REGIONAL COASTLINE CHANGES AND FUTURE PREDICTED SCENARIO ON SOUTHERN BRAZIL

Abstract

The Rio Grande do Sul (RS) coastline consists of a 615 km long sandy barrier, with a NE-SW orientation. The genesis of this geographical area is related to Quaternary sea-level changes, with a complex Lagoon-barrier system. This study presents a compilation of decades of studies about short-term monitoring and long-term projections conducted by the two local main research centers on the subject. Trends in shoreline behavior between 2002 to 2013 were analyzed. The specific causes of these variations are not yet fully understood. However, some factors are likely to be responsible for coastline behavior in the long and short term. The main erosive hotspots found along the RS coastline are influenced by wave energy due to the refraction caused by the bathymetric features and coastline orientation. The Cassino Beach sector, however, has a pronounced progradation which in the long term can be mainly related to its orientation, and more recently due to jetties built at the Patos Lagoon inlet, which provided more sediment retention of the prevailing net longshore drift to the northeast. This research also offers a review about shoreline changes along the four existing inlets. Coastal vulnerability to sea-level rise (SLR) analyzed through coastline recession rates in long-term scenarios (2030 and 2100) indicated that the most vulnerable sectors are those located along embayments, which coincide with low gradient shorefaces.