Tidal and low-frequency net displacement in a coastal lagoon

Four, 32-day current meter records from the Indian River lagoon, Florida, are used to characterize flow patterns along the Intracoastal Waterway in a coastal lagoon. The M2 tidal constituent amplitude decreases from 58 cm per s near the Fort Pierce Inlet to only 7 cm per s in the interior of the lagoon. The relative importance of the nontidal variance in the current meter records increases from 0.6% to 26.6% of the total over the same distance. Plots of net displacement over time intervals of one to 16 days suggest relatively rapid flushing near the inlet, but in the interior of the lagoon periods of little or no net movement are increasingly common. Low-frequency motions at all four sites are coherent with windstress over time scales in excess of approximately two days.