Environmental fragility analysis in reservoir drainage basin land use planning: A Brazilian basin case study

Reservoirs constructed for multiple water and land use changes alter the hydro-sedimentological dynamics of drainage basins, intensifying erosion and silting of water bodies. To ensure water and soil conservation, environmental fragility analysis is a notable tool in land use planning. Potential environmental fragility (PEF) is the dynamic equilibrium of the environment, understood as the natural susceptibility of physical parameters to erosion. In conjunction with the socioeconomic parameter of land use, it generates emergent environmental fragility (EEF). This study analyzes PEF and EEF of the Lobo Reservoir Drainage Basin, a small basin in southeastern Brazil, and recommends environmental zoning derived from its assessment. Physical parameters, on a 1:50,000 scale, and land use spatial data were used to create PEF and EEF maps, followed by recommendations for suitable use for the basin's sectors, taking into account their environmental fragility and current land use. The results indicate that the basin is primarily classified as medium EEF, which is related to its medium PEF and to the region's agricultural activities. The proposed environmental zoning designates nearly half the basin as suitable for anthropic use, while 28.5 % is considered a priority for environmental conservation. Areas identified as a priority for conservation/restoration represent some 16 % of the basin. Limitations and potential enhancements to the study's methodology were encountered, but none impaired the EEF analysis, which identified areas that could favor erosion. The land use planning proposed by the study based on its environmental fragility analysis provides a low cost, flexible, and easy to use method, facilitating its adoption by public managers and use by government technicians. Moreover, the study's methodology can be widely replicated in other regions and fine tuned in accord with their specific characteristics and morphodynamic patterns.