Efeitos da ocupação urbana na sustentabilidade ambiental do córrego Guará, Distrito Federal

Abstract

This dissertation analyses the effects of urban occupation on the environmental sustainability of the Guara stream, one of the main contributors to the Paranoa reservoir, in Brasilia, Brazil. The drainage area of this stream represents 13,6% of the Riacho Fundo basin, which houses the most aggressive human uses and presents the worst water quality within the five small basins that compose the Paranoa one. The surroundings of the stream are occupied by the urban settlements Guara I, Guara II and Candangolandia, and by Sector of Gas Stations and Motels at the right side; at the left side, they are occupied by Sector of Inflammables, Sector of Industry and Supply, Sector of Garage and the Zoological Garden of Brasília. It is an area of typical urban uses individual and collective housing, commerce, administrative buildings, garages for heavy vehicles, storage of loads and inflammables, parks, and sports and recreation plots. Such uses have been responsible for silting-up, erosion, compact and impervious soil, hydrological alterations, and vegetation fragmentation. These processes affect the water quality of the stream and, as a consequence, of the Paranoa reservoir. The method used for evaluation of the environmental sustainability of the Guara stream was the Ecological Risk Analysis (FARIA, 1996), which allows the quantification and space delimitation of the risk of damages presented by the human activities over the landscape's natural factors and, consequently, to human development sustainability, within a determined geographical space. It makes use of a model that aggregates indicators for measuring the natural factors sensitivity to damages caused by the human uses, and indicators for the intensity of damages potentially caused by human uses to the same natural factors. The aggregation method is based on logical functions of type and/or (Boolean algebra). The scientific knowledge about the ecological risks that threaten the Guara stream's sustainability is helpful to guide actions towards an urban land use committed to the hydrological resources conservation.