Flash Floods in Nepal Result in Over 160 Deaths, Linked to Glacial Instability

Flash floods in a region on the mountainous border of Nepal and Tibet resulted in approximately 160 deaths and left hundreds more, including international tourists, missing on Wednesday. Footage shared on social media depicted individuals fleeing from a wall of water that swept away buildings and vehicles. Initial assessments based on satellite imagery and reports from the Nepalese government suggest that the flooding was likely triggered by a landslide caused by a piece of glacier falling hundreds of feet. As temperatures in the region rise, the stability of its ice is decreasing, which increases the risk of severe flooding. Joseph Shea, an associate professor of geography at the University of Northern British Columbia, stated, "The glaciers over there are definitely in retreat," noting the thinning and retreating of glacier mass. Since 2000, the world’s glaciers have lost 5 percent of their ice, with more severe impacts in specific areas. Research indicates that Nepal’s glaciers lost nearly a quarter of their area between 1970 and 2010, and over 160 smaller glaciers in the country have disappeared entirely. A recent study warns that 40 percent of the world’s glacial ice could vanish if global warming exceeds 1.5 degrees Celsius. The impacts of warming on glaciers in Nepal can lead to cascading effects, as retreating glaciers may trigger landslides due to their inability to hold back sediment. Shea explained that the retreat of glaciers often results in the formation of large, dammed lakes at higher elevations, which pose risks of catastrophic flooding if a landslide occurs. Wednesday’s disaster is believed to be related to a glacial collapse into the valley below. Daniel Shugar, a geologist at the University of Calgary, indicated that satellite imagery suggested a 2,000-foot-wide piece of ice may have fallen nearly 4,000 feet, causing significant disruption. He noted that while it is too early to draw definitive conclusions about the floods' cause, warm temperatures likely contributed to the melting of snow on the glacier earlier in the week. The collapse and subsequent debris flow were substantial enough to be recorded as a magnitude 5.2 seismic event by the US Geological Survey. Similar glacier collapses have previously resulted in destructive outcomes, such as the collapse of a Swiss glacier last year that buried a town, and a glacier collapse in Italy in 2022 that killed 11 mountaineers, both linked to rising temperatures. Shea remarked that multiple factors in a warming climate can interact to destabilize glaciers, stating, "It’s summertime. There’s lots of warming, lots of melt happening, lots of water around." He also mentioned the thawing of alpine permafrost, which can lead to the movement of large blocks of ice that were previously frozen in place.