Developing a workbook and user guide to apply tier 2 RARS to EA flood detention reservoirs

Risk Assessment for Reservoir Safety management (RARS) guidance was developed for the Environment Agency (EA) to provide a methodology for the risk analysis, assessment, and management of reservoirs in the UK. It provides a framework for the risk assessment of typical impounding reservoirs that retain water almost continuously. However, the methodology is not directly applicable to impounding and non-impounding flood detention reservoirs (FDRs) which have slightly different risks and failure modes. For example, typically they do not impound for long periods of time, and determination of the highest risk structures on washland reservoirs, which generally have long but low embankments, can be subjective. The EA, as undertaker of more than 200 large raised FDRs, therefore required refinements to be made to the RARS methodology to allow it to be applied to FDRs and to create a workbook and user guide to allow consistent application of RARS across a portfolio of FDRs.