Experimental Research on Shear Stress of Submerged Vegetation in Ecological Riverbank

Model experiment about the scour-resisting capability of natural turf reinforced with three-dimensional vegetation net was carried out in flume. The basing principle is that the turf's critical shear stress on bed and the friction velocity in model should be equal to that of prototype. Experimental research illustrate that, the relationship between shear stress above vegetative bed and mean velocity is nonlinear, which is accord with the theoretic analysis; the experimental flow belongs to turbulent flow in hydraulic rough region, since the coarseness of vegetative bed varying with the flow velocity and duration during the scouring process; the Darcy-Weisbach friction factor relates not only to the mean flow velocity, but also to the ratio of average deflected height of vegetation under the action of flow to hydraulic radius of the flume. Furthermore, the critical flow condition of vegetative revetment obtained in this paper can be applied in practical channel directly to evaluate the situation of vegetative revetment destruction.