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Abstract: In this paper we propose a DEM-based GIS methodology for the identification and delimitation of riparian protection areas according to stream width. In Brazil, vegetation cover in buffer zones is monitored by mid-resolution satellite imagery, so our methodological approach includes procedures to ensure geometrical accuracy for multiple spatial layer overlay. For a study area in Mato Grosso, a sequence of DEM pre-processors was used to hydrologically correct a SRTM 90 m resolution digital elevation model. Then samples of river widths were obtained by measures using high-resolution IKONOS imagery and regressed against watershed contribution areas to define protection zone buffers. We propose a procedure to attribute the DEM-based width estimates derived from topographic maps and satellite imagery to the river networks. Validation using high-resolution IKONOS imagery indicates that the proposed methodology produces RMS errors of about 20 m on average for watercourses up to 600 m wide. This is a considerable improvement in protection area delimitation compared with current practice, particularly in headwater regions and along streams with widths of up to 200 m. Accuracy assessments indicate that environmental licensing procedures should include a tolerance of between 48% (<50 m) and 15% (200–600 m) of stream width, according to systematic errors included in the estimates. [Copyright &y& Elsevier]

Abstract: This study evaluates the environmental impacts caused by informal occupation in the city of Cuiabá, Mato Grosso, Brazil. In 10 selected districts, an assessment of 35 environmental indicators was conducted, evaluating secondary data as well as field survey results, air photo interpretation and geographical information system (GIS) analysis. A matrix approach was then applied to quantify the magnitude and relevance of 13 types of impacts on the following environmental components: surface water, soil, flora/fauna, air, land use and life quality. Impacts were analyzed in the spatial context of four main classes of municipal zoning. Redundancy analysis (RDA), a multivariate ordination method, was applied to evaluate the dependency of impacts from environmental and socio-economical factors. Total impact scores were the highest in areas devoted to environmental preservation according to municipal zoning, indicating a limited ability of authorities to control informal occupation processes and their impacts on the environment. Indicator analysis showed strong impacts along the stream network in areas susceptible to episodic flooding. RDA indicates that age and district organization have a significantly important impact in the sampled districts; they were found to be as important in ordination as environmental factors such as geo-technical units. [Copyright &y& Elsevier]