Abstract: The unsteady open channel flow conditions are described using the Saint-Venant equations, which regulate the flow in an alluvial stream. A one-dimensional mathematical model for calculating channel bed aggradation and degradation has been developed. In this analysis, the Mac-Cormack explicit finite difference scheme was used. This scheme is second-order accurate, manages shocks and discontinuities in the solution without special treatment, and allows simultaneous solution of the water and sediment equations, which eliminates the need for iterations. The addition of clear water flow to a stream that was previously in equilibrium leads to degradation of the bed and banks. Similarly, withdrawing clear water flow from an equilibrium stream causes aggradation. These processes will proceed until a new equilibrium is reached. The present study investigated the problems of aggradation and degradation caused by the removal and addition of clear water from/to an alluvial stream of constant width and in equilibrium. In the case of aggradation and degradation channel bed consisting of uniform sediments, the transient bed and water profiles were predicted using the developed mathematical model. The data of Yadav (1992) were used for the verification of model. The model is able to predict transient bed and water surface profiles satisfactorily.

Keywords: Numerical modelling, Aggradation, Degradation, Mac-Cormack finite difference scheme, Alluvial channel

| DOI: 10.17148/IARJSET.2021.8516