Objective Soil erosion is a prominent issue in the hilly region of northern Sichuan. Understanding the mechanism of runoff and sediment yield in typical soil under natural rainfall conditions is crucial for the precise prevention and control of regional soil and water loss.

Methods Based on a bare runoff plot of yellow soil in the hilly region of northern Sichuan, rainfall, runoff, and sediment yield data were obtained using rain gauges, field observations, and laboratory measurements. Key rainfall factors were identified and their influence quantified through stepwise regression and path analysis.

Results 1) A total of 138 erosive rainfall events occurred from 2014 to 2022, distributed from April to October. 2) The multi-year average runoff depth was 197 mm and soil loss amount was 1 057.63 t/km². 3) Stepwise regression identified that rainfall erosivity (R), rainfall (P), maximum 30 min rainfall intensity (I₃₀), and rainfall duration (D) were primary factors influencing runoff depth. For soil loss amount, the key driving factors were R, I₃₀, and D. 4) Path analysis revealed that R had the strongest direct positive effect on runoff depth (0.692), and its synergy with other factors increased the total effect to 0.906. Although I₃₀ exhibited a direct negative effect on runoff, its strong positive indirect effect (0.722) with other factors (R and P) resulted in a significant overall positive effect (0.501). Soil loss amount was primarily directly driven by R (0.836). While I₃₀ had a negative direct path coefficient, its synergistic indirect positive effect with R indicated that it still promoted soil loss in general.

Conclusions This study quantifies the interactive effects of multiple rainfall factors on slope runoff and sediment yield. It reveals that R is the key influencing factor. These findings provide a scientific basis for optimizing regional soil erosion model parameters and spatiotemporal configuration of soil and water conservation measures.