Dynamics of a high-energy dissipative surf zone

~Vright, L.D., Guza, R.T. and Short, A.D., 1982. Dynamics of a high-energy dissipative surf zone. Mar. Geol., 45: 41--62. Pressure and horizontal current (u, v) time series were measured at different positions across the inner 150 m of a wide (~500 m) surf zone of a microtidal high wave-energy beach. Incident waves had average heights of 3--4 m with maxima of 5 m and periods of 12 to 15 sec. Bores of broken waves diminished in height at a nearly constant rate as they progressed across the surf zone. The ratio, % of bore height H to local water depth h was everywhere less than 1 for even the highest bores and was on the order of 0.40 for the significant bores at incident wave frequencies. Rip circulation was weak or absent but a moderate longshore current was present. Shore-normal flows were vertically segregated with strong net onshore flows prevailing just below the surface accompanied by weaker net seaward flows near the bed. Spectra of water surface oscillations, ~ as determined from pressure, u, and v reveal that most of the energy in the inner surf zone was at infragravity frequencies (periods greater than 30 sec). Shoreward decay of wave energy at incident wave frequencies was accompanied by shoreward growth of infragravity energy. Near the beach the infragravity oscillations had heights on the order of 1 m. Cross-spectra show that the infragravity oscillations were standing in the shore-normal direction. From the relative magnitudes of infragravity versus incident wave currents, it is inferred that the surf beat may be an order of magnitude more important than incident waves to the transport of sediment in the inner surf zone.