Thesis
Guidance to ensure the stability of sediment in streambed simulation culverts for prolonged fish passage
Washington State University
Master of Science (MS), Washington State University
12/2020
DOI:
https://doi.org/10.7273/000004180
Handle:
https://hdl.handle.net/2376/124987
Abstract
Fish barriers prevent the movement of fish to their spawning grounds. The subsequent reduction of spawning grounds has led to widespread population decreases in the Pacific Northwest. In response, Washington State implemented new design policies in 1999 to replace the most common barriers, culverts. The new "stream simulation culverts" incorporate a sediment lining, providing an environment more conducive to movement. Design of the simulated streambeds must balance engineering and ecosystem factors, but there is little guidance on how to maximize the lifespan while preserving the overall channel shape and a low-flow channel to maximize passage at low flows. This research investigated design characteristics of coarse material (coarse bands) to a simulated streambed in a flume. The first objective was to examine if coarse band(s) can stabilize a channel without eliminating sediment transport. Three characteristics were tested: particle size, number of coarse bands, and the spacing between coarse bands. The second objective was to determine any relationship between the number and spacing of coarse bands and channel stabilization. Experimental streambeds were subjected to one, two-and-a-half, and five-year flood frequency events. Cross-section profiles were measured after each flood event and were analyzed to quantify the stability and sediment transport. Six coarse band layouts were tested that varied the amount and number of coarse bands. Four coarse bands increased stability and reduced sediment transport by 55.5%, whereas two coarse bands at three channel widths reduced sediment transport by 49.4%. Finally, the industry-standard HEC-RAS 1D and 2D models were used to simulate the experiments and determine if the relative changes in mobility could be inferred from standard numerical models. Two layouts were modeled using HEC-RAS but only HEC-RAS 1D simulations reflected experimental results. The main implication of these finding is that, at least for now, laboratory experimentation or field trials are needed to assess the performance of coarse bands in-stream simulation culverts. The guidelines for construction of coarse band(s): material size is D150, mimics channel cross-section, perpendicular to the flow, 1-2 particle diameters above and extend two particle diameters below the against streambed.
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Details
- Title
- Guidance to ensure the stability of sediment in streambed simulation culverts for prolonged fish passage
- Creators
- Tyler Tracy Fouty
- Contributors
- Nicholas B Engdahl (Advisor) - Washington State University, Civil and Environmental Engineering, Department of
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900896440901842
- Language
- English
- Resource Type
- Thesis