SEDIMENT SORTING AND BED CHANGES IN LARGE RIVERS

In natural streams the flow varies from time to time, cross-sectional geometry changes and bed material is not uniform. Therefore, in a realistic flow-sediment transport prediction model, it is necessary to incorporate unsteady, non-uniform flow computation components, a sediment transport equation and a grain sorting and armouring algorithm in order tomodel water -sediment movement satisfactorily. The non-linear coupled model incorporated with and without a grain sorting and armouring algorithm for uniform and graded sediments (NCM and NCMG models) were applied to real river data and some sediment routing examples werestudied. The relative merits of the models were also discussed. The Missouri river downstream of Garrison dam is selected as a case study to deal with the most serious problems involved within a natural river. Descriptions of thisriver, the data sets used, and the results of application of the NCM and NCMG models to flow and sediment routing arediscussed in the following sections.

Keywords:

Missouri river , NCM/NCMG models , Grain sorting , Armoring