How do tides circulate water through a barrier island lagoon?

Water circulation in a barrier island lagoon is primarily governed by the width of tidal inlets, the tidal range, and the volume of runoff from the surrounding land.1

Tidal currents move water into and out of the lagoon through these inlets, where they reach their maximum velocities. Because these channels experience the strongest currents, they typically contain only coarse sediment, while finer sediments settle in the quieter, more protected areas of the lagoon.12

Beyond standard tidal action, circulation can be influenced by other factors:
* Wind: Strong winds can force water into the lagoon, creating an outflowing current once the wind subsides. This process can also generate seiches, which are rhythmic oscillations of water within the basin.1
* River Discharge: In estuarine lagoons, the flow of a major river significantly impacts circulation and can increase current velocities, especially during flood events.1
* Storm Events: Severe storms or hurricanes can breach or overtop barrier islands, creating temporary washover channels that alter the lagoon's configuration and water exchange patterns.3