High-coverage grass on slope–gully systems effectively mitigates gravity erosion in the Loess Plateau

Abstract: Understanding how vegetation patterns control gravity erosion, such as avalanches, landslides, and mudflows, in slope–gully systems under heavy rainfall, remains a key challenge on the Chinese Loess Plateau. To address this, five 1-h simulated rainfalls were conducted, at an intensity of 1.4 mm/min, on experimental plots. These plots featured a gentle slope of 3° and a gully sidewall of 70°, and were covered with different vegetation patterns. Our results show that high-coverage grass on the gentle slope effectively reduced avalanche magnitude. The plot with 85% grass coverage had the lowest average avalanche volume, at 109.6 cm³, across the five rainfall experiments. Conversely, the excessive restoration of woody vegetation, or planting woody vegetation near the gully shoulder line, markedly increased landslide scale. Across the five rainfalls, the average landslide volume was 1,202.7 cm³ in the plot with 85% tree coverage and 983.3 cm³ in the plot with 60% shrub coverage along the gully shoulder line––both nearly triple that of bare land. Mudflow volumes in most of the plots accounted for less than 10% of the total gravity erosion. Avalanche and landslide volumes were significantly correlated with root mass density, silt content, bulk density, and organic matter, with all correlation coefficients exceeding 0.45. Consequently, implementing high-coverage grass on gentle slopes is one of the most effective strategies for mitigating gravity erosion on gully sidewalls.

Keywords: Gravity erosion; Vegetation pattern; Slope–gully systems; Grass; Loess Plateau