On-site experiment on the rainfall erosion process of soil slopes and its hydraulic mechanism

The Loess Plateau in China is facing serious ecological problems, such as ecological degradation and slope instability, as well as the threat of geological hazards. In this study, by selecting typical slope surfaces, an on-site rainfall simulation experiment was conducted, through which the erosion process, morphology, and dynamic characteristics under different rainfall intensity, slope gradient, and vegetation coverage were probed. Major findings include the following: (1) The time to first runoff varied under different conditions, ranging from 56 to 100 s. As the three factors of rainfall intensity, slope gradient and vegetation cover varied, surface infiltration, runoff yield and sediment yield all underwent significant changes. (2) Following rainfall, the morphological parameters of the rills underwent significant changes. DEM data further revealed that all rills exhibited the characteristic of being narrow and shallow at the top and wide and deep at the bottom, with rill development being most pronounced under a rainfall intensity of 90 mm/h. (3) Flow velocity within the rills increased with increasing rainfall intensity and slope, but decreased with increasing vegetation cover. Calculations of hydraulic parameters indicated that surface runoff exhibited turbulent flow. (4) A clear linear correlation existed between the average sediment yield rate and the three indicators. Based on a comparison of these three indicators, it was concluded that unit runoff power is more suitable for describing the sediment yield process in the study area.