Abstract
Tidal currents, waves and longshore currents combine their actions at tidal passes to make complex patterns of interaction. In general, the longshore drift will be somewhat disrupted at tidal passes, but will continue downcoast. Quite commonly, however, there is enough disruption of the longshore current so that local reversals of the current direction are seen on the downdrift side of passes.
Although this local reversal has been attributed to a number of causes, including wave refraction complications, another possibility is that eddy currents, or gyres are formed due to offshore shoaling and downdrift deflection of tidal currents.
These current reversals downdrift from passes can cause several problems, including 1) erosion of the beach, 2) the need for costly maintenance, and 3) the possibility of poor planning if the process is not understood.
