Influence of crack characteristics on the morphological development of Benggang and hydrological processes

Benggang is a special type of soil erosion, which widely distributes in the granite residual soil area of southern China. Owing to the influence of local climate and topography, shallow cracks having different morphological characteristics are easily formed on the slope surface. These shallow cracks damage the surface structure of the slope and accelerate water infiltration, making it easier to cause severe soil and water loss. However, the mechanism of Benggang process is still unclear, especially for slopes with different shallow crack characteristics. In this study, granite residual soil was collected from Benngang erosion area in Yudu County, Jiangxi Province, southern China. Three experimental treatments with slope surface crack rates of 0%, 5.23%, and 11.70% were performed. Simultaneous monitoring of moisture content and soil temperature in the slope were carried out during rainfall, and the characteristics of preferential flow were monitored with different crack rates. Morphological development and evolution process of Benggang with different crack rates were studied. Results show that high surface crack rate of the shallow surface on the slope accelerated the development of shallow gully erosion, leading to premature occurrence of gully erosion. As the shallow crack rate increased from 0% to 5.23% and 11.70%, the width-depth ratio of the rills at the slope bottom increased from 0.69 to 1.02 and 1.16, respectively. At the same time, a correlation between moisture and temperature data was observed for the process of water-heat coupled migration. The upper soil temperature of slope decreased quickly due to preferential flow. The simultaneous monitoring of soil moisture and temperature can effectively track preferential flow and indicate the water movement. Temperature data was a more sensitive indicator of the seepage paths of preferential flow compared to moisture data.