Hydrogeomorphology of the Trindade Island: The only permanent hydrografic network on Brazilian oceanic islands

Abstract

Among the Brazilian oceanic islands, all located in the South and Equatorial Atlantic area, Trindade is the only one that presents water courses and perennial springs, presenting, therefore, a sui generis hydrogeomorphological arrangement. Although the presence of fresh water has been documented since the arrival of the first visitors, there is a clear lack of hydrogeomorphological approaches about Trindade in the literature. The investigation of the spatial-temporal distribution of rainwater and fluvial water flows contributes to the understanding of their geomorphological mechanisms. This research has a hydrogeomorphological perspective and focuses on the hydrographic configuration of Trindade Island. It was sought to highlight the role of surface waters in terms of erosion and sedimentation processes, and major surface forms and materials. The research was based on field procedures (about 50 days) and geoprocessing techniques, which involved the use of morphometric analyses. The results show that Trindade’s fluvial system presents characteristics that are typical from sediment production zones or headwaters. In addition, it was pointed out the existence of areas that exhibit distinct characteristics in relation to the surface drainage behavior, that is, patterns or types of drainage areas. From this perspective, 33 river basins were identified, as well as many small runoff areas and 32 springs. There is the presence of well drained, very well drained, and above all exceptionally well drained basins, reflecting the high incidence of erosive features (ephemeral channels).