Equilibrium Flow Areas of Inlets on Sandy Coasts

The minimum flow area below mean sea level in the entrance channel of a tidal inlet on a sandy coast is a unique function of the tidal prism. Bottom material size, presence or absence of jetties, and magnitude of the littoral drift appear not to affect this relationship, within the accuracy of available data. The magnitude of the currents through the inlet channel are determined by the range of tide. The tendency for wave-induced littoral currents to transport sand towards an inlet and to reduce its flow area should vary with the intensity of wave action, but the data available do not show wide deviations from the equilibrium area, possibly because hydrographic surveys are made during calm weather. Reduction in the tidal prism of an inlet will reduce the equilibrium flow area at the minimum cross section of the inlet channel.