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.