WAVE OVERTOPPING EVENTS AT DIKES

Wave overtopping over dikes may cause dangerous situations, one of which is breaching of dikes. Wave overtoppmg can be characterised by mean overtopping discharges but this does not provide information on individual wave overtopping events. This paper focuses on parameters related to individual wave overtopping events with a low probability of exceedance. Measurements of velocities and the thickness of water layers have been performed at the crest and inner slope of dikes. The height, width and roughness of the crest have been varied and also the angle and roughness of the inner slope. Based on these tests, prediction formulae have been derived for velocities, the thickness of water layers, and low-exceedance wave overtopping discharges. The estimates of these quantities can be used to characterise the wave loading on the crest and inner slope of dikes, especially as the characteristic wave loading for the initial phase of breaching of dikes initiated by erosion at the crest or inner slope. Besides above mentioned quantities the measurements were used also to obtain more information on for instance mean wave overtopping discharges and on volumes of water within individual overtopping waves.