Nearshore processes on a fringing reef.

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A field experiment was conducted on Grand Cayman Island during 1972 and on Barbados during 1973 to determine the characteristics of wave-dominated nearshore processes in a fringing reef. Results from these field experiments indicate that nearshore processes on reefs occur in a distinctly different pattern from that on sandy coasts. Deepwater wave characteristics are significantly modified by reef morphology before the waves reach the shoreline. Shelf morphologic features produce a significant reduction in wave height (20%), owing to the combined effects of friction, scattering, and reflection, at a rate significantly greater than that occurring on sandy coasts. At the fringing reef crest energy loss resulting from breaking produces a substantial reduction in wave height which is accompanied by an extreme modification to the wave spectrum, including the introduction of multiple low-frequency peaks. Wave-induced currents cross the fringing reef crest and interact with lagoon geometry to produce a circulation pattern in the back-reef lagoon characterized by velocities which increase toward the main lagoon outlet. Sediment thickness within the lagoon decreases toward the lagoon opening and increases toward the shoreline. This pattern is in qualitative agreement with the generally predicted lagoon current movement. (A) (Microfiche)

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