Small-scale morphology related to wave and current parameters across the surf zone

Small-scale beach morphology (scales < 5 m) height variations were measured by combining the CRAB survey with bed elevation acquired from a 1 MHZ sonic altimeter mounted on the CRAB during the October phase of the DUCK94 experiment. Bedform types were observed using a 500kHZ side-scan sonar also mounted on the CRAB. Corollary waves and currents were measured. Three cases were examined in detail: mild waves and weak longshore currents resulting in wave ripples everywhere; storm waves with strong longshore currents resulting in lunate and straight crested megaripples in the trough of the barred beach; and narrow banded, normally incident waves with a strong rip current resulting in a relatively planar bed everywhere except in the throat of the rip where magaripples were measured. The predictive wave ripple height and length equations of Nielsen (1981) worked reasonably well for mild wave conditions, but did not predict ripples during moderate wave conditions. The wavenumber spectra were generally broad, indicating that newly formed ripples coexisted with residual ripples from the past to form complex, multi-scaled ripple patterns. (MM)http://archive.org/details/smallscalemorpho109457481U.S. Navy (U.S.N.) author