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Title: OPTICAL MEASUREMENTS OF GRAIN VELOCITY AND SEDIMENT CONCENTRATION IN SHALLOW UPLAND FLOWS

Author
item SURYADEVARD, M. - UNIV. OF MISSISSIPPI
item PRASAD, S. - UNIV. OF MISSISSIPPI
item Romkens, Mathias

Submitted to: International Symposium on River Sedimentation
Publication Type: Proceedings
Publication Acceptance Date: 9/13/2004
Publication Date: 10/21/2004
Citation: Suryadevard, M.R., Prasad, S.N., Romkens, M.J. 2004. Optical measurements of grain velocity and sediment concentration in shallow upland flows. International Symposium on River Sedimentation. CD ROM

Interpretive Summary: Soil erosioin on upland areas is a highly complex phenomenon involving rainwater in overland flow. The ability of surface flow to transport soil particles is determined by a host of factors such as the flow rate, flow velocity, particle size and quantity, surface roughness conditions, etc. This study presents data from optical measurements of sediment particle velocities in shallow flow, in which the sediment concentration was varied from a very low volume concentration of about 0.001 cc/cc to a 24-fold increase. The data show that the mode of particle movement changes from saltation to movement in clusters, domain, and stripes with increased concentrations. The significance of these findings is the changing nature of the mode of transport and the corresponding impact on the transport capacity.

Technical Abstract: This paper presents optical probe measurements on sediments in saltating flow in a laboratory flume for three particle sizes. Poly-dispersed sand particles exhibit greater resistance to the flow compared to the mono-dispersed glass beads. Cross-correlation of signals between twin Photonic probe data show smaller grain velocities with relatively higher solid concentration values due to grain collisions. However, turbulence modulation and reduction in the particle drag at relatively small solid concentration values depict acceleration of grains in a certain range. Grain velocity is correlated with the solid concentration, fall velocity, and the fluid Froude number.