Swiss glacier collapse renews focus on risks of climate change as glaciers retreat around the world

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00:00After the mudslide that wiped away 90% of Swiss Alps village, rescuers racing to prevent further disaster.

00:08There are vast mounds of unstable debris that have caused a huge lake to swell.

00:13The river that leads out of Blatton still missing a man in his 60s.

00:20Rescue efforts hampered by unstable grounds. Emerald Maxwell has more.

00:2490% of the village of Blatton has been wiped off the map, buried under a deluge of mud, rock and ice

00:34after the Birch Glacier crashed down the mountain Wednesday in Switzerland's southern Wallace region.

00:42The hamlet had been home to 300 people and was evacuated last week due to the impending danger.

00:48Now the worst case scenario has happened.

00:56This means that the 3 million cubic blocks that went onto the glacier all came down with the glacier.

01:02This is very, very rare.

01:07Rare, but becoming less so in the Alps with climate change.

01:12Close monitoring of the glacier helped avoid the worst Wednesday.

01:15But other collapses have been more deadly.

01:18In 2022, the Marmalade Glacier in Italy killed 11 people as it crumbled down the mountain.

01:25And in 2017, eight were killed and many homes destroyed,

01:29when the biggest landslide in over a century came down close to the village of Bondo.

01:33This type of collapse can happen pretty much anywhere in the Alps,

01:39especially at very high altitude.

01:41And it's linked to global warming and the disappearance of the permafrost, the frozen soil.

01:46So the ice that cements the rock gradually disappears.

01:51Back in Blatton, authorities are now monitoring the nearby river Lonza,

01:55which has been blocked by the debris,

01:57causing a new lake to form and posing a flood risk to the valley below.

02:01For more, let's cross to Lausanne in Switzerland.

02:05Stuart Lane is professor of geomorphology at the University of Lausanne.

02:09Thank you for speaking with us here on France 24.

02:12You're welcome.

02:14Let me begin with the latest there.

02:17And what is the risk right now with this debris basically forming a lake below that mudslide?

02:25Yes, that's right.

02:27I mean, it's still possible that further sediment comes down in the form of debris flows.

02:32But really, the biggest risk now is that the debris and ice that came down yesterday afternoon

02:38has made a major landslide dam.

02:42And so all of the water, the snow melt in particular, that's coming down the valley

02:46is accumulating behind the dam.

02:48That water has already flooded the homes that weren't destroyed when the landslide came down.

02:56And that dam will continue to be there.

02:59The late level will continue to rise until either there's some kind of intervention to manage that

03:08or, unfortunately, there is a catastrophic failure of the dam.

03:13And these landslide dams are known to fail.

03:16I mean, they're so far relatively rare in Europe, but in similar kind of geological settings in

03:22Alpine environments in the Himalaya, for instance, landslide failures, landslide dam failures

03:29are unfortunately quite common.

03:31And the Swiss Army has been roped in.

03:33What is the remit of the soldiers that are being brought in?

03:37Right.

03:38I mean, the Swiss Army, as well as the wider civil protection, will be there as soon as it is safe

03:44in order to start to try and put in mitigation measures.

03:48And their primary focus will effectively be to reduce the risk of any further loss of life.

03:54That's the first priority.

03:55And then the second will, of course, be reducing any further damages.

04:01The problem is that this deposit that's been created is itself extremely unstable.

04:08There could be more debris to come down.

04:11And if you have people working there when the actual failure of the dam were, the dam to fail,

04:18then you have an extremely serious problem.

04:20And to the best of my knowledge, the people who can actually start to try to manage the problem

04:25and reduce the effects or the risks of a landslide dam failure can't actually get into the site

04:33to do anything about it.

04:35Authorities, it seems, did a great job because people were evacuated beforehand.

04:41You could have had a very high death toll otherwise.

04:43But there is one man missing.

04:45And you talk about unstable deposits.

04:48Apparently, that's hampering the efforts to search for them.

04:53Yes, that's exactly right.

04:54I mean, when you do a search and rescue of this kind, your first priority is the safety

05:00of those doing the search and rescue.

05:02And the search and rescues have had to leave the site now because they've been unable to

05:07make any progress with finding him.

