| The profiles of the suspended sediment concentration by a combinedwave-current outside the surf zone is investigated in this paper. As field measurementsindicate the time-varying components of the velocity and concentration make asignificant contribution to the net sediment flux, the solution for these components isincluded in the development of the model.Since the solution using the time-invariant model of Wikramanayake was muchsimpler and valid for the full range of wave-current interaction, this model wasselected for the suspended sediment concentration model. In the hydrodynamic model,based on the different characteristics of wave and current motion scales to separate thelinearized boundary layer equation, the governing equations controlling the wave andcurrent interaction are derived. The hydrodynamic model can predict the velocitiesand bottom shear stresses which are the important parameters for the suspendedsediment concentration model.Based on the sediment convective-diffusion equation, the vertical profiles of thesuspended sediment concentration in a combined wave-current flow has beenanalyzed. The mean suspended sediment concentration predicted by the model isfound to be in good agreement with the measured profiles. The model can alsocalculate the instantaneous suspended sediment concentration under the wave-currentflow. The time-variation of the calculated time series of the concentration is found toshow some agreement with that of the observed time series. And in the governingequation of instantaneous suspended sediment concentration, the ratio of the velocityto wave celerity is taken into consideration, which is more reasonable.
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