CROSS-SHORE CURRENTS IN SURF-ZONE MODELING

The paper discusses two aspects of the problem of incorporating the cross-shore circulation into mathematical-numerical nearshore models that also predict wave heights and set-up. One aspect is related to the proper choice of boundary conditions for the undertow, the other one to the determination of the mean bottom shear stress tau OVER BAR //b. Two methods are compared for tau OVER BAR //b and found to yield comparable results. Both are based on the assumption of the existence of a bottom boundary layer with an eddy viscosity much smaller than that created at the surface by breaking waves. Both methods also yield results that very accurately reproduce measured undertow velocity profiles and hence confirm the basic ideas. Finally, it is found that both methods can be used as parts of comprehensive nearshore models. Additonal study results are discussed.