Avaliação de riscos geológicos associados a movimentos de massa e compartimentação geotécnica na porção sul do município de Diamantina, Minas Gerais

Abstract

Surface processes are responsible for shaping landscapes. However, anthropogenic interventions can accelerate them, generating significant impacts on the physical environment. Thus, urban planning plays an essential role in promoting the orderly growth of cities, minimizing both the impacts and the population’s exposure to geological risks. Diamantina lacks geotechnical mapping that reveals the potentialities of its terrains, as well as systematic studies on geological risks to guide public management. Characterized by disorganized urbanization and topographic constraints that limit its expansion, the city faces major challenges regarding land use and occupation. This research aimed to produce a geotechnical map for the southern portion of the municipality, in addition to assessing geological risks in urban areas and natural bathing sites. The region is mainly composed of rocks from the Gouveia Complex and the Rio Paraúna, Espinhaço, and São Francisco Supergroups. A total of 249 points were described. The rock masses were analyzed to verify their mechanical properties and the geometry of discontinuities. Soil characteristics and signs of instability were also observed. Among the surveyed points, 23 bathing sites were evaluated for geological hazard and classified into four categories: low, moderate, high, and very high hazard. Kinematic modeling was performed by comparing slope characteristics, such as inclination and orientation, with interpolated surfaces derived from the dip direction and dip angle of discontinuities. Structural data were analyzed according to their influence on the triggering of geodynamic processes. The final stage consisted of the assessment of urban geological risks, classifying urbanized areas into low to negligible, medium, high, and very high risk levels. The selection of areas was mainly based on historical records from Civil Defense and the Fire Department. Among the results, the geotechnical map stands out, identifying ten geotechnical units, along with susceptibility maps for planar and toppling landslides. Of the bathing sites analyzed, 15 were classified as low hazard, 2 as moderate, 4 as high, and 2 as very high hazard. From the urban risk assessment, 34 sectors were delineated as high risk and 2 as very high risk. It is important to highlight the temporal nature of these evaluations, as the scenario changes over time, requiring constant monitoring. The results are highly relevant, providing tools to support territorial management and to guide actions aimed at mitigating and controlling geological risks.