Impacts of Sea Level Rise on wave overtopping rates around the coast of England

There is unequivocal evidence that global sea levels are rising. It is therefore inevitable there will be socio economic impacts as a result of this. To aid mitigation, and the implementation of adaptation measures, it is vital the magnitude of the potential impact is quantified. Current approaches in the UK make simplifying assumptions regarding the relationship between present day and future economic damages relating to coastal flood risk. The analysis undertaken here supports improved sea level rise impact studies by providing national-scale estimates of changes in wave overtopping rates and flood defence overflow rates, as a result of different amounts of sea level rise. The analysis involves the application of components of an existing risk-based coastal flood risk analysis method. A subset of almost 600 flood defence assets around the country have been analysed for sea level rise rates up to 1m. The resulting analysis shows that, on average, the wave overtopping rate increases by up to 150 times above present day rates for lower return periods and by up to 5 times for higher return periods. This differential arises as a result of non-linearities in overtopping rates with increasing extreme sea levels.