Análise de cenário de fragilidade ambiental e indicação de áreas mitigadoras na Microbacia Hidrográfica do Rio Mato Grosso, município de Saquarema, RJ

Abstract

The present thesis aims to analyze areas indicated with priority to the mitigation of environmental fragility in a hydrographic micro-basin. Located in the far west of Saquarema, the Mato Grosso River hydrographic micro-basin is under pressure mainly due to population growth and its proximity to the municipality of Maricá, part of the Rio de Janeiro Metropolitan Region. It has undergone changes in land use and cover, according to Mapbiomas’ Project data, and has been indicated as susceptible to mass movements and flooding by the Geological Survey of Brazil. Despite this, few studies have been published about this hydrographic micro-basin., while in the neighboring municipality – Maricá – robust natural disaster management has been developed to reduce damage of extreme weather events. In this study, open-access data was used to estimate environmental fragility and socioeconomic vulnerability, to make this methodology applicable to the Saquarema Municipality, the Lagos São João Watershed Committee and other nearby micro-basins or watersheds. Geographic data on geology, soil type, rainfall intensity – by remote sensing – and slope – from a Hydrologically Consistent Digital Elevation Model – were processed, reclassified to the level of environmental fragility, converted to fuzzy logic and integrated using weights defined by the AHP hierarchical analytical process to estimate potential fragility in the free Geographic Information System (GIS) QGIS. Emerging fragility was estimated based on land use and land cover classified for 2010 (t1) and 2020 (t2) with higher spatial resolution images than those used by Mapbiomas’ Project. The calculation of environmental fragility considered potential and emerging fragility with the same weight. In addition, the transition of UCT classes was evaluated in QGIS, the predictive scenario of environmental fragility in 2030 (t3) was estimated in the commercial GIS IDRISI Selva, and this was analyzed in terms of the macro-zones of the Saquarema Master Plan, the census sectors, the susceptible areas to mass movements and flooding and socioeconomic vulnerability. Among the major results of this study, 6.1 km² (18.7% of microbasin) of fragile, susceptible and vulnerable areas were identified. On the other hand, areas with medium to very high environmental fragility (t3) were indicated in protected areas or near institutions that can be partners in developing mitigating solutions on 6.3 km², with emphasis on the banks of highways and watercourses, being highlighted for implementation and practices to mitigate environmental fragility. This methodology could be improved by updating the materials from the different themes considered in this study, such as the IBGE Demographic Census, and by adding new themes, subsidizing projects to mitigate environmental fragility and the Environmental and Territorial Planning in micro-watersheds, such as the Municipal Master Plan, the Watershed Plan and the preparation of an Environmental Disaster Risk Reduction Plan.