河岸植被覆盖影响下的河流演化动力特性分析

Dynamic characteristics of river evolution under the influence of riparian vegetation cover

河岸植被对河道的水流运动、主槽稳定及河湾迁移等均有重要的影响,尤其是在洪水期河流的演化过程中。为分析不同密度植被护岸对河流动力过程的影响响应,本文采用自然模型实验,通过改变河岸植被种植密度及单双岸布设方式,模拟河岸有无植被种植的河流演化过程。给定相同的造床流量、坡降、泥沙粒径等水沙边界条件,设定控制变量为河岸植被覆盖率,分别为0%,20%,40%,80%。实验结果表明:(1)单岸植被覆盖其主流稳定性较两岸植被覆盖为差;(2)河岸植被越密集,水流对河床的局部扰动越强烈,河演达到稳定状态周期越长;(3)两岸植被覆盖的蜿蜒河道其稳定曲率随植被覆盖率增大而减小,较大的水流剪切力会造成较大的河湾迁移。

Riparian vegetation has an important influence on the flow movement,the stability of main channel and river bend migration,especially in the process of fluvial evolution during flood period. In order to analyze the effect of different density vegetation revetment on river dynamic process,the natural model experiment was used to simulate the river evolution process by changing the planting density and unilateraland bilateral arrangement of riparian vegetation. Given the same discharge,gradient,grain size and otherwater and sediment boundary conditions,set the control variable for riparian vegetation coverage,respectively,0%,20%,40%,80%. The results show that：（1） The mainstream stability of unilateral vegetation coverage is worse than that of the bilateral vegetation;（2） the more dense the riparian vegetation is, the stronger the local disturbance of the water flow to the riverbed,the longer the period of river evolution reaches a stable state;（3） the stable curvature of the meandering channel covered by the bilateral vegetation decreases with the increase of vegetation coverage. The larger flow shear force will result in larger river bend migration.