Dynamic Analysis of Vegetated Water Flows

Abstract

Substantial energy losses occur when water flows over vegetated ground. Vegetation enhances surface resistance and decreases flow velocity, which results in energy loss. Since the ground is considered to be permeable, both surface and subsurface water flow are simultaneously resolved. The objectives of this study are to analyze the dynamic effects of vegetated flows including the distributions of velocity, shear stress, and energy by an analytical approach for better understanding the physical mechanism. An inflection point in the velocity distribution is found as that in conventional research for denser vegetation cases with a constant water depth. A new dimensionless parameter, δ2, related to permeability of porous medium and clearly affecting the shear stress distribution is proposed. The value of δ2 approximately equals 9.5 as the ratio of the water layer depth to the vegetation layer height is unity, then the shear stresses at the interface of water/vegetation layers and at the ground surface appear equivalent and reach a maximum. The results also reveal that most of the energy loss occurs near the interface of water/vegetation layers.