Scree soil surface flow erosion: characteristics and gravel mulch technology

The prevention and control of scree soil surface flow erosion in northwest China’s arid and semi-arid regions is crucial for ensuring the safety of oil and gas pipelines. This study investigates erosion characteristics through field experiments conducted on typical scree soils from Gaotai, Gansu Province, analyzing runoff dynamics and gravel particle movement across different slope gradients. We derive an energy consumption formula for channelized runoff and establish an “initiation particle size” model based on underwater particle mechanics, with theoretical calculations showing strong agreement (7.2–11.4% error) with field measurements. The research introduces an innovative gravel mulch technique that utilizes particles larger than the initiation size collected from downstream erosion channels. The mulch thickness is determined by upstream channel erosion depth, creating an economical and environmentally sustainable erosion control solution. Our findings demonstrate that: (1) rill erosion energy correlates with flow rate and velocity squared; (2) bend sections exhibit 15–20% higher erosion rates than straight channels; and (3) the critical particle size threshold for effective protection is 4.45 mm at 0.284 m/s flow velocity. This approach provides a scientifically-grounded methodology for pipeline protection in scree soil environments while optimizing resource utilization.