Soil Detachment Capacity by Overland Flow for Soils of the Beijing Region

Soil type may influence soil detachment process by overland flow, but few studies have quantified the effect fully and systematically. This study was undertaken to quantify the effects of soil type on soil detachment capacity using undisturbed soil samples collected from 11 soil types from the Beijing Region. The soil samples were placed in a 5.0-m long and 0.38-m wide hydraulic flume and eroded by overland flow under three slope gradients (17.4%-34.2%) and three unit discharges (1.32-5.26 x 10(-3) m(2) sec(-1)). The results showed that soil detachment capacities were significantly affected by soil types. Aeolian Sandy Soil was the most easily detached, whereas Wet Meadow Soil was the hardest. Soil detachment capacity was significantly affected by soil properties. For soil texture, loamy sand had the largest detachment capacity, followed by sandy loam, loam, and silt loam. Furthermore, detachment capacity was negatively correlated to clay and silt content and positively related to sand content and median diameter of soil particles. Both shear strength and organic matter content were negatively correlated to detachment capacity. Detachment capacity could be predicted reasonably well by stream power, clay content, and organic matter content (r(2) = 0.743) with a coefficient of Nash-Sutcliffe efficiency of 0.644. An equation was developed to estimate detachment capacity based on streampower and soil properties (r(2) = 0.704; Nash-Sutcliffe efficiency, 0.702). Rill erodibility ranged from 0.73 to 85.22 x 10(-3) sec m(-1), and the critical shear stress changed from 0.683 to 7.978 Pa. The results are helpful to understand the mechanism of soil detachment process under different soil types and to develop the process-based erosion models.