Rio Humboldt ou Vermelho flows through the Atlantic Forest remnants of Ilha de Santa Catarina in the state of Santa Catarina, southern Brazil. This small coastal river is part of the island's network of streams and drainages that empty toward the coast, winding through a landscape shaped by the rich biodiversity of the Atlantic Forest biome. Like the other coastal rivers of this region, it is characterized by relatively modest size, with a watershed composed primarily of streams and small river channels typical of the southern Brazilian coastal drainage system. The surrounding Atlantic Forest, though significantly impacted by urbanization and deforestation over the decades, still provides riparian cover and supports a diverse assemblage of native freshwater fish species. The rio Vermelho basin is one of several distinct drainage systems on the island, alongside the rio Ratones, rio Palha, rio Tavares, and the córrego Grande basin.