CHARACTERISTICS OF RIVER-BLOCKING EFFECT TRIGGERING BY HIGH ALTITUDE GEOHAZARDS IN THE CANYON AREA OF SOUTHEASTERN XIZANG

High-altitude geohazard chains in mountainous and extremely high-altitude regions often lead to downstream valley blockages and trigger outburst floods due to distal propagation distances. This study focuses on the southeastern Xizang canyon area,employing various technical methods including field surveys,multi-temporal remote sensing imagery,drones,and numerical simulations to elaborate on the types,scales,chain effects,damming of rivers,and evolution characteristics of these high-altitude geohazard chains. The results indicate that: (1)The number of high-altitude geological disasters in the study area reaches 187,primarily consisting of rockfalls,rock-ice avalanches,debris flows,and landslides. (2)Regarding river blockage types,the main causes are landslides and debris flows; disasters on the left bank of the mainstream account for 58.29% and those on the right bank for 41.71%. More than 50% of disaster points exceed ten million cubic meters in volume,mainly involving rock-ice avalanches and debris flows. (3)The segment from Lebai to Baimala exhibits the most developed high-altitude geohazard chain,forming a damming zone approximately 20 km long,leading to multiple channel diversions and an overall riverbed uplift of about 20 m. (4)The initial sliding mass,after descending from high altitudes,collides with the valley at high speeds,with maximum impact velocities exceeding 50 m · s^-1. Under intense dynamic erosion,the volume of the disaster increases several times,and after damming the river,the time for internal ice particles to melt and trigger a breach is significantly shortened. In the future,under the combined effects of climate change and tectonic activities,the risk of breach-type flooding due to high-altitude geohazard chains in southeastern Xizang is extremely high,necessitating enhanced monitoring and early warning for such disasters.