Response Relationship between Microtopographic Variation and Slope Erosion under Sand-Cover

Abstract

Slope microtopography is an important factor that affects the process of slope erosion. We quantified the responses between microtopography and the amount of erosion on overland sand slope and loess slopes through an indoor artificial simulated rainfall experiment. Three continuous rainfall tests under 1.5 mm/min rain intensity were used to analyze the spatial variation of slope microtopography and soil erosion with three-dimensional laser scanning technology. Our results show that under 0.5, 1.0, and 1.5 cm sand-covered slopes, the runoff time of the first rainfall is delayed by 18, 19, and 23 min, respectively, compared with the loess slope. Furthermore, the average sediment concentration on the slope decreased with subsequent rainfall events. The total erosion of the slope under 0.5, 1.0, and 1.5 cm sand was 4.24, 3.57, and 5.40 times that of the loess slope, respectively. The erosion of the sand-covered slopes was much larger than that of the loess slope. The length of the main sand production area was about 2.4 times that of the loess slope and the peaks of the erosion amount of the slope were mostly distributed in the lower part of the slope. As the rainfall progressed, the microtopographic factors of the loess slopes increased significantly (p < 0.05), and the microtopographic factors of the sand slopes increased, but not significantly (p > 0.05). We found that the microtopographic factors with the strongest erosion responses to the loess slope and the sand-covered slope were surface incision and surface roughness. The response relationship between microtopographic variation and erosion of the loess slope was stronger than the sand-covered slope, and suggests that other, unaccounted-for factors may be affecting the erosion of sand-covered slopes. This study provides a reference for erosion mechanisms of the wind–water erosion crisscross region.