R.T. Guza, E.B. Thornton


Simultaneous measurements were made of the offshore directional spectra of gravity waves, and longshore currents within the surf zone. The goal was to test theories which suggest a direct relationship between mean longshore currents (V) in the surf zone and offshore values of the off axis component of radiation stress (S ). Seventeen minute — xv averages of both S and V showed considerable temporal xv variation, and little or no tendency to vary together. There was also considerable longshore spatial variability of the 1ongshore"current. Attempts to measure gradients of S in the surf zone failed because of small errors in instrument orientation. The measurements suggest that considerable temporal and spatial averaging will generally be required to obtain a representative picture of longshore currents, even if no rip currents are present, due to the presence of "eddy" motions or long edge waves.


longshore current; current; current variability

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