The conundrum of specifying very low wave overtopping discharges

Abstract

The design of certain seawalls / breakwaters has often been required to achieve very low target overtopping discharges when these structures protect vulnerable infrastructure or activities. The balance between economically viable protection and performance requirements is often difficult to achieve without good knowledge on low overtopping. The paucity of data in this space and the high uncertainties associated with existing methods, increase the challenge. The occurrence of a low number of overtopping waves has the consequence that any test results are substantially more affected by the inherent variation of random waves, therefore more uncertain. The physical model test results presented hereafter were successful in obtaining low to very low overtopping discharge data. For low / very low overtopping, these test data present considerable scatter relative to the latest empirical prediction. A number of repetitions was performed for conditions giving very low overtopping discharges, which illustrated the inherent uncertainty associated with low overtopping.