WAVE OVERTOPPING OVER A SEA DIKE WITH STILLING WAVE BASIN AND SHALLOW FORESHORE

In the past decade, sea dikes were renovated at different locations along the Belgian coast using the concept of a stilling wave basin. Although different in geometrical details, all sea dikes use the same concept: (i) the impact of the incoming waves is reduced by the first seaward wall; (ii) overtopping waves are reflected by the second landward wall, positioned at a certain distance of the first wall on the dike’s crest and (iii) the overtopped volume is flowing back through voids in the seaward wall. In this way, overtopping discharges can be kept to tolerable limits whilst maintaining the crest elevation as low as possible (to minimize visual impact). In general, wave overtopping is calculated using numerical modelling. However, the specific geometry of a dike with stilling wave basin is a complicating factor in a (relatively) fast and accurate modelling approach. For an efficient assessment of the expected average wave overtopping discharge, employing a wave overtopping formula would be preferred.