Identification of Landslides Risk Areas in Piranga County, Minas Gerais, Brazil.

The increase of landslides in small cities in Brazil is directly related to the increase of urbanization. In the case of Piranga County, landslides are a large problem, mainly due to unrestricted urbanization, surface sealing and poor erosion/slope stability controls. The objective of this project is identifying and mapping landslides areas and the soils in Piranga County, Minas Gerais (MG), Brazil. Areas of risk were determined by using the following factors: soil type and depth, geologic formation, geological fractures, slope's geometry, precipitation, drainage, vegetation, and anthropic interferences (construction, roads design, and sewage network). The region of Piranga County has hills, with shallow soils (Inceptisol) and deep soils (Oxisols); and valleys, with Ultisols and Aquic Entisols. Thus, soils were the main factor for determination of risk areas. Risk qualification and quantification is an important instrument for the County's government. Therefore, four risk criteria were proposed: high risk, median risk, low risk, and no risk. A detailed map showing the landslides areas of risk was created. The high risk occurs where the risk is evident and can affect more than two houses, in areas with risk of landslides, movement of rock blocks, natural instable slopes, and launching of garbage. Mean risk occurs in not so evident areas, and interventions can avoid disasters, which includes areas dense populated. Low risk is “risk points”, with accumulation of rubbish, road cuts in steep slopes, lack of infrastructure, and areas dense populated. And finally, there are areas without risk of land movements. In conclusion, landslides occur basically in Inceptisols (shallow A and B horizons), instable geological areas, and low drainage areas. Thus, the knowledge of soil science is an important factor for management of natural disasters in Piranga County (MG), Brazil.