Abstract:Rill erosion rate and hydrodynamic parameters present evident spatial and temporal variation characteristics during rill development process on hillslopes. Based on 3D laser scanning technique (LiDAR) and intermittent simulated rainfall experiments, high-precision DEMs were extracted. Temporal and spatial variations of rill erosion and hydrodynamic parameters at different rill development stages on loessial hillslope were analyzed. Results showed that the maximum values of rill erosion rate and hillslope erosion rate occurred at the rill deep cutting dominated stage, while the minimum values of them occurred at the rill headcut dominated stage. Rill erosion rates and hillslope erosion rates were increased at first and then tended to be steady and fluctuated in a certain range with rainfall duration. Hillslope erosion rates reached steady state earlier than rill erosion rates. Rill erosion rates and hillslope erosion rates under 90mm/h rainfall intensity reached steady states earlier than those under 60mm/h rainfall intensity. Rill erosion rates were first increased and then decreased along hillslope and showed parabola trend. The maximum values of rill erosion rate occurred at the hillslope lengths of 6m and 7m. Shear stress, stream power and unit stream power under 90mm/h rainfall intensity were 1.3, 1.1 and 1.4 times as those under 60mm/h rainfall intensity. Hydrodynamic parameters of overland flow and rill flow showed different variation trends with the increase of rainfall duration. Shear stress, stream power and unit stream power were increased with fluctuations of unit slope length under two rainfall intensities. It showed strong positive linear correlation between rill erosion per unit width and three hydrodynamic parameters. The critical values of shear stress, stream power and unit stream power reached the maximum values at initial phase of rill development.
