PFRA) to Assess the Harmful Consequences of Past and Potential Future Flooding, and to Identify Areas of Significant Flood Risk (‘Flood Risk Areas’)
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Gloucestershire County Council Draft Preliminary Flood Risk Assessment March 2011 Gloucestershire County Council Preliminary Flood Risk Assessment Directorate : Environment Service : Flood Risk Management Relevant Legislation : Flood Risk Regulations 2009 Amendment Record: Revision Description Date Signed 1 First draft March 2011 A Cotton Gloucestershire County Council Preliminary Flood Risk Assessment Executive Summary Under the EC Floods Directive, which has been transposed into UK law through the Flood Risk Regulations (2009), Gloucestershire County Council must prepare undertake a Preliminary Flood Risk Assessment (PFRA) to assess the harmful consequences of past and potential future flooding, and to identify areas of significant flood risk (‘flood risk areas’). As a Lead Local Flood Authority (LLFA), Gloucestershire County Council has responsibility for preparing the deliverables of the Flood Risk Regulations for ‘local flood risk’ (flooding from surface runoff, ordinary watercourses and groundwater). The Environment Agency has responsibility for preparing the deliverables of the Flood Risk Regulations for flooding from Main Rivers and the Sea. This report, and associated spreadsheets, has been prepared by Gloucestershire County Council to fulfil the requirements of the Flood Risk Regulations for the PFRA. The methodology for undertaking the PFRA has been based on the Environment Agency’s PFRA Final Guidance (December 2010). The principal purpose of a PFRA is to assess past and future floods with significant harmful consequences, and to identify the areas of most significant flood risk across Europe. The first stage of the PFRA is to assess past floods which have had significant harmful consequences for human health, economic activity or the environment, or could have harmful consequences if they were to occur now. In the wake of the summer 2007 floods a large amount of information on flooded locations was collected by the relevant risk management authorities including the six district councils, the Environment Agency, Gloucestershire Highways, Lower Severn Internal Drainage Board and the water companies. Gloucestershire County Council collated, analysed and mapped this information as part of the pilot Surface Water Management Plan, which was completed in March 2010. This information was reviewed and updated by relevant risk management authorities for the PFRA to ensure it was as up to date and accurate as possible. For the PFRA Gloucestershire County Council only need to report past floods which have had significant harmful consequences. This was agreed locally as being five or more residential properties flooded internally, two or more commercial properties flooded internally, one or more critical service (e.g. school) flooded and a transport link flooded for a significant period. Annex 1 of the PFRA contains a spreadsheet of the past flood incidents which meet the locally agreed threshold. The PFRA has also considered the potential risk of future flooding in Gloucestershire. This has been principally based on hydraulic modelling which is able to predict the potential impact of flooding on people, property and the environment. In Gloucestershire the best available information on potential future floods is available from a variety of sources including Surface Water Management Plan mapping, mapping undertaken by Cotswold District Council and the national maps produced by the Environment Agency. This will be used to inform an assessment of the numbers of properties in Gloucestershire which are vulnerable to surface water flooding during an extreme rainfall event (similar to that experienced in Cheltenham in July 2007).. This calculation has yet to be completed. The final stage of the PFRA process is the identification of ‘Flood Risk Areas’. Indicative ‘Flood Risk Areas’ have been calculated by the Environment Agency using a threshold defined nationally by ministers at the Department for food and rural affairs (Defra). An indicative ‘Flood Risk Area’ has been identified where clusters of at least 30,000 people have been identified as being at risk of flooding from local sources. Of the ten indicative ‘Flood Risk Areas’ which have been identified nationally by the Environment Agency and Defra, none are located in Gloucestershire. Gloucestershire County Council is not proposing to add a new ‘Flood Risk Area’ for the purposes of the PFRA. It should be noted that the primary purpose of the Flood Risk Regulations is to identify specific areas at most significant risk across Europe. There may be areas within Gloucestershire which local partners consider to be locally important areas of flooding but are not considered to be a ‘Flood Risk Area’ for the Gloucestershire County Council Preliminary Flood Risk Assessment purposes of the PFRA. Management of locally important areas of flooding should be carried out through the local flood risk management strategies, which Gloucestershire County Council will be developing throughout 2011 as part of new responsibilities provided in the Flood and Water Management Act. Gloucestershire County Council Preliminary Flood Risk Assessment Contents Executive Summary ................................................................................................................... iii 1 Introduction ....................................................................................................................... 1 1.2 Overview of Flood Risk Regulations ......................................................................................... 1 1.3 Aims and objectives of the PFRA ............................................................................................. 2 1.4 Study area ................................................................................................................................ 3 2 Lead Local Flood Authority responsibility ............................................................................ 5 2.2 Partnership working ................................................................................................................. 5 2.3 Communication with the public ............................................................................................... 6 3 Methodology and data review ............................................................................................ 7 3.1 Information gathered on ‘past floods’ ..................................................................................... 7 3.2 Information gathered on ‘future floods’.................................................................................. 8 3.3 Availability of information ....................................................................................................... 9 4 Assessment of past floods ................................................................................................. 12 4.1 Locally agreed threshold for ‘significant harmful consequences’ ......................................... 12 4.2 Past floods in Gloucestershire with significant harmful consequences ................................ 13 5 Assessment of future floods .............................................................................................. 18 5.1 Locally agreed surface water information ............................................................................. 18 5.2 Future floods in Gloucestershire............................................................................................ 18 5.3 The impacts of climate change .............................................................................................. 19 5.4 Long term developments ....................................................................................................... 20 6 Review and identification of ‘Flood Risk Areas’ ................................................................. 21 7 Next steps ........................................................................................................................ 22 7.1 Ongoing work to support future PFRA reviews ..................................................................... 22 7.2 Scrutiny and review procedures ............................................................................................ 22 8 References ........................................................................................................................ 23 Annex 1 Detailed records of past floods with significant harmful consequences................... 24 Annex 2 Detailed records of future floods ........................................................................... 24 Annex 3 ‘Flood Risk Areas’ .................................................................................................. 24 Annex 4 Review checklist .................................................................................................... 24 Annex 5 Supporting figures and tables ................................................................................ 25 Gloucestershire County Council Preliminary Flood Risk Assessment 1 Introduction 1. This report, and associated spreadsheets, has been prepared by Gloucestershire County Council to fulfil the requirements of the Flood Risk Regulations for the PFRA. 2. Under the EC Floods Directive, which has been transposed into UK law through the Flood Risk Regulations (2009), Gloucestershire County Council must prepare undertake a Preliminary Flood Risk Assessment (PFRA) to assess past floods, to assess the possible harmful consequences of future floods, and to identify areas of significant