Workers use excavators clear mud at the Dhunge Bazaar

Five days after a glacier collapsed on the Nepal-Tibet border and unleashed a flood that has killed more than 900 people, rescue teams from three countries are focused on one of the most operationally complex high-altitude tunnel rescue efforts in recent Himalayan history: reaching an estimated 500 workers who may still be alive inside the same hydropower tunnels that were designed — and built robustly enough — to survive the disaster around them. The Nepal flood death toll has reached 903 in Nepal and 16 in Tibet, with hydropower workers trapped in tunnels at 12 affected projects in Nepal's Rasuwa and Nuwakot districts.

The engineering situation is described precisely by Arnold Dix, an Australian geologist and former ITA president of the International Tunnelling and Underground Space Association, who played a leading role in saving 41 workers from the 2023 Uttarakhand tunnel collapse in India and is now advising the Nepal operation remotely from Melbourne. "Normally, they collapse and I'm trying to get people out," Dix told CNN on August 30. "This time, they haven't collapsed, but everything around them has, and I'm trying to get in."

That distinction — tunnel structurally intact; tunnel entrance buried under meters of Himalayan debris — is the defining challenge of an ongoing rescue effort across at least 11 hydropower projects in Nepal's Rasuwa and Nuwakot districts. The Independent Power Producers' Association of Nepal, or IPPAN, which represents private power developers, reported that approximately 900 workers remained unaccounted for across 12 projects as of Monday morning, with its president, Mohan Kumar Dangi, estimating that 500 workers believed in tunnels. Nepal's government disaster agency, NDRRMA, put its NDRRMA missing hydropower worker count at 933.

How a Mountain Fell and Sealed the Tunnels

The flood began before dawn Nepal Standard Time on August 26, when a mass of glacier ice and bedrock detached from the northern slope of Langtang Lirung — a 7,234-meter (23,734-foot) peak on the Nepal-Tibet border — and plunged roughly 1,200 meters (3,940 feet) into the valley below. The U.S. Geological Survey, which initially detected the event as a magnitude 4.4 earthquake, re-examined seismic waveform data and satellite imagery and USGS reclassified the glacial collapse: no earthquake had occurred. The seismic signal was generated by the collapse itself, reclassified as a magnitude 5.2 glacial landslide.

The falling ice and rock temporarily dammed the Lhende Khola, a river draining toward the Nepal-China border crossing at Gyirong Port. When that debris dam failed, a surge of water, rock, and liquefied sediment tore southward through Nepal's Trishuli River system. At one monitoring point, the river rose 9 meters in minutes — nearly 30 feet in 30 minutes. The flood carried some victims 240 kilometers (150 miles) downstream into northern India.

By Monday, 903 dead and 4,247 missing had been confirmed in Nepal and 16 dead in Tibet's Gyirong County, with 546 more missing in China. The dead span citizens of at least 39 countries; 590 foreign nationals still missing, according to Nepal's foreign ministry.

Why the Tunnels May Have Saved Hundreds — and Why That Complicates Everything

Nepal's hydropower industry relies on large-bore tunnels bored directly through Himalayan rock to divert and carry water from river intakes to turbine chambers. These tunnels are engineering accomplishments built to exacting specifications for one reason: Himalayan rivers carry sediment, boulders, and seasonal floods that would destroy above-ground structures. The Upper Trishuli-1 hydropower project — the site where the largest number of workers, roughly 300, are believed trapped — has a 9,490-meter headrace tunnel breakthrough 2025, with a 7.5-meter (25-foot) horseshoe cross-section, constructed by POWERCHINA through difficult geological conditions and completed in late 2025. The tunnels at other affected projects are similarly sized — large enough, as Jakob Steiner, a geoscientist at the University of Graz in Austria, noted, "to drive trucks through."

That structural robustness is now both the source of hope and the source of difficulty. If the tunnels themselves survived the flood — as Dix believes is likely — then workers who were inside them when the surge hit may have had protection from the worst of the debris flow. But the portal entrances of those tunnels, which open onto the valley floor, were buried under the same debris that destroyed surface infrastructure across the flooded corridor. To reach anyone inside, rescuers must first clear those portals, which can involve moving tens of meters of packed boulders, mud, and rock under live monsoon conditions with active barrier lake secondary flood risk from two barrier lakes that formed upstream.

