Interactive Effects of Rainfall Intensity and Initial Thaw Depth on Slope Erosion

Seasonal freeze-thaw processes have led to severe soil erosion in the middle and high latitudes of the world, so understanding the freeze-thaw erosion process is of great significance for soil and water conservation as well as for ecological engineering. The area affected by freeze-thaw erosion in China exceeds 13% of the national territory. However, there is little data regarding the impact of rainfall intensity and initial thaw depth on soil erosion. Here, the effects that different rainfall intensities (0.6 mm/min, 0.9 mm/min and 1.2 mm/min) and different initial thaw depths (0 cm, 2 cm, 4 cm and 6 cm) had on the soil erosion process on the loess slope were studied under simulated rainfall conditions. The results showed that the infiltration rate decrease with prolonged runoff time, and then stabilized. Runoff occurred more quickly during increasingly intense rainfall, especially when little soil had thawed. The variation in runoff and sediment yield occurred in two stages: slow growth and rapid growth. As soil thawed to greater depths, rainfall intensity had less influence on the sediment. A linear relationship existed between the cumulative runoff and the sediment yield of all treatments. (R-2 > 0.92, p < 0.01). Rainfall intensity and thaw depth had interacting effects on erosion. At low rainfall intensities, the initial thaw depth played a leading role in the erosion process, but at higher rainfall intensities, rainfall intensity played a larger role. Stage II erosion amount accounted for more than 90% of the total erosion across all treatments. The results of this research provide a guide for furthering the understanding of the soil water erosion mechanism of thawing slopes.