Zoneamento da susceptibilidade à ocorrência de escorregamentos na Bacia Hidrográfica do Córrego do Yung

Abstract

In Brazil, the study of the processes related to the mass movements in urban areas has increased due to the high number of occurrences with fatal victims. In city of Juiz de Fora which belongs the Stream of Yung Basin, the growth of the occurrences of mass movements is related to the physical-environmental features and with the inappropriate occupancy of slopes. For the prediction of such type of process, several methods have been proposed in the scientific context. Among these, the determinist mathematical model SHALSTAB (Shallow Stability) deserves attention since it produces good results in several parts of world, like EUA, Italy, Canadian and Brazil. The aim of this work was to create a mapping of risk to mass movements in the Stream of Yung Basin by means an analysis of instability to the mass movements and an analysis of the type of coverage and use of earth. To obtain the mapping of risk, it was necessary to generate a digital model of elevation to get the geomorphologic parameters (declivity and area of contribution) which are the base of the mapping of susceptibility to the mass movements. For the mapping of coverage and use of earth, was used the aerophotogrammetric coverage of the area furnished by the Civil Defense/PJF highlighting six classes of use e.g., built-up areas, vegetal coverage area and areas related to water bodies. The results show that the Stream of Yung Basin is still in urbanization process, since only 12,2% of its area contains buildings, and 58,5% is occupied only by underwood or pasture. With respect to the analysis of instability of the basin, an extensive part of the areas classified with some grade of instability are located in the south and southeast of the basin, a region with a high index of occupation. The analysis show that 0,25 km2 or 0,55% of the basin area is considered unstable by the model SHALSTAB. It were mapped 47 of the scars.With respect to the risk zoning to the mass movements, 0,02 km2 or 0,10% of the total area of the basin is considered of very high risk to occupancy, and only 25,25% is considered as low risk. These results permit to conclude that the use of mathematical models associated to the knowing of the coverage and use of earth for predicting the mass movements is an important method to map the risk conditions in occupied areas in hydrographic basins. It is expected that this present work may serve as guidance for further researches as well as to help several competent public agents on management of areas of risk in the city of Juiz de Fora.