Draft River Hull Flood Risk Management Strategy May 2010
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Draft River Hull Flood Risk Management Strategy May 2010 River Hull Flood Risk Management Strategy Report River Hull Flood Risk Management Strategy Report Draft River Hull Flood Risk Management Strategy Strategy Report May 2010 Halcrow Group Limited has prepared this report in accordance with the instructions of their client, for their sole and specific use. Any other persons who use any information contained herein do so at their own risk. © Halcrow Group Limited 2010 . Document History JOB CODE: WBRHPS DOCUMENT REF: RHFRMS Strategy Report v6.doc Revision Purpose Description Originated Checked Reviewed Authorised Date 0 DRAFT JHG AJT TM MM 18/05/10 River Hull Flood Risk Management Strategy Report River Hull Flood Risk Management Strategy Report Contents Section Page Glossary of terms i At a glance vii 1. Introduction 1 1.1 The Environment Agency vision 1 1.2 Creating a better place – priorities and targets 2 1.3 Strategy policy links 2 1.4 Strategy aims and objectives 3 1.5 Benefits of a strategic approach 4 1.6 Strategy – development and review 5 2. Catchment overview 7 2.1 The River Hull catchment and definition of the study area 7 2.2 Environmental context 12 2.3 Definition of catchment areas 15 2.4 Links to other plans – opportunities and constraints 18 3. Flood risk 25 3.1 Definitions 25 3.2 Causes of flooding 25 3.3 Flood history 29 3.4 Flood management in the River Hull catchment 30 3.5 Assessment of current flood risk 35 3.6 Flood risk in the future 39 4. Appraisal of options 45 4.1 Appraisal criteria for River Hull Strategy options 45 4.2 Options for consideration 49 4.3 Options appraisal 50 4.4 Strategy elements and final options 56 4.5 Summary of economics 60 4.6 Summary of Strategic Environmental Assessment 64 4.7 Impact of climate change 65 5. Our Plan 67 5.1 Introduction 67 5.2 Proposed flood risk management measures 67 5.3 Strategy action plan 68 5.4 Procurement Strategy 71 5.5 Strategy risks 71 5.6 Strategy review 72 River Hull Flood Risk Management Strategy Report List of Tables Table 1.1 Our objectives for the River Hull Flood Risk Management Strategy 3 Table 1.2 Reasons for a strategic approach 4 Table 2.1 River Hull Strategy area overview 7 Table 2.2 Hull and Coastal Streams CFMP Policy units and preferred policies 18 Table 3.1 Recorded flood events in the River Hull catchment 29 Table 3.2 River Hull flood defence assets 31 Table 3.3 Onset of fluvial flooding for River Hull catchment (taking into account the effect of the defences) 38 Table 4.1 Summary of initial flood risk management options 49 Table 4.2 Benefit cost ratio for pumping station appraisal in the maintain option 53 Table 4.3 Benefit cost ratio for pumping station combinations appraisal in the maintain option 54 Table 4.4 Summary of Strategy options (combinations of Strategy elements) 56 Table 4.5 Summary of economic damages (Whole Catchment) 61 Table 4.6 Summary of economic damages (upper and middle catchment areas only) 12 63 Table 4.7 Summary of economic damages (lower catchment area only) 12 64 List of Figures Figure 1-1 Stages in the development of the River Hull Flood Risk Management Strategy 6 Figure 2-1 Strategy location and study area 8 Figure 2-2 Topography of the Strategy area 9 Figure 2-3 Upper River Hull from Wansford Bridge 10 Figure 2-4 Lower River Hull through Kingston-upon-Hull 11 Figure 2-5 Key features of the River Hull system 12 Figure 2-6 River Hull catchment areas 16 Figure 2-7 Local Authority boundaries in the River Hull Strategy study area 20 Figure 3-1 Overtopping of River Hull at Wilfholme 26 Figure 3-2 Flooding near Wilfholme caused by Beverley and Barmston Drain being unable to discharge 27 Figure 3-3 Location of natural springs 28 Figure 3-4 Surface water flooding in Hull 29 Figure 3-5 Flood defences in the study area 33 Figure 3-6 Predicted extent of flooding (present day) 37 Figure 4-1 Options appraisal process 46 Appendices Appendix A – Options Appraisal Report Appendix B – Environmental Report River Hull Flood Risk Management Strategy Report Glossary of terms Term Meaning / Definition Appraisal The process of defining objectives, examining options and evaluating costs, benefits, risks, opportunities and uncertainties before a decision is made. Biodiversity The 1992 Biodiversity Convention in Rio led to the formation of the UK Biodiversity Action Plan Steering Group which created action plans to conserve 116 species and 14 habitats (BAP) together with recommendations for future Biodiversity Action Plans (BAPs) as well as a number of Local Biodiversity Action Plans (LBAPs). The Environment Agency has an obligation to report to Government on all losses and gains of habitats and species protected by Biodiversity Action Plans that result from its flood and coastal defence work, and therefore any flood defence policies