Accurate predictions of the total rate of longshore sand transport (LST) and its cross-shore distribution pattern in the surf zone are central to many coastal engineering studies. Present understanding and methods for calculating the LST rate are largely developed based on field studies (e.g., Komar and Inman 1970; Inman et al. 1981; Kraus et al. 1982; Bodge and Dean 1987a, b; Dean 1989; Schoonees and Theron 1993; Miller 1998; Wang, Kraus, and Davis 1998; Wang 1998; Wang and Kraus 1999; Miller 1999). The Coastal Engineering Research Center (CERC) formula (Shore Protection Manual 1984), which is based on field measurements, is often used to calculate the total LST rate. Accuracy of the CERC formula is believed to be 30-50 percent and several parameters that logically might influence LST are excluded in the formula, such as breaker type and grain size. The GENESIS shoreline change model, a tool commonly used in shore protection and beach-fill project design, utilizes the CERC formula. In the GENESIS model, the cross-shore distribution of LST is assumed to be uniform across the surf zone. Laboratory data (Bodge 1986; and Kamphuis 1991) and field data (Zenkovitch 1960; Ingle 1966; Bodge and Dean 1987a, b; Miller 1998) suggest that the distribution is not uniform.
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