Numerical model for coastal wave propagation through mild slope zone in the presence of rigid vegetation

Abstract

The study of wave propagation on coastal vegetation field is fundamental to assessing the effectiveness and limitations of vegetation in coastal protection. This paper presents a refraction–diffraction wave model for the investigation of wave propagation through a coastal mild slope zone in the presence of rigid vegetation via numerical simulation. The model is based on the implementation of a module for vegetation-induced wave energy dissipation in the parabolic mild slope equation. The model is capable of simulating both wave refraction and diffraction and economical in computation and may bridge the gap between the wave energy spectrum and the phase-resolved models for wave propagation through coastal vegetation fields. The model is validated through by comparison with experimental results. The model is subsequently applied to a simulation of a wave propagating on a plane in the presence of different patterns of rigid vegetation. The sensitivity of the wave height to the plant height, the diameter and the stem density is investigated by comparison of the numerical results for wave height attenuation that results from different patterns of rigid vegetation. The numerical results show that wave height attenuation due to rigid vegetation has a higher variability for the different rigid plant conditions and that the attenuation of the wave height due to the rigid vegetation increases alongside the plant height under water as well as the diameter and plant stem density. The results further indicate that for wave propagates through coastal rigid vegetation zones with a high plant height under water, large diameter and high stem density, the wave height along the propagating direction is decreased nonlinearly with the increase of the wave propagating distance, and nonlinearity is more obvious for the plant with a higher height under water as well as a larger diameter and higher stem density.