HR: 17:25h
AN: H54E-06    [Abstracts]
TI: Experimental Study of Different Sized Tracer Particles in a Gravel-Bed Laboratory Flume
AU: * Hill, K M
EM: kmhill@umn.edu
AF: St. Anthony Falls Laboratory, University of Minnesota, 2 Third Ave. SE, Minneapolis, MN 55414, United States
AU: DellAngelo, L A
EM: dell0047@umn.edu
AF: St. Anthony Falls Laboratory, University of Minnesota, 2 Third Ave. SE, Minneapolis, MN 55414, United States
AB: The prediction of particle movement in bedload transport is complicated by the fact that particles tend to segregate by size. Well-known examples in gravel-bed rivers include armouring, where the surface layer is coarser than the subsurface layer, and grain size patchiness, where relatively well-sorted gravel patches form along the river bed. The mechanics that drive these sorting effects have important implications for river restoration efforts and the management of river systems. We study how bedload transport movements vary according to the size of the sediment particles in a simple experimental system. We use a gravel bed sediment-feed flume to perform controlled experiments under conditions similar to the bank-full discharge in natural gravel-bed rivers. To minimize spatial and temporal variations that might otherwise obfuscate the results, we operate the flume under plane-bed equilibrium transport conditions, with well-sorted unimodal gravel as bed material. Tracer particles, colored according to their size and initial position in the bed, indicate how streamwise and vertical movements of particles depend on particle size. We found that even under plane-bed equilibrium transport conditions, particles very close in size have measurably different streamwise and vertical transport. A simple scaling relationship models the distribution function along the bed. A stochastic model we developed incorporating each phase of the bedload transport describes this behavior well. We discuss these results, as well as their implications for size sorting in alluvial systems.
DE: 3265 Stochastic processes (3235, 4468, 4475, 7857)
DE: 4460 Pattern formation
DE: 4475 Scaling: spatial and temporal (1872, 3270, 4277)
DE: 4558 Sediment transport (1862)
SC: Hydrology [H]
MN: 2007 Fall Meeting