River Avon Tidal Flood Risk Management Strategy
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River Avon Tidal Flood Risk Management Strategy Strategy Technical Report November 2017 TABLE OF CONTENTS 1. EXECUTIVE SUMMARY ............................................................. 3 1.1 Introduction .................................................................................. 3 1.2 Strategy Objectives ...................................................................... 3 1.3 Strategic Case ............................................................................. 3 1.4 Economic Case ............................................................................ 5 1.5 Commercial Case ........................................................................ 6 1.6 Financial Case ............................................................................. 7 1.7 Management Case ...................................................................... 8 2. THE STRATEGIC CASE ........................................................... 11 2.1 Introduction ................................................................................ 11 2.1.1 Background ................................................................................ 11 2.1.2 Flood risk ................................................................................... 12 2.2 Business Strategies / Planning Frameworks .............................. 16 2.2.1 Flood and Coastal Risk Management ........................................ 16 2.2.2 Planning Policy .......................................................................... 16 2.3 Environment and other considerations ...................................... 16 2.3.1 Environmental studies ............................................................... 16 2.3.2 Environmental designations ....................................................... 17 2.3.3 Cultural heritage ........................................................................ 17 2.3.4 Others sources of flooding ......................................................... 17 2.4 Investment objectives ................................................................ 17 2.5 Current arrangements ................................................................ 18 2.5.1 Flood defences / infrastructure .................................................. 18 2.5.2 Management authorities ............................................................ 20 2.6 Main benefits ............................................................................. 21 2.7 Main risks................................................................................... 21 2.8 Constraints ................................................................................. 23 2.9 Dependencies ............................................................................ 23 2.9.1 Existing assets ........................................................................... 23 2.9.2 Partnership funding .................................................................... 23 3. THE ECONOMIC CASE ............................................................ 25 3.1 Introduction ................................................................................ 25 3.1.1 Time epochs .............................................................................. 25 3.1.2 Stages of the appraisal .............................................................. 25 3.2 Critical success factors .............................................................. 26 3.3 Long list options ......................................................................... 26 3.3.1 Long list measures ..................................................................... 26 3.3.2 Long list options ......................................................................... 27 3.3.3 Long to short list appraisal ......................................................... 27 3.4 Measures comprising the short list options ................................ 29 3.4.1 Do Minimum ............................................................................... 29 3.4.2 Property level protection and temporary / demountable defences .................................................................................... 30 3.4.3 Low defences ............................................................................. 31 3.4.4 High defences ............................................................................ 32 3.4.5 Narrow Tidal barrier ................................................................... 33 3.5 Economic appraisal ................................................................... 35 3.5.1 Damages and Benefits .............................................................. 35 3.5.2 Costs ......................................................................................... 35 3.5.3 Present values ........................................................................... 36 3.5.4 Option ranking and economic appraisal ..................................... 37 3.6 Non-financial benefits appraisal ................................................. 40 3.6.1 Methodology .............................................................................. 40 3.6.2 Objectives – Environment .......................................................... 41 3.6.3 Objectives – Development opportunities.................................... 41 3.6.4 Summary ................................................................................... 42 3.7 Selecting the preferred option .................................................... 43 3.8 Sensitivity testing ....................................................................... 45 STRATEGY TECHNICAL REPORT 1 3.8.1 Barrier costs ............................................................................... 45 3.8.2 Raised defence costs ................................................................ 45 3.8.3 Do Minimum ............................................................................... 46 3.9 The preferred option .................................................................. 47 3.9.1 Defence phasing ........................................................................ 47 3.9.2 Standard of protection ............................................................... 47 3.9.3 Adaptive Capacity ...................................................................... 49 3.9.4 Outline design ............................................................................ 50 3.9.5 Economic assessment ............................................................... 52 3.9.6 New Cut Greenway .................................................................... 53 3.9.7 Residual risk .............................................................................. 54 3.9.8 Fluvial flood risk ......................................................................... 56 3.9.9 Environmental compliance ......................................................... 56 4. THE COMMERCIAL CASE ........................................................ 58 4.1 Introduction and procurement strategy ...................................... 58 4.2 Key contractual terms and risk allocation .................................. 58 4.3 Procurement route and timescales ............................................ 59 4.4 Efficiencies and commercial issues ........................................... 59 5. THE FINANCIAL CASE ............................................................. 60 5.1 Financial summary ..................................................................... 60 5.2 Partnership funding scores ........................................................ 60 5.2.1 Scheme breakdown ................................................................... 60 5.2.2 Baseline ..................................................................................... 61 5.2.3 Scores........................................................................................ 61 5.2.4 Recommendations for funding ................................................... 62 5.3 Impact on revenue and balance sheet ....................................... 63 5.4 Overall affordability .................................................................... 63 5.5 Other sources of funding............................................................ 64 6. THE MANAGEMENT CASE ...................................................... 66 6.1 Project management .................................................................. 66 6.2 Communications with stakeholder engagement ........................ 66 6.3 Change management ................................................................ 66 6.4 Benefits realisation .................................................................... 66 6.5 Risk management ...................................................................... 67 6.5.1 Safety plan ................................................................................. 67 6.6 Contract management ............................................................... 67 6.7 Assurance .................................................................................. 67 6.8 Post project evaluation .............................................................. 67 6.9 Contingency plans ..................................................................... 67 6.10 Next steps .................................................................................. 67 APPENDICES ................................................................................................ 69 Appendix A – Key documents ........................................................................ 69 Appendix