The effect of bottom roughness on sediment transport due to three-dimensional wave-induced streaming in the seabed boundary layer has been investigated for following and opposing linear propagating waves and current where the wave propagation forms a non-zero angle with the current. Visualizations are given by mean Eulerian wave-averaged suspended flux profiles, as well as the time series of bed shear stress over a wave period. The bedload transport rate along with suspended flux and total sediment transport rate have been presented. For linear propagating waves, the turbulence is induced by the Longuet-Higgins streaming and the classical wave-current interaction. Sediment transport is always in the wave propagation direction for the Longuet-Higgins streaming and increases with decreasing bottom roughness, or as the mean grain diameter decreases
