Frequency of Extreme Storms Based on Beach Erosion at Northern Assateague Island, Maryland

Abstract

This paper examines morphologic response to storms at northern Assateague Island, MD. Time series of hindcast waves and water level were input to drive the SBEACH beach erosion and overwash numerical model to estimate beach response, groundtruthed by documentation and available evidence of storms that caused significant morphologic change at the site. The analysis proceeded through application of the generalized Pareto distribution, with tropical and extratropical storms treated as separate populations. Five storm-related parameters were examined and correlated with volume of beach erosion: peak surge, peak water level (surge plus tide), storm duration, and two new parameters called the integrated hydrograph and the integrated significant wave height, “integrated” referring to the product of time and water level or wave height above a threshold. Storm-induced erosion was found to be only weakly correlated or not correlated with the individual parameters of peak storm surge and peak water level. For tropical storms, erosion is strongly correlated with integrated wave height, and to a lesser extent with storm duration and integrated hydrograph, whereas for extratropical storms, erosion is found to be significantly correlated with the integrated hydrograph and to a lesser extent with integrated wave height and storm duration. ADDITIONAL KEYWORDS: Beach, dune, storm surge, overwash, tropical storm, extratropical storm, waves, recurrence.