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.

Understanding the impact of hydrodynamics on coastal erosion in Latin America: a systematic review

“…In the south, "hot spots" have been identified where hydrodynamic processes are more relevant to shoreline loss. On the coast of Rio Grande do Sul (RS), erosion of 41% has been recorded, mainly affecting the beaches of Hermenegildo and Faro de Conceição (Alves, 2009;Nicolodi et al, 2021). Northeast waves in summer and southwest waves in Frontiers in Environmental Science frontiersin.org winter contribute to coastal instability in this area, along with cyclonic storm surges that sometimes exceed 1.50 m in height and intensify erosion processes when they coincide with high tides (Esteves et al, 2003;Silva et al, 2016).…”

“…The beaches of Hermenegildo and Faro de Conceição in Rio Grande do Sul (RS), Brazil, undergo erosive processes due to the concentration of wave energy generated by small-scale changes that result in the convergence of wave rays at certain points along the coast known as "focuses of surf" (Esteves et al, 2002;Calliari et al, 2003;Dillenburg et al, 2004;Nicolodi et al, 2021). These bathymetric effects extend from Faro de Conceição to Cabo de Polonio in Uruguay.…”