Laboratory experiments on wave-induced fluxes over and through shore-defense detached permeable breakwaters

Wave overtopping flux over coastal structures is normally studied in the laboratory or dedicated field experiments. However, overtopping by wave-induced flux through structures has received less attention. A better understanding of their magnitude is crucial for explanation of the hydrodynamics at the structural backside (transmission of wave energy, transmission of water mass, water set-up, near-shore circulation). This article presents conducted laboratory experiments on permeable breakwaters under different wave tests conditions. A methodology for the analysis of experimental measurements in order to obtain both flux components is proposed. This methodology is based on the mass balance equation that involves the two unknowns (wave overtopping flux and the wave-induced flux) as well as the return flux, the mean free surface level on the rear structure and the permeability coefficients of the structure. The obtained results suggest that the wave-induced filtration flux through the upper part of a permeable breakwater is higher than the wave overtopping flux in case of rare overtopping as well as in case of relatively frequent overtopping.