The municipalities of Herculândia and Quintana, located in the interfluve of the Peixe and Aguapeí rivers, west of São Paulo State, present a great gully concentration (erosive linear processes). That feature is due to the occurrence of the lithostratigraphic units belonging to the Bauru Group (especially in the Marília and Adamantina formations), sedimentary sequence essentially sandy with age attributed to the Cretaceous. Several authors discuss the evolution of the erosive processes in the area IPT (1986 and 1995) Oliveira et. al (1987), Iwasa et al (1987), Ponçano and Prandini (1987), Queiroz Neto (1988 and 1993) and Pinto (1998).

In the study area it stands out the Plateau of Marília with sharp slopes, interfluve of the basins. The soils are sandy varying among podzolizics and latosoils.

The Marília Formation (fine sandstones the medium ones, with cement and carbonate concretions: conglomeratic sandstones and sandstones with carbonate cement), in the study area it is in basal contact, with the Adamantina Formation (fine to very fine sandstones; show locally with carbonate cement and nodule). The transition is made of abrupt change of litology. The geologic contact among the formations coincides with knickpoint, among the steep slopes, close to the top of the plateau and the hills with convex slopes and low slope angle in the inferior portion. In that knickpoint it can happen the blooming of the freeground water.

That knickpoint can favor the appearance of erosive linear processes. About the Marília Formation (with carbonate cement), gullies appear, that concentrate the overland flow. The flow, of water, when reaching the Adamantina Formation essentially sandy, is associated to the piping, taking to the linear gully appearance.

When the deforestation takes place, in the area of the lithologic contact where are originated the knickpoint, it breaks the morpho-hydro-pedologic balance and transforming that place, where that process occurs in place with high potential hazard to a linear erosion.