HR: 1340h
AN: H43A-0364    [Abstracts]
TI: Evolution of the size distribution of fine suspended sediments during downstream transport: Role of stream-subsurface exchange
AU: * Ren, J
EM: jianhong.ren@tamuk.edu
AF: Department of Environmental and Civil Engineering, Texas A&M University-Kingsville , MSC 213, Kingsville, TX 78363 United States
AU: Packman, A I
EM: a-packman@northwestern.edu
AF: Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road , Evanston, IL 60208 United States
AB: In the classical view of fine sediment transport and deposition in streams, particles are expected to be removed simply by direct sedimentation onto the streambed. However, recent research has demonstrated that fine sediments can propagate into pore spaces in the streambed due to hyporheic exchange and be removed from suspension by a combination of physical and chemical (cohesive) processes. This behavior can significantly alter fine sediment size distributions during downstream transport because the mobility of fine particles and their attachment to bed sediment grains are both functions of particle size. To illustrate the effects of these processes, we simulated the stream-subsurface exchange and deposition of suspended sediments with a bimodal size distribution under different flow conditions. We also applied this approach to analyze the results of two laboratory flume observations of suspended sediment deposition. Model simulations clearly show that the rate of particle deposition increases with increasing particle size. Thus, larger particles are preferentially removed from mixtures, resulting in a fining of the suspension over time. The temporal evolution of the particle size distribution is also a strong function of the stream flow rate. These results clearly demonstrate the effects of stream-subsurface exchange on the temporal evolution of the suspended sediment size distribution during downstream transport.
DE: 4809 Colloids
DE: 4863 Sedimentation
DE: 4558 Sediment transport
DE: 1815 Erosion and sedimentation
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting