Comparison of Empirical Equations' Application in the Advection-Dispersion Equation (ADE) on Sediment Transport Modelling

This paper describes the effect of applying the appropriate methods for estimating some empirical coefficients in the Advection-Dispersion Equation (ADE) on the accurate suspended sediment concentration predictions. In this study three existing empirical sediment discharge equations, four particles fall velocity formulas and three dispersion equations used in the ADE were evaluated for accurate estimation of suspended sediment concentrations. The main model used was the one dimensional FASTER model in which, the Saint Venant equations were numerically solved by the finite difference central with a staggered implicit scheme and the numerical method used for the solution of the ADE was a combination of the implicit finite volume central and ULTIMATE QUICKEST schemes. Since the source of FASTER program was available, a computer model was developed and all considered experimental equations for dispersion coefficient, sediment discharges and particles fall velocity were included to the model, enabling the user to apply any combination of these equations. The model was then applied to Karoon River located in south west of Iran for two separate periods. Comparison of the predicted suspended sediment concentrations with the corresponding measured values at the survey site showed that the Van Rijn sediment discharge model, Fischer et al dispersion equation and Cheng settling velocity equation performed very well in comparison with all considered experimental equations. It was found that using an appropriate experimental equation for these important parameters in the ADE can significantly increase the accuracy of estimation of suspended sediment concentrations along rivers.