Local businessman Kedar Prasad Adhikari was standing on the bank of the Trishuli River when he saw the tsunami of destruction barreling toward his home.

Adhikari, 59, remembers the plume of dust that got kicked up as it rushed down the river from the north.

“Initially, it didn’t look like water,” Adhikari said through an interpreter.

The surge of river, mud and rock slammed into the mountainside opposite where he was standing, at a spot where the Trushuli River bends, and whirled into his hometown of Betrawati Bazaar. His wife and son were there.

Terrified for his family, Adhikari watched nearly all 200 buildings in his hometown get knocked down in an instant. He could see that people had rushed to the bridge near his house to take photos of what they thought was a “normal flood.” The bridge — and those people — were swept away.

Massive flash floods sparked by a rock-ice avalanche in the Himalayas struck Nepal and the autonomous Chinese region of Tibet on Aug. 26, leveling towns and leaving more than a thousand people confirmed dead. In a place prone to flooding and already vulnerable to climate change, the destruction was larger than expected. Thousands of people remain missing as recovery efforts continue.

“We never expected this kind of disaster to happen here,” Adhikari said. “It was unexpected, and because of that, so many lives were lost.”

Adhikari himself was high enough up on the riverbank that he was safe, but that morning, he told The World that he had passed out from fear. And because phone service and electricity went out, it was an agonizing wait before he learned whether his wife and son were safe.

Destabilized by climate change

This region is accustomed to climate-fueled natural disasters.

The Himalayas are warming faster than the rest of the world, and downstream communities are feeling the impact. Thawing permafrost and melting glaciers are causing more landslides, routinely blocking roads, destroying farmland, and stranding residents of mountain villages. Rarely, landslides flatten entire communities.

Glacial lakes, fed by meltwater, are popping up in new places or swelling. When those lakes burst their banks and trigger what scientists call a “glacial lake outburst flood,” the results for downstream communities can be deadly.One hit the Trushuli River valley just last year, killing at least nine people.Locals know this hazard well.

“As the temperatures keep rising, the snow and ice in the mountains begin to melt,” said Govinda Chitrakar, 75, who’s from the devastated riverside town of Devighat.

“When the mountain lakes overflow and landslides carry the water downhill, we end up suffering,” he said, pointing to a mound where a temple and shrine used to be. Until recently, Chitrakar’s hometown was best known as a Hindu holy place.

But what happened late last month was not a glacial lake outburst.

Triggered by ice and rock avalanche

On the morning of Aug. 26, at an elevation of 17,000 feet, a massive chunk of glacier and mountainside broke off the northern side of Langtang Lirungpeak near the border between Tibet and Nepal. It fell some 5,000 feet, where the ice and rock were pulverized. That debris dropped thousands of feet more before slamming into the Trishuli River and creating a slurry of rock, water and sediment that rushed through the narrow mountain valleys at 100 miles an hour.

Nitesh Khadka, a scientist at Kathmandu’s Tribhuvan University, who has studied water and climate risks in the affected area, said it’s not accurate to call what came down the river “floodwater” because there was so much rock and debris in it.

“If it carries something like that, the destructive power of the flood will be high, much more than what we see in typical floods,”Khadka explained. As he walked along the riverbank, he noted the thick layer of sediment the debris slurry deposited on the ground under his feet. It acts like quicksand, one of the many factors confounding rescue and recovery efforts.

The wall of water and rock was initially so high — Khadka estimates roughly 150 feet tall — that it knocked out Nepal’s flood monitoring sensors near the Nepal-Tibet border within a few minutes.

Nepal’s government didn’t even know a flood had been triggered until survivors in the village of Syabrubesicontacted emergency officials to alert them. Only then — roughly half an hour after the flooding started in Nepali territory — did an emergency warning message go out to cell phones in affected areas.

Baseline conditions

Scientists are still decoding exactly what triggered the tragedy.  

Both rock and ice fell from 17,000 feet, but it’s unclear if a bedrock collapse took a glacier down with it or a glacial collapse triggered the piece of mountainside underneath it to break away, too.

“It’s both, but which is more?” asked Kathmandu University glaciologist Mohan Bahadur Chand.  

International scientists studying satellite imagery argue it was a bedrock failure that caused the incident. But Chand, who’s studied the glaciers on Langtang Lirungpeak up close in the field, seems to consider the question still open.

He said that after retreating nearly a mile up the mountain in recent years, the glaciers that collapsed were “hanging at the top of a rock cliff” with nothing to support them from below. Warming temperatures also mean it’s raining more at these elevations than it used to, and if rainwater seeped through cracks in the glacier, Chand said that could have acted as a lubricant between the glacier and the bedrock, making the ice above the rock slip.

Like glaciers, the bedrock in the Himalayas is not immune to climate change. As glaciers retreat up mountain slopes, Chand said, more rock is exposed to the elements and the same kind of destructive freeze-thaw cycle that creates potholes in roads.

“Of course, the freezing and thawing process that is happening on these elevations, I think these are due to the increasing temperatures,” Chand said. “That could have triggered the collapse.”

Permafrost that has long held these mountain landscapes together is also thawing at higher altitudes, increasing risks in the Himalayas.

To Chand, the link between rising temperatures and what happened to communities in the area is clear — even if the disaster’s cause is still debated.

Other scientists are more cautious, saying more study is needed to pinpoint the cause of the rock-ice collapse before we can understand what fingerprints climate change may have left on the scene.

‘Nobody expected this’

Everyone agrees, however, that whatever caused the devastation did so in a mountain ecosystem already destabilized by warming temperatures, including people with some of the most intimate knowledge of the area.

Dibas Shrestha, a glaciologist at Tribhuvan University in Kathmandu, has been monitoring glaciers in Nepal since 2013.

He took his students to the temple town of Devighat to gain a more visceral understanding of what happened.  

“Now I realize, I think we neglected glacial hazards,” Shrestha said. “This is a new thing, and I think we should consider this very seriously.”

Nepal’s Foreign Minister, Shisir Khanal, has brought climate change into the conversation very publicly.

The week after the disaster, he called on countries that have done the most to fuel warming temperatures by burning fossil fuels to create a fund to help countries like his become more resilient in the face of natural disasters.

“My call to the global community is to not just see this as an unfortunate, one-time incident that occurred in a distant land, but something that human activity, especially climate change caused by human activities, are beginning to have real impact in people’s lives,”Khanal told The World.

That funding is needed not to recover from individual disasters, he said, but to do the work to make future disasters less deadly and destructive.

“If we treat this just as disaster recovery, then we’re not really doing the long-term work that we need to be doing to support our community.”

‘Wouldn’t be able to sleep at night’

More than two weeks after the disaster, 150 people in the town of Betrawati Bazaar are still missing — roughly a fifth of its residents.

After the debris and water retreated, local businessman Kedar Prasad Adhikari eventually learned that his wife and son were safe.

His son had run up stone steps built into the riverbank to safety. His wife hadn’t been able to run in time, but she caught another break.

“Luckily, the flood came in waves,” Adhikari said, and one of them “pushed my wife quite high on the bank, to the trees, and she grabbed onto one of them.”

The three buildings he used to own, which included his home, hotel, restaurant and a wholesale vegetable business, are now gone. He pointed to the spot where they used to be, which is now just a surging river.

“I won’t rebuild here,” he said through an interpreter. “We’re too scared, we wouldn’t be able to sleep at night.”

Additional reporting by Hannah Chanatry.