Flood Investigation Report
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Somerset County Council Lead Local Flood Authority Flood Investigation Report Parsonage Lane, The Street, Church Lane, Broadway and Greenditch Close, Chilcompton 17 th June 2016 Final Draft January 2017 Revision Schedule Checked Rev Date Details Author Approved by by Draft for 1 06/10/16 stakeholder A. Lambart consultation 2 16/01/17 Final draft A. Lambart D. Martin D. Martin Table of Contents Executive Summary ......................................................................................... 1 1. Introduction ........................................................................................... 2 & 3 2. Risk Management Authority Responsibilities ............................................... 4 2.1. Recording Flood Incidents .............................................................................. 4 2.2. Key Responsibilities ........................................................................................ 4 3. Flood Incident Summary and Impact ........................................................... 5 3.1. Site Location ................................................................................................... 5 3.2. Site characteristics and drainage .................................................................... 6 4. Drainage and Flood History ......................................................................... 8 4.1. Previous Flood Incidents ................................................................................. 8 4.2. Flood incident of 17 th June 2016 ..................................................................... 9 4.3. Rainfall Analysis ........................................................................................... 10 5. Probable Cause ....................................................................................... 111 5.1. Heavy rainfall in a relatively short period of time ........................................... 11 5.2. Housing within the pre-existing topographical context ................................... 11 6. Rights & Responsibilities ........................................................................... 12 6.1 The Lead Local Flood Authority (Somerset County Council) .................. 12 & 13 6.2 Environment Agency ...................................................................................... 13 6.3 Highway Authority .......................................................................................... 13 6.4 Landowners and residents ............................................................................. 13 6.5 Riparian Owner’s Responsibilities .................................................................. 13 7. Drop-in metting 10 th November 2016 .............................................. 124 & 15 Conclusion ................................................................................................... 146 Executive Summary On 17 th June 2016 three residential properties, and St John the Baptist Church in Chilcompton, were internally flooded up to a depth of 80mm and the highway up to a depth of 600mm. The subsequent investigation detailed below identifies the contributory factors of this flooding event. As the Lead Local Flood Authority (LLFA) Somerset County Council’s (SCC’s) Flood and Water Risk Management (FWRM) team have carried out site inspections and met with residents. This document has been written after a number of additional site meetings with residents, landowners, and the review of the informative comments from submitted Flood Incident Reporting Forms. Thank you to all those individuals who contributed to this report. 1 1. Introduction Lead Local Flood Authority Duty to Investigate Under the Flood and Water Management Act 2010, Somerset County Council (SCC) is designated as the Lead Local Flood Authority (LLFA) for Somerset. This Act sets out a number of responsibilities for the County Council with regard to flooding, including a duty to investigate flood events within its area as it deems necessary: (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. Section 19, Flood and Water Management Act 2010. Somerset County Council deemed it necessary to complete and publish an investigation into the flood event originating at the The Street and The Pitchings, Chilcompton on the17 th June 2016 as the event affected a significant number of properties and resulted in much correspondence and local concern. This report provides a summary of the event and probable causes. It records the actions taken and/or proposed and the organisation or individuals responsible for completing them. A ‘Risk Management Authority (RMA)’ means: (a) the Environment Agency (EA), (b) a lead local flood authority, (c) a district council for an area for which there is no unitary authority, (d) an internal drainage board, (e) a water company, and (f) a highway authority. When considering if it is necessary or appropriate to investigate a flood event Somerset County Council (SCC) will review the severity of the incident, the number of properties affected and the frequency of such an occurrence, and also other areas of particular concern. This incident saw four properties internally flooded and received many concerns from the community, as such the Lead Local Flood Authority (LLFA) SCC decided to investigate the event. 2 This report has been produced to comply with legislation and to determine the main causes of the flooding. It should be noted that in order to progress with their flood risk management function SCC has opted to develop this report further by considering the various actions that should be considered by the relevant RMAs. SCC as the LLFA will continue to monitor the list of actions with all of the RMAs and will assist in the delivery where practical to do so. Each affected area or group of smaller areas investigated within this report will have a number of recommended actions to be taken forward by the relevant RMAs or in some cases, by the landowner or local community action group. There are various levels of action that can be taken depending on the severity of the situation and the practical solutions available to reduce the risk of further flooding. The recommended actions will generally fall into one of the following categories: Delivery of Quick win schemes: a solution that can be implemented quickly by the Risk Management Authorities or Local Authority at relatively low cost. Further investigation/research: Further investigations such as catchment studies and hydrological/hydraulic assessments to understand the flow rates and directional paths and evaluate the extent of flooding. These would provide evidence for future capital investment. Development of Future schemes: Where immediate action is not financially viable or a solution not readily available then a larger scale flood alleviation scheme may be required. In such cases national funding would need to be secured together with additional contributions from others, such as local levy, local authorities and other third parties. Land owner action: Members of the public who own land adjacent to watercourses have riparian responsibilities and therefore have a duty to maintain their section of watercourse to ensure there is no impediment of flow. Other works to protect their property may also need to be funded by themselves to ensure delivery within their timescales. Community action: In some cases it may be prudent for community groups to join forces and deliver and maintain their own local schemes. In some cases this may generate further contributions from local levy or the LLFA. This investigation report will provide a starting point, with suggested actions being further refined in the light of further studies and where possible, through further dialog with the affected communities. 3 2. Risk Management Authority Responsibilities 2.1. Recording Flood Incidents 2.2. Key Responsibilities Risk Management Authorities (RMAs) in Somerset all have their own roles and responsibilities. The following Table 2.2 summarises the relevant flood risk management functions for each of the RMAs and the different sources of flood risk that the SCC investigation procedure follows. Table 2.2 Relevant flood Risk Management Authorities that will take the lead in managing the risk from various local sources of flooding. Flood Source Environment Lead Local Flood District Council Water Highway Agency Authority Company Authority (Somerset County Council) Rivers: Main river x Ordinary x x watercourse Surface Runoff: Surface water x Surface water origination on x the highway Other: Sewer flooding x The Sea x Groundwater x Reservoirs x 4 3. Flood Incident Summary and Impact 3.1. Site Location The catchment area covered by the investigation includes consideration of the farmland surrounding Chilcompton and the highway drainage system. Flood investigation study area Figure 1 – Parsonage Lane, The Street, The Pitchings, and Church Lane Figure 2 – Broadmead, Parsonage Lane, and Greenditch Close 5 Figure 3 – Contour lines of Chilcompton highest point 180m AMSL and the