André de Souza Avelar

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.

Landslides and Disasters in Southeastern and Southern Brazil

Abstract Landslide conditions and problems involve functional relationships among natural elements (climate, topography, rocks, soil, vegetation and fauna) and artificial elements (related to land use) of the landscape, which may change over space and time. Two characteristic rainfall regimes might express rainfall–landslide relationships in southern and southeastern Brazil: less intense events of longer duration tend to favor deep rotational failures along channel banks and road cuts, colluvium-deposit creep in valley bottoms, and shallow translation failures on steep lands; extreme rainfall events tend to favor shallow translational slides and debris flows on steep lands, block-rich debris avalanches along main valley bottons and rock falls on vertical scarps. Landslide disasters are commonly associated with less frequent, intense, and spatially nonuniform rainfall events during the summer rainy periods. Critical events have prevailed along the highly populated coastal region, especially in the upper portion of steep mountain slopes. In this text the authors draw special attention to case studies of historical landslide disasters in the most populated area of Rio de Janeiro State, and also include some other case studies in southeastern and southern Brazil.

January 2011: The Extreme Landslide Disaster in Brazil

This work describes the extreme event of landslides occurred in January 2011 in the Rio de Janeiro mountainous region and discusses its relationship to the spatial and temporal variation of critical and prior rainfall. Interviews in the field let us establish the landslide initiation timing around the automatic pluviometer stations which supply detailed data on the rainfall intensity. The study concludes that the accumulated rainfall during the last months associated with high rainfall levels over 24h, along with local conditions like the direct impact of lightning and tremors resulting from landslides, formed the relevant conditions for thousands of landslides.

Assessment of organochlorine pesticide residues in Atlantic Rain Forest fragments, Rio de Janeiro, Brazil.

A superficial water quality survey in a watershed of the Paraíba do Sul River, the main water supply for the most populated cities of southeastern Brazil, was held in order to assess the impact of the expansion of agricultural activity in the near border of the Atlantic Rain Forest. The aim of this study was to investigate the presence of priority organochlorine pollutants in soils and superficial waters of Atlantic rainforest fragments in Teresópolis, Rio de Janeiro State. Soil sample preparations were compared by using ultrasound, microwave assisted extraction and Soxhlet extraction. Recoveries of matrix spiked samples ranged from 70 to 130%. Analysis of a certified soil material showed recoveries ranging from 71 to 234%. Although low concentrations of organochlorine residues were found in water and soil samples, this area is of environmental importance and concern, thus demanding a monitoring program of its compartments.