Rainfall Erosivity Assessment for Soil Conservation Planning in Cross River State

Rainfall erosivity, the capacity of rainfall to detach and transport soil particles, is a foundational parameter in soil erosion prediction models used for land management and conservation planning. This study assesses spatial and temporal patterns of rainfall erosivity in Cross River State, Nigeria's South South zone, using the Modified Fournier Index (MFI) and the RUSLE R-factor computed from monthly rainfall records at seven NiMet stations across the state for the period 2015 to 2022. Spatial interpolation using kriging was performed to produce continuous erosivity maps at the state scale. Results indicate that Cross River State exhibits among the highest rainfall erosivity values in Nigeria, with annual R-factor estimates ranging from 8,500 to over 14,000 MJ mm per hectare per hour per year. Elevated erosivity values coincide spatially with the forested highlands of Obudu and Ikom where rainfall totals exceed 2,800 millimetres annually. Temporal analysis reveals that the months of June, July, and August contribute over 60 percent of annual erosivity, highlighting the importance of conservation measures during peak rainfall. The study demonstrates that current land management practices in many farming communities fail to account for the extreme erosion risk posed by high-intensity storm events. Recommendations include adoption of erosivity-informed soil and water conservation guidelines in Cross River's agricultural extension programs. Keywords: rainfall erosivity, RUSLE, Modified Fournier Index, Cross River, soil conservation.