The Foredunes and Their Function of Protection due Coastal Floods: Validation of Two Erosive Models as a Tool for the Coastal Management Applied at the Beach of Mar Grosso, RS

Abstract

Since 2016, Brazil has developed the National Adaptation Plan for Climate Changes (PNA, in Portuguese). Elaborated by the Ministry of Environment (Brasil, 2016) this plan intends to reduce the national vulnerability due to climate changes and the implementation of risk management associated to this phenomenon. This Plan gives special attention to the coastal zones of the country. In the state of Rio Grande do Sul (RS), the Coastal Zone is subject to the impact of high-energy meteorological events during autumn and winter period.  Storm surges and floods are common during and after the passage of these events, putting people, infrastructure and ecosystems in danger. The foredunes constitute the continent’s first line of natural defense against the ocean’s floods and coastal erosion. Therefore, the present study applies the Dune Erosion Rule’s model in order to quantify the foredunes’ erosion on the south shoreline of Rio Grande do Sul State (RS). This application seeks to validate the model for the beaches of RS. The performed characterization of the erosion process was based on the Storm Impact Scale, categorizing the analyzed events within four categories.  The dune erosion model had shown high values of dune erosion due to the configuration of the used parameters, which must be modified in order to improve its applicability on the shoreline of RS. The combined application of these two models has relevant potential for direct use in the management of coastal ecosystems, since after being properly adapted to the local scale, it infers in the necessary dimensions and characteristics so that the foredunes can effectively fulfill the function of coastal protection.