WAVE OVERTOPPING OVER A DIKE FOR VARIABLE WATER LEVEL

Abstract

The still water level (SWL) during a storm is always dynamic (storm surge). The variability of the water level can be schematized as a time-varying hydrograph of a certain duration. The average wave overtopping discharge q is a function of the ratio between the freeboard Rc (the structure crest elevation above SWL) and the significant wave height Hm0. Since the variation during a storm of the SWL changes the freeboard Rc, the wave overtopping discharge is variable. Typically, in the laboratory the wave overtopping on coastal defense structures is investigated for a constant water level (CWL) and a pre‐determined structural exposure time frame. This exposure time frame is often representative for the storm surge peak or for a statistically representative number of individual waves (e.g. 1000 waves), not considering any variable water level (VWL). For the case of wave overtopping in VWL conditions, no validated prediction formulae exist (Kerpen et al. 2020) and the prediction is rather based on safe assumptions and engineering judgement. This research investigated the influence of a VWL on the prediction of the average wave overtopping discharge q.