Experimental and numerical investigation of the influence of submerged breakwaters on wave hydrodynamics of tsunami-like waves over coral reefs

In recent years, anthropogenic activities have significantly intensified on coral reef ecosystems. Concurrently, the combined effects of climate change and rising sea levels are accelerating the degradation of coral reefs, substantially altering their wave hydrodynamic characteristics. As a result, coral reefs and associated island systems in tropical and subtropical regions are becoming increasingly susceptible to tsunami hazards. Therefore, there is an urgent need to implement effective coastal protection strategies to mitigate flooding risks in low-lying coastal zones located behind these reefs during tsunami events. Submerged breakwaters (SBWs), as a conventional yet effective coastal defense structure, have been widely adopted in various coastal environments globally. However, their protective efficacy in the context of coral reef settings remains insufficiently understood. This study presents an experimental investigation into the hydrodynamic effects of SBWs on tsunami-like wave propagation over coral reefs. Key influencing parameters, including submergence depth, incident wave height, and breakwater positioning, are systematically analyzed. Furthermore, high-resolution numerical simulations are conducted to evaluate additional factors such as backreef slope and breakwater slope. The results indicate that SBWs can significantly enhance wave breaking, reduce wave height across the reef flat, and diminish wave runup. It is anticipated that the findings of this research will contribute to a deeper understanding within the scientific community regarding the hydrodynamic interactions between SBWs and tsunami-like waves over coral reef topographies.