Variability and driving factors of the soil saturated hydraulic conductivity along the horizontal and vertical directions in the upper catchment of Benggang

Tiny niche terrain induces gully headcut retreat

“…In this study, the niche development in a collapsing wall in the Benggang area of southern China was taken as an example, and for the purpose of quantification, the soil properties were calculated according to the vertical profile of a collapsing wall in a typical Benggang area. Based on indoor test data and reference to previous relevant research (Tang, Duan, et al, 2023; Wang et al, 2022), the soil bulk density is 1.25 g/cm 3 , the water density is 1.00 g/cm 3 , the cohesion is 25 kPa, the internal friction angle is 30°, and the gravitational acceleration is 9.8 m/s 2 . Based on field investigations of typical Benggang erosion and NC morphological parameters in southern China, the water depth in the fissure is set to half of the crack depth, and the vertical distance between the top of the niche and the back edge of the top of the gully is 2.5 m. When a certain parameter changes, the other parameters are set as follows: The niche height is 1 m, the niche angle is 60°, the catchment slope angle is 0°, and the tension crack depth is 0.5 m.…”

“…In the Benggang granite of southern China, there are two types of widely distributed niche, the NCs and NEGs, both of which are concentrated in areas with sparse vegetation, strong water erosion, and sandy layer outcrops (Gao et al, 2022; Lin et al, 2023; Tang, Duan, et al, 2023). NCs mostly develop in collapsing walls, and their formation process is similar to that of the above two niche types, which are formed by wall flow down a collapsing wall that erodes a soil layer with weak resistance to erosion, and the developmental process can be divided into three stages: prototype, development, and formation (Figure 3).…”