Numerical simulation of circulation in a Caribbean-type backreef lagoon

A numerical model based on the vertically intergrated equations of motion and continuity was used to simulate circulation in a shallow, well-mixed, Caribbean-type backreef lagoon. As the focus of previous research, Great Pond Bay, St. Croix, provided a suitable study site. Tides, wind, and the effect of waves impinging on the reef were incorporated within the model. Direction of simulated flow under various wind and wave regimes agrees well with patterns found during current meter and drogue tracking experiments. When momentum transfer over the reef due to wave breaking and set-up is added, the magnitude of flow within the lagoon, ranging 5–30 cm/s, also compares favorably to in situ measurements. Model results indicate a relatively rapid and realistic flushing period of less than one day. Results of this study indicate that numerical modeling techniques potentially offer an accurate and cost-effective means to predict the pattern of water movement within coral-reef lagoons.