Field measurements of infragravity wave motions were collected on a natural barred beach with a cross-shore array of co-located pressure sensors and bi-directional current meters extending from the beach face to 5m depth. Cross-shore variations of infragravity pressure and velocity variances are examined in relation to the incident wave energy and the mean alongshore current. During low-energy incident wave conditions, infragravity pressure variances decrease with increasing depth qualitatively consistent with the theoretically predicted unshoaling and trapping of graivty waves. However, during high-energy incident wave conditions, the observed infragravity pressure variances are nearly uniform across the surf zone, suggestign strong scattering effects in a wide surf zone. Strong tidal modulatios of both infragravity velocity variances and the mean longshore current indicate that shear instabilities of the longshore current contribute significantly to the infragravity velocity field.
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