Wave Overtopping of Rock and Stepped Coastal Revestments With Very Shallow Foreshores

Abstract

Coastal revetments are commonly constructed at the land-sea boundary to control shoreline retreat and protect infrastructure from coastal hazards, such as wave overtopping and coastal flooding. An innovative approach to enhance existing rock revetments involves incorporating steps, which can improve coastal amenities by providing seating and viewing areas. However, current empirical wave overtopping formulations do not consider hybrid configurations combining rock and stepped elements. This study investigates overtopping performance for both conventional and hybrid rock revetment solutions. To address the lack of empirical data for such hybrid structures - commonly found along the Portuguese coast - physical modelling tests have been conducted with two revetment cross-sections: (i) a conventional double layer rock armour slope and (ii) a hybrid one where the upper layer of rock was replaced with concrete steps. Existing semi-empirical formulations provided in the EurOtop Manual were compared with measured values of the relative mean wave overtopping discharge. Results showed that semi-empirical formulations underpredict the relative mean wave overtopping discharge values by up to a factor of 33 for rock-only revetments and up to 23 for hybrid rock and stepped revetments.