Wave overtopping at rubble mound breakwaters with submerged berms

One of the trend topics in coastal engineering concerns the adaptation of existing coastal structures to the growing environmental loads caused by climate change. Rising sea levels, storm surges, and intensified wave action are expected to significantly increase wave overtopping, threatening the effectiveness of traditional coastal defenses. This study focuses on assessing wave overtopping at conventional rubble mound breakwaters (RMB) modified by a submerged berm. While previous studies have shown that emerged berms on the seaward slope can reduce overtopping, limited attention has been given to the performance of submerged berms. The aim is to evaluate their effectiveness. Then, a combined physical and numerical modeling approach has been adopted. Laboratory tests have been conducted at the Environmental and Maritime Hydraulic Laboratory (LIam) of the University of L’Aquila, using a 45 m wave flume equipped with a piston-type wave generator and active reflection control. Three configurations have been tested: a conventional RMB and two RMBs with submerged berms of different lengths. Four tests have been performed to analyze the sensitivity of overtopping to sea level rise and to verify whether berms mitigate this effect. Results confirmed that higher water levels greatly increase overtopping, while submerged berms significantly reduce it, especially when longer. To further investigate, numerical simulations have been performed using the IH2VOF model, solving RANS and VARANS equations. The model, validated against experimental data, proved suitable for parametric studies varying berm geometry (berm length and height). The goal is to derive a predictive coefficient, linking the overtopping reduction to berm geometry. Data analysis is ongoing and results will be presented at the conference.