There are 51 tributaries in the middle reaches of the Yarlung Zangbo River (YZR), and the confluences of 87% of the tributaries west of Jiacha Gorge are high-angle or perpendicular, reflecting the anomalous development of these tributaries. In this paper, field investigation and digital elevation model (DEM) methods were used to analyse the causes of this anomalous phenomenon, and it was found that there was a watershed in the area of the Jiacha Gorge. The palaeo-YZR west of the Jiacha Gorge flowed westward before the early Pleistocene into the Zada, Zhongba, Jilong and Gamba–Dingri palaeolakes, which featured a large amount of total accommodation space in the western Qinghai–Tibet Plateau; thus, this river was a continental river. With the intensification of the collision between the Indian plate and the Eurasian plate, the Qinghai–Tibet Plateau experienced rapid uplift and formed a landscape with high elevations in the west and lower elevations in the east, promoting the headward erosion of the eastward-flowing river. During the early Pleistocene, the river east of the Jiacha Gorge crossed the watershed and captured the palaeo-YZR, causing a reversal in the flow direction of the palaeo-YZR.

In the Tibetan Plateau, pronounced topographical relief (steep mountains and deep valleys) coupled with intense weathering processes generates highly fragmented slope surfaces, creating debris-flow source materials with exceptionally heterogeneous grain-size distributions. These conditions frequently produce debris flows that exhibit extraordinary impact forces which cause severe damage to sediment-trap dams. Through 27 sets of flume experiments that systematically varied the particle-size distribution ( d _max ), bulk density ( γ ) and flume slope ( θ ), this study investigates the impact mechanisms of wide-graded debris flows on sediment-trap dams. The results demonstrate that debris-flow interactions with sediment-trap dams occur through three distinct phases: (1) impact run-up, (2) rotational backflow and (3) depositional back-silting. Lower bulk-density flows exhibited greater run-up heights and more pronounced phase differentiation. Measured impact forces ( F ) showed an inverse relationship with bulk density ( γ ↑→ F ↓), while displaying positive correlations with both slope gradient ( θ ↑→ F ↑) and maximum particle size ( d _max ↑→ F ↑). This occurs because higher- γ flows experience increased internal shear resistance, resulting in a reduction in velocity. Steeper slopes enhance kinematic energy, while larger particles generate more concentrated momentum transfer during impact. Sensitivity analysis revealed that d _max exerts dominant control over impact dynamics compared to γ and θ . These findings provide critical insights for sediment-trap dam design in high-altitude debris-flow mitigation systems.

The Woka-Cuona rift zone, situated in the easternmost portion of southern Tibet, displays complex geological conditions. It consists of three distinct grabens or half grabens, spanning the Himalayan and Gangdese terranes from south to north. Examining the distribution patterns and genetic mechanism of the geothermal system in the Woka-Cuona rift zone holds significant guidance for studying the genetic mechanisms of geothermal systems and the production and utilization of ge-othermal resources in the rift zones of southern Tibet. Based on the geological conditions of the study area, the mechanism of rift formation and the distribution characteristics of geothermal water in the three distinct grabens were analyzed through data collection, ground surveys, geochemical analysis, and isotope analysis. Alongside topographic, drainage, and structural features, the Woka-Cuona rift zone was subdivided into four zones from north to south - Woka, Qiongduojiang, northern Cuona, and southern Cuona grabens. Additionally, the study investigated the geochemical char-acteristics, recharge sources, and water-rock interactions of geothermal water in different zones, providing a scientific foundation for subsequent geothermal energy production.