Numerical Study For Wave Propagation In Vegetation Field Based On SWAN

The extreme weather frequently occurred,which was affected by global climate change.Marine disasters like the tsunami and storm surge were a serious threat to people's life and property.It has found that the vegetation in coastal field could effectively dissipate wave energy.Therefore,it has certain academic value and engineering application value to enlarge the study for wave propagation in vegetation field and to have an in-depth understanding for the influence of vegetation on wave attenuation under extreme weather conditions.The present paper studied the wave propagation in vegetation field based on SWAN.The main contents of this paper were as follows:(1)The SWAN-VEG model was used to test the influence of vegetation parameters and incident wave parameters on wave height's attenuation.The results showed that wave height's attenuation due to vegetation increases with the increase of plant height,plant density and the width of plant area as well as incident wave height and wave period.The dissipating effect was not obvious with very small plant height,plant density and incident wave height.The dissipating effect was stable when the wave period reached a certain value.Wave height has better attenuation effect in the front of plant area.The width of plant area had no effect on the attenuation process of wave height,and it decided the wave height at the end of plant area.(2)During extreme weather conditions,the marshes were in submerged condition,and the wave heights were bigger.The numerical model was based on SWAN,and it was validated on wave propagations that approach a salt marsh at Hellegat in the Western Scheldt estuary in the Netherlands.The established model was then applied to a simulation of a wave propagating on the salt marsh in the presence of different high waves and large water depths that occur during storms.The numerical results showed that the wave height decreases along the propagating direction on the salt marsh,which was resulted from depth-induced wave breaking,bottom friction and wave attenuation by vegetation.The dissipating effect was more obvious with larger incident wave heights and smaller water depths.Moreover,by analyzing the effect of vegetation to wave attenuation at salt marsh,it was found that the presence of vegetation leads to a more gradual dissipation of wave energy,and prevents intense wave breaking to occur.(3)To simulate the propagation of typhoon wave in the coastal sea area,the mangrove coast of Zhanjiang was chosen as the study area,the Typhoon KAI-TAK illustrated by the Holland typhoon model was selected as the meteorological background,and the three level nested grids were set to establish the SWAN model.Based on the typhoon wave results,the numerical model for typhoon wave propagation in vegetation field was built by arranging vegetation along Zhanjiang coast,and the vegetation impacts on typhoon wave propagation were analyzed by the model.The results showed that the wave height's attenuation due to vegetation increases with the increase of plant height and plant density,as well as the width of plant area.