Transformações na condição hidrogeomorfológica da Bacia do Ribeirão Brandão (Volta Redonda, RJ): uma análise com índices espectrais e referencial geomorfológico

Abstract

This research analyzes geomorphological and environmental transformations in the Ribeirão Brandão watershed, located in the municipality of Volta Redonda (Rio de Janeiro State, Brazil), in the Middle Paraíba do Sul River Valley—an area subjected to intense urbanization and industrialization processes since the mid-twentieth century. The main objective is to identify and analyze trends in land-use and land-cover change in watersheds tributary to the Paraíba do Sul River through the application of spectral indices derived from remote sensing, in order to support complementary diagnostic assessments aimed at detecting transformation trajectories of fluvial systems. To this end, the Ribeirão Brandão watershed and the Curral-Leste Stream sub-basin were selected as the spatial focus, considering the period from 2014 to 2024 due to significant technogenic alterations identified in this interval. The study is based on the processing of 106 Landsat 8 satellite images, from which the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Water Index (NDWI), and the Normalized Difference Built-up Index (NDBI) were calculated. Annual mean values of these indices were spatialized into thematic maps and analyzed both qualitatively and quantitatively, and subsequently integrated with a previously developed geomorphological interpretation of the fluvial system, with emphasis on valley confinement and bank typology. The results indicate that mean NDVI values range from 0.28 to 0.31, reflecting the predominance of sparse and discontinuous vegetation within the basin. NDWI values are persistently negative, ranging from −0.31 to −0.285, indicating low surface water availability, whereas NDBI values remain negative, between −0.115 and −0.08, characterizing an intermediate degree of artificialization in which built-up surfaces coexist with exposed soils and residual vegetation. The inverse relationship observed between NDVI and NDBI shows that periods of higher relative vegetation vigor correspond to a lower presence of impervious surfaces, suggesting a progressive reduction of residual vegetation in areas associated with urban expansion. Land-use and land-cover analysis reveals a decrease in grassland vegetation, a marked increase in exposed soil, and a moderate expansion of urbanized and arboreal areas, resulting in a fragmented land-use mosaic whose implications are reflected in the geomorphological conditions of the analyzed fluvial systems.