Initiation of bed deformation in meandering channels: A theoretical and numerical study.

It is attempted to investigate whether the initial flow patterns computed by the vertically averaged hydrodynamic model of Silva 1995, 1999 for small sinuosity (theta0 \u3c≈ 30°) and large sinuosity (theta0 \u3e≈ 70°) channels, are able to predict the expected erosion-deposition patterns for both small and large sinuosity channels, by themselves, without invoking cross-circulation. The significance of cross-circulation in producing the characteristic bed deformation patterns in meandering channels is also studied. Moreover, the function relating the variable resistance factor introduced by Silva 1995, 1999, to the channel curvature and the width-to-depth ratio (which, for a flat bed, is a function of only the deflection angle theta 0 and the width-to-depth ratio B/hm), is investigated. For this purpose, two numerical models are developed and used along with the hydrodynamic model of Silva 1995: the sediment transport model, for the computation of the bed deformation; and the meander path model, which facilitates post-processing of the results. A framework to run the three distinct models sequentially, is presented. Some numerical simulations are then performed, making extensive use of experimental conditions and field measurements from the works of other authors. The results of these numerical experiments clearly illustrate that the initial flows computed by the hydrodynamic model of Silva 1995, 1999 can, indeed, produce the characteristic bed deformation patterns for both small and large sinuosity channels, without invoking cross-circulation. It is also shown that cross-circulation plays an insignificant role in determining the overall erosion-deposition patterns on the bed. Finally, the function defining the variable resistance factor , as estimated by Silva 1995, 1999, is modified, and a new form of this function is suggested.Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2000 .B36. Source: Masters Abstracts International, Volume: 40-03, page: 0743. Adviser: Ana M. A. F. Da Silva. Thesis (M.A.Sc.)--University of Windsor (Canada), 2000