Tunis:A new scientific synthesis has revealed that the mountain slope involved in the Gyirong-Rasuwa disaster was deforming significantly before its failure, with up to 40 centimeters of movement recorded between July 7 and August 24, 2026. This slope deformation was detected by Sentinel-1 InSAR satellite observations, indicating significant movement before the disaster occurred.
According to National News Agency Nepal, the disaster resulted in at least 1,451 fatalities in Nepal, with 5,745 people reported missing. In China, authorities reported 43 deaths and 519 missing persons. These findings were discussed at Nepal’s National Conference on Disaster Risk Reduction, where experts gathered to analyze recent disasters and assess emerging risks in the Himalaya region.
The report, titled “Understanding the Gyirong-Rasuwa Disaster of 26 August 2026,” was presented by Pema Gyamtsho, Director General of ICIMOD. The findings come as scientists also investigate a recent incident in the Budhi Gandaki basin involving an ice-rock avalanche and glacier collapse. Both events, occurring within a short span, highlight the increasing threat of cascading mountain hazards in the region.
The synthesis reported that about 132 million cubic meters of rock and glacier ice detached from Langtang Lirung’s northern face, leading to a debris flood into the Lhende Khola valley. Although the observed slope movement suggested instability, researchers note it could not predict the exact timing of the collapse. However, such findings emphasize the potential of satellite monitoring in identifying high-risk slopes for further study.
The disaster was characterized not as a traditional glacial lake outburst flood but as a massive bedrock failure that initiated a chain of cascading hazards. Pema Gyamtsho emphasized the need for practical risk reduction measures through enhanced monitoring and cooperation.
The report calls for improved integration of satellite monitoring, seismic and hydrological data, and cross-border information sharing to mitigate future risks. Factors contributing to the collapse may include geological weaknesses, effects of the 2015 Nepal earthquake, thawing permafrost, and glacier changes. No specific trigger has been confirmed.
The implications of these findings extend beyond individual events, as the Gyirong-Rasuwa corridor has experienced multiple disasters in a short period, underscoring the need for a deeper understanding of how various factors contribute to these hazards in the Hindu Kush Himalaya region.
The report advocates for using Earth observation data to identify other potentially unstable slopes, with technologies like radar satellites playing a crucial role. ICIMOD and partners plan a joint field mission to collect additional evidence and support further monitoring and risk assessment efforts in the region.