Geomorphology and morphodynamics of a sand apron, One Tree Reef, Southern Great Barrier Reef

Harris, D.L., Webster, J.M., De Carli, E.V. and Vila-Concejo, A., 2011. Geomorphology and morphodynamics of a sand apron, One Tree Reef, southern Great Barrier Reef. Journal of Coastal Research, SI 64 (Proceedings of the 11th International Coastal Symposium), 760 - 764. Szczecin, Poland, ISSN 0749-0208 Sand aprons are ubiquitous formations in coral reef systems that are important components of reef evolution and ecological functioning. Despite this little is known of the morphodynamic processes that drive their evolution. One Tree reef is a mature lagoonal patch reef located in the southern Great Barrier Reef (GBR) that includes a well developed southern sand apron. Current knowledge of sand apron evolution suggests that they are active progradational features which are predominately driven by wave generated swash. However, there have been few process based assessments that actively measure the evolution of these formations. This study investigates the sediment transport processes on the One Tree reef southern sand apron through direct hydrodynamic measurement, morphological surveying and analysis of sediment textural parameters. Results indicate that sediment transport pathways and current flow direction are associated with morphological formations. Channel depressions in the sand apron are ebb dominated with sediment transport pathways and residual currents moving in the direction of these ebb channels. Shallower sections of the sand apron are flood/swash dominated with sediment transport in the direction of the lagoon. These results show that sediment transport on the sand apron is complex and can occur under average hydrodynamic conditions. They also indicate that there are similarities between the processes acting in coral reef settings and typical siliciclastic systems such as tidal inlets and estuaries.