Master's Thesis

Stream Bed and Water Profile Responses to In-Channel Restoration Structures in a Stream Meander

Highlights: 

  • Designed river table (6ft x 12ft x 1ft) with digital water flow controller, downstream V-notch weir, groundwater discharge holes, recirculating water system, and sliding rails for mounting ultrasonic sensors and other equipment.
  • Constructed scaled, mobile-bed, physical model of meandering river channel and in-channel rock vane structures.
  • Wired and tested ultrasonic distance sensors for detecting river stage changes with sub-millimeter precision.
  • Performed close range photogrammetry and produced digital elevation models of scaled physical river model in ADAM Technology 3DM Analyst software.
  • Used ESRI ArcGIS software to perform geospatial analyses of water depth, water surface profile, stream bedform, and bank erosion and deposition volumes.
    Abstract:
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.

Subpages (1): River Table
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