Nepal Flood Disaster Caused by Glacier Collapse and Landslide, Experts Say

Joseph Shea, a glaciologist and Associate Professor at the University of Northern BC, characterizes the disaster as a compound event where a glacier failure and a massive landslide occurred together. Shea’s analysis places the disaster within the broader transformation of the Himalayas under climate change, noting that warming high-mountain environments may increasingly require scientists to identify subtle precursors to rare cascading hazards.

Casualties and Scale of Destruction

The scale of the disaster has left nearly 1,500 missing, with at least 165 reported dead, according to Reuters. According to authorities, among the missing are at least 800 foreigners, including dozens of Americans.

USA TODAY was told by Alton Byers, a faculty research scientist at the University of Colorado at Boulder’s Institute of Arctic and Alpine Research, that the power of the debris flow was nearly impossible to comprehend. Byers described the event as “one of the largest events” of its kind that he’s seen in some 30 years of research.

The flow consisted of a hyper-concentrated slurry like cement, which Byers said unleashed boulders “as big as houses.” According to the International Centre for Integrated Mountain Development, water levels in the Bhote Koshi basin started rising rapidly around 9 a.m. According to the International Centre, water levels further downstream on the Trishuli River reportedly climbed by more than 27 feet within a 30-minute window.

Geological Triggers and Mechanics

The U.S. Although it was first logged as an earthquake, the seismic activity was actually a 5.2 magnitude debris flow, glacial collapse, and landslide.

Jeffrey Kargel with the Tucson, Arizona-based Planetary Science Institute provided a rapid assessment to the government of Nepal, identifying two sources of initial materials near the Langtang Lirung peak in the Nepalese Himalayas near the border with Tibet. One source was rock located very close to the peak, while the other consisted of snow and glacier ice a few kilometers to the east. Kargel noted there may have been extensive failure all along the area in between.

Kargel stated that the failure propelled a massive amount of ice and rock—estimated between 13 million cubic yards and potentially 10 times that amount—down the mountain. This amount represents a minimum of 500,000 large dump truck loads of ice and rock. At times, the debris may have traveled faster than 186 miles per hour, picking up additional water, debris, and rock as it raced along the river and down the mountain.

Dan McGrath, an associate professor in the geosciences department at Colorado State University, told USA TODAY that the most likely mechanism for the flooding is a glacier collapse. McGrath stated that the ice would have melted during its cascade, “providing the source water for the flood.”

Climate Change and Regional Risk

While some scientists said it’s too soon to definitively link the event to the region’s warming climate, Alton Byers told USA TODAY that flood events of various origins are being seen with “increasing frequency and magnitude” as the Himalayas and other high mountain regions warm faster than most of the world.

As high-mountain environments are altered by warming, there may be a growing need for scientists to detect subtle precursors to cascading hazards that are rare but potentially devastating.