Obliquely incident irregular waves in surf and swash zones

A time-dependent numerical model is developed for predicting the free surface elevation and depth-averaged cross-shore and alongshore velocities in the swash and surf zones under obliquely incident irregular waves. The assumption of small incident angles is made to simplify the finite-amplitude, shallow-water equations and allow the computation of the cross-shore fluid motion using the existing one-dimensional model for normally incident waves. The developed numerical model is compared with available field data. The time-dependent model is shown to be capable of predicting the cross-shore variations of the root-mean-square wave height and longshore current in the surf zone. The numerical model predicts large cross-shore and alongshore velocities near the shoreline. The causes of these large velocities are examined but cannot be ascertained for lack of velocity data near the shoreline.