When global warming melts glaciers, meltwater can collect and form lakes. But if they cross the boundaries of the basins created by the glacier, these liquid masses pose a significant natural hazard. Indeed, glacial lake burst flooding (GLOF) can continue to cause countless deaths as well as damage to property and infrastructure.
More than half of the population living under this risk is found in just four countries: India, Pakistan, Peru and China.
Around 15 million people worldwide could be threatened by flooding in glacial lakes. The inhabitants of villages and cities in the high mountains of Asia and the Andes are the most exposed to danger, according to a study published in Nature Communications. More than half of the population living under this risk is found in just four countries: India, Pakistan, Peru and China.
“GLOFs can have far-reaching consequences, from the local to the national scale”, Caroline Taylor, doctoral student at the Institute of Geography, Politics and Sociology at New Castle University (UK) and co-author of the work.
“At the local level, they can cause loss of life, livestock, agricultural land or property, with obvious social and economic repercussions”, he explains. adds the researcher.
Between 1900 and 2021, there have been around 2,800 floods due to this type of overflow worldwide.
Caroline Taylor
These natural disasters occur with remarkable frequency: “There is evidence that between 1900 and 2021 around 2,800 GLOFs occurred worldwide”, says the glaciologist.
“Examples include the devastating flood of Lake Chorabari in 2013 in Kedarnath city (India) or the 2018 incident in Ishkoman valley (Pakistan), which damaged 40 homes and caused loss of livestock and physical assets in Badswat city,” he said. list.
These glacial floods can occur without warning when a natural dam fails.
The researcher stresses that this type of flooding is a “natural cross-border risk”. Therefore, the damage is not limited to the territory where the disaster occurs, but “the social, economic and environmental repercussions can affect several countries”.
This is “the first time” that “the number of people exposed to GLOF on a global scale” has been calculated, according to the scientist, since, until now, studies have been limited to accounting for damage “at the local or regional level” .
“Today we can determine which countries and which river basins should be considered a priority for further analysis and risk reduction,” said Taylor.
The urgency of seeking solutions
The study’s first author, Thomas Robinson, senior lecturer at the School of Earth and Environment at the University of Canterbury, New Zealand, says GLOFs can occur without warning when a natural dam fails.
Keeping global warming below 1.5ºC is an urgent measure
Caroline Taylor
“Continued ice loss and expansion of glacial lakes due to climate change show that glacial lake flooding is a natural hazard of global importance that requires urgent attention to minimize future loss of life,” says Robinson.
The glaciologist proposes “early warning systems” for communities located downstream. “But for people living close to glacial lakes, within 5 to 10 km, they are unlikely to be effective, as there is unlikely to be enough time to warn and safely evacuate people before the flood hits,” he adds.
Potential risk mitigation solutions can be costly and traumatic for local communities
For her part, Taylor regrets that there is no one-size-fits-all solution to reducing that risk. “Limiting climate change and keeping atmospheric warming below 1.5 degrees Celsius are key measures, as they will help slow the growth of glacial lakes and prevent the danger from continuing to increase,” he says. However, “we have to find effective measures for the threatened population, working with national and regional governments, as well as with the communities themselves”, says the researcher.
In this regard, Thomas Robinson highlights the interest in collaborating with public administrations “to help identify and explore possible mitigation options, carry out evacuation exercises and have early warning systems for floods. It is about working together to minimize the risk to human lives.”
think locally
Taylor recognizes the difficulty of finding efficient and accessible measures: “There are engineering solutions, such as the installation of gates to manually lower the lake levels and control the flow of water, but they are expensive and do not guarantee the resolution of the problem if, for example, , a landslide or ice avalanche occurred on the lake.
Regulating land use to avoid building in risky locations can also be complex for local communities. The relocation of residents may be another option, “but it is expensive and traumatic for these communities”, qualifies the author of the study.
Peru has the third highest risk of flooding due to overflowing glacial lakes worldwide
thomas robinson
“None of these options will work alone, and what is appropriate and works in one place may not work in another, so now it’s really about looking at the local scale and finding appropriate measures for endangered populations.”
An ignored hot spot
The Himalayas have been a popular research topic (36% of glacier eruption flood studies conducted between 2017 and 2021). However, the paper mentions the Andes as an understudied hot spot regarding the danger of GLOFs.
“While the Asian highlands have the greatest potential for impact, we highlight the Andes Mountains, which primarily affect people living in Peru and Bolivia, as a region of concern with similar risk,” says Robinson.
On the Asian plateau, the professor points out that “about one million people live 10 kilometers from a glacial lake”. But the number of these water bodies has grown by 37% since 1990, while in the Andes it has increased by up to 93%. “Peru has the third highest risk of flooding due to the overflow of glacial lakes in the world,” he warns.
Corruption, poverty and educational level indicators show the Andean region as very vulnerable
The work points out that the most dangerous areas are not those with the largest, most numerous or fastest growing glacial lakes. What determines the risk is the number of inhabitants in the region and their ability to face catastrophes. Some valleys contain many large glacial lakes but record very few people living downstream. It implies that they are comparatively less dangerous.
However, in some areas of Pakistan, India and Peru, there are large numbers of people living in these valleys. In addition, the inhabitants of the Andean region are very vulnerable to the consequences of a catastrophe of this type, according to the indicators of corruption, poverty, education and other factors used by the researchers. Instead, the study identifies New Zealand as the least vulnerable country.
What determines the risk of a region is not the size of the glacial lakes, but the number of people who live there.
thomas robinson
“If you want to understand risk, you don’t just look at danger, but you have to think about where people are and how vulnerable they are,” says Robinson. “We cannot focus on the Himalayas because it is the most visible area and ignore the risks in the Andes. We must ensure that we consider the big picture and the areas with the most vulnerable people.”
The evolution of GLOF’s risk in the future is still up for debate. The climate crisis will continue to expand glaciers in number and extent, which will change the pattern of endangered areas. The authors consider it necessary to promote research to assess the conditions of the lagoons, exposure and vulnerability, in order to determine the relative role of each of them in the risk of flooding.
Reference
Robinson, T. et al. “Flooding from glacial lake explosion threatens millions worldwide”. Nature Communications (2023)
