Final Report Submitted to Submitted by Stevenage Borough Council AECOM 63-77 Victoria Road St Albans AL1 3ER United Kingdom Stevenage Borough Council Level 1 Strategic Flood Risk Assessment Update June 2016 AECOM Project No. 60486866 AECOM Level 1 Strategic Flood Risk Assessment Update Page i Prepared by: Luis Martin Checked by: Gordon Boote Graduate Engineer Senior engineer Approved by: Fida Choudhury Associate Director Rev No Comments Checked by Approved by Date 3 Final Report (minor revision in section 2.7) GB FC 23.06.16 2 Final Report GB FC 13.06.16 1 Draft Report for Client and Stakeholder Review GB FC 09.05.16 63-77 Victoria Rd, St Albans, AL1 3ER, United Kingdom Telephone: 01727535000 Website: http://www.aecom.com Job No 60486866 Final Report June 2016 Project Number: 60486866 June 2016 AECOM Level 1 Strategic Flood Risk Assessment Update Page ii Limitations AECOM Limited (“AECOM”) has prepared this Report for the sole use of Stevenage Borough Council (“Client”) in accordance with the Agreement under which our services were performed (Stevenage Borough Council SFRA Update Tender Submission of 15th January 2016). 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Project Number: 60486866 June 2016 AECOM Level 1 Strategic Flood Risk Assessment Update Page iii Contents Executive Summary ............................................................................................................................................................. 1 1 Introduction and Background ..................................................................................................................................... 2 1.1 Terms of Reference .............................................................................................................................................. 2 1.2 Project Background .............................................................................................................................................. 2 1.3 Approach to Flood Risk Management .................................................................................................................. 2 1.4 Partner Organisations ........................................................................................................................................... 3 1.5 Level 1 SFRA Approach ........................................................................................................................................ 5 1.5.1 Gathering data and analysing it for suitability .............................................................................................. 5 1.5.2 Producing strategic flood risk maps, GIS deliverables and a technical report ............................................ 5 1.5.3 Providing suitable guidance ......................................................................................................................... 5 2 Legislative and Planning Policy Context .................................................................................................................... 6 2.1 Introduction .......................................................................................................................................................... 6 2.2 Flood and Water Management Act ....................................................................................................................... 6 2.2.1 National Strategy for Flood and Coastal Erosion Risk Management ........................................................... 6 2.2.2 Local Flood Risk Management Strategy ...................................................................................................... 7 2.3 Flood Risk Regulations ......................................................................................................................................... 7 2.3.1 Preliminary Flood Risk Assessment ............................................................................................................. 8 2.4 Thames River and Great Ouse Basin District Flood Risk Management Plans ...................................................... 8 2.5 National Planning Policy Framework .................................................................................................................... 9 2.5.1 NPPF Guidance SuDS Policy (April 2015) .................................................................................................... 9 2.6 Local Planning Policy ............................................................................................................................................ 9 2.6.1 Local Flood Risk Management Strategy .................................................................................................... 10 2.7 Water Cycle Strategy.......................................................................................................................................... 10 2.8 National Receptor Dataset ................................................................................................................................. 11 2.9 Summary ............................................................................................................................................................. 11 3 Assessing Flood Risk ................................................................................................................................................. 12 3.1 Introduction ........................................................................................................................................................ 12 3.2 Study Area .......................................................................................................................................................... 12 3.2.1 Location ..................................................................................................................................................... 12 3.2.2 Hydrogeology ............................................................................................................................................. 12 3.3 Summary of Flood Sources ................................................................................................................................ 12 3.4 Flooding from Rivers ........................................................................................................................................... 13 3.4.1 Sources ...................................................................................................................................................... 13 3.4.2 Structures .................................................................................................................................................. 14 3.4.3 Historic Records of River Flooding ............................................................................................................ 14 3.4.4 NPPF Flood Zones ...................................................................................................................................... 14 3.4.5 Flood Risk Management Measures ............................................................................................................ 18 3.4.6 Flood Warning Areas .................................................................................................................................. 19 3.5 Flooding from Surface Water ............................................................................................................................