Air Date: Week of September 11, 2026

The flash flooding that occurred the morning of August 26, 2026 completely destroyed areas such as Gyirong Port, a border crossing between China and Nepal, as seen above. (Photo: CCTV screenshot, Wikimedia Commons, Public Domain)

The devastating August 2026 flash floods in Nepal and Tibet were triggered in part by a glacial collapse, a phenomenon likely to become more frequent as the Earth continues to rapidly warm due to human caused climate change. Alton Byers, a mountain geographer with the Institute of Arctic and Alpine Research at the University of Colorado—Boulder who has worked in the Himalayas, joins Host Paloma Beltran to explain why climate change is making mountains and glaciers more unstable, and how early warning systems and less development in floodplains could prevent future loss of life.

Transcript

DOERING: From PRX and the Jennifer and Ted Stanley Studios at the University of Massachusetts Boston, this is Living on Earth. I’m Jenni Doering.

BELTRAN: And I’m Paloma Beltran.

On August 26, a large mass of ice and rock broke off a Himalayan mountainside, triggering disastrous flash floods in parts of Nepal and Tibet. This catastrophe occurred during the South Asian monsoon season, when rivers are already swollen with rain. And as climate change destabilizes glaciers around the globe, especially the “Third Pole” region of the Himalayas, unimaginably large floods are likely to pose increasing risks to human populations. The United Nations recently reported that the Earth will soon exceed 1.5 degrees Celsius of warming, making extreme events more frequent and severe. Joining me now is Alton Byers, a mountain geographer at the Institute of Arctic and Alpine Research at the University of Colorado, Boulder who has worked in the Himalayas. Alton, welcome to Living on Earth!

BYERS: Thank you. Thank you for having me.

BELTRAN: So, briefly walk us through what happened on the morning of August 26. What exactly caused this avalanche, and how did it turn into such a destructive flood downstream?

BYERS: Well, I can tell you what we know so far. We have the basics down, but I'm convinced that we're really not going to know until we get to the site and do some on-the-ground research. Basically what we do know pretty much for sure is that this was started by bedrock failure and glacier collapse at about 5,200 meters, about 17,000 something feet, on the north face of a major mountain in the Himalayas, the Langtang Lirung, at 7000 meters. So what we had was this major detachment, and this is huge. It's like one and a half kilometers wide and 50 million tons of material. But that was detached, started to fall down. It plummeted 2000 meters down before it hit the glacier below, and as it falls down, contact with air creates friction. Friction heats and melts the ice, and we get water. We get the beginnings of a new accumulation of water. Meanwhile, everything else is turning into sort of a slurry, okay? And when it hit the ground. It hit with the force of an atomic bomb, and we saw the seismic signal that the USGS recorded. But meanwhile, the slurry funnels on down and blocks the river, an already monsoon-swollen river. So we get a backup of water into a massive lake, and then that slurry dam, which is holding back the lake, breaks. And then we get a release of millions of cubic meters of not just water but boulders and this hyper-concentrated slurry again that looks and feels exactly like liquid concrete. Imagine not just a flood barreling down the river valley at heights that we could never imagine before, but it's also like liquid concrete going on down. And I've interviewed people who have seen these villagers in Nepal, and they say that it's a horrific experience. The noise is deafening, but it sounds like somebody is moaning in agony as this as this plummets down the valley. Anyway, that's basically the series of what we call a cascading series of events that led to this catastrophic flood in Nepal.

BELTRAN: And Alton, to what extent is climate change and warming temperatures accelerating events such as these?

BYERS: Well, I mean, part of climate change is warming, and the world has been warming since the end of the Little Ice Age, about 1860. As the world has gotten warmer, so has the permafrost, and that's the perpetually frozen ground at high altitude that acts as sort of a glue, like a cryospheric glue that holds the rocks and the glaciers and the debris together. Now, when that softens, which it has been doing for certainly the last 80, 100 years, like a stick of butter, take a stick of butter out of the refrigerator and put it on the counter. When that softens, then glaciers and bedrock and debris no longer has the resistance to gravity that it used to have, so therefore is much more likely to break and begin the process of cascading down into a major landslide, and there are other factors involved as well. Melting glaciers lubricate the interface between the glacier and the rock, so things are more likely to slide off. Catastrophic or unusual weather events, high levels of precipitation, snowfall can also act as triggers as well. But basically, from my point of view, I'm a field practitioner. I'm someone who looks for solutions. I don't spend a whole lot of time studying climate change. But what I know is that the mountains have gotten warmer, and with increases in temperature, we've gotten an increase in the instability of mountain environments. Now, mountains are unstable anyway. They're geologically unstable, they're tectonically unstable. But when you add to that warming trends that are melting the ice and softening the permafrost, we're just seeing an acceleration, an increase in the frequency and magnitude of these major events.

