“Stream Bed and Water Profile Responses to In-Channel Restoration Structures in a Stream Meander”
Grade control and flow deflection structures (i.e. cross-vanes and J-hooks) are commonly installed in stream channels as stream restoration treatments. Few studies have pre- and post-treatment data to evaluate the impact of these structures on channel hydraulic gradients and morphology, both of which have implications on hyporheic exchange. We developed a physical model of a meandering stream – with and without a cross-vane and 6 J-hooks – on a mobile-bed river table, and applied close-range photogrammetry techniques to obtain 3-D water and ground surface profiles with sub-millimeter accuracy of our stream model. Results indicated that the cross-vane caused an average local head loss that represented 16% of the total stream reach head loss. Backwater caused by the cross-vane steepened the closest water table profile by an additional 4.2%, and was the primary driver of statistically significant hydraulic gradient increases. Installation of the in-channel structures resulted in 34% decrease in average net bank erosion, statistically greater bank sediment deposition volume, and different spatial patterns of surface-water to groundwater gradient and patterns of bank and bed scour.