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Abstract

Shallow coastal zone is extremely dynamic region, where the hydrodynamics are complicated as evident in the refraction, diffraction, shoaling and breaking of water waves, as well as the presence of wave-induced near-shore currents. In this paper, the distribution of waves and wave-induced long-shore currents formed by the breaking of obliquely incident random waves at Leadbetter Beach, Santa Barbara, USA are numerically studied. In the present numerical models, the random water waves are simulated based on the parabolic mild slope equation, and so the wave radiation stresses exerted on waveinduced currents are calculated based on variables in the parabolic mild slope equation, and the wave-induced longshore currents are simulated based on these. The numerical results have also been validated by field data and show good agreement with field data. In the process of numerical modeling, it is found that the bathymetry gradient is determinant to the distribution of wave transformation and wave-induced long-shore current in this coastal zone. In the areas where the bathymetry gradients are greater, the break line is closer from the shoreline, and the radiation stresses and radiation stress gradients are both greater than else areas associating with the presence of the relatively greater maximum wave heights, which result in slightly greater wave-induced long-shore currents, whereas, in the areas where the bathymetry gradients are smaller, the distribution of the break line, wave heights and wave-induced long-shore currents are just opposite. On the side, the wave-induced long-shore current deflects with the variation of bathymetry gradients.

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