Numerical Study For Wave Propagation In Rigid Vegetation Area

Costal vegetation can protect the shoreline from the erosion caused by the wave efficiently. The wave energy will be dissipated partially in the process of wave propagation through the vegetation area and the wave height will attenuate accordingly, which reduced the wave erosion effects on the beach; Meanwhile, the ability of wave's material transportation will be reduced with the attenuation of wave height, which has important impact on the evolution of coastal hydrodynamic environment. However, with the developments of the ocean resource and the building of the coastal constructions, the original distribution form and number of vegetation was changed, which influenced the hydrodynamic environment and the ability of wave's material transportation badly. Therefore, the research about the wave propagation under the effects of coastal vegetation has important significance in analyzing the coastal hydrodynamics and beach stability.The numerical model for wave propagation in rigid vegetation water was developed based on Boussinesq equation in which the drag force due to vegetation was added, on the basis of reliability verification for this model, the model was used to test the effects of vegetation parameters as well as the incident wave parameters on wave attenuation. Then we concluded as follows.(1) In the process of wave propagation through vegetation area, the ratio of wave height attention and wave energy attenuation due to vegetation increase with the increase of plant density and plant diameter.(2) In the process of wave propagation through vegetation area, the ratio of wave energy attenuation is closely related to the arrangement of vegetation area. Suppose that the amount of vegetation is constant, the vegetation arrangement of multi segment can increase the ratio of wave energy attenuation compared with the single segment, but with the increase of segment number, the ratio tends to be stable.(3) In the process of wave propagation through vegetation area, the ratio of wave height attention and wave energy attenuation due to vegetation increase with the increase of incident wave height.(4) In the process of solitary wave run-up at sloping bed, the characteristic parameters of vegetation effect importantly the wave propagation. The numerical results show that vegetation can effectively dissipate wave energy and reduce wave run-up and the water level will increase in front of the vegetation area. Besides, the time of climbing slope becomes later and receding process time becomes earlier due to vegetation's effects. With the increase of vegetation density and submerged height, the ratio of wave energy dissipation and wave height becomes bigger, the water level in front of the vegetation becomes deeper, the time of climbing slope becomes later and the receding process time becomes earlier. Besides, the arrangement way of vegetation on the slope effects the solitary wave propagation.