The influence of submerged coastal structures on nearshore hydrodynamics

Submerged coastal structures (e.g., submerged breakwaters and natural and artificial reefs) are common in nearshore waters globally. By locally reducing water depths from the surrounding bathymetry, they modify the incident wave field, mean currents, runup and sediment transport around them. Although submerged structures are generally assumed to promote coastal protection by dissipating waves offshore and creating sheltered conditions in their lee, their interaction with waves can result in wave-driven circulation patterns that may either promote shoreline accretion or erosion (Ranasinghe et al., 2006). A meta-analysis of the coastal changes resulting from the construction of submerged breakwaters found that, contrary to expectation, in the majority of the cases erosion occurred in their lee (Ranasinghe and Turner, 2006). Therefore, a detailed understanding of the wave structure interactions and resulting hydrodynamics is paramount to predict coastal changes in their lee. Here we explore the detailed wave-driven hydrodynamics in the lee of submerged structures using phase-resolved modelling.