that are formulated for the catchment should seek to protect, or where possible, enhance sites which are important for BAP habitats and species. Catchment A surface water catchment is the total area that drains into a river. Catchment Catchment Flood Management Plans (CFMPs) are a large-scale strategic planning Flood framework for the integrated management of flood risks to people and the developed and Management natural environment in a sustainable manner. The Aire CFMP will incorporate flood risk Plan (CFMP) policy into strategic and local plans and ensure its local implementation through development control. This will prevent inappropriate development in the floodplain, thereby reducing the risk of flooding. Conservation A Conservation Area is an area of special architectural or historic interest, the character Area (CA) or appearance of which it is desirable to preserve or enhance. County A County Structure Plan sets out policies and major proposals to guide new Structure Plan development, and conserve the natural and built environment. It must implement national and regional polices, in particular the Planning Policy Guidance (PPG) notes, and shapes planning and development. Critical Ordinary A watercourse which is non main river, but which the Environment Agency and operating Watercourse authorities deem critical as they have the potential to put large numbers of people and (COW) property at risk from flooding. Environment Our vision for the environment and a sustainable future is: ‘A healthy, rich and diverse Agency environment in England and Wales, for present and future generations’ To achieve the Environmental targets that will make the ‘vision’ a reality the Agency has identified nine key ‘themes’ or Vision ‘frameworks for change’ through which it will work for a more sustainable future. 1. A better quality of life: the Agency will work with all sectors to enhance the quality of the environment and the services it provides – for business, anglers, the boating community and other users of the waterways, farmers, planners and all sections of the community. 2. An enhanced environment for wildlife: the Agency will ensure that its activities and those it authorises do not threaten key species and habitats; 3. Cleaner air for everyone 4. Improved and protected inland and coastal waters: the Agency will work to clean up polluted waters and to reduce the risk of further pollution; 5. Restored protected land with healthier soils. 6. A ‘greener’ business world 7. Wiser sustainable use of natural resources 8. Limiting and adapting to climate change 9. Reducing flood risk: the Agency will improve flood defences and information on flood risks For further information refer to our website http://www.environmentagency.gov.uk/aboutus/286233/106775/106809/ Environmental And Environmental Impact Assessment is a statutory process for a development which is Impact likely to have an adverse environmental impact, with the impacts identified and assessed Assessment to determine their significance. (EIA) Flood A scheme designed to reduce the risk of flooding in a specific location. Alleviation Scheme (FAS) Flood Defence A structure (or system of structures) for the alleviation of flooding. Floodplain Any area of land over which water flows or is stored during a flood event or would flow but for the presence of flood defences. River Hull Flood Risk Management Strategy Report i Term Meaning / Definition Flood Risk The activity of modifying the frequency or consequences of flooding to an appropriate Management level (commensurate with land use), and monitoring to ensure that flood risks remain at the proposed level. This should take account of other water level management requirements, and opportunities and constraints. Flood Map Maps showing the Agency’s best estimate of the extent of the floodplain. These cover all Main Rivers and some ordinary watercourses. The floodplain is defined as the area having a 1% per annum risk of fluvial inundation, or a 0.5%p.a risk of tidal inundation. Defended areas are also shown. These maps are sometimes referred to as the Indicative Flood Map. Flood Storage An area of land which may be used to temporarily store an increased depth or extent of Area floodwater to reduce flood risk to communities downstream. Flood Zones This map shows natural floodplain 'zoned' into three areas based on risk for the purpose of PPG25. They show the flooding that would occur if there were no flood defences and have been created from a combination of detailed models where available, generalised models based on the national Digital Terrain Model and relevant historic flood data. Watercourses that have a catchment size of less than 2 square kilometres have not been included. Geographical A GIS is a computer-based system for capturing, storing, checking, integrating, Information manipulating, analysing and mapping spatially referenced data.