Hull City Council Preliminary Flood Risk Assessment Draft Report
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Sustaining & Improving the Quality of People’s Lives Hull City Council Preliminary Flood Risk Assessment Draft Report Halcrow Group Limited Otley Road Leeds LS6 2UL 0113 220 8220 Halcrow Group Limited has prepared this report in accordance with the instructions of their client, Hull City Council. Any other persons who use any information contained herein do so at their own risk. The required data has been made available from previous studies (Hull Catchment Flood Management Plan, River Hull Flood Risk Management Strategy, Hull Strategic Flood Risk Assessment, and Hull Surface Water Management Plan, Hull Flood Mitigation Investment Plan & Hull Aqua Green Feasibility Study). Hull City Council should identify and add to the PFRA any additional or changed data. Any information provided by third parties and referred to herein has not been checked or verified by Halcrow unless otherwise expressly stated in the document. © Halcrow Group Limited 2011 Page i Sustaining & Improving the Quality of People’s Lives Page ii Sustaining & Improving the Quality of People’s Lives Preliminary Flood Risk Assessment Revision schedule Date Document reference Stage Author Reviewer 9.5.2011 PFRA Working draft Phillip Mcloughlin Donald Daly v0.2 28.07.11 PFRA & all Final Steve Wragg annexes amendments and submission Hull City Council Page iii Sustaining & Improving the Quality of People’s Lives Executive Summary This report summarises the Preliminary Flood Risk Assessment undertaken for Hull City Council. The PFRA has been undertaken to assist Hull City Council to meet its duties as a Lead Local Flood Authority, with the delivery of the first stage of the Flood Risk Regulations (2009). These regulations implement the EU Floods Directive in the UK. The PFRA is a high level screening exercise that compiles information on significant local flood risk (any flood risk that does not originate from main rivers, the sea or large reservoirs) from past and future floods, based on readily available and derivable information. The PFRA also includes the identification of flood risk areas where the final two stages of the Flood Risk Regulations apply; stage three delivers Flood Risk Maps and stage four delivers Flood Risk Management Plans. This study has identified June 2007 as a flood that is considered to have had significant harmful consequences. This is based on the following local definition of harmful consequences: ‘Memorable past floods or otherwise registered on a national scale even if only occurring over a relatively small area.’ The 2007 flood in Hull affected over 8,000 homes and 1,300 businesses, and more than 90 of the city's schools. The estimated cost of the June 2007 flood damage to Hull City Council’s own housing stock was in the order of £41M (with the total cost considerably higher than this figure). Future flood risk is estimated to be high in the city. Based on the Areas Susceptible to Surface Water Flooding (AStSWF) outputs, it is estimated that approximately 19,557 properties are estimated to be at risk from flooding during a rainfall event with a 1 in 200 annual chance of occurring. This includes 4600 properties within the adjacent East Riding of Yorkshire. The indicative flood risk areas provided by the Environment Agency have been reviewed based on the local knowledge of past and future floods. The outcome of this review is that the indicative flood risk areas can be used as the flood risk areas for the undertaking of stages three and four of the regulations with some agreed boundary changes between the two LLFA’s. The FRA for Hull covers an area of the East Riding of Yorkshire Council, it is intended to rename the area as the Kingston upon Hull and Haltemprice FRA and both authorities will work in partnership to deliver the requirements of the latter stages of the regulations. Page iv Sustaining & Improving the Quality of People’s Lives Preliminary Flood Risk Assessment Table of Contents Executive Summary iv Glossary vii 1 Introduction 1 1.1 What is a Preliminary Flood Risk Assessment? 1 1.2 Background 2 1.3 Aim and Objectives of the PFRA 2 1.4 Study Area 3 2 Lead Local Flood Authority Responsibilities 5 2.1 Legislative Background 5 2.2 Leadership and Partnership 6 2.3 Public Engagement 7 2.4 Other Responsibilities 7 3 Methodology and Data Review 9 3.1 Data Sources 9 3.2 Availability 12 3.3 Limitations 12 3.4 Security, Licensing and Use Restrictions 12 3.5 Quality Assurance 13 4 Past Flood Risk 15 4.1 Introduction 15 4.2 Surface Water Flooding 15 4.3 Sewerage Network Flooding 16 4.4 Groundwater Flooding 16 4.5 Interactions with Other Flooding Sources 17 4.6 Summary of Past Floods 17 4.7 Significant Harmful Consequences 23 5 Future flood risk 24 5.1 Summary of Future Flood Risk 24 5.2 Locally Agreed Surface Water Information 24 5.3 Ground Water Flooding 26 5.4 Potential Consequences of Future Flooding 26 5.5 Impact