HR: 0800h
AN: H51C-0386    [Abstracts]
TI: Lee Slope Processes on a Small Artificial Flow-Transverse Dune
AU: * Cupp, K C
EM: kcupp@dri.edu
AF: Desert Research Institute, Division of Earth and Ecosystem Science, Reno, NV 89512 United States
AU: Lancaster, N
EM: nick@dri.edu
AF: Desert Research Institute, Division of Earth and Ecosystem Science, Reno, NV 89512 United States
AU: Nickling, W G
EM: nickling@uoguelph.ca
AF: University of Guelph, Wind Erosion Laboratory, Department of Geography, Guelph, ON N1G2W1 Canada
AB: Abstract Sand is primarily deposited on the upper lee slope of dunes by grainfall and is transported downslope by reptation and grainflow (avalanching). Grainfall occurs as saltating sand grains from the stoss slope are blown over the dune crest and fall on the lee slope. Reptation and grainflow then transport these sand grains downslope. The resulting grainflows deposit lobes of sand, primarily on the lower lee slope, which are often preserved in the rock record. An understanding of the processes and conditions that produce lower lee slope deposits could provide important information regarding dune morphology, sand availability and transport rates as well the depositional environment. Despite their importance there have been few studies of grainfall, reptation, and grainflow because the lee slope is a fragile and easily disturbed environment. To overcome these obstacles the Wind Erosion Laboratory, Department of Geography, University of Guelph and the Desert Research Institute have constructed a dune simulation wind tunnel. The wind tunnel contains a small, but true-scale artificial flow-transverse sand dune that is 9 m long, 1.2 m high, and 1 m wide. Experiments in the wind tunnel were run at wind speeds ranging from 5 to 8 m/s measured 30 cm above the dune crest. The dune simulation wind tunnel provides an opportunity to study lee slope processes in a well-constrained environment by controlling wind speeds and direction, dune geometry and composition, and allows for extensive instrumentation and close observation of depositional processes. Experiments on the lee slope in the dune simulation wind tunnel indicate that grainfall decreases exponentially with distance from the crest. Grainfall distance downslope and magnitude increases with increasing wind speeds. Reptation transports and redistributes sand from grainfall primarily on the upper lee slope. Measurements of reptation rates and slope profiles show the formation of a large sediment bulge on the upper lee slope. Grainflow frequency increases with increasing wind speeds. Grainflows commonly originate at or near the point of reattachment of the return cell, in the area between the upper and lower lee slope. The point of reattachment of the return cell and the exponential decay rate of grainfall are two important factors in the location of the point of grainflow origination.
DE: 1809 Desertification
DE: 1815 Erosion
DE: 1824 Geomorphology: general (1625)
DE: 1861 Sedimentation (4863)
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: Fall Meeting 2005