Residents of Juneau, Alaska, have been urged to evacuate after an overflowing glacial lake sent water surging down the Mendenhall River.
Forecasters said river levels could break a record between 8 a.m. and noon local time on Wednesday, threatening homes and roads in parts of the state capital, which has a population of more than 30,000.
Such floods have been a recurring problem in Juneau since 2011, but recent years have seen record-setting surges as rising temperatures cause glaciers in the area to melt more rapidly. Alaska has warmed faster than the global average, and the fastest of any state, according to the Environmental Protection Agency.
Flooding from the glacial lake in Juneau last August inundated several hundred homes with four to six feet of water, although no deaths or injuries were reported. The city put up a temporary levee along the river in response.
Here’s what to know about these floods.
What’s a glacial lake outburst flood, or GLOF?
As glaciers melt, they tend to retreat uphill, leaving an empty bowl at the bottom of the valley where the ice once sat. Meltwater from the glacier starts pooling in this bowl, and over time a lake forms.
But the sides of the lake are fragile. They might be formed of loose dirt and rock or ice. If one day an avalanche or a landslide occurs, or a piece of a nearby cliff plunges into the water, the disturbance can cause the sides of the lake to collapse. In a flash, most of the lake’s water might cascade down the valley, threatening towns and cities below.
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The post Some Juneau Residents Evacuate as Melting Glacier Threatens to Flood Town appeared first on New York Times.
