Rill erosion processes on a constantly saturated slope

Rill erosion processes on saturated soil slopes are important for understanding erosion hydrodynamics and determining the parameters of rill erosion models. Saturated soil slopes were innovatively created to investigate the rill erosion processes. Rill erosion processes on saturated soil slopes were modelled by using the sediment concentrations determined by sediment transport capacities (STCs) measurement and the sediment concentrations at different rill lengths. Laboratory experiments were performed under varying slope gradients (5°, 10°, 15°, and 20°) and unit‐width flow rates (0.33, 0.67, and 1.33 × 10−3 m3 s−1 m−1) to measure sediment concentrations at different rill lengths (1, 2, 4, and 8 m) on saturated soil slopes. The measured sediment concentrations along saturated rills ranged from 134.54 to 1,064.47 kg/m3, and also increased exponentially with rill length similar to non‐saturated rills. The model of the rill erosion process in non‐saturated soil rills was applicable to that in saturated soil rills. However, the sediment concentration of the rill flow increased much faster, with the increase in rill length, to considerably higher levels at STCs. The saturated soil rills produced 120–560% more sediments than the non‐saturated ones. Moreover, the former eroded remarkably faster in the beginning section of the rills, as compared with that on the non‐saturated soil slopes. This dataset serves as the basis for determining the erosion parameters in the process‐based erosion models on saturated soil slopes. A series of laboratory experiments on saturated soil slope were performed under various hydraulic conditions involving four slopes and three unit‐width flow rates. The measurements of erosion process and the sediment concentrations at the STC level were used to model the rill erosion process as a function of rill length. We concluded that the saturation of rill bed enhanced erosion, and saturated soil rills were eroded remarkably faster within the beginning rill section than the non‐saturated ones.