Soil detachment by overland flow on steep cropland in the subtropical region of China

Accurate prediction of soil detachment capacity is fundamental to establish process-based erosion models and improve soil loss assessment. Few studies were conducted to reveal the mechanism of detachment process for yellow soil on steep cropland in the subtropical region of China using field experiments. This study was performed to determine soil detachment characteristics and explore the relationships between soil detachment capacity (D-c) and flow rate, slope gradient, mean velocity, shear stress, stream power and unit stream power. Field experiments were conducted on intact soil with flow rates ranging from 0.2 x 10(-3) to 0.5 x 10(-3) m(-3) s(-1) and slope gradients varying from 8.8 to 42.4%. The results showed the following. (a) D-c of yellow soil was smaller than other soils because of its high clay content. (b) D-c was more susceptible to flow than to slope gradient. Power functions were derived to depict the relationship between D-c and the flow rate and slope gradient (R-2 = 0.91). (c) D-c was better simulated by power functions of the stream power (R-2 = 0.83) than functions of the shear stress or the unit stream power. (d) Considering its accuracy, simplicity and accessibility, the power function based on flow rate and slope gradient is recommended to predict D-c of yellow soil in the field. The results of this study provide useful support for revealing soil detachment mechanism and developing process-based soil erosion models for the subtropical region of China.