Flood Routing ................................................................................................................................. 33 5.13 Flood Warning and Evacuation Plans ............................................................................................. 34 6 Guidance for the Application of Sustainable Drainage Systems (SuDS) .................................................. 35 6.1 What are SuDS? ............................................................................................................................. 35 6.2 Management Train .......................................................................................................................... 35 6.3 SuDS Costs .................................................................................................................................... 36 6.4 Infiltration SuDS Specific to Swindon ............................................................................................. 39 Prepared for: Swindon Borough Council AECOM Level 1 Strategic Flood Risk Assessment Update Swindon Borough Council 6.5 What is the role of the SBC as LLFA? ............................................................................................ 40 7 Guidance for preparing site-specific FRAs ............................................................................................... 43 7.1 What is a Flood Risk Assessment? ................................................................................................ 43 7.2 When is a Flood Risk Assessment required? 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