Equilibrium beach profile model for reef-protected beaches

A beach equilibrium model for reef-protected beaches is presented. The prof iles analyzed in this work intersect a reef and, consequently, the entire p rofile is not sand rich. The model assumes uniform energy dissipation per u nit volume and considers the wave decay due to the wave breaking over the s ubmerged reef. The resulting beach profile form is similar to the one propo sed 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 sh ape parameter for reef-protected beaches and the A value for non-reef-prote cted beaches is determined using the ANDERSEN and FREDSOE (1983) wave decay model. The proposed relationship is validated using over 50 profiles measu red 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 sim ple function of the sediment grain size or fall velocity. It is also conclu ded that no equilibrium beach profile is possible within a distance of abou t 10 to 30 h, from the edge of the reef, where h(r) is the water depth over the reef.