HR: 14:50h
AN: H33J-05    [Abstracts]
TI: Evaluation of Pool-Riffle Maintenance Processes in an Incised Urban Channel Using a 3D Hydrodynamic Model: Implications for Stream Restoration
AU: * Schwartz, J S
EM: jschwart@utk.edu
AF: University of Tennessee, Dept. of Civil & Environmental Engineering, Knoxville, TN 37996, United States
AU: Neff, K J
EM: kneff1@utk.edu
AF: University of Tennessee, Dept. of Civil & Environmental Engineering, Knoxville, TN 37996, United States
AU: Dworak, F E
EM: fdworak@geiconsultants.com
AF: GEI Consultants, Inc., 6950 South Potomac Street, Suite 300, Centennial, CO 80112, United States
AB: Channel adjustments due to watershed urbanization include incision, widening, and loss of pool-riffle structure, a result of modifications in hydrology, local hydraulics, and geomorphic processes. In theory, pool-riffle sequences are maintained hydraulically by channel-scale helical flow patterns, both in meandering and straight channels. Through the use of FLOW-3Dâ, a three-dimensional (3D) computational fluid dynamics model, flow structures were characterized in an incised straight channel with woody bank vegetation impeding near-bank flood flows. The 3D model was applied to a 110-m section of Beaver Creek in Knox County, Tennessee, which included a survey of channel topography and 122 bank trees. Three model simulations were conducted during bankfull flow stage; they were: 1) channel with bank trees, representing the channel's current state, 2) trees removed from the channel, and 3) a restoration design using three clusters of original trees in the channel to promote flow acceleration-deceleration patterns. In addition, one simulation was conducted to evaluate model performance, in which an acoustic Doppler velocimeter was used to collect instream 3D velocity data during a one-half bankfull flow event. Overall, simulations suggest flow structures along the study reach are highly influenced by bank trees, do not scale to the channel, and may possibly explain pool-riffle loss in incised channels with woody bank vegetation. In the restoration design simulation, flow acceleration-deceleration patterns were successfully induced along the channel. This simulation illustrated the importance of considering bank structure and hydraulic roughness in designs to promote pool-riffle maintenance, rather than relying solely on bed weir structures.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1847 Modeling
DE: 1856 River channels (0483, 0744)
DE: 1860 Streamflow
SC: Hydrology [H]
MN: 2007 Fall Meeting