One Year Almost To The Day Since Last One, Bigger Glacial Outburst Flood Hits Juneau Alaska

The torrent of frigid meltwater that burst from an Alaskan glacier Tuesday and flooded at least 100 homes, swamped cars and forced residents to wade to safety has become a summertime scourge for the residents of Juneau who live in its path — and one with no easy solutions. A year ago almost to the day, another glacial outburst flood scoured away homes and undercut riverfront condominiums as then-record amounts of water eroded vast swaths of the bank along the Mendenhall River. The floodwaters originate in a hemmed-in basin above the city that fills up with rain and glacial meltwater in the summer until the pressure becomes so great that billions of gallons of water suddenly force their way underneath the Mendenhall Glacier and down into Juneau.

Last year’s damage prompted residents and local officials to discuss a wide range of possible defenses: from giant siphons to suck out the basin to underground tunnels to riverbank barriers to bombing the glacier. But such costly and complicated ideas didn’t progress far, and scientists at the time were unsure whether a flood of that size would happen again soon or at all.

This week’s flood turned out to be the biggest yet. The water level in Mendenhall Lake — at the foot of the glacier — reached nearly 16 feet at 3:15 a.m. on Tuesday, a foot higher than last year’s record, according to the National Weather Service. While the prior outburst proved destructive to homes right along the river, this year flooding was far more extensive and inundated neighborhoods farther away. “There was a tremendous amount of water that came out at one time,” said Aaron Jacobs, senior service hydrologist with the National Weather Service in Juneau.

Glacial outburst floods have poured out of Suicide Basin more than 30 times since 2011. It is challenging to predict exactly how large they will be, since conditions change each year. The jumble of icebergs in the basin keep melting — adding more liquid water to the pool — and the glacier that acts as a dam keeps thinning and retreating as the atmosphere warms, so scientists don’t know exactly when the pent-up water might release.

EDIT

https://www.washingtonpost.com/climate-environment/2024/08/07/glacial-lake-outburst-juneau/

https://wapo.st/46CgF3y