The vegetation affects the flow process and water environment, thus drawing increasing attention to river environment management. Previous research is mainly focused on flow through vegetation in a channel with fully covered single-layer vegetation. However, in natural rivers, different heights’ vegetation often co-exists along one or two sides of a river. This paper experimentally studies how the flow velocity distribution is affected by the two different-layered vegetation allocated along two sides of an open-channel. The vegetation was simulated by dowels of two heights, 10 cm and 20 cm, and arranged in a parallel pattern along two sides of a flume under partially submerged conditions. The velocities along a cross-section were measured by Acoustic Doppler Velocimetry (ADV). The results of lateral velocity distribution show that a strong shear layer exists between vegetation and non-vegetation zones, indicating the retarding effect of vegetation. Meanwhile, as the flow depth increases, the relative velocity in the free flow zone decreases compared with that in the vegetated region, indicating that vegetation resistance to the flow decreases as increasing depth under the same vegetation configuration. These ?ndings would help understand the role of multi-layered vegetation in riparian management.
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