BELTRAN: And Alton, as someone who has lived and worked in the mountains of Nepal, describe for us what this must have felt like for nearby communities.

BYERS: Well, you know, in 2015, we were wrapping up a project in Nepal that was funded by the U.S. Agency for International Development. But USAID, right after, right when the contract ended, the earthquake happened. So USAID sent us over immediately to look at three glacial lakes, potentially dangerous glacial lakes, and look at what the impacts of the earthquake may have been. And what I remember vividly is how traumatized people were. And I mean, this event is horrible, and it's so sad. It just breaks your heart. But I just remember seeing everybody that I met when we went, and we were some of the first outsiders to go into these areas. Nobody else wanted to go. It was too dangerous. They were afraid of landslides that were still happening because everything was still unstable. But we held meetings after we did our survey of the lakes. We held meetings with the local communities, and I’ll just never forget the the look of fear, and they're so traumatized, and that's what's happening right now. All you have to do is look at the, the film clips of these poor people. They've lost their families. They've lost their homes. Some of them had their homes destroyed during the earthquake, and now they've had their homes destroyed again. So it's just sad beyond belief. Just as the magnitude of the event has forced us to reset our mental models of what can happen, it is absolutely the biggest thing I have ever seen in my life in terms of a catastrophic debris flood like that.

BELTRAN: It's so devastating, and at the time of this recording, over 1000 people have been confirmed dead, and a few thousand more are still missing. What precautions and early warning systems are in place to protect people from events like this?

BYERS: Well, sadly, very few. Now there have been attempts to establish early warning systems on at least two glacial lakes in Nepal. One was established right after the earthquake in 2015, and I'll never forget how the villagers, when we had our meetings, they said, "Well, yeah, they installed an early warning system." It's quite sophisticated, laser-based to measure the rises in the water and signals back to Kathmandu. But they said, "But nobody told us how it works, what it sounds like, or what to do in the event that it goes off." So there was a clear disconnect between technology and communication, but I think what you're going to see, I certainly hope we'll see this, is a renewed focus on early warning systems that work. We need to develop catastrophic event-specific early warning systems, and they could take a whole range of shapes. It could be cell phone based, and cell phones have become very effective in terms of warning people. The government sent out 600,000 messages that saved hundreds, maybe thousands of lives. Another thing people ask all the time, could we have predicted this? And the answer is no. You can't predict a glacial lake outburst flood. You can't predict a bedrock failure, a glacier collapse such as this. But we can flag areas of high concern. For example, a mass of overhanging ice, just like the one above Langtang Lirung, with a village 10 kilometers downstream. That is a red flag. In other words, we need a fresh look at the power of remote sensing and remote sensing analysts to flag these places and somehow monitor them. One of the most important things, though, is that the reason it's a catastrophic event is because so many people died and so many buildings were destroyed. I think we're going to see an effort to discourage, to avoid building in floodplains similar to this. But those are the basic directions I think we need to move, and I think we will move in the coming months and years.

[MUSIC: Kanchenjunga Lows]

BELTRAN: We’re speaking with CU Boulder mountain geographer Alton Byers, and we’ll be right back after the break. Stay tuned to Living on Earth!

ANNOUNCER: Support for Living on Earth comes from the Waverley Street Foundation, working to cultivate a healing planet with community-led programs for better food, healthy farmlands, and smarter building, energy and businesses.

[CUTAWAY MUSIC: Kanchenjunga Lows]

DOERING: It’s Living on Earth, I’m Jenni Doering.

BELTRAN: And I’m Paloma Beltran.

