Analyzing the relationship between the occurrence of landslides and terrain attributes in the extreme rainfall event in southern Brazil, May 2024

Abstract

At the end of April and beginning of May 2024, extreme rainfall occurred in the state of Rio Grande do Sul, leading to mass movements and causing loss of materials and lives. Carrying out an inventory of landslides and analyzing relief attributes is an important step towards understanding the dynamics of the occurrence of these events, enabling their prediction in future events. Through visual analysis of high spatial resolution RapidEye images, 59 landslides were identified in the Cerro Comprido basin. The landslide scars were mainly concentrated at altitudes ranging from 290 to 440m, with emphasis on the slope limit of 70% to 75%, which presented 8 scars and a high value in the frequency ratio. Regarding the characteristics of the slope, the most susceptible to landslides were those oriented in the north and east quadrants and with a convex-divergent profile. These landslides are related to the occurrence of extreme precipitation events where the accumulated precipitation values in four days were more than double the monthly average for the region, which is the main factor in triggering the landslides, occurring even in less susceptible areas.

Keywords:
Mass movements; Morphometry; Rio Grande do Sul; Hillslope