Reduction of wave overtopping on a smooth dike by means of a parapet

A return wall or parapet is a very efficient construction built to reduce wave overtopping over sea structures. One of its main advantages is that this relative small construction can be built in a dike without increasing the crest height yet creating a major reduction in wave overtopping. In this paper only non-breaking waves attacking smooth dikes are investigated. A normal smooth dike, a smooth dike with vertical wall and a smooth dike with parapet have been tested. The results lead to reduction factors for a vertical wall or a parapet that can be introduced in the van der Meer formulas for wave overtopping over smooth dikes. The optimal geometry of the parapet has been subject of the research as well.