Procedures of engineering geological mapping applied to urban planning in a data-scarce area: Application in southern Brazil

Abstract

Resultsfrom an engineering geological mapping study of the urban area of Ouro Preto in the state of Minas Gerais, Brazil, are presented. The goal of the study was to verify the efficacy of procedures, methods and classification schemes based on engineering geological mapping principles to generate data and maps for urban planning, restructuring (rehabilitation) and engineering projects. The study was developed at a 1:10,000 scale and based on field and laboratory studies and on the analysis and interpretation of aerial photography and satellite images. The selected study area has been urbanized for over 300 years and requires territorial planning and reorganization of land uses. The area is composed of highly variable rock types, unconsolidated materials and terrain features. Data collection and mapping were performed to identify and delineate 51 engineering geological units in terms of the spatial distribution of geological materials, genetic characteristics, mineralogy, the estimated strength, hydraulic conductivity interfaces and potential failure surfaces. All units were assessed in terms of excavatability conditions, predisposition to erosion and shallow translational landslide, suitability for sustainable urban drainage systems (SUDS), contaminant flow conditions, potential use as construction materials and foundation-related aspects. Recommendations for a detailed site investigation were made, and the suitability of geological materials for engineered fill was evaluated. A constraint zoning analysis was carried out to contextualize urban planning. The adopted procedures, methods and classification schemes were shown to be efficient when implemented in conjunction with intensive field studies and enabled the delineation of units with different engineering geological characteristics that are important for urban planning involving different users.