Sections of Alaska’s capital metropolis are bracing for the arrival of what may very well be document floodwaters resulting from rainwater and snowmelt flowing downstream from a basin dammed by the Mendenhall Glacier.
Some Juneau residents within the flood zone have evacuated, heeding warnings, and officers there intensified their warnings Tuesday, saying “Do not wait, Evacuate TONIGHT.”
On Tuesday morning, authorities confirmed water had began escaping the ice dam, with flooding anticipated into Wednesday.
USGS/Handout by way of Reuters
The Mendenhall Glacier is about 12 miles from Juneau, dwelling to 30,000 folks, and is a well-liked vacationer attraction resulting from its proximity to Alaska’s capital metropolis and easy accessibility on strolling trails. Houses on town’s outskirts are inside miles of Mendenhall Lake, which sits beneath the glacier, and lots of entrance the Mendenhall River, into which the glacial outburst is flowing.
The Nationwide Climate Service mentioned it anticipated flooding to to peak round 8 a.m. to midday native time (midday – 4 p.m. ET) on Wednesday.
“This can be a brand new document, based mostly on the entire data that we now have,” Nicole Ferrin, a climate service meteorologist, advised a information convention Tuesday.
Flooding from the basin has develop into an annual concern since 2011, and lately has swept away homes and swamped a whole lot of properties. Authorities businesses put in non permanent obstacles this yr in hopes of defending a number of hundred properties within the inundation space from widespread harm.
The flooding occurs as a result of a smaller glacier close to Mendenhall Glacier retreated — a casualty of the warming climate — and left a basin, often known as Suicide Basin, that fills with rainwater and snowmelt every spring and summer time. When the water creates sufficient stress, it forces its method below or across the ice dam created by the Mendenhall Glacier, enters Mendenhall Lake and ultimately flows down the Mendenhall River, as it did Tuesday.
Earlier than the basin started overtopping, the water stage was rising quickly – as a lot as 4 toes per day, in keeping with the Nationwide Climate Service.
Town noticed successive years of document flooding in 2023 and 2024 — with the river final August cresting at 15.99 toes, a few foot over the prior document set a yr earlier — and flooding extending farther into the Mendenhall Valley. This yr’s flooding was predicted to crest at between 16.3 and 16.8 toes.
Final yr, practically 300 residences had been broken.
Video posted on social media two years in the past confirmed towering timber behind a house falling into the speeding Mendenhall River because the water ate away on the financial institution. Ultimately, the house, teetering on the edge, additionally collapsed into the river.
A big outburst can launch some 15 billion gallons of water, in keeping with the College of Alaska Southeast and Alaska Local weather Adaptation Science Middle. That is the equal of practically 23,000 Olympic-size swimming swimming pools. Throughout final yr’s flood, the circulate price within the speeding Mendenhall River was about half that of Niagara Falls, the researchers say.
Metropolis officers responded to issues from property homeowners this yr by working with state, federal and tribal entities to put in a short lived levee alongside roughly 2.5 miles of riverbank in an try to protect in opposition to widespread flooding. The ten,000 “Hesco” obstacles are basically big sandbags supposed to guard greater than 460 properties fully throughout an 18-foot flood occasion, mentioned emergency supervisor Ryan O’Shaughnessy.
The U.S. Military Corps of Engineers is at first of what is anticipated to be a yearslong means of finding out situations within the area and analyzing choices for a extra everlasting answer, comparable to a levee. The timeline has angered some residents, who say it is unreasonable.
Outburst floods are anticipated to proceed so long as the Mendenhall Glacier acts as an ice dam to seal off the basin, which might span one other 25 to 60 years, in keeping with the college and science heart researchers.
