Effects of Emergent Vegetation Patterns on Flow Velocity, Turbulence, and Erosion Around River Banks

The effects of two different emergent vegetation patterns on the flow velocity and turbulent kinetic energy (TKE) along the vegetated banks are experimentally investigated with natural reed stems. The results reveal that vegetation patterns can significantly alter the distributions of flow velocity and TKE. At locations for the maximum TKE, closed concentric circles named recirculation cells are observed. The location for the maximum TKE which may induce potential soil erosion for partly vegetated pattern moves forward 1m in comparison with the vegetated pattern. An empirical function is found to describe the variations of TKE along the flow direction. Gentler distributed flow velocity and lower TKE at the rear part of the vegetation section for partly vegetated pattern suggest that vegetation pattern is an important factor for aquatic vegetation recovery in rivers. The findings of the research may provide some guidance for the engineering practices of river ecological restoration with aquatic vegetation.