Mechanisms of the Recent Catastrophic Landslides in the Mountainous Range of Rio de Janeiro, Brazil

Catastrophic mass movements occurred in January 2011 in a mountainous area of Rio de Janeiro leaving more than 1,500 dead people and large destruction. Heavy thunderstorms occurred on January 11th (~100 mm/day) and 12th (~150 mm/day) and triggered thousands landslides on steep slopes with trees and block rich debris materials converged into the river channels, hence avalanches down valley. Through fieldwork, mainly translational slides and debris flow types were observed, as well as some rotational slides and rock fall. Initial studies show that translational slides occurred in saprolite soil with 1–3 m depth and on more than 30° slopes. Debris flows initiated in small catchments with very steep slopes and run out along the valley bottom where colluvial soils are present. This study focuses geological analysis and correlation between soil properties and geotechnical behavior in order to explain this catastrophic slope movement mechanisms and processes.