Role of Armor Roughness in Overtopping Response of Upgraded Multilayer Rubble Mound Breakwaters

Abstract

Wave overtopping needs to be estimated in the design of rubble mound breakwaters, because a high overtopping rate could reduce the capacity and functionality of the structure. The existing formulas, among others, provide estimation of the mean overtopping rate, depending on the hydraulic and structural characteristics. This paper investigates the role of the armor roughness coefficient in the prediction of overtopping. Different rubble mound configurations have been tested by means of two-dimensional physical models. The novelty of the present research lies in providing values of the roughness coefficient for unconventional rubble mound breakwaters. Considering the existing trend and future projections of the sea level and wave climate, there is a need to find upgraded solutions for existing breakwaters, where these structures become more exposed to overtopping risk. Among the possible upgraded solutions, here we consider the case of adding an extra armor layer.