of Climate Change 27 5.6 Long Term Developments 28 Page v Sustaining & Improving the Quality of People’s Lives Preliminary Flood Risk Assessment 6 Review of Indicative Flood Risk Areas 30 6.1 Extent of Indicative Flood Risk Areas 30 6.2 Review Comments 32 7 Identification of Flood Risk Areas 33 7.1 Amendments to FRA 33 7.2 New FRA 33 8 Next Steps 34 8.1 Scrutiny and Review 34 8.2 Data Collection and Management 34 8.3 Incident Recording 35 8.4 Other Flood Risk Regulation Requirements 35 9 References 36 Figures Figure 1.1 – Extent of Hull City Boundary Figure 2.1 – Legislative Background Figure 4.1 – Historic Flood Events from Local Sources of Flooding Figure 5.1 – 1 in 200 year rainfall event extents (Areas Susceptible to Surface Water Flooding) Figure 5.4 – Squares above threshold (Areas Susceptible to Surface Water Flooding) Figure 6.1 – Indicative Flood Risk Areas in England Figure 6.2 – Kingston upon Hull Indicative Flood Risk Areas Figure 7.1 – Kingston upon Hull and Haltemprice Flood Risk Area Tables Table 1.1 – Stages of the Flood Risk Regulations Table 3.1 – Summary of Key Data Table 3.2 – Objectives of the Virtual Site Visit Table 3.3 – Data Restrictions and Licensing Details for Strategic Data Providers Table 3.4 – Data Quality System from SWMP Technical Guidance (March 2010) Table 4.1 – Summary of DG5 Register for Sewer Flooding in Hull Table 4.2 – Summary of Past Floods Table 5.1 – Number of Residential Properties at Risk of Flooding Annexes Annex 1 – Records of past floods and their significant consequences (Preliminary Assessment Spreadsheet) Annex 2 – Records of future floods and their significant consequences (Preliminary Assessment Spreadsheet) Annex 3 – Records of Flood Risk Area and its rationale (Preliminary Assessment Spreadsheet) Annex 4 – Review Checklist Annex 5 – GIS Layer of Flood Risk Area(s) Page vi Sustaining & Improving the Quality of People’s Lives Preliminary Flood Risk Assessment Glossary Term Definition Aquifer A source of groundwater comprising water bearing rock, sand or gravel capable of yielding significant quantities of water. AMP Asset Management Plan is a tactical plan for managing an organisation's infrastructure and other assets to deliver an agreed standard of service. Area susceptible Coarse scale national mapping showing areas that are to groundwater susceptible to groundwater flooding. flooding AStSWF Areas Susceptible to Surface Water Flooding is the first generation national mapping outlining area of risk from surface water flooding across the country. It is reported with three susceptibility bandings (less, intermediate and more). CFMP Catchment Flood Management Plans considered all types of inland flooding, from rivers groundwater surface water and tidal flooding and are used to plan and agree the most effective way to manage flood risk in the future. CDA Critical Drainage Area is an area within Flood Zone 1 which has critical drainage problems and which has been notified to the local planning authority by the Environment Agency. CIRIA Construction Industry Research and Information Association. Civil Contingencies This Act delivers a single framework for civil protection in the UK. As part of Act the Act, Local Resilience Forums must put into place emergency plans for a range of circumstances including flooding. CLG Government Department for Communities and Local Government. Climate Change Long term variations in global temperature and weather patterns caused by natural and human actions. CSO Combined Sewer Overflow is a structure that discharges excess wastewater directly to nearby streams, rivers, or other water bodies when the wastewater volume in a combined sewer system exceeds the capacity of the sewer system or treatment plant. Culvert A channel or pipe that carries water below the level of the ground. Defra Government Department for Department for Environment, Food and Rural Affairs. DEM Digital Elevation Model represents the earth's surface and includes all objects on it. DG5 Register A water-company held register of properties which have experienced sewer flooding due to hydraulic overload, or properties which are 'at risk' of sewer flooding more frequently than once in 20 years. Page vii Sustaining & Improving the Quality of People’s Lives Preliminary Flood Risk Assessment Term Definition DTM Digital Terrain Model represents the bare ground surface without any objects like plants and buildings. EA Environment Agency is the leading public body for protecting and improving the environment in England and Wales. Indicative Flood Risk Areas determined by the Environment Agency as indicatively having a significant Areas flood risk, based on guidance published by Defra and the use of certain national datasets. These indicative areas are intended to provide a starting point for the determination of Flood Risk Areas by LLFAs. FMfSW Flood Map for Surface Water is the updated (second generation) national surface water flood mapping which was released at the end of 2010.