Mid-Latitude Coastal Hazard

A mid-latitude coastal hazard is a coastal flooding or erosion threat driven by extratropical cyclones rather than by tropical storms. These mid-latitude depressions track across the 30 to 60 degree latitude belt and generate storm surge, large fetch-limited and swell wave fields, and prolonged high water over wide coastlines, as in North Sea and North Atlantic events. The hazard combines surge plus tide as a storm tide, with wave run-up and overtopping on top. Because the systems are large and persistent, the resulting extreme sea levels are analyzed with return-period statistics to set defense crest heights and future sea-level allowances.