HR: 16:25h
AN: H34A-02    [Abstracts]
TI: An Assessment of Pulsed Flows on Foothill Yellow-legged Frog Habitat Hydraulics in a Regulated River using Two-Dimensional Hydrodynamic Modeling
AU: * Yarnell, S
EM: yarnell@geology.ucdavis.edu
AF: University of California, Davis, Center for Watershed Sciences, Davis, CA 95616, United States
AU: Lind, A
EM: alind@fs.fed.us
AF: U.S. Forest Service, Sierra Nevada Research Center, 2121 Second Street, Ste. A-101, Davis, CA 95616, United States
AU: Kupferberg, S
EM: skupferberg@pacbell.net
AF: Questa Engineering, 818 Mendocino Avenue, Berkeley, CA 94707, United States
AB: We used a freely available two-dimensional model, River2D, to evaluate changes in habitat suitability and availability for Foothill yellow-legged frog egg masses and tadpoles during pulsed flow events. Two study sites in Northern California, one on the unregulated South Fork Eel River and the other on the regulated North Fork Feather River, were selected for modeling. Simulated depths and velocities agreed well with measured field values. When coupled with a definition of breeding habitat suitability that encompassed the variability of field- measured values and the range of error within the model output, the model accurately predicted suitable breeding locations throughout the survey reach. Using data on percentages of egg mass and tadpole loss associated with increased velocities, we assessed several scenarios of how pulsed flows affected habitat availability and suitability. In a seasonal (spring) pulse scenario, lower discharges provided the greatest weighted usable area for breeding, but higher initial discharges provided the greatest buffering capacity against lethal increases in velocity. In an aseasonal (summer) pulse scenario, only 20-30% of the suitable tadpole habitat in the unregulated site and <5% of the suitable habitat in the regulated site remained suitable during the pulse regardless of initial flow level. In both scenarios, the unregulated study site provided 2-3 times the buffering capacity of the regulated site. This was likely due to differences in channel morphology; the regulated site had an entrenched channel with steep banks, while the unregulated site had an asymmetric cross-sectional shape where shallow overbank areas provided refuge from high velocities as flows fluctuated. This type of model-based methodology that can evaluate effects from flow fluctuation on individuals and local habitat conditions for multiple life stages would be useful for managing Foothill yellow-legged frog or similar aquatic species in regulated river systems.
DE: 1808 Dams
DE: 1847 Modeling
DE: 1856 River channels (0483, 0744)
DE: 1860 Streamflow
DE: 1880 Water management (6334)
SC: Hydrology [H]
MN: 2007 Fall Meeting