A UK best-practice approach for extreme sea-level analysis along complex topographic coastlines

The impacts of storm surges represent an increasing risk to the world\textquoterights coastlines. Coastal planners require accurate estimates of flood risk in order to provide suitable defensive measures. Therefore a reliable methodology is required for the estimation of extreme sea-level probabilities at high spatial resolution along coastlines. This paper describes a new method for estimating these probabilities, with application to the UK coastline. The method consists of two components: the estimation of extreme sea-levels by applying a newly developed statistical method, termed the Skew Surge Joint Probability Method, with tide gauge records, and the use of hindcast sea-levels to dynamically interpolate these estimates around complex coastlines. The skew surge parameter is a more reliable indicator of meteorological impacts on sea-level than the non-tidal residual used in the Revised Joint Probability Method, as previously used in the United Kingdom. The method has been applied to the UK coastline to provide a database of extreme sea-level probabilities for the Environment Agency for England and Wales and the Scottish Environment Protection Agency. The database will be used to inform coastal defense strategy, flood mapping and forecasting and to support policy, implementation and operational decision-making.