Let’s get back to my conversation with Alton Byers. He’s a mountain geographer at the Institute of Arctic and Alpine Research at CU-Boulder. Alton studies glacial hazards in the Himalayas like the one that caused the devastating floods in Nepal this August.

BELTRAN: And Nepal is, of course, one of the most vulnerable countries to climate impacts, but it's only contributed 0.01% of total planet warming emissions. What international efforts are underway to help Nepali communities adapt to rapid climate change, and what role, if any, is the U.S. playing in that effort?

BYERS: Well, I mean, I think the international community has a responsibility, just from a humanitarian point of view, you know, not necessarily from a climate change point of view. I think they have a responsibility to help Nepal and help the world develop these types of early warning systems. I know Nepal a year ago received a 34.1 million dollar grant from the Green Climate Fund. I think some of those funds could go into funding things such as early warning systems and increasing our capacity to identify high risk areas in the mountains. So as I mentioned before, USAID was generously funding programs, including ours, to help people adapt to climate change. The U.S. has canceled USAID, that's no longer there, but the Brits and the Germans and the Norwegians and others are still actively involved in programs, to my knowledge, again, same climate change adaptation program. So it's not dead. It's moving forward. I think you'll see it will be even more enhanced in the coming months and coming years as international donors once again refocus on a new set of urgent needs to help mitigate the impacts.

BELTRAN: And how likely is it that we'll see another event like this, you know, in Nepal or elsewhere?

BYERS: Inevitable. It's just a matter of time, and maybe one has happened similar already. Well, as I said, we don't always know. These Himalayas are huge. These are massive mountain ranges, and often events happen that people simply don't report. So again, another story. I hope you don't mind my stories.

BELTRAN: Oh, please, please do share.

BYERS: I was a Fulbright scholar in 2022, so we lived in the Kanchenjunga Conservation Area for six months. And we were interested in, of course, in glacial lakes, dangerous glacial lakes, and local people told us about one called Nupchu, especially dangerous. So we said, "Hey, that's just up the valley here. It's going to take about two days to get to it. Let's go up and take a look at it." So for some reason, instead of the, the day we were supposed to depart, we had to delay by one day. The next day, we loaded up our dzopkio. Those are yak and cattle crossbreeds. So we had four dzopkio, like yaks, and the yak driver. So we started going up the valley toward the glacial lake, and we came around a bend, and the entire valley had been buried in material exactly like I described earlier, like liquid concrete, 30, 40 feet, 50 feet high, okay? There had been a massive breakage of material, identical almost to what we saw last week, that created this massive slurry that if you could, just covered this whole valley in, in this sediment. So it's very lucky we hadn't gone the day that we had planned to go, and fortunately the dzopkio found a way around the edge that was firm enough that we were able to go up, cross it, and then go up and study this lake, but you know there's an example of things happening all the time. And when we went back to Khambachen, that's a potato growing and tourist village. The local people had no idea it had happened. It was only four or five miles up valley, and no one knew it had happened.

BELTRAN: Alton, what do you hope the western world will take away from this catastrophe?

BYERS: Well, again, that this is proof that, undeniable proof, that the world is changing. The world is getting warmer. It's getting hotter, and with it, mountains that are so important to the rest of humanity, in terms of, they're only 25 percent of the Earth's surface, but they're in almost all of the world's countries, and they provide a bulk of the world's fresh water, and minerals, and timber, natural resources. They're spiritually important. They're culturally important, and you know we need to pay greater attention to our mountains and take care of our mountains. Just like we try and take care of our oceans and our rainforests, we need to also recognize the importance of mountains. And unfortunately, it's the people in the mountains who bear the brunt of the damage and the grief and the tragedy. So, what I think we need to do is buckle down and figure out well, what do we do about it? How do we adapt to it? How do we help people adapt to it? How do we develop better early warning systems, better mechanisms of identifying potential hazards, ways to discourage building in high hazard zones? I think that's the way forward.

BELTRAN: Alton Byers is a mountain geographer at the Institute of Arctic and Alpine Research at the University of Colorado, Boulder. Alton, thanks so much for joining us.

BYERS: Oh, thank you for having me.

 

Links

The Conversation | “When a Mountain Falls: How Ice and Rock Triggered Nepal’s Catastrophic Flood – and Why Climate Change Is Raising the Risks”

Learn more about Alton Byers