Runoff erosion process on different underlying surfaces from disturbed soils in the Three Gorges Reservoir Area, China

• Runoff regime on underlying surface manifest as turbulent and subcritical flow.
• Runoff yield rate exists fluctuations and sudden changes phenomenon.
• Rill erosion has few influence on runoff yield at >15 L/min flow discharge.
• Collapse on gully wall is a important cause for sediment yield fluctuations.
• Influencing degree of hydrodynamic parameters on sediment yield is γQ > γP > γv > γτ > γƒ.

Disturbed soil accumulation caused by all man-made activities during the producing and constructing process of large-scale projects is the main landform occurred artificial water and soil loss. Because of its different producing sources and soil-rock ratios, the underlying surfaces from disturbed soil accumulation often characterize a unique soil erosion process under same runoff scouring condition. Taking the ubiquitous purple soil deposits and yellow sand deposits associated with different soil-rock ratio as examples, the study aimed to explore the difference in both hydraulic properties and sediment yield characteristics on disturbed soils. Some field scouring experiments were conducted in Chongqing, China. These results indicate that: (i) Runoff regime on all underlying surfaces from disturbed soils often manifest as turbulent and subcritical flow during runoff scouring process. (ii) For rocky disturbed soils from purple soil, sediment production rate shows continuously waving variations, and the average sediment production rates are 0.28, 11.65, 33.69, 73.00, and 177.37 g/(m2·min), respectively, when flow discharge increase from 5 to 25 L/min gradually; the collapse on gully wall caused by its gravity from underlying surfaces is the important cause for the fluctuating variations of the sediment production rate. (iii) The influencing degree of hydrodynamic parameters on sediment yield is in such order as γQ > γP > γv > γτ > γƒ. These study results could be used to control artificial erosion caused by production and construction projects and to provide some important parameters for soil and water loss predicting in the Three Gorges Reservoir Area of Chongqing.