05:09So, yes, indeed, there's not going to be much progress, I think, in that avenue, certainly today.

05:14Stuart Lane, have you ever seen anything like this?

05:18No, I mean, I've been working in the Alps for more than 30 years.

05:21I've never seen anything quite like this.

05:23And it's an exceptional event.

05:25It's what we call a cascade event.

05:27So, as your previous speaker said, we have melting permafrost.

05:31The rock fell on the glacier.

05:32The weight of the rock on the glacier made the glacier flow, flow very fast.

05:38It lost all its resistance to motion.

05:40And it just collapsed down onto the valley side before.

05:43And I have never seen anything quite like this in all the time I've been working here.

05:46So, what conclusions should authorities draw?

05:52I mean, as you said earlier, the authorities did a very good job of evacuating the population.

05:59So, the short-term management of this crisis was actually, I don't think you could have done

06:04anything different.

06:05The problem is, is you can't engineer yourself out of something of this size.

06:10You can't build engineering structures that could stop this happening.

06:15And that requires a much more difficult process of thinking about land use zoning,

06:21of identifying where these risks are going to happen in the future.

06:25With climate change, we're going to see more of that.

06:28And then making interventions in the land use planning,

06:31such that zones that are at risk are not developed,

06:36and in some cases may actually need to be abandoned.

06:40And of course, that's a much more difficult social and economic question

06:44than simply building some kind of engineering structure.

06:47So, you're saying that there are entire villages that will have to be evacuated in the Alps?

06:54We already have two at the moment.

06:56We have Blatton itself.

06:57We have another one in the southeast of Switzerland,

07:00in Brent, which has had to be evacuated

07:03and may well have to be evacuated again.

07:06I think it's worth emphasising that these kinds of situations are, at the moment, exceptional.

07:12And the real work that has to be done now is to work out where in these areas

07:17that for many decades and centuries have been entirely safe,

07:23there could now be an elevated risk of this kind of event happening.

07:26And that requires very, very careful geophysical analyses,

07:31analyses using satellite data to try and work out where these instabilities are.

07:35And then to see where interventions might be needed.

07:39So, we know that with global warming,

07:41and there was a new report out this week about how it's going faster than expected,

07:46temperatures are rising and that makes glaciers melt.

07:48The other big effect of climate change is more extreme weather.

07:53So, if you have increased amounts of big rainstorms in the Alps,

07:59is that an avalanche and a mudslide risk?

08:03Yes, it is.

08:05I mean, in two senses.

08:06I mean, the event yesterday afternoon was triggered by a relatively small rainfall event.

08:11But that just determined when the event happened.

08:14It would have probably happened anyway.

08:17And the whole question of extreme rainfall,

08:19rainfall on unstable sedimentary deposits,

08:23is without a doubt a serious risk in the alpine environment.

08:27And I mean, that is something that we're only starting to really see in the last 10 to 15 years.

08:33But it is without a doubt something that is going to make zones that were previously safe at potential risk.

08:41Now, Blatton is a long way off from where you are by the banks of Lake Geneva.

08:46But you've done research that shows that Lake Geneva is changing because of global warming.

08:51Yes, I mean, the amount of sediment arriving in Lake Geneva is changing quite dramatically.

09:00Although I have to say that it's not simply due to global warming.

09:03I mean, we know that as climate is warming, that glaciers are melting,

09:09they're producing more sediment.

09:11And you can see that in the signal in Lake Geneva.

09:14But the signal in Lake Geneva is an interesting one.

09:16It's actually also due to things like how much sediment we take out for construction.

09:20So when we had the financial crisis in 2008, 2010, there was less sediment deposit.

09:26There was more sediment deposit in Lake Geneva because we took less out for the construction industry.

09:32So these are complicated systems.

09:34But there is without a doubt a signal of greater sediment delivery to all our alpine lakes at the moment,

09:40which we attribute to climate change.

09:44Stuart Lane, so many thanks for being with us from Lausanne.

09:48You're welcome.

09:49More news to come here on France 24.

09:53Plus, we will raise the curtain on the Champions League final on Saturday.

09:59Paris Saint-Germain bidding to become only the second French team to win Europe's premier footballing club title.

10:07That's coming up right here on France 24.

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