One-Dimensional Model for Sediment Transport: An Application to the Design of Silt Basins

Suspended sediment transport modeling has been of great concern to scientists and engineers interested in understanding the complex dynamics of sediment motion in fluid flows. Traditional models based on simplistic hypothesis have been applied in the past in the design of sediment handling and control structures. However, most often the spatially heterogeneous nature of the flow is not properly accounted for, despite the importance that such aspect may have in practical applications. This paper presents a one-dimensional model that incorporates the dispersion transport component in suspended sediment transport, in order to consider the effect associated with the cross-sectional heterogeneity of the velocity and concentration distributions. The longitudinal dispersion coefficient has been evaluated considering different parameterization alternatives. A sensitivity analysis of the model has been developed using dimensionless parameters. The model has been applied to the design of the intake silt basins of the Coca Codo Sinclair hydropower station in Ecuador based on the sediment removal capability of such structures. It has been concluded that accounting for dispersion results in smaller sediment removal efficiency and, therefore, longer silt basins. The comparison made with a simplistic method whose application is widespread for the dimensioning of silt basins, shows that it greatly overestimates their sediment removal capacity.