Bristol City Council Strategic Flood Risk Assessment Level 1 SFRA - Final Report March 2009 Halcrow Group Limited Bristol City Council Strategic Flood Risk Assessment Level 1 SFRA - Final Report March 2009 Halcrow Group Limited Halcrow Group Limited Ash House, Falcon Road, Exeter, EX2 7LB Tel +44 (0)1392 444252 Fax +44 (0)1392 444301 www.halcrow.com © Halcrow Group Limited 2009 Bristol City Council Strategic Flood Risk Assessment Level 1 SFRA - Final Report Contents Amendment Record This report has been issued and amended as follows: Issue Revision Description Date Signed 0.1 Draft Report May 2008 JMD 1.0 Final Report July 2008 JMD 2.0 1 Final Report March 2009 JMD (Minor Changes) Halcrow Group Limited Ash House, Falcon Road, Exeter EX” 7LB Tel +44 (0)1392 444252 Fax +44 (0)1392 444301 www.halcrow.com Bristol City Council Strategic Flood Risk Assessment Table of Contents 1 Introduction.................................................................................................... 1 2 The Bristol City SFRA Area .......................................................................... 3 2.1 Overview ..................................................................................................................... 3 2.2 Bristol City ................................................................................................................... 3 2.3 Rivers in Bristol City .................................................................................................... 4 2.4 Flood Risks ................................................................................................................. 5 2.5 Geology....................................................................................................................... 6 3 SFRA Approach & Methodology .................................................................. 8 3.1 Overview ..................................................................................................................... 8 3.2 Purpose of this SFRA.................................................................................................. 8 3.3 Outcomes of the SFRA Process ................................................................................. 9 3.4 The Sequential Test .................................................................................................... 9 3.5 The Exception Test ................................................................................................... 11 3.6 Level 1 SFRA methodology ...................................................................................... 11 3.7 The need for Level 2 SFRA....................................................................................... 12 3.8 SFRA User Guide ..................................................................................................... 13 4 Planning policy framework......................................................................... 15 4.1 Overview ................................................................................................................... 15 4.2 Planning Policy Framework....................................................................................... 15 4.3 National Policy .......................................................................................................... 15 4.4 Regional Planning Policy .......................................................................................... 17 4.5 Local planning policy................................................................................................. 19 4.6 Summary................................................................................................................... 20 5 Data sources................................................................................................ 21 5.1 Overview ................................................................................................................... 21 5.2 Consultation process................................................................................................. 21 5.3 Environment agency Flood Zone maps .................................................................... 22 5.4 Detailed hydraulic modelling ..................................................................................... 22 5.5 Localised flooding ..................................................................................................... 22 6 Assessment of potential causes of flooding............................................. 23 6.1 Overview ................................................................................................................... 23 6.2 Sources of flooding ................................................................................................... 23 6.3 Probability of flooding................................................................................................ 24 6.4 SFRA flood maps ...................................................................................................... 25 6.5 Tidal flooding............................................................................................................. 25 6.6 River flooding ............................................................................................................ 26 6.7 Groundwater flooding................................................................................................ 28 6.8 Surface water flooding - land drainage ..................................................................... 32 6.9 Sewer flooding .......................................................................................................... 32 6.10 Reservoirs ................................................................................................................. 34 6.11 Other artificial water retaining structures................................................................... 36 6.12 PPS25 Flood zones .................................................................................................. 37 6.13 Existing services/infrastructure within Flood Zones .................................................. 39 7 Assessment of flood risk management practices .................................... 42 7.1 Overview ................................................................................................................... 42 Bristol City Council Strategic Flood Risk Assessment 7.2 Flood risk management responsibilities .................................................................... 42 7.3 Existing flood defences ............................................................................................. 42 7.4 Groundwater Flood Risk Assessment....................................................................... 45 7.5 Flood warning areas.................................................................................................. 47 8 Assessment of the capacity for the use of SuDS ..................................... 50 8.1 Overview ................................................................................................................... 50 8.2 Types of SuDS systems............................................................................................ 50 8.3 SuDS at the planning stage ...................................................................................... 51 8.4 Application of SuDS within Bristol City...................................................................... 51 8.5 Constraints on discharges to ground ........................................................................ 52 9 Flood risk & climate change....................................................................... 54 9.1 Overview ................................................................................................................... 54 9.2 Flood risk & climate change ...................................................................................... 54 9.3 Integrated urban drainage......................................................................................... 55 9.4 Potential increase in flood risk caused by future development ................................. 55 9.5 Potential effect of flood defence failure (residual risk) .............................................. 56 9.6 Extent & costs required to raise flood defence standard........................................... 57 9.7 Sustainability of land use in medium and high risk flood areas................................. 59 10 Strategic Land-Use Planning...................................................................... 60 10.1 Overview ................................................................................................................... 60 10.2 Flood risk management policy .................................................................................. 60 10.3 Strategic flood risk management studies .................................................................. 60 10.4 Growth areas for development.................................................................................. 62 10.5 Planning recommendations....................................................................................... 63 10.6 Planning response .................................................................................................... 65 10.7 Development within areas affected by surface water and sewer flooding................. 66 10.8 Recommendations for reducing existing flood risks.................................................. 66 10.9 Key messages for development