Landslide Susceptibility in Brazil

The disorganized urban development in Brazilian municipalities is an ongoing issue that has intensified since the 1970s. In the city of Ouro Preto, Minas Gerais, Brazil, this situation is aggravated due to its geology that increases landslide susceptibility.

The underground water flow is mainly controlled by geological factors, such as existing structures and lithologies, and directly influences the mechanical behavior of rocks. Therefore, the delimitation and control of these flows is essential to prevent accidents such as landslides and block falls, which can result in the eviction of residents, destruction of property, and human fatalities.

To address this issue, the Society of Applied Geophysics (SAG) has developed a low-cost standard approach for geotechnical analysis using non-invasive geophysics methods that can also be replicable in other areas. This approach is being implemented in a pilot risk area of landslide of Ouro Preto city, a UNESCO’s World Heritage city, with the support of the Civil Defense department of Ouro Preto, BOG Geofísica, National Geological Service (CPRM) and the Federal University of Ouro Preto (UFOP).

The selected pilot area comprises of the eastern portion of the city of Ouro Preto, in the neighborhoods of Taquaral, Morro da Queimada, Piedade and Alto da Cruz with a total area of 1.48 km² (approximately 6 square miles). The methodology consists bibliographic review and landscape recognition through high resolution areophotogrammetric images and topography. The processing and integration of the data obtained by various geophysical methods (regional magnetometric, total-field magnetic and magnetic susceptibility survey) will be used for better characterizing and classifying, to identify which areas are more prone to risks.

It is expected that the assessment obtained will help collaborate with the civil defense and local government in understanding how hillsides behave during the rainy season. This will help implement adequate infrastructure for safety and monitoring as well as raising awareness of the population about dangers of occupying steep areas. This project will also be an example of a geotechnical risk assessment methodology that integrates applied geophysics and society’s needs, in order to achieve greater humanitarian benefits.

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