Discharge and velocity variation of flows in open channels partially covered with different layered vegetation

The role of vegetation in the natural environment has drawn great interest recently. The vegetation can change the velocity distribution due to its additional resistance on the flow, consequently affecting the nutrient and pollutant transport, and the habitats. Due to the complexity of flow and vegetation interaction, many previous researchers have studied the flow structure of channels with uniform vegetation. Few studies have been done on the flow of open channels partially covered vegetation of different heights on one side of the channel, which commonly exists in natural rivers. Through novel experiments for such a vegetated flow, this paper shows the influence of different layered vegetation on the velocity profile and discharge, which indicates that the velocity in the vegetation zone is significantly smaller than that in the free-flow zone and that the velocity profiles in the short and tall vegetation zones are very different. The flow through the free-flow zone is dominant (about 75%) despite its half width, and its discharge percentage slightly decreases as increasing flow depth.