Quantitative analysis in energy loss and vertical mass transport of various channel restoration structures using physical based modeling

• Main Author: Snyder, Katie May
• Other Authors: Odgaard, A. Jacob
• Format: Others
• Language: English
• Published: University of Iowa 2016
• Subjects: Backwater; Channel Restoration Structures; Iowa Vane; Re-aeration; Stream Barb; Vertical Mass Transport; Civil and Environmental Engineering
• Online Access: https://ir.uiowa.edu/etd/2144; https://ir.uiowa.edu/cgi/viewcontent.cgi?article=6601&context=etd

Physical based modeling was conducted to improve channel restoration efforts through direct comparison of submerged structures of various design and orientations. In-stream structure technologies studied are used to provide bank stabilization, flow control, scour and sediment control, as well as ecological enhancement through turbulent dispersion and vertical mass transport. Quantitative analysis evaluates flow effects induced by common channel restoration structures in their ability to provide mixing in our streams and rivers without significant impacts on flooding through excessive energy loss and backwater effect. Physical, fixed-bed flume experiments were performed under high-Reynolds number subcritical steady-state flow conditions. Theoretical energy loss relationships were developed, compared, and evaluated experimentally for stream barbs, spurs, submerged vanes, blocks and boulders. Extensive surface dye-trace experiments were performed to determine centerline mixing and vertical mass transport produced by stream barbs, vanes and boulders. The research presented in this thesis illustrates that the use of dispersion relationships to assess length of vertical mass transport based on the change in energy slope, and estimated shear velocity, of the channel does not properly correct for boundary layer formation and advection or angular motion produced by channel restoration structures. Submerged vanes were found to provide efficient vertical mixing with minimal energy loss or flood risk, as compared to stream barbs, spurs, blocks, and boulders. The deterioration of water quality and the need to provide bank stabilization with limited flood risk require updated NRCS and ASCE design standards and selection tools for vertical mass transport and energy loss relationships of channel restoration structures. The research conducted in these two studies have provided data for a select number of such structures.