A massive mudslide triggered by a glacier collapse in Nepal struck Gyirong Port in southwest China's Xizang Autonomous Region on August 26. Rescue teams are racing against time to search for the missing, clear debris and monitor the barrier lake. But the operation is exceptionally difficult. What makes the rescue at Gyirong Port so challenging?

A cascading disaster with extraordinary destructive force

This was far more than an ordinary mudslide. An ice-rock avalanche at an altitude of about 5,200 meters in Nepal swept down more than 3,000 meters toward Gyirong Port, which sits at an elevation of about 1,800 to 2,000 meters. Along the way, it picked up huge amounts of loose material, forming a high-speed debris flow that eventually swept into Gyirong Port.

The resulting ice-rock debris flow traveled about 22 kilometers at an average speed of around 50 meters per second, according to Liu Weiming, a researcher at the Institute of Mountain Hazards and Environment under the Chinese Academy of Sciences and the Ministry of Water Resources.

Rescuers are not dealing with simply "a flow of mud and water." Instead, they are confronting a cascading process in which each stage of the disaster intensified the next, said Dai Zili, deputy secretary-general of the International Consortium on Geo-disaster Reduction.

As the ice and rock moved down the valley, they eroded the surrounding slopes and swept up loose deposits that had accumulated in the mountains. More than 30 million cubic meters of material was ultimately involved, Dai noted.

The surrounding mountains further concentrated the energy. Confined by steep, V-shaped valleys, the debris had little room to spread sideways and instead surged rapidly downstream, concentrating its destructive force along the valley.

Steep mountains, narrow valleys leave little room for rescue

Gyirong Port is surrounded by steep mountains and narrow valleys. Heavy machinery can only advance along the valley, while search operations, road repairs and disaster monitoring have to take place within the same confined space.

The main access road, National Highway 216, was also heavily damaged, preventing large numbers of vehicles and heavy equipment from reaching the hardest-hit areas.

The soft debris left behind by the mudslide presents an additional danger. Some areas may look solid on the surface but can suddenly give way under a person's weight, forcing rescuers to work with ropes.

Poor weather conditions have further restricted rescue options. Persistent rain, dense fog and complicated airflow have made helicopter operations difficult, while unstable slopes continue to pose risks to personnel on the ground.

Building a road through the water

As of 5 p.m. on Monday, repair teams had pushed the National Highway 216 access route to within 1.1 kilometers of the port, entering the most difficult final stretch.

But in some sections, rescuers are not simply clearing a road. They are effectively building one through the river.

The force of the mudslide raised the riverbed and altered the course of the river, pushing water toward the original road. While much of the roadbed remains intact, sections without a solid foundation can swallow heavy machinery into the mud.

At a large bend along the route, fast-moving water can wash away loose rocks almost immediately. Workers therefore have to reinforce the road with materials such as steel-reinforced stone cages and drainage pipes.

In other sections, layers of mud and gravel appear firm but behave like soft, unstable ground. Excavators have to work in the water to remove the mud and retain the more stable gravel and rocks before people and heavy machinery can pass.

Secondary hazards remain a constant threat

Opening the road is only part of the challenge. Rescue teams must also keep watching for new hazards.

Tian Bingwei, an associate professor at Sichuan University's Institute of Disaster Reconstruction and Management, said continued rainfall could destabilize slopes and trigger rockfalls, landslides or new debris flows.

Rescue teams have therefore deployed dedicated personnel and monitoring equipment, including laser and AI-based video systems, to watch for changes in the surrounding slopes.

Glaciers around the impact area of the Cuojian River in Nepal could still collapse, posing a significant risk, according to the Ministry of Water Resources.

On Monday, China Anneng Group installed three rope-ladder emergency evacuation routes, with a combined length of about 180 meters. The routes allow rescuers to quickly move to higher ground if river levels suddenly rise or another mudslide occurs.

The highway remains under intensive repair. Once the final stretch is reopened, large numbers of rescuers, heavy equipment and emergency supplies will be able to reach the core disaster zone, significantly expanding the scope of the search and rescue operation.