Direct hazards from wave overtopping - the forgotten aspect of coastal flood risk assessment?

Any assessment of flood risk for a coastal site should include assessment of direct hazards caused by wave overtopping as well as flood extent and volumes. The direct hazards are likely to be critical for users and property on or immediately behind the defence line. This paper summarises recent advances in methods to predict wave overtopping; summarises present guidance on levels of direct hazards caused by wave overtopping; and discusses key areas where present knowledge and guidance are insufficient.

Recent work in UK, the Netherlands and Germany has derived substantially improved and extended guidance on the prediction of wave overtopping in the new EurOtop Manual http://www.overtopping-manual.com/. The EurOtop Manual has drawn together results of national and European research projects to formulate the best prediction methods and advice available. Those tools are based on results of previous field and laboratory studies, most of which require simplifying the structure being analysed. The paper discusses the manual, but will also highlight areas for future improvement, both in prediction tools for overtopping, and its consequences, and hence guidance on tolerable limits.