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 (Vmax). 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 ≤ Rc/Hm0 ≤ 2.83) and three armor layers (Cubipod®-1L, rock-2L and cube-2L) in depth-limited breaking wave conditions (0.20 ≤ Hm0/hs ≤ 0.90) and with two bottom slopes (m = 1/25 and m = 1/50). The 2-parameter Weibull distribution was used to estimate Vmax* = Vmax/(gHm0T012) with coefficient of determination R2 = 83.3%. In this study, the bottom slope (m = 1/50 and m = 1/25) did not significantly influence Vmax or the number of overtopping events, Now. During the design phase of a mound breakwater, q is required to use the methods given in the literature to estimate Vmax. 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 Vmax with q estimated using CLASH NN, the prediction error of Vmax* is R2 = 61.7%. With the method presented in this study, the ratio between estimated and measured Vmax* 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 Now and Vmax 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).