Areas of Alaska’s capital are on high alert as officials prepare for what could be record-breaking floodwaters, triggered by snowmelt and rain rushing downstream from Suicide Basin — a side basin dammed by the Mendenhall Glacier.
The glacier, located about 12 miles from Juneau, is a major tourist draw thanks to its proximity and easy walking trail access. But for some of the 30,000 residents who live on the city’s outskirts, especially near Mendenhall Lake and the river that flows from it, the glacier’s beauty is now a source of danger.
“A glacial outburst has occurred at Suicide Basin. The basin is releasing and flooding is expected along Mendenhall Lake and River,” Juneau officials said in a news release on Tuesday. Residents in flood zones were advised to evacuate immediately.
Families in the flooding
For Sam Hatch, a civilian Coast Guard vessel safety regulator, the threat means sending his three daughters, ages 11, 10 and 8, to a friend’s home outside the danger zone, even though he and his partner plan to stay put.
“The girls are having sleepovers outside the flood zone,” Hatch told The Associated Press. “A friend from work has three daughters as well so we shoved them all in one house and they’re having a six-girl epic four-day right-before-school-starts sleepover. I really owe my friend for taking them.”
An annual threat, getting worse
Suicide Basin has unleashed glacier lake outburst floods, known as “jökulhlaups," every year since 2011, according to the National Weather Service. The floods have been growing in scale, with 2024 setting the previous record when water reached 15.99 feet.
By Wednesday morning, floodwaters had already risen more than 7 feet since Tuesday’s first warning, surpassing last year’s record. The NWS says the surge is being fueled by both the basin release and several days of steady rain.
“This will be a new record, based on all of the information that we have,” weather service meteorologist, Nicole Ferrin, told a news conference Tuesday.
Last year, nearly 300 residences were damaged. This year, temporary barriers have been installed in hopes of protecting several hundred more, according to AP.
The scale of the outburst
A major release from Suicide Basin can send nearly 15 billion gallons of water hurtling downstream, the equivalent of almost 23,000 Olympic-sized swimming pools, according to the University of Alaska Southeast and the Alaska Climate Adaptation Science Center. During last year’s flood, the Mendenhall River’s flow rate reached about half that of Niagara Falls.
This year, flooding is expected to peak around 4 p.m. Wednesday, with homes closest to the river most at risk.
Why has this become an annual concern for Alaska residents
A 2024 study found that glaciers are melting and losing mass at a rapid pace, creating more glacial lakes and increasing the risk of large, sudden releases.
Since the first glacial outburst at Suicide Basin in 2011, these events have occurred nearly every summer, although the overall frequency has not increased substantially. What has changed, experts say, is the timing, intensity and potential impact, according to an article by the Alaska Beacon.
Rising temperatures are causing glaciers to melt faster, with floods now starting earlier in the season than in past decades. Retreating glaciers and weakening ice dams are also forming new water-filled basins, creating additional potential sites for sudden outbursts, according to the same report.
The trend reflects a broader global pattern. Worldwide, glacial lake volume has risen sharply due to climate warming, increasing the likelihood of catastrophic drainage events.
For Juneau, these annual outbursts are no longer rare occurrences; they have become part of the seasonal rhythm. Scientists and officials now monitor water levels in real time, construct protective barriers, and coordinate evacuations to reduce risk, per the Alaska Beacon.
Officials urge evacuation
As glaciers retreat and lake levels rise, each year brings the possibility of faster-rising rivers and expanded flood zones. Officials are bracing for the worst, coordinating evacuations and mobilizing resources to keep people safe.
On Sunday, Alaska Gov. