The existence of vegetation not only significantly affects flow, but also increases resistance to flow. To understand the effect of vegetation on flow velocity and water depth, a
semi-analytical approach was proposed to study flow passing over vegetated areas under a uniform rainfall event. In this study, the flow region was divided into three layers-- homogenous water layer,water-plant mixing layer, and infinitely thick permeable soil layer (briefly denoted by water layer,vegetation layer, and soil layer).The flow of the water layer was governed by the Navier-Stokes equations.
The vegetation and soil were both regarded as porous media and Song’s (1993) laminar model modified from Biot’s theory of poroelasticity was applied. The semi-closed solutions were then obtained via the Runge-Kutta method. Three cases--submerged vegetation, emergent vegetation and submerged-emergent vegetation were discussed. The results were compared with those of the unplanted ground case, showing the flow velocity obviously decreases with vegetation. Additionally, the effect of slope, rainfall intensity, and permeability on the flow and the resistance resulting from vegetation were also discussed. The results are believed to be helpful in environmental and ecological engineering
design and surface water management.
Key Words : Poro-elasticity theory, overland flow, uniform rainfall, vegetation.