Vegetation effects on cross-sectional flow in a large amplitude meandering bend

摘要

Cross-stream circulation, which develops in meandering bends, exerts an important role in velocity redistribution. This paper investigates how the presence of vegetation could affect the evolution pattern of cross-stream flow along a high-curvature meandering bend. The analysis is conducted with the aid of data collected in a meandering laboratory flume over non-vegetated and vegetated beds. The experiments reveal that, once the vegetation is introduced, the flow pattern determined by the channel's curvature is interrupted. In the presence of vegetation, the central-region circulation cell seems to be divided into thin circulation cells developing at the top of the vegetated layer and the counter-rotating cell, which develops within the outer-bank region; it includes a fluid area more extended than that observed in the absence of vegetation. As consequence, in the presence of vegetation, the core of high velocity is always found away from the outer bank.