Numerical Modeling Of Bed Changes In Alluvial Channels Considering Nonuniform Bedload Sediment

Abstract

In this research, the basic assumptions and considerations usually proposed in modeling the bed evolution in alluvial channels due to bed load transport are investigated. Theoretical and conceptual approaches are developed searching for new concepts to modify the equations governing the phenomenon. Theoretical development of a modified gradually varied flow formula for alluvial channel is investigated through proposing a set of modification factors to correct the normal flow depth, the critical flow depth and the water slope. These factors are related exponentially to a sediment characteristics parameter. Furthermore, a new formula, sediment transporting energy head, is derived as a function of the sediment properties and incorporated in the development of a modified flow equation. The equation is conceptually derived flow equation, developed for alluvial channels from the basic principles. The modified equation, theoretically and conceptually, is tested and verified using SAFL large-scale laboratory experiments. The newly developed transporting energy slope is used to propose a new bed-load formula as a function of a dimensionless critical shear stress parameter. Accordingly in this research, SEDTREN mobile-bed model is formulated in which the new developments are considered. The model is calibrated using field data of the Rhone River reach, in France, and utilizing the results presented by a previously CARICHAR model presented by Rahuel et al (1989). Parametric evaluation of the SEDTREN model is carried and the verification is shown to be satisfied. Finally, the proposed model is applied to a simplified case for Atbara River reach, in Sudan.