Flood Investigation Report Greater Manchester 26 December 2015
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OFFICIAL- SENSITIVE v1.5 – 29th July 2016 Flood Investigation Report Greater Manchester 26 December 2015 Photo courtesy of Debbie Cruse showing flooding to Rochdale town centre Published xxxx 1 OFFICIAL- SENSITIVE v1.5 – 29th July 2016 This report is written to comply with Section 19 of the Flood & Water Management Act, 2010. This Draft Report shall be regarded as ‘Official – Sensitive’ until all direct recipients of it have had opportunity to comment on its contents and it has been suitably amended before wider distribution 2 OFFICIAL- SENSITIVE v1.5 – 29th July 2016 Table of Contents 1. Executive Summary ........................................................................................................................ 6 2. Purpose of Investigation Report .................................................................................................... 8 2.1 Section 19 Investigation requirement .................................................................................... 8 2.2 Purpose ................................................................................................................................... 8 2.3 Scope ....................................................................................................................................... 9 3. Roles and responsibilities ............................................................................................................. 10 3.1 Relevant Risk Management Authorities ............................................................................... 10 3.2 Manchester Ship Canal Company ......................................................................................... 12 Flood Event Impacts .............................................................................................................................. 13 3.3 Before and during the flood .................................................................................................. 13 3.4 Rainfall .................................................................................................................................. 14 3.5 River levels and flows ............................................................................................................ 15 3.6 Locations Affected ................................................................................................................ 17 3.7 Infrastructure Impacts .......................................................................................................... 21 Electricity Supply .......................................................................................................................... 21 Bridges .......................................................................................................................................... 21 Transport ...................................................................................................................................... 21 Gas Supply .................................................................................................................................... 22 Environment Agency Assets ......................................................................................................... 22 Wastewater Treatment ................................................................................................................ 22 Water Supply ................................................................................................................................ 23 Manchester Ship Canal ................................................................................................................. 23 3.8 Other impacts ....................................................................................................................... 23 Environmental Impacts ................................................................................................................ 23 Public Health Impacts ................................................................................................................... 24 4. Response and Recovery ............................................................................................................... 25 4.1 Multi-Agency Response ........................................................................................................ 25 4.2 Flood Warnings ..................................................................................................................... 25 4.3 Communications and community engagement .................................................................... 27 4.4 Asset inspection and Future Maintenance ........................................................................... 27 4.5 Future investigation of options ............................................................................................. 28 3 OFFICIAL- SENSITIVE v1.5 – 29th July 2016 5. Summary and Conclusions ........................................................................................................... 29 5.1 Scale and impacts .................................................................................................................. 29 5.2 Incident response and recovery ............................................................................................ 29 5.3 Conclusions ........................................................................................................................... 30 6. Recommendations ....................................................................................................................... 31 7. Next Steps .................................................................................................................................... 37 8. Acknowledgements ...................................................................................................................... 38 Appendix 1 – Local Flood Information (all sources) .............................................................................. 39 4 OFFICIAL- SENSITIVE v1.5 – 29th July 2016 Glossary and Abbreviations Annual Probability Throughout this document, flood events are defined according to their likelihood of occurrence. The term ‘annual probability of flooding’ is sometimes used, meaning the chance of a particular flood occurring in any one year. This can be expressed as a percentage. For example, a flood with an annual probability of 1 in 100 can also be referred to as a flood with a 1% annual probability. This means that every year there is a 1% chance that this magnitude flood could occur. Catchment The watershed of a surface water river system COMAH Control of Major Accident Hazards (COMAH) DCLG Department for Communities and Local Government Flooding Asset The register is a record of all structures or features designated by the Environment Register Agency, the Lead Local Flood Authority, or District Council which have an effect on flood risk. More information on Flooding Asset Registers can be found on Council websites and in Schedule 2 of the Flood & Water Management Act (2010). Flood Risk These ‘functions’ are powers or responsibilities listed in the Act (or related Acts) Management which may be exercised by a risk management authority for a purpose connected Function with flood risk management. GMCA Greater Manchester Combined Authority Groundwater Occurs when water levels in the ground rise above the natural surface. Low-lying flooding areas underlain by permeable strata are particularly susceptible. Internal property Flooding to ground floors of properties, including attached garages or flooding outbuildings, and basements/cellars only if used as living accommodation. LLFA Lead Local Flood Authority Main river A watercourse shown as such on the main river map, and for which the Environment Agency and Natural Resources Wales has responsibilities and powers Ordinary All watercourses that are not designated Main River, and which are the watercourses (OW) responsibility of Local Authorities or, where they exist, Internal Drainage Boards. Reservoir A natural or artificial lake where water is collected and stored until needed. Reservoirs can be used for irrigation, recreation, providing water supply for municipal needs, hydroelectric power or controlling water flow. Risk management Organisations that have a key role in flood and coastal erosion risk management as authorities (RMAs) defined by the Act. These are the Environment Agency, Natural Resources Wales, lead local flood authorities, district councils where there is no unitary authority, internal drainage boards, water companies, and highways authorities. RFCCs Regional Flood and Coastal Committees Riparian owner Owner of land adjoining, above or with a watercourse running through it. River flooding (Fluvial Occurs when water levels in a channel overwhelms the capacity of the channel. flooding) Surface water Flooding from rainwater (including snow and other precipitation) which has not flooding entered a watercourse, drainage system or public sewer. uFMfSW Updated Flood Map for Surface Water 5 OFFICIAL- SENSITIVE v1.5 – 29th July 2016 1. Executive Summary The impacts of Storm Eva on Boxing Day 2015 caused some of the most widespread flooding ever experienced in Greater Manchester. Prolonged, intense rainfall falling on already saturated catchments led to high river levels and flooding, causing significant impacts to communities, businesses, infrastructure and the environment. Many rivers in Greater Manchester experienced the highest levels ever recorded. Over