Soil erosion estimation in the Bagmati River basin of Nepal using RUSLE modeling to assess priority areas for conservation

Soil erosion is a major issue, resulting in the loss of topsoil and fertility. This study estimates total and average soil loss, analyses the effect of land use and land cover (LULC) on soil erosion, and prioritizes the soil erosion risk zone in the Bagmati River basin using the revised universal soil loss equation (RUSLE) model. Rainfall erosivity factor (R), soil erodibility factor (K), topographic factor (LS), cover management factor (C), and support practice factor (P) ranged from 94.25 to 666.11 MJ mm ha⁻¹ h⁻¹ yr⁻¹, 0.104 to 0.154 t h MJ⁻¹ mm⁻¹, 0 to 24.05, 0 to 0.28, and 0.55 to 1, respectively. The computed annual soil loss values in the basin ranged from 0 to 201.334 t ha⁻¹ yr⁻¹in 2010, and 0 to 204.687 t ha⁻¹ yr⁻¹ in 2016. The average soil loss rate of the basin was 21.5 t ha⁻¹ yr⁻¹ in 2016 and 21.14 t ha⁻¹ yr⁻¹ in 2010. The average annual soil loss was highest in barren land (10.28 t ha⁻¹), while the minimum was in water bodies (0.69 t ha⁻¹). The maximum erosion potential was found in the agricultural land (204.69 tha⁻¹) and the minimum in the water bodies (87.54 t ha⁻¹). Application of bioengineering techniques can control soil losses in the Bagmati River basin. Overall, the application of modern methods and technology, i.e., RUSLE and GIS, will be helpful for the prediction of potential soil losses from river basins. Thus, managers and policymakers can implement adequate conservation programs with high erosion risk that will reduce soil loss in the future.