Análise do movimento translacional raso ocorrido em 2022 na enseada da praia de Itaguaçu em Ilha Grande – RJ

Abstract

Mass movement is a significant phenomenon in regions characterized by steep terrain, influenced by a complex interaction of geomorphological, geological, pedological, and hydrological-climatic factors. In the state of Rio de Janeiro, the municipality of Angra dos Reis stands out as a particularly susceptible region to the occurrence of these events. This vulnerability can be attributed to the geological context of the region, nestled within the Serra do Mar, and the high incidence of rainfall. On April 1st and 2nd, 2022, an exceptional volume of 592 mm of rain was recorded in the Ilha Grande region, serving as the triggering factor for the shallow translational movement that occurred in the Itaguaçu Beach cove. In this sense, the main objective of this research is to understand the mechanism of rupture of this mass movement. To achieve this, fieldwork and aerial surveys using drones were conducted to characterize the morphology of the affected area and obtain high-resolution geospatial data. The analysis of the material revealed the presence of orthogneiss and charnockite blocks along the entire scar, as well as a diabase dike in the upper third of the movement. These observations suggest two hypotheses for the origin of the movement: the rupture of the dike due to soil saturation or the fall of orthogneiss blocks, causing the rupture of the dike and, consequently, the movement. The Ilha Grande region has experienced similar mass movements in the past, including tragedies such as the one in the Bananal Cove in 2010. In this regard, recognizing potential areas for similar events is challenging but crucial to prevent future tragedies.