Sediment transport under combined wave-current sheet flow condition is predicted by a wave-period-averaged (WPA) profile model based on a diffusion concept. The total transport rate is split into current induced and wave induced components with associated model parameters. The current induced transport rate is evaluated through vertical profiles of wave-period-averaged flow velocity and sediment concentration. A new wave-induced transport profile is also proposed utilising the wave-induced current residual velocity and period-averaged sediment concentrations. Important sheet flow processes, including turbulence dumpling in the suspension layer, sediment particle’s hindered settling and phase-lag effects are taken into account through a number of model parameters that have been validated by available laboratory measurements. Sediment size gradient is also considered by a conventional multi-fraction approach with special treatment for the sediment mixing parameters for fine and coarse sediment fractions. Model results for both laboratory and field measurements show its encouraging accuracy for the sediment transport prediction under sheet flow condition.
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