Latest / DEEP INSIGHT / Two lakes threaten Nepal after deadly flood in 'hazard-prone' region

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Two lakes threaten Nepal after deadly flood in 'hazard-prone' region · DEEP INSIGHT

• 0:00
  Speaker 1: What is already a dangerous race to locate survivors has
• 0:03
  Speaker 1: been further complicated by the risk of additional possible flash
• 0:07
  Speaker 1: flooding and landslides. Operations were briefly paused this morning when
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  Speaker 1: a newly formed barrier lake began to overflow, and now
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  Speaker 1: a second lake has been observed in aerial footage of
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  Speaker 1: the flood zone. I want to go to CNN's Tom
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  Speaker 1: Foreman at the Magic Wall to help explain what we're
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  Speaker 1: seeing here. Tom, talk to us about the formation of
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  Speaker 1: these lakes so high up in the mountains.
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  Speaker 2: Yeah, it is a real challenge here. Let's put ourselves
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  Speaker 2: into the map first. India down here, Nepal right through here,
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  Speaker 2: China up here, Mount Everest over this way, just in
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  Speaker 2: case you're wondering. This is where this is all happening.
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  Speaker 2: If we move in to take a look at the
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  Speaker 2: area where that glacier collapsed yesterday, happened that you were
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  Speaker 2: talking about a short while ago. That's right over here.
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  Speaker 2: That gave way, sending all sorts of debris and mud
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  Speaker 2: and water rocketing down into this river valley here, more
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  Speaker 2: than 100 miles an hour and creating all that havoc.
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  Speaker 2: You want to see how much is involved there? All
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  Speaker 2: you have to do is go over here and look
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  Speaker 2: at this. We'll slide it over and you can see
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  Speaker 2: the damage. The before, this is the after. And in
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  Speaker 2: this after, John, that is where you can see the
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  Speaker 2: very thing we're talking about now. A lake that has
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  Speaker 2: formed right there and a lake that has formed right here.
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  Speaker 2: Because as more water flows down and the debris is
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  Speaker 2: blocking its progress, those lakes have been building up there.
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  Speaker 2: And that is really the worry. The worry is that
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  Speaker 2: if all of the material blocking those lakes right now
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  Speaker 2: gives way, if that somehow breaks through in a catastrophic way,
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  Speaker 2: you could send another sort of pulse of, A liquid
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  Speaker 2: shockwave right through the area that the rescue and recovery
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  Speaker 2: is being operated right now, John.
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  Speaker 1: So what, if anything, can be done to alleviate the
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  Speaker 1: risk of those lakes just bursting?
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  Speaker 2: Well, one of the ideas would be, first of all,
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  Speaker 2: you monitor them to see if maybe they're draining at
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  Speaker 2: a slower rate. Maybe that helps off. Maybe they're a
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  Speaker 2: natural thing. Maybe not as much rain things that would
• 2:01
  Speaker 2: help out a little bit. I suppose in severe cases,
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  Speaker 2: they might see if there were some way to drain
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  Speaker 2: it off. But right now, what they're mainly doing is
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  Speaker 2: talking about trying to get some cameras and more sensors
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  Speaker 2: in place to see what's going to happen and telling
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  Speaker 2: the workers down below what they're telling them right now.
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  Speaker 2: You have to be ready, even amid all this dismal
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  Speaker 2: and dangerous work, you have to be ready to run
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  Speaker 2: for higher ground at a moment's notice if one of
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  Speaker 2: these lakes burst free.
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  Speaker 3: What happened, we think, is that some of the bedrock
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  Speaker 3: high in the mountain just below the summit of Langtang,
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  Speaker 3: Lirung Peak, failed. It was fractured and it collapsed. And
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  Speaker 3: there was a small glacier resting on top. There still
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  Speaker 3: is part of the glacier remaining there. And that piece
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  Speaker 3: of the glacier collapsed with the bedrock. And then on
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  Speaker 3: the way down, Just the frictional energy, we call it
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  Speaker 3: gravitational potential energy, turning into heat, which melted the ice.
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  Speaker 3: And so it was almost entirely melted by the time
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  Speaker 3: it reached the first really damaging point at the China-Nepal border.
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  Speaker 3: And so just horrific. I've never seen anything like this.
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  Speaker 3: in my career to date in terms of Himalayan hazards
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  Speaker 3: and disasters.
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  Speaker 1: And Dan, picking up on that point, you point out
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  Speaker 1: this is one of the most hazard prone landscapes on
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  Speaker 1: the planet. I mean, how much ice are these glaciers
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  Speaker 1: losing every year?
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  Speaker 4: Absolutely. This is a major plate boundary. We have two
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  Speaker 4: continental plates crashing into each other over the last 50
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  Speaker 4: million years, building the highest mountains on Earth. This has
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  Speaker 4: produced incredibly steep slopes and a tremendous amount of elevational
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  Speaker 4: relief from the valley bottoms to the tops.
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  Speaker 3: Of these mountains.
