In this paper, the concentration and velocity profiles of sediment water mixtures for open-channel flows are modelled numerically and validated with experimental results. A continuum approach, the drift flux model, is used. The mixture consists of volume fractions with different particle sizes. Hindered settling is taken into account with the closure relation of Richardson and Zaki. Transport equations are used for sediment transport. Turbulence is modelled with the LES (large eddy simulation) WALE model. The discretization of the transport and Navier-Stokes equations is done with the finite volume method. The Navier-Stokes equations are solved using a fractional step method. The numerical results are compared with experimental results concerning open-channel flows.