The influence of a crown wall on wave overtopping over rubble mound structures

The crest of a breakwater is often equipped with a crown wall with multiple functions such as a border of the pedestrian walkway, support of the rubble mound or concrete armour units, and reduction of the wave overtopping over the structure in storm conditions. However, the knowledge on how a crown wall influences the overtopping discharge is yet still limited. EurOtop (2016) advises to take the maximum of the crest freeboard Rc and the armour freeboard Ac in case a crown wall is present, and to use the average between Ac and Rc when no crown wall is present. This advice is based on expert judgement rather than on experimental research. The goal of the present work is to carry out experimental research and confirm or update the advice on overtopping over a crown wall for rubble mound structures