Influence of Antecedent Topography on Coastal Evolution as Tested by the Shoreface Translation-Barrier Model (STM)

Abstract

This paper demonstrates that antecedent topography played a very important role on the coastal evolution of Rio Grande do SuI (RS) in Brazil during the Holocene. By modeling the last 9 ka of sea level change using the general morphology of the present shelf as the substrate over which barriers have translated a successful reconstruction was obtained showing the position of the coastline at the time of the Post-Glacial Marine Transgression maximum (5 ka). Not only has the antecedent topography played an important role in the definition of the coastal shape of RS, it has also pre-determined the type of coastal barrier: prograded barriers along coastal reentrances, and receded and mainland beach barriers along coastal projections. Analysis of sediment budget indicated that more than half of sediments needed for progradation along coastal reentrances came from the shelf. The Shoreface Translation-Barrier Model (STM) was used to recreate Holocene coastal shorelines and to simulate sediment volumes.