At least 100 homes have been damaged by flooding in the Alaskan capital of Juneau after rain and meltwater caused the local river to burst its banks in an incident known as a “glacier lake outburst flood”.
It’s a type of event expected to be more frequent as the earth heats up.
Around 15 million people around the world are thought to be vulnerable to outburst floods.
No injuries were reported in Juneau, but the city said “the community is now facing a long recovery”.
The Mendenhall River, which flows through Juneau’s northeastern suburbs, rose to 15.99 feet on Tuesday, beating a record set last August when the river crested at 14.97 feet and swept away a large house.
The river has now subsided but the city fears such dangerous floods could become an annual event.
Outburst floods
Outburst floods happen when spring and summer thaws spark a chain of events made possible by global heating.
To the north of Juneau is the Mendenhall glacier, at the northern end of Mendenhall Lake, which feeds the Mendenhall River.
Behind the glacier to the north is a dry basin in the earth called Suicide Basin, left by the now-retreated glacier Suicide Glacier.
In spring and summer, that basin fills with glacial meltwater and rain, which is temporarily dammed by the Mendenhall Glacier.
This year and last year, the basin filled enough to overtop the glacier.
When that happens, the water’s pressure forces it out suddenly through channels underneath the glacier and into the lake and the river to the south.
The city of Juneau said it was “like pulling out the plug in a full bathtub”, CNN reports.
Making it worse was the fact that Juneau saw nearly twice the normal volume of rainfall in July.
15 million people at risk
A study published last year found that some 15 million people around the world live in areas at risk from glacial lake outburst floods.
More than half of them live in four countries: India, Pakistan, Peru, and China.
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