Processos erosivos lineares nas encostas na Bacia do Rio Tibiri, ilha do Maranhão

Abstract

As slopes constitute a highly predominant relief on the Earth's surface, they have been the object of study in several sciences, such as Geomorphology, one of the purposes of which is to understand their development and the processes that act throughout their historical course. To this end, this work has a preliminary analysis of the geomorphology of the Tibiri River Basin region, first with a bibliographical analysis, in the context of the different forms and dynamics that contextualize it, then as a study objective to analyze the influence of the slopes' inclination, in the face of the erosion process, in the Tibiri River Basin, such as the slopes and the use of soil cover, highlighting the behavior of the slopes in the face of the erosion process of the gullies of the municipality of São Luís, located in the Tibiri River Basin, Maranhão Island. The location and use and occupation maps of soils were prepared using the Arcmap 10.2 software. The final results show that the predominant soils are Neosols Quartzarenic Orthic Aluminic, Argisol red-yellow concretionary and Gleysols Typomorphic. The geology of the area is made up of the Itapecuru formations, characterized by the presence of siltstones and leaflets, present in a large part of the island; the Açui formation characterized by clayey-sandy sediments with origins in the Pleistocene and Holocene, thus they are represented as fluviomarine deposits composed of gravel, sand, silt and clay. The Barreiras Group is made up of poorly sorted clastic sediments, normally with a reddish or yellowish coloration, its composition is represented by limestone, sandstone and clayey rocks, characterized by alluvial and colluvial deposits, and mangrove deposits; the relief is predominantly tabular with flat tops and the presence of convex slopes; The hydrography has channels that are irregular and narrow, with a gradual increase in width; near the mouth, the main channel reaches 794.5 meters in width; land use and occupation reflect a process of social segregation in the eyes of capital, which as a consequence gives rise to peripheral neighborhoods located on hills and valleys, placing this population in a risky situation, resulting from soil compaction and deforestation of slopes for the construction of their residences, however being a great favor for erosion with the appearance of furrows, ravines and gullies, in more serious cases leading to mass movements, as commonly known as landslides