Author(s): Graham Macky
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Keywords: No Keywords
Abstract: The evolution of straight uniform gravel-bed channels is modelled numerically and variations to the model are tested in order to discover why experimental stable channels are narrower and deeper than predicted using existing theory. This discrepancy is insensitive to several features of the description of the physics and to initial conditions. The diffusivity of mobile bed particles is advanced as a likely cause of the discrepancy between experiment and theory. Bedload diffusivity, which allows a minority of bedload particles to be transported up a sideslope, has been observed experimentally but has not previously been incorporated into theories and models describing channel development. When it is incorporated, the modified numerical model predicts that a cross-channel gradient in downstream shear stress can negate the effect of an opposing side slope, and that a stable region of mobile bed therefore need not be level as previously assumed. Stable channels can thus be narrower and deeper than conventional theory predicts, in closer agreement with experimental data.
Year: 2010