Equilibrium Beach Profile Model for Reef-Protected Beaches

Abstract

A beach equilibrium model for reef-protected beaches is presented. The profiles analyzed in this work intersect a reef and, consequently, the entire profile is not sand rich. The model assumes uniform energy dissipation per unit volume and considers the wave decay due to the wave breaking over the submerged reef. The resulting beach profile form is similar to the one proposed by LARSON and KRAUS (1989); however, the profile shape parameter is not the same as the A value used in the usual DEAN (1977) equilibrium profile, due to the wave decay dependence. A simple relationship between the new shape parameter for reef-protected beaches and the A value for non-reef-protected beaches is   determined using the ANDERSEN and FREDSOE (1983) wave decay model. The proposed relationship is validated using over 50 profiles measured on seven beaches. It is concluded that the shape parameter usually used in equilibrium profile models can not be represented in all cases by a simple function of the sediment grain size or fall velocity. It is also concluded that no equilibrium beach profile is possible within a distance of about 10 to 30 h, from the edge of the reef, where h, is the water depth over the reef.