Physical Modeling Study on Hydrodynamic Performance of Vertical Seawalls Defended by Submerged Reef Breakwaters

An increase in sea levels and wave conditions due to climate change may affect the functionality of existing vertical seawalls. Submerged reef breakwaters are being used as retrofits to the existing vertical seawalls to control or prevent damage to coastal infrastructure from coastal flooding. The present study is based on laboratory experiments with a physical model to investigate the effectiveness of impermeable submerged breakwaters as a retrofit to vertical seawalls. This work considers a vertical seawall made of acrylic with a 1:15 smooth, impermeable foreshore slope. A total of 168 tests are considered, including regular and random waves. Random waves are generated using the Joint North Sea Wave Project (JONSWAP) spectrum. Each test consists of approximately 1,000 pseudorandom waves with a peak enhancement factor of 3.3. Key parameters, including wave run-ups, reflection characteristics, wave-induced pressures, wave forces, and wave overtopping, are measured for various wave conditions. The reductions in wave run-ups, forces, and mean wave overtopping are examined for different relative water depths and wave heights. The analysis of experimental measurements reveals a significant reduction in both horizontal forces and mean wave overtopping discharges for the given wave conditions. The new predictive relationships are proposed to evaluate the forces and the mean overtopping discharge of retrofitted vertical seawalls with submerged reef breakwaters.