Flood from “glacial eruption” destroys at least 2 buildings, prompts evacuations in Alaska’s capital Juneau

At least two buildings have been destroyed and residents of others evacuated in Juneau after flooding caused by water pouring from a glacier-dammed lake, officials said Sunday.

The Mendenhall River flooded Saturday due to a large release from Suicide Basin over Alaska’s capital, a press release from the City and Borough of Juneau said.

Video posted to social media showed towering trees behind a house falling into the fast-flowing river as the water eroded away from the bank. Finally, the house too, teetering on the edge, collapsed into the river.

River levels fell on Sunday, but the city said the river’s banks remain highly unstable. Some roads have been blocked by silt and debris from the floods, it said.

Such floods, known as glacial outburst floods, do occur as glaciers melt and pour massive amounts of water into nearby lakes. A study published earlier this year found that such floods pose a risk to 15 million people around the world, more than half of them in India, Pakistan, Peru and China.

The National Weather Service explains that the Suicide Basin is a side basin of the Mendenhall Glacier above Juneau.

“Since 2011,” the agency says, “Suicide Basin has produced flooding from glacial lakes causing flooding along Mendenhall Lake and Mendenhall River.”

Mendenhall Lake meters peaked at 11:15 p.m. Saturday at a maximum level of 5 feet, the service noted, “well above the previous record high of 11.99 feet set in July 2016.”

The lake level was 8 feet (2.2 meters) at 5:15 p.m. Sunday and the water continued to fall, the agency noted.

Significant flooding was reported with water in areas that had never been flooded before, the agency said. “Significant bank erosion has also been reported, with a few structures lost to the river. Treefall and debris are in the river,” he said.