HR: 0800h
AN: H31A-1274    [Abstracts]
TI: The Role of Hydraulic Geometry on Hydraulic Jump Regime and Energy Dissipation at River Steps
AU: * Wyrick, J
EM: jrwyrick@ucdavis.edu
AF: University of California - Davis, 219 Veihmeyer Hall, LAWR, Davis, CA 95616 United States
AU: Pasternack, G
EM: gpast@ucdavis.edu
AF: University of California - Davis, 219 Veihmeyer Hall, LAWR, Davis, CA 95616 United States
AB: One driver for evolution within fluvial channels is the river step. This transient feature in turn becomes the focus of other geomorphic processes, such as knickpoint migration and channel scouring. Inherent to a river step is the associated hydraulic jump, whose regime is a primary control on channel erosion. In turn, the hydraulic jump regime is controlled by the independent variables discharge, sediment load, geology, and wind. A new conceptual model linking these variables to step dynamics and bed incision has been developed and quantified using a numerical code. Previously, the model delineated jump regimes and quantified energy dissipation accounting for jump submergence and discharge in a uniform channel. In this next stage, the equations have been further generalized to account for the role of channel geometry upstream and downstream of a step. For specific combinations of upstream and downstream hydraulic geometries, the model shows that hydraulic jumps almost always occur at lower discharges, but diverge to either complete supercritical flow (downstream widening channels) or complete submergence (downstream narrowing channels) as discharge increases. For the wide range of hydraulic geometries used in the study, the model showed that channels with lower slopes were more likely to have submerged jumps. This model has also been applied to an actual river step on the Bear River in north-central California and the results compared to measured conditions.
DE: 1825 Geomorphology: fluvial (1625)
DE: 1847 Modeling
DE: 1856 River channels (0483, 0744)
SC: Hydrology [H]
MN: Fall Meeting 2005