Current meter performance in the surf zone

Statistics of the nearshore velocity field in the wind-wave frequency band estimated from acoustic Doppler, acoustic travel time, and electromagnetic current meters are similar. Specifically, current meters deployed 25-100 cm above the seafloor in 75-275-cm water depth in conditions that ranged from small-amplitude unbroken waves to bores in the inner surf zone produced si milar estimates of cross-shore velocity spectra, total horizontal and verti cal velocity variance, mean currents, mean wave direction, directional spre ad, and cross-shore velocity skewness and asymmetry. Estimates of seafloor location made with the acoustic Doppler sensors and collocated sonar altime ters differed by less than 5 cm. Deviations from linear theory in the obser ved relationship between pressure and velocity fluctuations increased with increasing ratio of wave height to water depth. The observed covariance bet ween horizontal and vertical orbital velocities also increased with increas ing height to depth ratio, consistent with a vertical flux of cross-shore m omentum associated with wave dissipation in the surf zone.