Avaliação multicritério em ambiente SIG para identificação de áreas de risco à erosão na bacia do São José dos Dourados - SP

Abstract

Human activity in the São José dos Dourados river basin in the state of São Paulo accelerated the erosion processes in the soil and, consequently, the siltation of rivers and lakes. Therefore, this work aimed to identify and rank the areas more susceptible to erosive processes using geoprocessing and data analysis techniques. For this, SRTM data (Shuttle Radar Topography Mission) and thematic maps provided by INPE (National Institute for Space Research), MapBiomas, DataGeo, INDE (National Spatial Data Infrastructure) and the QGIS software for processing were used. The maps of land use and occupation, slope, NDVI, hypsometry and pedology were collected, assigning a risk value to each item in its legends according to its degree of influence on erosive processes. Then, the Hierarchical Analysis Process (AHP) method was applied to establish a relationship of related importance between the factors represented by the theme of each map, this hierarchy was translated mathematically through weights assigned to each of the maps. Using a Map Algebra with each one duly weighted, the water erosion risk map was built, integrating the maps of land use and occupation, slope, NDVI, hypsometry and pedology. From the analysis of the results, it was found that the São José dos Dourados river basin has a high erosion potential, about 69.45% of its total area is in a region of high erosion potential and 17.52% of the area has very high erosive potential. This very high vulnerability is associated with soil characteristics, both the type of soil, Red-Yellow Argisol, which has low erosion resistance and occupies most of the basin area, as well as its use and occupation, advanced by intense human activity as in sugarcane, soy, orange and also in livestock. The methodology was applied efficiently and appropriately, since the results meet the requirements of the Water Resources Situation Report UGRHI 18 (2018), which classified the region in relation to its erosion risk, but more generally than the present work, not differentiating intraregional variations. In this way, the products obtained are technical and managerial tools to aid the decision-making necessary to mitigate the socio-environmental impacts resulting from the loss of soil. In this sense, it is necessary to superimpose the drainage network and subsurface waters in the risk map generated for the protection of these areas of the drainage network as a priority, as well as the containment of slopes, measures already debated and recognized in the scientific literature to avoid , recover, manage, minimize and monitor erosion processes in urban or rural areas.