An approach that studies the effects of the dynamic coupling between turbulent flow and sediment in suspension on the mean velocity and the sediment concentration profiles of sediment-laden open-channel flows is systematically developed. The analysis is based on the Boussinesq approximation to the governing equations that treats the mixture of the liquid and sediment as a single fluid with changing density over the flow depth. As a result, it permits the direct systematic comparison between the turbulent flow of clear water and that with suspended sediment. By further employing the mixing length approach for the related turbulent closure problem, the coupling effects on mean velocity and concentration profiles are evaluated, and the resulting distributions are compared with available experimental data. The derived mean velocity distribution contains profiles of existing models as special cases and thus unifies the results of existing major models conceptually and quantitatively. Moreover, the analysis clearly demonstrates the importance of the coupling effect on the suspended sediment concentration profile and, consequently, a more generalized formula of concentration profile is obtained. Although the mean velocity and concentration profiles are the main concern of this paper, the approach establishes a framework for further study of the effects of the dynamic interaction on other physical quantities. ¿ American Geophysical Union 1995