Fifteen Million People at Risk of Severe Floods From Melting Glaciers

Rising temperatures could worsen glacial lake outbursts, unleashing massive inland waves on downstream communities, a study finds

Glacial lake in Nepal
Dig Tsho, a glacial lake in Nepal that burst in August 1985 MattW via Flickr under CC BY-NC-ND 2.0

Melting glaciers are one of the most visible consequences of a warming planet. And as glaciers thaw amid human-caused climate change, they’re putting an estimated 15 million people around the world at risk of suffering sudden, deadly and destructive flooding events, according to new research.

Communities situated downstream from glaciers and their accompanying glacier lakes are the most vulnerable—with more than half of those at risk living in four countries: China, India, Peru and Pakistan, according to a paper published Tuesday in Nature Communications.

Glaciers are massive bodies of moving ice formed as snow accumulates over centuries. This movement can carve a depression in the ground that fills with meltwater, creating a glacial lake. While these chilly lakes are typically beautiful and calm, they can burst without warning, releasing powerful torrents of water, rocks and debris. Scientists call this phenomenon, which is similar to a dam bursting, a glacial lake outburst.

“These glacial dams are no different to constructed dams,” says study co-author Tom Robinson, a disaster risk and resilience researcher at the University of Canterbury in New Zealand, to CNN’s Rachel Ramirez. “If you take the Hoover Dam, for instance, you’ve got a massive lake behind it, but if you suddenly remove the Hoover Dam, that water has to go somewhere, and it’s going to come cascading down a valley in massive flood waves.”

In 2020, a 330-foot-tall wave burst from a glacial lake in British Columbia, Canada, but no one was hurt. In the Cordillera Blanca mountain range in Peru, floods from glacier lake outbursts have killed thousands in the last 70 years alone. 

To assess the risk posed by future glacial lake outbursts around the world, scientists considered the geography, human development, climate, population and the likely flood prevention and response efforts of 1,089 glacial basins.

The number of glacial lakes around the world has increased rapidly over the last 30 years—and these pools are also getting bigger, both in area and in volume. At the same time, more people—along with their buildings and farms—have populated vulnerable areas downstream of glacial lakes.

As a result, millions now live within 30 miles of a glacial lake. The communities with the highest risk are those located in the high mountains of Asia, such as Nepal, Pakistan and Kazakhstan. In this region, one million inhabitants live just six miles from a glacial lake, where the chance of having early warning of an outburst is low, the study finds. The risk is lower in areas such as the Pacific Northwest, where the population is less vulnerable, and Greenland, where fewer people live near glacial lakes.

“In a warming world, we certainly expect more and larger glacial lakes,” Dan Shugar, a geoscientist at the University of Calgary in Canada who was not involved in the research, tells the Associated Press’ Seth Borenstein in an email. “But the threat that these lakes might pose critically depends on where people are living and what their vulnerabilities might be.”

Already, glacial lake outbursts are deadly and destructive. But as temperatures continue to rise because of heat-trapping greenhouse gas emissions, glaciers are likely to melt even more quickly. This means that, in the event of a glacial lake outburst, it would unleash a larger quantity of water.

All hope is not lost, however. Communities can implement strategies to lower their risk, such as investing in early warning systems and running evacuation drills, per the researchers. They can also implement land-use strategies that limit development in areas prone to flooding. Halting the progression of global warming will also help limit future glacial melting and lake growth.

“It sounds quite dire, but it doesn’t need to be,” says Robinson to the Washington Post’s Kasha Patel. “With thoughtful investment and careful planning, we can avoid these [flooding disasters].”

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