Individual wave overtopping volumes on mound breakwaters in breaking wave conditions and gentle sea bottoms

Abstract

Mound breakwaters are usually designed to limit the mean wave overtopping rate (q) or the maximum individual wave overtopping volume (V_max). However, rarely do studies focus on wave overtopping volumes on breakwaters in depth-limited breaking wave conditions. This study analyzes 2D physical tests on mound breakwaters with relevant overtopping rates (0.33 ≤ R_c/H_m0 ≤ 2.83) and three armor layers (Cubipod®-1L, rock-2L and cube-2L) in depth-limited breaking wave conditions (0.20 ≤ H_m0/h_s ≤ 0.90) and with two bottom slopes (m = 1/25 and m = 1/50). The 2-parameter Weibull distribution was used to estimate V_max* = V_max/(gH_m0T₀₁ ²) with coefficient of determination R² = 83.3%. In this study, the bottom slope (m = 1/50 and m = 1/25) did not significantly influence V_max or the number of overtopping events, N_ow. During the design phase of a mound breakwater, q is required to use the methods given in the literature to estimate V_max. Thus, q must be estimated for design purposes when measured q is not available. In this study, CLASH Neural Network (CLASH NN) was used to estimate q with R² = 63.6%. If the 2-parameter Weibull distribution proposed in this study is used to estimate V_max with q estimated using CLASH NN, the prediction error of V_max* is R² = 61.7%. With the method presented in this study, the ratio between estimated and measured V_max* falls within the range 1/2 to 2 (90% error band) when q is estimated with CLASH NN. The new estimators derived in this study provide good predictions of N_ow and V_max with a method simpler than those in the literature on overtopped mound breakwaters in depth-limited breaking wave conditions on gentle sea bottoms (1/50 ≤ m ≤ 1/25).