Glacial flooding poses a natural hazard to millions globally

15 million people are at risk of floods caused by glacial lakes, with more than half of those exposed living in just four countries, according to a press release.

Critically, the most vulnerable regions are neither those with the most lakes nor those expanding most quickly. Instead, it's the size of the population, how close people are to a glacial lake, and, most significantly, how well-prepared they are for a flood that determines how dangerous the somewhat overlooked natural hazard is. 

Which countries are most vulnerable to glacial flooding?

The first global assessment of regions most in danger from glacial floods was created by an international team of scientists led by Newcastle University in the U.K. They identified China, Peru, India, and Pakistan as "priority locations" for mitigation.

As the temperature warms, glaciers retreat, and meltwater builds up at the glacier's front, creating a lake. These lakes have the potential to rupture suddenly, causing a fast-moving Glacial Lake Outburst Flood (GLOF) that can travel more than 74 miles (120 kilometers) from the initial site. 

GLOFs have the potential to be highly destructive, causing considerable property, infrastructure, and agricultural land damage as well as fatalities.

A fatal Himalayan glacial lake outburst in 2021 serves as an example, which killed at least 31 people in the mountainous state of Uttarakhand in India. Some scientists even theorize that glacial lake flooding played a part in the 2022 Pakistan floods.

The press release stated climate change had caused a sharp increase in glacier lakes since 1990. The number of people residing in these catchments has also significantly increased at the same time.

The research team examined 1,089 glacial lake basins worldwide for indicators of vulnerability to GLOFs. Indicators included the number of people who lived within 31 miles (50 kilometers) of each, the degree of development in those regions, and other sociological variables.

Glacial lake flooding, an overlooked natural hazard

Following that, they evaluated the ability of communities to respond successfully to a flood. They quantified and ranked the potential harm from GLOFs on a global scale.

The findings showed that 15 million people reside within 31 miles (50 kilometers) of a glacier lake. Critically, high Mountain Asia (including the Tibetan Plateau, from Kyrgyzstan to China) has the greatest GLOF danger, with 9.3 million people possibly at risk. India and Pakistan alone have around five million exposed people. 

"Understanding which areas face the greatest danger from glacial flooding will allow for more targeted and effective risk management actions," said Dr. Rachel Carr, Head of Physical Geography at Newcastle University and a co-author.

"Which in turn will help minimize loss of life and damage to infrastructure downstream as a result of this significant natural hazard," she concluded.

The study was published on February 7 in Nature Communications.