August 13, 2025
The Glacier Outburst of the Juneau, Alaska Area:
Flooding last August from the same glacial lake inundated several hundred homes in Juneau 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. Residents this week were urged to evacuate ahead of the latest round of high water.
Alaskan River Reaches Record High From Melting Glacier. An overflowing glacial lake caused a surge in the Mendenhall River on Wednesday, prompting flood alerts and evacuations in Juneau.
An overflowing glacial lake north of Juneau, Alaska, caused the Mendenhall River to surge to a record height on Wednesday, flooding homes and streets 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 last August from the same glacial lake inundated several hundred homes in Juneau 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. Residents this week were urged to evacuate ahead of the latest round of high water.
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.
Glacial lake outburst floods can be catastrophic because, by the time the water reaches downstream settlements, it has picked up huge amounts of sediment and boulders along the way, turning it into a thick slurry that can knock down buildings.
In 2023, a GLOF in northern India killed at least 55 people and destroyed a hydropower dam. All in all, 15 million people around the world live within 50 kilometers, or 31 miles, of a glacial lake and less than a kilometer from the potential path of a GLOF, scientists estimated in a scientists estimated in a 2023 study.
The glacial lake that is overflowing this week in Alaska sits at the foot of the Suicide Glacier, an ice mass north of Juneau. Decades ago, the Suicide Glacier flowed into a much larger river of ice, the Mendenhall Glacier. But as the Suicide melts and shrinks, a steep gap has opened up between it and the Mendenhall. This gap is now called Suicide Basin.
