Coastal current

A coastal current is the net flow of water near the shore that moves sediment along and across a coast. The longshore current, driven by waves breaking at an angle in the surf zone, carries the littoral drift that feeds and starves beaches and shoals navigation channels. Tidal, wind-driven, and density currents act alongside it and set cross-shore exchange. Current speed and direction govern dredging frequency at an entrance, scour at piers and breakwater heads, and the dispersion of a dredging sediment plume. The CERC and Kamphuis longshore-transport formulas relate breaking-wave height and angle to the drift rate the current carries.