Mapping spatiotemporal variations in soil erosion using RUSLE model in Anambra State, Nigeria

Soil erosion is a geomorphic hazard that has significantly degraded much of Anambra State’s landscape. To assess the spatiotemporal variations from 2017 to 2022, we employed the Revised Universal Soil Loss Equation (RUSLE) model and trend analysis. The mean erosivity ranged from 1565.17 to 1817.60 MJ mm ha⁻¹ h⁻¹ yr⁻¹, with a coefficient of variation (CV) between 8.68 % and 11.29 %. The C-factor has CV values that ranged from 90.91 % to 103.45 %. The mean annual soil loss varied from 21.32 to 26.51 t ha⁻¹ yr⁻¹. The lowest erosion was recorded in 2017, and the highest in 2019; however, a general increase in erosion was observed from 2017 to 2022. Soil loss, C-factor, and R-factor displayed rising trends, with p-values of 0.13, 0.01, and 1.00, respectively. This indicates that land cover change is a dominant driver of accelerated soil erosion in the state. Nevertheless, the critical role of erosivity is evident, as the year with the highest rainfall erosivity corresponded with the maximum soil loss. Soil loss is especially severe in ten local government areas (LGAs): Oyi, Nnewi North, Aguata, Idemili North, Anaocha, Nnewi South, Awka South, Njikoka, Idemili South, and Onitsha North. The findings reveal an increasing soil erosion trend at a rate of 0.75 t ha⁻¹ yr⁻¹ annually in the state. Accordingly, we recommend aggressive reforestation, and intensive conservation agriculture practices such as reduced to no-till agriculture, cover-cropping, and agroforestry. Additionally, the Anambra State Erosion, Watershed, and Climate Change Agency (ANSEWCCA) should also extend their intervention and stabilisation efforts to rill erosion through nature-based approaches.