Study on wave attenuation in following and opposing currents due to rigid vegetation

Abstract

The regular wave attenuation in following and opposing currents due to rigid, emergent vegetation has been studied by physical and numerical simulation in this study. Firstly, laboratory experiments were conducted to investigate the effect of currents on wave attenuation due to vegetation. Then, to overcome the limitation of the experimental conditions, a numerical model, based on the Boussinesq equations and validated by the experimental results, was applied to further investigate the effects of current velocity, vegetation density and water depth on wave attenuation due to vegetation in currents with larger α (the ratio of current velocity to the amplitude of the horizontal wave orbital velocity) range. The results show that both following and opposing currents can enhance or suppress wave attenuation due to vegetation depending on α. For the studied vegetation densities and water depths, the effect of wave attenuation due to vegetation in currents first decreases and then increases with the increase of α. Moreover, wave attenuation due to vegetation in currents is increased with the increase of vegetation density and decreased with the increase of water depth, and both of them have no influence on the relationship between relative wave height decay and α.