Effects of Emergent Riparian Vegetation on Spatially Averaged and Turbulent Flow within an Experimental Channel

Interest has been renewed in understanding the interactions between flow, vegetation, and sediment transport because of the growing popularity of river restoration and streambank stability programs utilizing vegetation. To further this research, an experimental channel was systematically vegetated with emergent, wooden dowels of varying density to document how the vegetation alters both the spatially averaged and turbulent flow. Results show that (1) surface waves, vortical structures, flow separation, and dead zones were associated with the vegetation zones, and these turbulent flow structures greatly enhanced fluid mixing processes, and (2) as vegetation density increased, flow resistance, bed shear stress, flow depth, and thalweg sinuosity increased, while flow velocity decreased. Design considerations for stream restoration programs using managed vegetation plantings to trigger desired morphologic and ecologic responses are presented and discussed.