Procedimento baseado em rotina de apoio à decisão aplicado à redução de risco de movimentos gravitacionais de massa em margens de cursos dágua: estudo de caso em Rio Branco/AC

Abstract

The advanced process of consolidating occupation on marginal slopes of the Amazon hydrographic system, verified in recent decades, has generated negative economic and social consequences in most of the urban centres in the northern region of Brazil. Regional awareness of the population regarding the use and occupation of these areas, the precarious infrastructure installed and the uniqueness of the natural processes that develop in this region have inhibited the proper characterization and prioritization of areas of risk, especially concerning the adoption of preventive or corrective measures aiming at the reduction of geological accidents. In this sense, it is considered appropriate to suggest and incorporate quantitative techniques that could help with the use of basic information and allow the reduction of subjectivity in the decision-making process, thus promoting adequate allocation of resources and the early management of risk. Therefore, the objective of this work was the development of a semi-quantitative base methodology, able to assist in the indication of potentially unstable or critical areas concerning the risk to the population. The methodological approach was applied in a test area of the city of Rio Branco-AC, Brazil. Because of the specificity of the topic, multiple criteria had to be developed or adapted in a way that would allow the analysis to consider environmental, economic, and social particularities. The decision-making process was divided into two main stages. The first, called zoning, had the purpose of optimizing the identification of potentially unstable areas; and the second, developed to a higher level of detail and named intervention priority, sought to evaluate, quantify, and prioritize the conflicting relations between the use and occupation of the soil and the adverse phenomenon. The decision support routine called Analytic Hierarchy Process (AHP), was the technique used to structure the decision-making process andto assess the consistency of the evaluation performed in each one of the stages of the proposed methodology. Recognizing that the current stage of knowledge does not allow a proper understanding of the concepts and principles governing the phenomenon evaluated, it was sought to verify the susceptibility to gravitational mass movements, following the partition of physiographic and geological-geotechnical characterization of the different land spaces. The results were synthesized and represented in three maps: Map of Gravitational Mass Movement Susceptibility, Intervention Priority Map, and Map of Risk Mitigation Actions.