Theoretical and Analytical Approaches for Investigating the Relations between Sediment Transport and Channel Shape

This study investigated the effect of cross sectional geometry on sediment transport rate. The processes of sediment transport are generally associated to environmental management, such as pollution caused by the forming of suspended sediment in the channel network of a watershed and preserving physical habitats and native vegetations, and engineering applications, such as the influence of sediment transport on hydraulic structures and flood control design. Many equations have been proposed for computing the sediment transport, the influence of many variables on sediment transport has been understood; however, the effect of other variables still requires further research. For open channel flow, sediment transport capacity is recognized to be a function of friction slope, flow velocity, grain size, grain roughness and form roughness, the hydraulic radius of the bed section and the type and quantity of vegetation cover. The effect of cross sectional geometry of the channel on sediment transport is one of the variables that need additional investigation. The width-depth ratio (W/d) is a comparative indicator of the channel shape. The width is the total distance across the channel and the depth is the mean depth of the channel. The mean depth is best calculated as total cross-sectional area divided by the top width. Channels with high W/d ratios tend to be shallow and wide, while channels with low (W/d) ratios tend to be narrow and deep. In this study, the effects of the width-depth ratio on sediment transport was demonstrated theoretically by inserting the shape factor in sediment continuity equation and analytically by utilizing the field data sets for Yalobusha River. It was found by utilizing the two approaches as a width-depth ratio increases the sediment transport decreases.

Authors:

• Nidal Hadadin

Keywords:

• Sediment transport
• shape factor
• hydraulicgeometry
• flow discharge
• width depth ratio.

References:

[1] Stream Habitat Restoration Guidelines (2004) Prepared for: Washington
State Aquatic Habitat Guidelines Program.
[2] Schumm, S. A. (1960). The shape of alluvial channels in relation to
sediment type,U.S. Geological Survey, Professional Paper 352-C,
Washington, DC: U.S. Department of the Interior, Geological Survey,
pp. 31-70.
[3] Schumm, S. A. (1971). Fluvial geomorphology: the historical
perspective, and channel adjustment and river. In: Fluvial
geomorphology in river mechanics. PA: Dowden and Culver, Inc., pp.
365-417.
[4] Henderson, F. M. (1966). Open Channel Flow. New York, NY:
MacMillan, 522 pp.
[5] Bagnold, R. A. (1980). An empirical correlation of bedload transport
rates in flumes and natural rivers. Proceeding of the Royal Society,
London, England, pp. 453-473.
[6] Rosgen, D.L. (2001) "A stream channel stability assessment
methodology," in Proceedings, 7th Federal Interagency Sedimentation
Conference. March 25-29. Reno, NV
[7] Gates, T. K., Watson, C. C., and Rodney, J. W. (1998). How spacing of
cross-section surveys affects understanding of variability in channel
hydraulic geometry. In: Abt, S.R, Young-Pezeshk, J., and Watson, C.C.,
Eds., Water Resources Engineering, 98, Proceedings of the International
Water Resources Engineering Conference, ASCE, Vol. 2, pp. 1703-
1708.
[8] Gates, T. K., and Al-Zahrani, M.A. (1996). Spatiotemporal stochastic
open channel flow. I: Simulation experiments. J. Hydraulic Division,
ASCE, 122(HY11):641-651.
[9] USACE (1993). HEC-6 Scour and Deposition in Rivers and Reservoirs,
Hydraulic Reference Manual, U.S. Army Corps of Engineers,
Hydrologic Engineering Center.
[10] Pickup, G. (1976). Adjustment of stream channel shape to hydro- logic
regime. Journal of Hydrology, 30, 365-373
[11] USACE (1997). HEC-RAS river analysis system. U.S. Army Corps of
Engineers, Hydrologic Engineering Center. Survey data for Yalobusha
River by Vicksburg District.
[12] Brownlie, W. R. (1981). Prediction of flow depth and sediment
discharge in open channels. Report No. KH-R-43A, California Institute
of Technology, W. M. Keck Laboratory, Pasedena, CA, 232 pp.
[13] USACE (2008). HEC-RAS river analysis system. Hydraulic Reference
Manual, U.S. Army Corps of Engineers, Hydrologic Engineering Center
[14] Shen, H. W., and Hung, C. S. (1971). An engineering approach to total
bed material load by regression analysis. Proceedings of the
Sedimentation Symposium, Berkeley, CA.