Caribbean Beach-Face Slopes and Beach Equilibrium Profiles

Field measurements performed on two Caribbean islands revealed that two-dimensional nearshore bottom morphology is well represented by Dean's (1977) model of the beach equilibrium profile, h = A x^m, where h is depth below mean water level at a distance x offshore and A is a scale factor. For the curvature, m, we obtained an average value of approximately m = 1/2 through least squares curve fitting of observed profile data, yielding a more concave and therefore steeper profile inshore than m = 2/3, the average previously reported by Dean for quartz sand beaches in the United States. Furthermore, an objective measure of beach steepness was found to be A^1/m, a quantity which utilizes both of Dean’s parameters and which may serve as a surrogate for the beach-face slope, tan β, on highly concave beaches. Reasonable correlations were found between A^1/m and the environmental parameter, ${{\text{H}}_{\text{b}}}^2/{\text{gDT}}^2$ , where H_b is breaker height, D is sediment grain size, T is wave period and g is gravitational acceleration. Improved prediction of Caribbean beach slopes and beach equilibrium profiles is an important practical result.