At the Trishuli-3A powerhouse in Nuwakot District, the tunnel portal was completely buried. Heavy excavation equipment had to be disassembled and airlifted in by helicopter to reach the site. On August 29, a controlled blast broke into tunnel in the upper section, allowing rescuers to pump in fresh air and lower a camera — a moment of cautious relief. Dix, advising from Melbourne with access to technical drawings, satellite images, and aerial video, warned that once inside the portal, rescuers still faced an unknown: "We don't know how much of that tunnel is full of mud or water," he told CNN. "So, we might only have to dig 10 meters [33 feet], or we might have to dig 100 meters [330 feet]." He also flagged a separate turbine room emergency shutdown risk: if the plant's emergency shutdown systems failed when the flood hit, the turbine rooms themselves could have flooded, potentially drowning any workers sheltering there.

At the Upper Trishuli-1 site in Rasuwa District, the numbers are larger and the status less clear. IPPAN's Dangi said as many as 576 workers were unaccounted for at that project, with an estimated 300 workers believed in tunnel. By Monday morning, 208 workers had been rescued from a third Trishuli project on August 29 alone — 43 of them foreign nationals, including 38 Chinese and 5 Indian workers — and a combined total of approximately 361 workers accounted for August 31 through rescue or self-evacuation across all affected sites.

Nepal's Army spokesman, Brig. Gen. Raja Ram Basnet, was direct about the Nepal Army's challenge opening tunnels. "A large amount of debris has been deposited, and that is posing us a big challenge to open the tunnels," he told Reuters on Monday. "Our main focus is on opening the tunnels."

What a Teacher's Decision Tells You About the Warning Gap

While the tunnel rescue dominates Monday's rescue effort, what happened at a secondary school in Nuwakot District illuminates how little warning time communities had. Rajendra Dawadi, headmaster of Tribhuvan Trishuli Secondary School, ordered the school evacuation 10 minutes before flood — evacuating more than 900 students approximately 10 minutes before the flood reached the school. By any measure, that decision saved hundreds of lives. By any engineering measure, 10 minutes is not a warning system — it is a headmaster's judgment call.

The absence of a structured warning has been documented before in this same watershed. In July 2025, a glacially triggered flood swept away the Nepal-China border bridge at Gyirong, killing at least nine people. After that event, Nepal and China verbally agreed to establish a cross-border data-sharing system for river levels and glacial flood risks. As of August 26, 2026, that cross-border data agreement never signed — it had never been formalized.

Survivors Speak

Among the workers who escaped, Ram Chandra's six-hour tunnel escape has become emblematic of what those inside faced. He grabbed hold of a rung bolted into the ceiling as water churned around him. "The water was rising and it was difficult to move my legs," he said. "If I had let go from that rung I would have fallen." He and five colleagues spent six hours making their way toward the portal, passing a sheet of tin between them as an improvised foothold, emerging without the clothing the floodwater had torn from them.

The Madan Singh Budha flood account was starker. He had finished a night shift when the water came. He looked out and ran uphill. "Those who weren't able to climb up were swept away," he said.

Hundreds of bodies, many unidentified, were buried in shallow graves as decomposition accelerated in Nepal's late-monsoon humidity. Relatives gathered at mass burial sites in Chitwan, some searching faces for their missing, others in grief over those already recovered.

Three Nations Dig

Nepal Prime Minister Balendra Shah, who initially declined broader foreign assistance, Nepal reversed foreign assistance decision as the scale became clear. By Monday, approximately 21,000 security personnel were deployed across affected districts.

China mobilized more than 2,100 rescue workers and disbursed 220 million yuan in relief funds — approximately $33 million USD. Chinese teams deployed thermal cameras and acoustic detection equipment specifically designed to locate signs of life in enclosed underground spaces. Chinese President Xi Jinping, speaking from Bishkek, Kazakhstan, on Monday, Xi confirmed Beijing's search efforts for both Chinese and foreign nationals.

