Numerical Model Study on the Wave and Current Control by Coastal Vegetation

Abstract

In this study, three-dimensional numerical simulations were conducted to investigate the effect of the coastal vegetation on the wave and current controls. The model was modified to apply three-dimensional Navier-Stokes solver based on porous body model for the direct simulation of the wave energy dissipation through the vegetation. The new formula of a vegetation drag coefficient based on the wave-vegetation interaction was proposed through the hydraulic model tests and the formula was implemented to the model. The modified numerical model was tested and the results were compared with the experimental results to verify the numerical model capability. The model results well reproduced the wave energy dissipation inside the vegetation zone. Moreover, the numerical modeling was also conducted for the hydrodynamics on permeable submerged breakwater and the model results were compared with the results of vegetation. Inside the vegetation zone, the wave energy slowly decreased and the water level behind the vegetation was not increased seriously. Since the vegetation reduces the wave energy gradually, the width of the vegetation zone is an important factor for the effective control of the wave energy. Because the water level behind the vegetation zone did not increase too much, the return flow was small compared with that in the gap between the submerged breakwater cases. Therefore, if we deploy coastal vegetation effectively, this may be a better measure than coastal structures in terms of effectiveness and economy.