Procedimentos metodológicos para determinação da fragilidade ambiental de bacias hidrográficas

Abstract

The aim of this study was to promote the adaptation of new procedures for determining the environmental fragility of hydrologic basins, based on the method proposed by Ross (1994), taking as a case study the Dourados river watershed. The assessment of environmental fragility provides the definition of guidelines and actions to be implemented at the level of the physical territory, serving as a basis for environmental zoning and watershed management. Environmental fragility is thus divided into potential and emerging, where potential fragility is conceptualized as being the vulnerability of a natural environment in terms of its physical characteristics such as slope and soil type, while emerging fragility in addition to physical characteristics, also includes the degrees of protection of different types of soil use and vegetation cover. GIS work used the Geographic Information System software SPRING as a tool and LANDSAT/TM 5 images as a cartographic base. The potential fragility map was prepared by the overlap of information layers of slope, erosivity, erodibility and geology, and the emerging fragility map was obtained by cross-referencing the map of potential fragility with the map of soil use. Results showed that: the adaptation of the methodological base proposed by Ross (1994), with the integration of factors of analysis, such as slope, erodibility, erosivity and geology promoted a significant differentiation in the production of the final map for environmental fragility; the use of continuous ratings by the weighted average allowed for an analysis of the environmental fragility according to the scale of work used; the SPRING Geographic Information System software, combined with algorithms of map algebra, proved effective in the theoretical analysis of environmental fragility, confirming the possibility of applying the methodology in studies of environmental planning of river basins.