The transformation of random wave heights during shoaling, including waves breaking in the surf zone, was measured with an extensive array of instruments in the field. The initially Rayleigh height distributions in 10‐m depth were observed to be modified by shoaling and breaking into new distributions which are again nearly Rayleigh but with some energy loss. Using locally measured Hrms, the Rayleigh distribution describes the measured central moments of H1/3 and H1/10 with average errors of −0.2% and −1.8%, respectively. The Rayleigh distribution is used to describe the random nature of wave heights in a single‐parameter transformation model based on energy flux balance. The energy losses associated with wave breaking are parameterized using observed breaking wave distributions coupled with a periodic bore dissipation model. Using incident waves measured in 10‐m depth as input conditions, the model predicts Hrms at shoreward locations within a rms error of ±9%. The single free parameter of the model, a constant B representing the fraction of foam on the face of a wave, was chosen to best fit the data. The resulting large value of B implies that the simple periodic bore dissipation function substantially underestimates the actual dissipation.

Run-up (swash) oscillations were measured on a gently sloping beach face for a variety of incident wave conditions. Run-up energy spectra at wind wave frequencies show anf -3 dependence and energy levels that are independent of incident wave height. This suggests saturation. In contrast, run-up energy at surf beat periods increase approximately linearly with increasing incident wave energy. Thus, in the inner surf zone, where wave breaking limits the energy at wind wave frequencies, the principal manifestation of large incident wind waves is energetic surf beat.

[1] The morphodynamic response of the nearshore zone of an embayed beach induced by wave groups is examined with a numerical model. The model utilizes the nonlinear shallow water equations to phase resolve the mean and infragravity motions in combination with an advection-diffusion equation for the sediment transport. The sediment transport associated with the short-wave asymmetry is accounted for by means of a time-integrated contribution of the wave nonlinearity using stream function theory. The two-dimensional (2-D) computations consider wave group energy made up of directionally spread, short waves with a zero mean approach angle with respect to the shore normal, incident on an initially alongshore uniform barred beach. Prior to the 2-D computations, the model is calibrated with prototype flume measurements of waves, currents, and bed level changes during erosive and accretive conditions. The most prominent feature of the 2-D model computations is the development of an alongshore quasi-periodic bathymetry of shoals cut by rip channels. Without directional spreading, the smallest alongshore separation of the rip channels is obtained, and the beach response is self-organizing in nature. Introducing a small amount of directional spreading (less than 2°) results in a strong increase in the alongshore length scales as the beach response changes from self-organizing to being quasi-forced. A further increase in directional spreading leads again to smaller length scales. The hypothesized correlation between the observed rip spacing and wave group forced edge waves over the initially alongshore uniform bathymetry is not found. However, there is a correlation between the alongshore length scales of the wave group-induced quasi-steady flow circulations and the eventual alongshore spacing of the rip channels. This suggests that the scouring associated with the quasi-steady flow induced by the initial wave groups triggers the development of rip channels via a positive feedback mechanism in which the small scour holes start attracting more and more discharge.

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