Development and morphodynamics of beaches on horizontal shore platforms on the microtidal southeast coast of Brazil

Abstract

The differences between beaches completely composed of sand and beaches underlain or fronted seaward by hard structures have been well addressed in the current literature. Considering their morphological and morphodynamic particularities, Trenhaile (2004) modeled the accumulation and dynamics of beaches on shore platforms, on mesotidal and macrotidal coast. Although, this model had not been verified or tested in the field, it can be useful to understand coastal geomorphology. Therefore, this study aims to apply the Trenhaile (2004) model to beaches on horizontal shore platforms, located on the microtidal coast of Espírito Santo (Brazil), and validate it using local data. For this, the morphological and morphodynamic particularities of the studied beaches were considered when applying and interpreting the model results. Besides the Trenhaile (2004) model variables, the role of wave runup was considered in the upward growth of the berm and then in the beach height. The model results and field data showed that the gradients and elevations of shore platforms in the study area are suitable to form the beaches while wider shore platforms seem to contribute to the development of wider beaches. The platforms in the study area also influence accommodation space, cross-shore sediment exchanges and beach mobility. Field data was used to test the applicability of Trenhaile's (2004) model in the study area. The model was found to be a potentially useful tool in coastal management helping to understand coastal geomorphology.