Characteristics and formation mechanisms of sand-flow talus slopes in cold–arid Valleys, Southeastern Tibet

Abstract

Talus slopes are prevalent throughout alpine mountain regions. In southeastern Tibet, along the Bomi–Ranwu section of the G318 National Highway, sand-flow talus (SFT) deposits pose a significant threat to the road. This research explores their development, environmental influences, and formation processes through field surveys, remote sensing, laboratory tests, and spatiotemporal data analysis. The findings show that factors such as precipitation, elevation, the aridity index, and stream order play crucial roles in shaping these slopes. Approximately 72 % of the slopes are found close to first-order streams. Detrital particles primarily originate from the physical weathering of granites, which are primarily made up of mineral particles such as quartz and feldspar, with minimal clay content. The weathered material comes from medium- to coarse-grained granite bedrock and is shaped by dense structural planes in cold-arid valley conditions. Daily temperature fluctuations induce thermal fatigue and freeze–thaw cycles, which primarily facilitate the physical weathering of rock. The development of SFT slopes involves rock-mass collapse, gravity-driven downward movement, and particle transport over long distances via flow zones. Hydraulic erosion processes, such as interrill and rill erosion, primarily drive the movement and accumulation of grain materials. This study offers new insights into the formation mechanisms of SFT slopes in alpine mountain environments and establishes a scientific basis for hazard prevention.