Análise geoespacial do processo erosivo hídrico linear no estado de Goiás e Distrito Federal

Abstract

The intense conversion of the Cerrado into agricultural and livestock areas resulting from the expansion of the agricultural frontier, especially since the second half of the last century, led to the incorporation of their lands into the national productive system, based on an agroexport model anchored in commodities, especially associated with the binomial meat and grains. Despite being economically successful, this process caused a reduction of its continuous area by about 50% and several environmental impacts, such as deforestation and occupation of sensitive areas accompanied by the development of water erosion processes. Such processes, in the form of ravines and gullies, especially medium and large, have been extensively studied in the Southwest of Goiás, where factors favorable to their development dominate. However, there was no study of the preferential distribution of the existing erosive foci, nor of the conditions and their susceptibilities on the state scale. The present thesis started from the hypothesis that the linear water erosion process results from favorable conditioning factors related to the physical and biotic environment, which gives them greater susceptibility, and also to the discrepancy in land use and management. The objective of the thesis is to analyze the preferential distribution of linear erosive foci in the state of Goiás and its interrelationships with the components of the physical and biotic environment, in order to identify the critical areas and the respective attributes that indicate the process. The methodological strategy was based on a decreasing geospatial multi-scalar approach accompanied by physical-based geocartography, starting with the inventory and mapping of erosive outbreaks (focus) with the aid of remote sensing and geoprocessing, using Geographic Information System (GIS). It´s proceeded with the elaboration of the isodensity map of the outbreaks that allowed the identification of Critical Areas, with a greater density of outbreaks. Next, two areas of the most critical ones were selected, which were analyzed in detail regarding the morphopedological compartmentalization, the erosive susceptibility and its relationship with the distribution of the erosive outbreaks and the conditioning factors of the physical and biotic environment, in order to identify the main causes of the process. The results revealed 5 Critical Areas in the State, the largest being in the Southwest region, in which the predominance of outbreaks is located in the morphopedological compartments supported by sandy soils with high erodibility, in flat to smooth undulating reliefs, with high water erosion susceptibility and predominant use with pastures, although without discrepancy in use. It is concluded that the management of susceptible areas is not adequate and is the main responsible for the erosive occurrence in the most critical areas.