Multicriteria geospatial analysis for prioritizing soil erosion risk areas in a reservoir-contributing watershed

Soil erosion is a serious threat to sustainable land use management, making the identification of erosion-prone areas increasingly important. This study aimed to identify areas with riska to soil erosion in the Piquiri River basin, a significant tributary of the Paraná River and a key contributor to the Itaipu Hydroelectric Plant reservoir. A Multi-Criteria Analysis (MCA) integrated with geospatial techniques was used to map areas most susceptible to erosion. Several factors were considered: topography, land use and cover, soil erodibility, landslide susceptibility, proximity to rivers, time of concentration, and pasture quality. The criteria were analyzed using the Analytic Hierarchy Process (AHP), which allowed for weighting the relative importance of each factor based on expert consultation. The factors were combined using two multi-criteria methods: Weighted Linear Combination (WLC) and Ordered Weighted Averaging (OWA). The maps indicated that the highest erosion risk areas are mainly concentrated in the upper and middle parts of the basin, associated with steep slopes and degraded pastures. Furthermore, it was found that regions close to rivers also presented high priority for intervention. The OWA method, by varying the level of risk and compensation, made it possible to simulate different decision-making scenarios. The methods were compared with MUSLE and similarity was verified between the priority areas estimated by multicriteria analysis and soil loss. The study concludes that multicriteria techniques, integrated with geospatial tools, are effective in identifying priority areas for intervention, supporting soil conservation and erosion mitigation actions.