A new empirical formula for coastal washover sediment volume

Coastal overwash, a serious and widespread issue affecting barrier coasts around the world in general and the United States in particular, results from complex geologic and oceanographic processes such as extreme storms or hurricanes, changes in sediment supply at the coast, and sea-level rise. The estimation of washover sediment volume due to overwash processes is useful for coastal planning. A new empirical formula for predicting deposited washover volume was derived. The new formula was developed by modifying previous empirical models using new assumptions based on the governing physical processes, taking into account the excess runup height over the beach crest and the duration of the overwash event. An empirical coefficient was calibrated using field data sets from the United States. Verification of the model with a further fourteen field data sets from the United States and Japan shows that the formula yields predictions which are comparable to the measured field data, with most of predicted washover volumes falling within a factor of two of observed volumes.