Assessment of soil erosion risk in the mountainous region of northeastern Turkiye based on the RUSLE model and CMIP6 climate projections

Water erosion leads to significant environmental, social, and economic challenges, such as the loss of fertile soil, reduced agricultural productivity, and water pollution. This study evaluates erosion-prone areas in the Oltu Basin, northeastern Turkiye, using the RUSLE model for the reference year (2023) and future climate scenarios (SSP245 and SSP585, 2041-2060/2061-2080). The average erosion rate for 2023 was determined as 49.90 t/ha/year, classifying 36.71% of the basin as severe or higher erosion risk. The critical vulnerability is attributed to the basin's steep topography, with an LS factor (similar to 9.87) significantly exceeding the European average. Under future climate scenarios, average erosion rates remain relatively stable (49.87-52.53 t/ha/year). However, notable spatial variations emerge, particularly in the western basin, where high-risk erosion areas are expected to increase. These changes are driven by shifts in rainfall erosivity (R factor), with a decline in maximum values but a rise in minimum values. The R factor decreased from 148.64 MJ mm/ha/h/year in 2023 to 144.90 MJ mm/ha/h/year under SSP245 (2061-2080); however, soil loss increased slightly from 49.90 t/ha/ year to 50.57 t/ha/year due to the uneven spatial distribution of the R factor within the basin. This study emphasizes the spatial shifts in erosion sensitivity rather than overall averages, providing critical insights for targeted erosion control strategies. The findings will assist decision-makers in mitigating soil erosion risks and developing climate-adaptive land management policies.