Abstract: Sedongpu gully, situated in the Yarlung Zangbo Grand Canyon in Xizang, is an area of frequent massive river-damming landslides that threaten the geological safety of border towns and major engineering projects. This study focused on a detailed analysis of two river-damming events that occurred on April 15 and May 14, 2024. The disaster formation processes, main causes, and developing trends were widely analyzed. From the methods of water level monitoring, ground motion monitoring, investigating by helicopter, and survey by high-altitude and Unmanned Aerial Vehicles, the formation and development processes of these river-damming events were identified and analyzed. It was found that the disaster body slid along the gully reached 8 minutes and the river-damming lasted over 10 hours. The second disaster was relatively more serious because the landslide-dammed lake had not completely burst, which significantly aggravated the damming of the main channel of the Yarlung Zangbo River. Their causes were examined from topographical and geological conditions, seismic factors, and climate factors. It was determined that the Sedongpu gully has large height differences, fractured rock structures, and a rich source of loose deposits, which provides favorable conditions for disaster formation; the temperature rising during the alternation of the spring and summer leads to the acceleration of glacier melting and the enhancement of hydrodynamic effect, triggering the occurrence of river-damming disaster chain. Furthermore, it is believed that Sedongpu gully has entered an active period of river-damming disaster chain, based on the interpretation of the comprehensive remote sensing images. Our findings revealed that the major river-damming hazards that occurred in 2018 had caused significant changes to the river morphology of the Yarlung Zangbo River; subsequent large-scale river-damming events resulted in more and more clogged up with the river channel, which increased the risk of forming a giant landslide dam. Finally, this paper provided some suggestions for addressing the issues related to river damming, rising water, outburst flooding, monitoring, early warning, and disaster reduction measures for the high-altitude and long runout disasters in the Sedongpu gully.