Numerical study of nearshore hydrodynamics and morphology changes behind offshore breakwaters under actions of waves using a sediment transport model coupled with the SWASH model

This paper presents the results of numerical study on the wave-induced currents and morphology changes due to the complicated interaction between waves and a sandy beach with shore-parallel breakwaters set on. The study was based on the SWASH wave model coupled with a sediment transport model developed in this research. The simulated results of the coupling model were compared with the published laboratory experimental data. The good agreements were obtained for both wave-induced currents and formation of salient and tombolo behind breakwaters. The models were also applied for studying the evolution of wave-induced currents associated with topography changes of a sandy beach. The wave-induced currents and sediment transport processes have a strong relationship and their interaction could reach a quasi-equilibrium state in which the changes of current pattern and bathymetry become very slow. Numerical results of shoreline response mode were also compared with a published empirical formula and confirmed good agreements.