Experimental study on the influence of vegetationon the velocity distribution of open channel flows

Vegetation is an important feature of natural rivers.Based on the flume experiments with aluminum cylinders simulating rigid vegetation and the laser Doppler velocimetry,the influences of vegetation submergence and density on the velocity distribution are investigated in this study.The analyses indicate that the mean streamwise velocity can be expressed by a function of flow discharge,channel width,water depth and vegetation density for non-submerged vegetated flows.For submerged cases,it is difficult to find a function to express the velocity distribution change with the whole water depth.The velocity deviation between both the upper layer and vegetation layer and the vegetation top become larger with the increment of vegetation submergence and density.The location of the maximum velocity of submerged vegetated flow is higher than that of non-vegetated flow with the same aspect ratio.The vegetation enhances the bed level or reduces the effective aspect ratio of channel.