What are Glacial Lake Outburst Floods?

Columbia Icefields
Columbia Icefields Glacier - BVN File Photo

Do you know what “glacier lake outburst floods” are? Glacier lakes eventually can rise or possibly create new rivers and lakes around them. Bigger lakes pose greater hazards to mountain communities, because the water is often loosely dammed by glacier debris and can suddenly burst through, causing catastrophic flooding.

According to Wikipedia, a glacial lake outburst flood (GLOF) is “a type of outburst flood that occurs when the dam containing a glacial lake fails”. That failure may happen, for example, due to erosion, a buildup of water pressure, an avalanche of rock or heavy snow, an earthquake, or cryoseism, volcanic eruptions under the ice.

Icelandic people have seen that melting glaciers normally lead to growing rivers and lakes and that situation puts in risk populated villages located close by. In 1996 in Iceland the second biggest river in the world was created in a few days after a volcano part of the Vatnajökull glacier located under the Grímsvötn lakes erupted and the river Skeiðará flooded the land in front of Skaftafell, now part of Vatnajökull National Park. The jökulhlaup (an Icelandic word that means jökull = glacier, hlaup = run) reached a flow rate of 50,000 cubic metres per second, and destroyed parts of Iceland Road #1. The flood carried ice floes that weighed up to 5000 tons with icebergs between 100–200 tons. The tsunami released was up to 4 metres (13 ft) high and 600 metres (660 yd) wide. The flood carried with it 185 million tons of silt. The jökulhlaup flow made it for several days the 2nd largest river (in terms of water flow) after the Amazon. The ruins are well marked with explanatory signs today as a popular tourist stop.

Dan Shugar at the University of Calgary in Canada and his colleagues analyzed more than 250,000 images taken by the Landsat satellites and they saw that glaciers on Earth are melting faster than many people expected and lakes are growing very fast because of it. According to that research, between 1990 and 2018, the number of glacial lakes rose from 9,414 to 14,394. The lakes’ total surface area increased by 51%, and their volume by 48%. The extra water would fill more than 20 million Olympic swimming pools. Lake volumes increased most at high latitudes.

“This is an issue for many parts of the world where people live downstream from these hazardous lakes, mostly in the Andes and in places like Bhutan and Nepal, where these floods can be devastating,” Shugar said.

The study also says that a possible GLOF may lead not only a flood disaster, but also possible problems to provide drinking water for a big part of the population of Alberta. If all the water contained in these glacial lakes were to reach the ocean, it would increase global sea level by 0.43 millimeters.

It is important to keep studying how fast our glaciers are melting and keep designing ways to manage the risk before a natural disaster happens and to prepare an action-plan in case something like that happens in the Canadian Rockies.

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