Effects of soil crust on the collapsing erosion of colluvial deposits with granite residual soil

Collapsing erosion is a unique phenomenon commonly observed on the granite residue hillslopes in the tropical and subtropical regions of southern China, characterized by its abrupt occurrence and significant erosion volumes. However, the impacts of soil crust conditions on the erosion of colluvial deposits with granite residual soils have only been studied to a limited extent. To address this issue, this study investigates the impacts of three soil crust conditions (i.e., without crust, 10-minute crust, and 20-minute crust) on gully morphology, rainfall infiltration, and runoff and sediment yield during slope erosion of colluvial deposits with granite residues (classified as Acrisols) in Yudu County, Ganzhou City, Jiangxi Province, China, using simulated rainfall tests and photographic methods. The results showed that as the strength of the soil crust increased, the capacity of moisture infiltration and the width and depth of the gully as well as the sediment concentration and yield ratio decreased; at the same time, the runoff ratio increased. The sediment yield in the without-crust test was found to be 1.24 and 1.43 times higher than that observed in the 10-minute crust and 20-minute crust tests, respectively. These results indicate that soil crusts can effectively prevent slope erosion and moisture infiltration, while providing valuable insights for the management of soil erosion in natural environments.