India sent tunnel rescue specialists — 18 army officers trained in tunnel operations — alongside six forensic teams equipped for DNA-based identification of flood victims. India also supplied prefabricated Bailey bridges to reconnect communities severed from the road network when the flood washed out crossings, and delivered four tranches of humanitarian aid including generators, water purification tablets, tents, and medicine.

International support has also arrived from the United Nations, the International Federation of Red Cross and Red Crescent Societies, Australia, South Korea, and the United States. The Red Cross estimated that more than 90,000 people had been affected by the disaster.

Secondary Flood Threat Hangs over the Rescue

The disaster has not stabilized. Two large barrier lakes formed from debris deposited by the initial flood in the upper Lhende watershed. The lower lake subsequently drained through natural outflow; the upper barrier lake half drained, according to China's water ministry. But Nitesh Khadka, a Nepali physical geographer who specializes in glacial floods, warned that a sudden failure of the remaining upper lake could send a surge directly into the active tunnel excavation sites — into the same spaces where rescue workers are operating.

Chinese state media additionally warned that glaciers near the original collapse site on Langtang Lirung could be further destabilized, raising the possibility of a second collapse event.

On Sunday night, monsoon rain temporarily flooded excavation sites across several tunnel locations, halting work before conditions eased. A Nepal Army statement confirmed that teams had army resumed drilling and excavation using "drilling machines, excavators, hydraulic cutters and other equipment."

Warming World, More Workers at Risk

The Langtang region was devastated by an ice-and-rock avalanche during the 2015 Nepal earthquakes. Glacially triggered floods struck the same corridor in 2025. A comparable glacier-flood event destroyed the Upper Bhote Koshi Hydropower Plant in 2016. Analogous disasters struck Chamoli, India, in 2021 and Blatten, Switzerland, in 2025.

Scientists are explicit about the limits of attribution: no single event can be directly linked to climate change without specific causation evidence. What the broader record does show is that the Himalayan region is warming considerably faster than the global average, and as it warms, the permafrost that once stabilized mountain slopes thaws, glacier tongues thin and retreat, and the mechanical foundations of peaks that have stood for millennia begin to fail. The ICIMOD glacier ice loss doubled since 2000, according to the organization's March 2026 glacier assessment of the Hindu Kush Himalaya region.

"Rising temperatures are changing the Hindu Kush Himalaya region and melting glaciers," said Saswat Sanyal, a disaster risk reduction specialist at ICIMOD. "We have to be cautious and not draw a connection yet. However, the chances of such disasters increase." That cautious climate change attribution statement reflects the scientific consensus: individual events resist direct attribution; the accelerating pattern does not.

The pattern matters for what Nepal has built. Academic research has documented for years that hydropower projects across High Mountain Asia face compounding, climate-driven hazards: glacial detachments, rock-ice avalanches, permafrost-triggered landslides, and the outburst floods of glacially and landslide-dammed lakes. The 2026 Nepal disaster has brought those risk assessments to catastrophic life. As researchers at The Conversation noted this week: as countries build more infrastructure in these places, the hazard risk rises because more people and assets are exposed.

What the disaster has also revealed is that Nepal's tunnel-heavy hydropower construction model — built for a mountain environment — created an unintended and undesigned form of worker protection against glacial flooding. The tunnels held. But no protocol existed for warning workers inside them to evacuate, because no early-warning system exists for the category of glacial hazard that triggered this flood, and no systematic evacuation plan has been required for tunnel workforces in Nepal's hydropower licensing framework.

What Comes Next

Nepal's energy sector faces a difficult reckoning. The 27 hydropower plants damaged or destroyed represent a severe blow to a national grid already struggling to meet demand. As Prime Minister Shah acknowledged, a full damage assessment remains impossible while active rescue operations and secondary flood threats continue.

For now, everything depends on the tunnels. Whether the emergency shutoffs functioned, whether the workers inside have air and dry space, and whether the portals can be cleared before monsoon weather closes in again are questions whose answers will determine not only the fate of hundreds of individuals but the political reckoning that Nepal's hydropower development strategy will face in the months ahead.

"Just to find the tunnel is a miracle," Dix told ABC News Australia on Monday. The search for what lies inside it — and who — continues around the clock.

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Originally published on Tech Times