A NOTE ON THE 3-DIMENSIONAL SHEAR-STRESS DISTRIBUTION IN A SURF ZONE

The three-dimensional time-mean shear stress distribution in a surf zo ne is analyzed, thereby determining the vertical distribution of the d riving forces due to wave-breaking. It is found that on a uniform coas t the longshore current can be described as driven by a surface shear stress equal to the cross-shore gradient in the shear component of the radiation stress. The near surface shear stress is found to be in the direction of wave propagation, having a magnitude determined by the d issipation of wave energy. It can be determined as the shear force act ing on the waves from the surface rollers of spilling breakers or brok en waves.