Mapeamento de áreas suscetíveis a movimentos de massa no perímetro e zona de expansão urbana do município de Dois Vizinhos - PR

Abstract

Mass movements are among the most common natural disasters in urban areas, causing significant economic and environmental impacts. These types of disasters are aggravated by natural factors (slope, soil type, vegetation, climate, among others) and anthropic factors, mainly related to land use and occupation. Mass movements can be prevented by mapping the risk areas, using geoprocessing and geostatistical techniques. The objective of this work was to evaluate the areas susceptible to mass movements in the perimeter and urban expansion of Dois Vizinhos (PR). The work physically characterized the study area, with data available in the literature, government agencies and also through satellite images for mapping land use and occupation. Then, soil samples were collected from ten random locations of the perimeter and urban expansion, spatially well distributed. In addition to the spatial distribution, we sought to contemplate the various types of soil in the study area, especially close to areas at risk of landslides, which have already happened or in places with greater slope. Samples were collected by drilling into the soil with a Dutch auger, which were then sent to the laboratory for analysis of physical and mechanical indices. In addition, 84 point reports were obtained with SPT (Standard Penetration Test) soil soundings for soil cohesion and friction angle calculations. Afterwards, a deterministic method based on the calculation of the Safety Factor was used, identifying risk sites in the study area, in conditions of saturated soil or not, and also with or without native vegetation. The zones at risk of instability (mass movements) were identified for the study area, only under estimated conditions with saturated soil and no vegetation. These areas are mainly concentrated in the central north and east of the urban area, which are precisely the areas in the city with more occurrences of instability, due to their slope, soil with lower clay content, greater anthropogenic occupation and lesser amount of native vegetation.