Stream Channel Stability. Appendix J. Numerical Model for Routing Graded Sediments in Alluvial Channels

摘要

This report describes a one-dimensional numerical model designed to simulate sediment transport in natural channels. The physical processes associated with the sediment movement are reproduced using a variety of algorithms. These algorithms incorporate sets of equations that operate on input data in a predetermined sequence to generate output data reproducing the actual physical process. A satisfactory model must include the more relevant aspects of that process. Sediment moves driven by hydrodynamic forces exerted by the flow of water which in many instances is highly time dependent. The sediment transport model must, therefore, account for unsteadiness in sediment movement. The dependence of sediment motion on flow conditions makes it also dependent on the longitudinal variations the flow experiences as a result of stream boundary irregularities. These variations are reflected in the spatial variability of the sediment load distribution. Depending on particle size, some particles may be carried primarily in suspension, while others move entirely as bed load. In addition, depending on flow conditions, particles moving in suspension at one place may be moving as bed load farther downstream.