Environmental fragility to erosion in an anthropogenic watershed in the northeast of the state of São Paulo, Brazil

The functionality of the natural environment is altered by the anthropic interventions, so the change in the soil structure can cause events that cause negative impacts that alter the environmental quality of an area, making it more fragile, for example, the occurrence of erosive processes. Thus, adequate planning of the physical space is necessary in order to protect and control the activities developed in a given area. In view of this scenario, the environmental fragility of the Rio Claro Hydrographic Basin (BHRC), located in the municipality of Santa Rita do Passa Quatro (SP), was determined to encompass 251.91 Km² of the UGRHI unit of the Mogi Guaçu-Mogi River and constitutes in an area of great importance to the abstraction of surface water for public supply. The study was developed over a period of 16 years (2001-2017), in the scale of 1: 50.000 and involved four attributes of the physical environment and the use and cover of the soil, considering five classes of fragility: Very Low; Low; Average; High; and Very High. The changes between the middle and upper classes (5%) are due to changes in the types of land use and land cover. These two classes represent the highest percentages of area and require greater care, since they are located in regions where the soil presents a sandy texture and depth of more than 10 m, constituting a scenario favorable to the appearance of erosive features, which may lead to soil degradation and sedimentation of the watersheds of this river basin, if protectionist measures are not adopted.