Estudo das mudanças na linha de costa e vulnerabilidade costeira associada no litoral sul do Rio de Janeiro (SE Brasil)

Abstract

The coastline pattern is indicative of the trends to which the coastal system is subjected, since it is the contact interface of the continent-ocean transition. In this context, the Restinga da Marambaia and the Macumba/Recreio-Barra da Tijuca beach arcs (SE Brazil) were evaluated as to shoreline response to meteo-oceanographic forcings at the long and medium term time scales, as well as their vulnerability degrees were mapped. On the long-term scale (1986-2018), Landsat satellite imagery, wave reanalysis data from the WaveWatch3 model, meteorological records, and mean sea level measurements were used. At the medium-term scale (2016-2018), eleven topographic profiles were surveyed, with sediment sampling, at Macumba/Recreio-Barra beaches, in addition to the analysis of oceanographic buoy records in deep and shallow waters. Finally, this information allowed the elaboration of a Coastal Vulnerability Index to erosion and flooding. In general, 18% of the coastline is eroded, 52% is stable, and 30% is advancing. In the analyzed period, about 400 storm events were accounted for, which during the La Niña years were more energetic and culminated in more severe erosion. The sea level in the region shows a tendency to increase (1.93 mm/year). The combination of these results and the degree of urban occupation of the studied beaches show low vulnerability in the western sector of Marambaia, while the central and extreme eastern sectors are highly vulnerable. In Macumba the western sector exhibits low vulnerability, in contrast with the eastern sector that is very vulnerable. In the Recreio-Barra arc, vulnerability increases from west to east. These are indicative that human influence plays an important role in areas that are naturally prone to high vulnerability, requiring a greater understanding of the natural conditions associated with human interventions.