Cross-shore Structure of Longshore Currents During Duck94
Falk Feddersen, R.T. Guza, Steve Elgar, T.H.C. Herbers
Proceedings of the 1996 Coastal Engineering Conference
The cross-shore structure of the mean longshore current on a barred beach
is investigated with observations from the Duck94 field experiment.
Maxima of the hourly-averaged longshore current are most
frequently located either slightly inshore of the bar
crest or near the shoreline.
At low tide the longshore current maxima are located
closer to the bar crest, and the current is stronger and narrower
than at high tide.
The tidal cross-shore displacement of the longshore current
maximum is qualitatively consistent with
the observed radiation stress, Sxy although the maximum
currents are displaced shoreward of the maximum Sxy gradients
at both high and low tide. This spatial lag
suggests that some mechanism (such as wave rollers) delays the transfer of
momentum from waves to the mean flow.
Bathymetric longshore inhomogeneities
may also affect the cross-shore structure of the longshore
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