HR: 1330h
AN: H52A-1156    [PDF]
TI: Bedload Transport in Gravel-Bed Streams: Collaborative Field and Flume Research Using Tracer Stones
AU: * Brown, T
EM: tmbrown@u.washington.edu
AF: University of Washington, Department of Civil and Environmental Engineering Box 352700, Seattle, WA 98195-2700 United States
AU: Wong, M
EM: wong0228@umn.edu
AF: University of Minnesota, St. Anthony Falls Laboratory 2 3rd Ave SE, Minneapolis, MN 55414 United States
AU: DeVries, P
EM: pdevries@r2usa.com
AF: R2 Resource Consultants, 15250 NE 95th St., Redmond, WA 98052 United States
AU: Parker, G
EM: parke002@umn.edu
AF: University of Minnesota, St. Anthony Falls Laboratory 2 3rd Ave SE, Minneapolis, MN 55414 United States
AU: Burges, S
EM: sburges@u.washington.edu
AF: University of Washington, Department of Civil and Environmental Engineering Box 352700, Seattle, WA 98195-2700 United States
AB: Estimates of bedload transport rates in gravel-bed streams are typically derived from empirical formulae or from sampling. A less common, but promising, approach involves the use of tracer stones and the derivation of the bedload transport rate from individual particle displacement history. A combination of field and experimental (flume) work has begun in a collaborative effort to produce, using tracer data, i) a general predictive formulation for streamwise tracer movement (the longitudinal displacement problem), and ii) a probabilistic form of the Exner equation for sediment continuity and bed elevation fluctuations involving erosion and deposition functions (the vertical mixing problem). We are conducting field and flume studies to identify a relationship between the measured horizontal displacement of tracer stones and the associated excess shear stress over a small increment of time, and to predict the vertical sorting of the sediment among the bed, and the influence of this on the bedload transport rate. Two sediment-recirculation flumes 0.50-m wide and 9-m and 27-m in length have been set up at St. Anthony Falls Lab for this purpose. In addition, two streams with flume-like reaches of adequate length have been selected in western Washington. We present preliminary results that illustrate the types of sampling problems that this research is investigating, and raise fundamental questions that remain to be addressed more thoroughly in a coupled field and flume study than has occurred to date. To these ends, painted tracers stones (magnetized for field purposes) will be tracked in terms of their horizontal and vertical displacement in the field and flume. While sonar will be used in the lab, scour monitors will be used in the field to obtain a predictor of the probability density function for the bed elevation fluctuations.
DE: 1800 HYDROLOGY
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2003 Fall Meeting