Laboratory Study On Wave Energy Dissipation Due To Vegetation On Tidal Flats

Wetland vegetation play an important role in construction and protection of coastal ecological environment,and provide habitats for marine life and aquatic organisms,beautify ecological landscapes,and protect coastal hard levees by reducing waves.Scirpus mariqueter is a perennial salt marsh vegetation and an important pioneer species in the coastal region of the Yangtze river delta,which is of great value in restoration of wetland ecosystems in this region.Meanwhile,Scirpus mariqueter communities also play an important role in attenuating wave energy and thus protecting coastal hard embankment.However,compared with wave attenuation effect of other species in this region,such as Spatina alterniflora and Phragmites australis,wave attenuation effect of Scirpus mariqueter is weaker,and there are few studies on wave energy attenuation effect of Scirpus mariqueter under different specific factors.Therefore,this study will simulate wave dissipation ability of Scirpus mariqueter under different variable conditions.The Froude similarity law was used to construct vegetation model for hydraulic experiments.Through variable designs for plant density,wave height,water depth and wave type,wave energy dissipation ability of the species was investigated.The experimental results are as follows:(1)In the experimental study of wave energy dissipation due to different vegetation densities,The effects of the density of Scirpus mariqueter on wave energy dissipation were studied by controlling other variables.The results showed that wave energy dissipation rate changes with the changes of vegetation densities.The greater the vegetation density is,the more significant the effect of wave energy dissipation becomes.(2)When other variables were the same and wave height was different,wave energy dissipation rate increases nonlinearly,and the amplitude of dissipation gradually became gentle as wave height increases,indicating that the effect of wave dissipation of Scirpus mariqueter increased with the increases of wave height and gradually became constant.(3)When the density of vegetation,wave height and other variables were the same,wave energy dissipation due to vegetation was significantly reduced as the water depth increased.Water depth was below the height of vegetation model(16cm),that was,when vegetation model was not been submerged and just been submerged,wave energy reduction effect was stronger;when water depth was greater than the height of vegetation model,as water depth increased,vegetation model still had a dissipating effect on wave energy dissipation,but the amplitude was obvious reduced.(4)When the other variables were the same,wave dissipation effect of vegetation models of Scirpus mariqueter in regular wave conditions was a little significant than that in irregular wave conditions,but there was no significant difference.To sum up,it is of great significance to protect ecological environment and engineering of coastal wetlands by increasing planting density and planting area of Scirpus mariqueter,and rationally cultivating Scirpus mariqueter communities according to the actual situations in this area and giving full play to its attenuating effect on wave energy.