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

The Mendenhall River flooded Saturday because of a major release from Suicide Basin above Alaska’s capital city, a news release from the City and Borough of Juneau said.

A drone view shows a house before it collapses into a river due to glacial floods in Juneau
A drone view shows a house before it collapses into a river due to glacial floods in Juneau, Alaska, on August 5, 2023 in this screengrab obtained from a video on social media. 


Video posted on social media showed towering trees behind a home falling into the rushing river as the water ate away at the bank. Eventually, the home, teetering at the edge, also collapsed into the river.

River levels were falling Sunday but the city said the banks of the river remain highly unstable. Some roadways have been blocked by silt and debris from the flooding, it said.

Record flooding along Alaska river near Juneau prompts evacuations
View of flooding following a glacial dam outburst, in Juneau, Alaska, in image released on August 5, 2023 and obtained from social media. 

National Weather Service Juneau via Reuters

Such floods, known as glacial outburst floods, happen when glaciers melt and pour massive amounts of water into nearby lakes. A study released earlier this year found such floods pose a risk to 15 million people around the globe, 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.

Suicide Basin, near Juneau, Alaska

National Weather Service

“Since 2011,” the service says, “Suicide Basin has released glacier lake outburst floods that cause inundation along Mendenhall Lake and Mendenhall River.”

Mendenhall Lake gauge crested at 11:15 p.m. Saturday at a maximum level of 4.97 feet, the service pointed out, “well above the previous record stage of 11.99 feet set in July 2016.”

The lake level was 7.22 feet at 5:15 p.m. Sunday and waters continued to recede, the service noted. 

Significant flooding was reported with water in areas that had never been flooded before, the service said. “Significant bank erosion has been reported as well with a few structures lost to the river. Tree-fall and debris are in the river,” it said.

The Suicide Basin area at Juneau, Alaska

National Weather Service