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In order to undertake a flood risk analysis, the performance of different flood defence structures under varying load conditions needs to be represented. This paper reports on work undertaken through the FLOODsite Project (Task 4) in bringing together available information on failure modes for a number of representative flood defence structure types, to support the development and implementation of system wide models for flood risk assessment. The work comprised a review of structures and failure modes which have occurred in the past, and an investigation of limit state equations and associated uncertainties for both the models and the input parameters. Summaries of all failure modes were combined to create a single reference document; it is hoped that this will be maintained and updated into the future as knowledge on different failure mechanisms evolves. Additional research into selected failure modes and embankment processes was also undertaken and is summarised in this paper, including recommendations as to areas where future research should be focussed.

There are regulatory driven requirements for UK water companies to reduce the number of properties at risk of sewer flooding. One of the potential causes of sewer flooding is the presence of persistent sediment deposits in sewers. This is a common problem in many combined sewers. Although the regulation is risk based, there is a gap in current knowledge on how risk assessment is affected by the uncertainty in sewer solids behaviour prediction. This paper describes a UK case study exploring the possibility of estimating uncertainty in sewer sediment deposit level predictions, using Monte Carlo simulations combined with a response database.