MORPHODYNAMICS OF A CARIBBEAN BEACH FRINGED BY A CORAL REEF

Abstract

The morphological response of two adjacent beaches, on the Mexican Caribbean coast, exposed to the same offshore wave climate is compared, where one of the beaches is fringed by a coral reef and the other is not. Detailed topographic and bathymetric measurements were collected from 2007 to 2011using a differential GPS and double-frequency echo-sounder. Offshore waves were continuously measured by the NOAA 42056 directional buoy, and nearshore waves were measured from May to September 2007 using an acoustic wave and current profiler to validate the use of offshore waves in the analysis of beach morphodynamics. Investigations showed that the beach with the fringing coral reef was the more stable under the same offshore energetic wave conditions of different directions. The implications of the fringing reef on the local hydrodynamics and energy dissipation were evaluated with the SWAN third-generation spectral wave model. The model was first validated with wave measurements collected at intermediate (forereef) and shallow waters (reef lagoon) with Aquadop profilers. Numerical results indicate that during shore-normal energetic conditions, the fringing reef is capable of reducing the incoming wave energy by up to 65%.