Masters Thesis

Sensitivity analysis and comparison of the velocity method with the power and energy method for assessing fish passage through culverts

Culverts installed at road-stream crossings have been shown to impede or block the passage of migrating fish. This is a problem for adult anadromous fish seeking spawning habitat as well as juveniles and resident species seeking resources including food, protection, and overwintering habitat. Several models have been developed that assess the ability of various fish species to negotiate culverts. The models predict culvert hydraulics and compare them to fish swimming abilities to evaluate passability under a given set of conditions. The FishXing software incorporates an open channel flow hydraulic model with two fish swimming models, "Velocity" and "Power and Energy." This study examines the sensitivity of the FishXing model to the necessary assumptions and compares the two swimming models. Results indicate that the two models are in very close agreement. Both are very sensitive to the choice of high passage design flow. When modeling flow rates in the vicinity of the failure flow rate the FishXing model becomes sensitive to small perturbations in several parameters, particularly fish swimming abilities, culvert slope, and Manning's roughness coefficient. It is recommended, therefore, that new culverts be designed for passage at flow rates at least 10% higher than the high passage flow.

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