Grasmere Flood Investigation Report th Stock Lane, 5 December 2015 Flood Event 5-6th December 2015 Cumbria County Council This flood investigation report has been produced by the Environment Agency as a key Risk Management Authority under Section 19 of the Flood and Water Management Act 2010 in partnership with Cumbria County Council as Lead Local Flood Authority. Version Prepared by Reviewed by Approved by Date David Webb Jonathan Coates, EA Working Draft for Piergiorgio Graham Fardell Tom McCormick, May 2016 discussion with EA Costa SLDC Doug Coyle, CCC Himz Mistry v2.0 Jonathan Coates, Incorporating Piergiorgio Kathryn Tanner, EA 28 June 2016 comments Costa EA Tom McCormick, SLDC Jonathan Catherine Evans, Kathryn Tanner, v3.0 Final December 2016 Coates, EA EA EA 2 Flood Investigation Report: Grasmere (5th-6th December 2015) Cumbria County Council Contents Executive Summary ............................................................................................................................................. 4 Introduction.......................................................................................................................................................... 5 Scope of this report ................................................................................................................................................ 5 Flooding History ..................................................................................................................................................... 6 Event background................................................................................................................................................ 7 Flooding Incident ................................................................................................................................................... 7 Existing Flood Defences ...................................................................................................................................... 13 Investigation ...................................................................................................................................................... 16 Rainfall Event ...................................................................................................................................................... 16 Map of Flow Routes ............................................................................................................................................. 19 Impacts and Likely Causes of Flooding ................................................................................................................ 21 Timeline ............................................................................................................................................................... 21 Lake Area .................................................................................................................................................... 21 Left Bank River Rothay, Stock Lane & Church Bridge .................................................................................. 24 White Bridge & Village Centre...................................................................................................................... 30 Environment Agency Flood Incident Response .................................................................................................... 34 Maintenance Activities ................................................................................................................................. 36 Recommended Actions ..................................................................................................................................... 37 Next Steps .......................................................................................................................................................... 40 Appendices ........................................................................................................................................................ 41 Appendix 1: Acronyms and Glossary .................................................................................................................... 41 Appendix 2: Summary of Relevant Legislation and Flood Risk Management Authorities ....................................... 43 Appendix 3: Links to Other Information on Flooding ............................................................................................. 46 Appendix 4: Flood Warnings and Alerts................................................................................................................ 47 3 Flood Investigation Report: Grasmere (5th-6th December 2015) Cumbria County Council Executive Summary As a result of Storm Desmond, there was a period of prolonged, intense, rainfall across Northern England during the 5th and 6th of December 2015. The rainfall fell on already saturated catchments, which led to high river levels and flooding throughout Cumbria. In response to the flood event, this Flood Investigation Report was developed by the Environment Agency as a key Risk Management Authority (RMA), working in partnership with Cumbria County Council as the Lead Local Flood Authority. The report, as required by Section 19 of the Flood and Water Management Act 2010, provides details on the flooding that occurred in Grasmere on the 5th and 6th of December 2015. The report refers to several sources of data including information provided by affected residents, site visits, surveys of the area, data collected by observers, and river and rainfall telemetry during the flood event. This data has been compiled by CH2M, specialist consultants in flood risk management, who have also commented on the mechanisms that led to the flooding and made recommendations for managing flood risk going forward. Approximately 90 properties were directly affected by the flooding in and around Grasmere, as a result of high water levels in the River Rothay, Easedale Beck, Greenhead Gill and Grasmere lake (south of the village). Many properties, including St Oswald’s Church, experienced flooding for the first time. This report indicates the likely causes of flooding and associated flow routes within the village. A draft version of the Grasmere Flood Investigation Report was published online in July for public consultation. Following the draft publication, a public meeting chaired by Cumbria County Council was held in Grasmere on the 5th July, where the Environment Agency formally presented the report to the local community. Other Risk Management Authorities were also present at the meeting to answer any questions raised during a question and answer session following presentation of the report. Through the public meeting and local consultation with the community, including with the Grasmere Flood Action Group, a range of feedback has been provided on the report. The Environment Agency have reviewed this feedback and, where appropriate, updated the Final version of the report to reflect the required amendments. Please note that references to left and right bank in this report are for the observer looking downstream with the flow of water. In response to the flooding, a number of community meetings have taken place, and these will continue in order to ensure that all those affected have the opportunity to contribute ideas for reducing the flood risk in their area of the village. Any additional information that residents and others can provide to the Environment Agency and Cumbria County Council to help develop our understanding of the flooding is welcomed. A lot of information has already been provided, much of which has been used to inform this report. The scale of this report means that not every piece of information can be incorporated into the document. Any additional information should be provided to; http://www.cumbria.gov.uk/planning-environment/flooding/floodriskassessment.asp 4 Flood Investigation Report: Grasmere (5th-6th December 2015) Cumbria County Council Introduction Under Section 19 of the Flood and Water Management Act (2010) Cumbria County Council, as Lead Local Flood Authority (LLFA), has a statutory duty to produce Flood Investigation Reports for areas affected by flooding. Section 19 of the Flood and Water Management Act states: (1) On becoming aware of a flood in its area, a lead local flood authority must, to the extent that it considers it necessary or appropriate, investigate: (a) which risk management authorities have relevant flood risk management functions, and (b) whether each of those risk management authorities has exercised, or is proposing to exercise, those functions in response to the flood. (2) Where an authority carries out an investigation under subsection (1) it must — (a) publish the results of its investigation, and (b) notify any relevant risk management authorities. This section of the Act leaves the determination of the extent of flood investigation to the LLFA. It is not practical or realistic for Cumbria County Council to carry out a detailed investigation into every flood incident that occurs in the County, but every incident, together with basic details will be recorded by the LLFA. Only those with 5 or more properties/businesses involved will have investigations published. An investigation will be carried out, and a report prepared and published by the LLFA when the flooding impacts meet the following criteria: where there is ambiguity surrounding the source or responsibility of flood incident, internal