Models for Surf Zone Dynamics

Longshore current models have been tested using NSTS measurements at Leadbetter Beach, Santa Barbara. The NSTS provided data on nearshore currents for a variety of wave conditions including narrow banded (in frequency and direction) swell waves of small and moderate height and wide banded waves during local storms. The theoretical models include a two-dimensional, finite element, monochromatic wave driven model (Wu et al., 1985) and one-dimensional (i. e., no longshore variations) random wave driven model (Thornton and Guza, 1986). These models assume the waves are narrow banded in frequency and direction and use a single frequency and direction to describe the input wave field. In keeping with the narrow band wave assumption, data from four days with narrow band swell (3–6 February) were used for comparisons. Empirical orthogonal eigenfunctions were used to find longshore current patterns during all directional wave conditions (Guza et al., 1986). This chapter summarizes these papers and presents additional comparisons to a simple one-dimensional monochromatic wave model (Longuet-Higgins, 1970).