A glacial dam burst in Alaska’s capital, Juneau, causing flooding and damage. Two homes were completely lost and a third partially so. The flooding was caused by a Jökulhlaups, a phenomenon in which a snow-and-ice dam bursts. Jökulhlaups are relatively rare in the U.S., but they can be devastating.

The flooding in Juneau came from a side basin of the Mendenhall Glacier. The basin used to be covered by the Suicide Glacier, which has retreated as the climate warms. This has left a lake in the basin dammed by the Mendenhall Glacier. When the lake’s water level got too high, it burst through the ice dam and caused flooding downstream.

Crazy video of the house falling into the Mendenhall River during record jökulhlaup flooding tonight. @NWSJuneau Via Sam Nolan on FB. pic.twitter.com/cX3sROtzQb

— Eric Stone (@eriwinsto) August 6, 2023

The flooding caused extensive damage to homes and businesses along the Mendenhall River. The ground along the river is made up of loose glacial deposits, which makes it especially susceptible to erosion. The damage could have been much worse if the flood coincided with heavy rains.

Here are some additional details:

• The flooding happened on Saturday, May 21, 2023.
• The water level in the Mendenhall River rose to about 1.5 times the highest previously recorded.
• The flooding damaged eight buildings, including two homes that were completely lost.
• There were no reports of injuries or fatalities.
• Climate change is melting glaciers around the world, which could increase the risk of jökulhlaups.
• The variability in the timing and volume of jökulhlaups makes it difficult to prepare for them.