Melting glaciers pose flash flood risk for 15 million people, study finds – The Washington Post

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Shishpar Glacier in northern Pakistan began to melt rapidly during a record-breaking heat wave last spring. Melted snow and ice poured into a nearby ice-covered lake until water levels rose too high, triggering a large flash flood that wiped out a key bridge and battered a village downstream.

It is not a one-time event. In the most icy parts of the world, communities live with the looming threat of inland tsunamis – massive walls of water moving rapidly and forcefully from melting glaciers, known as lake floods. glacial.

A study published Tuesday in Nature Communications found that around 15 million people live at risk from such glacial flooding. More than half of those at risk are in four countries: India, Pakistan, Peru and China.

“It sounds pretty bad, but it doesn’t have to be,” said Tom Robinson, study co-author and risk researcher at the University of Canterbury in New Zealand. “With thoughtful investment and careful planning, we can avoid these [flooding disasters].”

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Glacial lake floods have been around as long as glaciers, but the risk has increased dramatically in recent decades due to climate change, Robinson said in an interview. A warming planet melts glaciers faster, draining additional water into nearby lakes and causing greater flooding when a breach can occur. The number and total area of ​​glacial lakes around the world have increased by about 50% since 1990, according to previous research.

Glacial lake flooding “presents a significant global hazard, and that hazard appears to be getting significantly worse with climate change,” Robinson said.

Although not all glacial floods are caused by heat waves like the one that triggered the Shishpar flood, climate change is also making extreme heat more common. A study has shown that climate change has made last year’s record heat in India and Pakistan 30 times more likely to occur and raised heat wave temperatures by about 1.8 degrees Fahrenheit (1 degree Celsius) compared to pre-industrial times.

Global populations have also skyrocketed, especially downstream of many glacial lakes. In 1942, a glacial lake explosion near Huaraz, Peru killed more than 1,000 people. A breach on this glacial lake today, which many fear, could affect more than 100,000 people living downstream.

Taking into account lake conditions and the number of people within a 30 mile radius downstream, the study released on Tuesday assessed the areas most at risk from glacial lake floods. They also looked at the level of human development, determined by the United Nations, and a non-profit Transparency International Corruption Index for each location, which could influence how resources are allocated to prevention and response. to floods.

They found that high mountain Asia, home to the Himalayas, was the most dangerous, with 9 million people exposed to 2,211 lakes. Pakistan and China had the highest risk in the world, with nearly 2 million and 1 million people exposed respectively.

The High Arctic, like Greenland, presented the lowest danger. Even though Greenland had the most number of glacial lakes in the world, very few people live there and are in danger. The Pacific Northwest, particularly in Canada, also had a large number of glacial lakes, although the population was not as vulnerable.

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The most surprising part of the study took place in the Andes, Robinson said. Peru ranked third in the world for hazard risk. Overall, danger in the Andes ranks second only to high mountain Asia, but the study found that the region receives far less attention from the scientific world.

The number of glacial lakes across the Andes has increased by 93% over the past two decades, compared to 37% in high mountain Asia. Yet researchers found that the Himalayas accounted for 142 studies in English-language journals between 1990 and 2015. Fewer than 100 studies of glacial lake flooding in the Andes have been published in similar journals since 1979, according to the study.

“The focus in recent years on high mountain Asia is good,” Robinson said. “But it shouldn’t come at the expense of other very dangerous places, like the Andes.”

Juan Torres, a risk researcher at the National Institute for Glacier and Mountain Ecosystem Research in Peru, said he and his colleagues had published numerous Spanish-only studies in four sub-basins in the region and planned to publish more next year. He agrees that the field is not well studied in general and wants more collaboration between his organization and other universities around the world.

“Fortunately, this type of hazard can be identified and at least we could know where it will occur,” Torres, who was not involved in the new study, said by email. “We would need to carry out many additional studies to cover the greatest number of potentially dangerous lagoons due to overflow.”

Dirk Hoffmann, a former director of the Bolivian Mountain Institute which has published studies of Andean glaciers, said parts of the region, such as the Cordillera Blanca region, have also been better researched than other parts, such as the high Andes in Bolivia. and that there needs to be more studies of potentially dangerous glacial lakes.

It’s important to identify “possible future sites for these lakes (as global warming worsens, glaciers will continue to melt, new lakes will form),” Hoffman wrote, who also didn’t participated in the study, in an e-mail. “If the goal is to avoid damage or even the death of [glacial lake outburst floods]the only way is to look at concrete local conditions and realities.

Despite the potential risks, researchers say glacial floods can still be avoided with proper preparations and responses. For example, early warning systems in Nepal and Bhutan alert people further downstream to move to a safer location in the event of a glacial lake rupture. Early warning systems aren’t very useful for those who live closer to a lake, however, Robinson said.

Also in Nepal, Bhutan and Peru, governments and researchers have put in place mechanisms to lower the level of glacial lakes to prevent ruptures. Researchers have proposed doing another drainage at Lake Palcacocha in Peru, the site of the 1942 glacial outburst, but the cost is $4 million.

Study co-author Caroline Taylor said more efficient land use planning downstream of glacial lakes can also help by preventing people from building in vulnerable places in the first place. However, this would be complicated for many existing communities.

“None of these options will work on their own, and what is appropriate and works in one place may not work in another,” said Taylor, a glaciologist at Newcastle University. “It’s really now about looking at the local level and finding the appropriate measures for populations at risk.”

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