The mudslide disaster site in Xigaze City, Southwest China's Xizang Autonomous Region Photo: Xinhua

A mudslide disaster that struck Gyirong Port in Xigaze City, Southwest China's Xizang Autonomous Region on Wednesday, causing three dead and 558 missing as of Thursday, was triggered by a high-altitude ice avalanche in Nepal, according an expert from China's Ministry of Natural Resources, the Xinhua News Agency reported on Thursday.

At around 10:30 am on Wednesday, a mudslide on the Nepal side caused major casualties and left people missing at Gyirong Port in Gyirong County in Xizang.

An expert from the ministry's geological disaster investigation and monitoring center explained that the ice avalanche from a high-altitude glacier rapidly traveled downhill, picking up glacial debris along its path and developing into a high-speed debris flow. The flow then entered the Donglin Tsangpo River , eventually striking infrastructure at Gyirong Port before continuing downstream toward Nepal.

"This disaster was caused by a debris flow triggered by an ice avalanche," said Guo Zhaocheng, director of the geological disaster investigation and monitoring center at the China aero geophysical survey and remote sensing center for natural resources.

"Specifically, a high-altitude ice avalanche collapsed from the mountainside and, as it moved at high speed, entrained glacial debris along the channel, forming a fast-moving debris flow. It then traveled along the channel, evolved into a mudslide, hit port facilities and areas abroad, and continued moving toward Nepal," Guo said.

Such incidents have occurred in the Qinghai-Xizang Plateau region in the past, but they are relatively rare, Guo noted. Compared with glacial lake outburst floods, this type of disaster can generate greater impact forces and travel farther distances.

According to estimates, the debris flow triggered by the ice avalanche that caused the mudslide that hit Gyirong around 50 meters per second. It moved so rapidly that there was virtually no time to react, while its impact extended more than 20 kilometers, resulting in severe losses, according to the expert. 

"Therefore, in disaster prevention and mitigation efforts on the Qinghai-Xizang Plateau, we need to prepare for extreme scenarios while fully considering these complex situations," Guo said.

Following the mudslide disaster, a significant barrier lake has formed near the confluence of the Chhochen Khola and Purepu Tsangpo rivers. 

As of the morning of Thursday, the reservoir's water storage was estimated at around 2 million cubic meters. According to forecasts, rainfall is expected to bring approximately 3 million cubic meters of additional inflow into the barrier lake over the next three days. 

The risk of a breach is high, potentially causing further damage to Gyirong Port and downstream areas along the river, according to Xinhua.

Reporters visited several hotels in Gyirong Town and found that most tourists had begun leaving the town gradually on Thursday morning. The town is a major land gateway for travelers going between Kathmandu and China's Xizang. 

Based on tourists' individual travel arrangements, a total of 555 affected visitors have been evacuated and relocated with assistance from local cultural and tourism authorities and other relevant departments. 

No tourists remain stranded, and all 499 affected people from Gyirong county have been properly resettled, the Global Times learned from the local authority of Xigaze.

Global Times