“Glacial Lake Outburst Floods: The Growing Risk to Millions of People Worldwide”
A glacial lake at the foot of Mount Jomolhari in Bhutan.
Up to 15 million people are at risk of catastrophic flooding from glacial lakes that could breach their natural levees at any time, according to a new study.
The study, led by Newcastle University, is the first global attempt to map potential hotspots for such flooding.
As the climate warms, glaciers retreat and meltwater collects and forms lakes.
The impact of global warming on glacial lake flooding has yet to be defined, but it has increased both the volume and number of glacial lakes worldwide.
The study, published in the journal Nature Communications, assessed the health of lakes and the number of people living downstream from them, which has also increased significantly.
“There are large numbers of people around the world who are at risk from the effects of these floods,” said Rachel Carr, a glaciologist at Newcastle University and the paper’s author.
“It can happen at any time — that makes them particularly dangerous because it’s hard to predict when they’ll happen.”
The authors say those facing the greatest threat live in mountainous countries in Asia and South America.
People living in India, Pakistan, Peru and China make up more than half of the risk group. In Asia, about a million people live within a 10 km radius of a glacial lake.
“It’s important how close people are to these lakes and how they can respond to the disaster,” said Dr. Carr.
“People have done a lot of inventory studies [of the lakes] …but our study reversed that.
“What’s downstream is just as important, if not more so. I think it’s an important realignment in the way we think about it.”
Lakes formed by melting glaciers have natural dams of loose rock and ice that can fail suddenly and unpredictably.
Subsequent floods come quickly and severely, and in many cases are severe enough to destroy vital infrastructure.
A bridge partially collapsed due to flooding from a glacial lake outburst in Pakistan last year
Dam failures are complex but are often triggered when a boulder or ice falls into the lake from the surrounding mountains.
This causes a wave to spread across the lake like a tsunami, destabilizing the dam when it reaches it.
Other factors include a gradual buildup of meltwater, increasing pressure on the dam, and the melting of ice cores holding it together.
Rather than predicting which dams would be most likely to fail, the study’s authors looked at which lakes would pose the greatest threat if they erupted.
They also stress the importance of early warning systems such as time-lapse cameras.
“It’s an important paper,” said Stephan Harrison, a leading expert on the effects of climate change on glacial lakes at the University of Exeter, who was not involved with the research. “It warns policymakers about the likely impacts of future climate change.”
dr Harrison added that the research is just a first step in better understanding how climate change is affecting what are known as Glacial Lake Outburst Floods (GLOFs).
This relationship is complex and complicated by what scientists suspect is a long time lag between cause and effect.
Research shows that an increase in flooding, which began in the early 20th century and peaked in the 1970s, may be a delayed response to past climate changes.
While scientists expect glacial flooding to increase as a result of human-caused climate change, there hasn’t been such an increase to date.
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