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  Speaker 4: And there's a very large number of glaciers across high
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  Speaker 4: mountain Asia, something on the order of about 95,000. And cumulatively,
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  Speaker 4: that area is about the area of South Korea. And
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  Speaker 4: these glaciers are losing mass very rapidly. If we take
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  Speaker 4: the amount of mass that's being lost every single year
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  Speaker 4: from these glaciers and that meltwater and put it onto
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  Speaker 4: the island of Manhattan, it would inundate the island to
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  Speaker 4: over 1,200 feet. So we're looking at the top of
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  Speaker 4: the Empire State Building submerged in water every single year
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  Speaker 4: from glaciers across this region. Wow.
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  Speaker 2: And we call it water, right?
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  Speaker 1: We turn into liquid there, Jeff, but we've heard one
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  Speaker 1: scientist describe it as, as liquid concrete. This isn't, you know,
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  Speaker 1: like water that comes out of your faucet here. It's
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  Speaker 1: just this incredible destructive mass and impossible to outrun. You
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  Speaker 1: said it was like the equivalent of at least 500,000
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  Speaker 1: large dump truck loads of rock and ice at minimum.
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  Speaker 1: Talk to me about that, Jeff.
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  Speaker 3: Yeah, I think that is a minimum. In fact, um,
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  Speaker 3: the amount of mass that detached from the mountain top
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  Speaker 3: might not be all the mass of the flow that
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  Speaker 3: did all this destruction, because as it flowed down, it
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  Speaker 3: picked up more rock debris, and once it reached the
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  Speaker 3: Boticosi River, there was additional water that it could pick up.
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  Speaker 3: And so the final mass of this was even more
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  Speaker 3: than what detached from the mountain, But there is a question,
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  Speaker 3: have we identified all the entire source of water in
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  Speaker 3: this event?
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  Speaker 1: It really is interesting. There's still so many questions. with
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  Speaker 1: something that in some ways is so photographed. We've seen
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  Speaker 1: so much video of the destruction, but we really still
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  Speaker 1: don't have perfect eyes on what happened at the very beginning.
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  Speaker 1: You know, Dan, what would it have taken, if anything,
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  Speaker 1: to have seen this exact disaster coming?
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  Speaker 4: It's a very difficult thing to predict. In this region,
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  Speaker 4: we've seen a large number of glacial lakes form and
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  Speaker 4: grow through time, and these are actively monitored, and the
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  Speaker 4: most hazardous of these have been identified. But this is
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  Speaker 4: a totally different hazard. This is not something, you know,
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  Speaker 4: when we think about the 95,000 glaciers across the region,
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  Speaker 4: we can't go out and monitor every single one of
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  Speaker 4: those with time-lapse cameras or other radar systems. And so
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  Speaker 4: this is a real challenge. And historical, you know, early
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  Speaker 4: warning systems where we might have a stream gauge on
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  Speaker 4: a bridge to give warning are not capable of providing
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  Speaker 4: sufficient warning. Those bridges were completely washed out during this event.
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  Speaker 1: And Jeff, how dangerous are these ongoing rescue efforts? I mean,
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  Speaker 1: they did pause them for a time this morning, you know,
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  Speaker 1: given the composition of debris and the possibility of the
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  Speaker 1: lakes bursting. How dangerous would you say it is?
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  Speaker 3: John, you just showed some information that I wasn't aware
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  Speaker 3: of until this show. That is the lake forming high
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  Speaker 3: up in the mountain. This is extremely concerning because we
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  Speaker 3: already know that water perched up there would be an
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  Speaker 3: unstable mass. And, you know, there may have been some
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  Speaker 3: additional water that was unseen sort of hiding up there
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  Speaker 3: in the glacier, maybe not on the surface. And now
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  Speaker 3: we see a surface lake. You've got it highlighted in
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  Speaker 3: your box there. And this is very worrisome, even more
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  Speaker 3: so than the landslide dammed. lake because this is perched
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  Speaker 3: high up and it could burst forth and flow into
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  Speaker 3: that landslide dammed lake and together they could burst out
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  Speaker 3: very very rapidly I do not want to be alarmist
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  Speaker 3: here but the alarm bells are ringing and the rescue
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  Speaker 3: crews have to be ready like you said to move
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  Speaker 3: to higher ground at every moment they have to be
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  Speaker 3: thinking like if something happens, where exactly am I going
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  Speaker 3: to ascend the slope? Because running alongside the road ahead
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  Speaker 3: of the flood isn't going to do it. We just
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  Speaker 3: saw a video, you showed a video showing some people
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  Speaker 3: running along the road, and I don't know the details
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  Speaker 3: of that particular location, but In general, that's not the
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  Speaker 3: thing to do. You have to get to higher ground,
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  Speaker 3: not just a higher building.
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  Speaker 1: This does not seem to be the type of disaster
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  Speaker 1: you can outrun. Jeffrey Cargill, Daniel McGrath, thank you so
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  Speaker 1: much for helping us understand some of the science behind this.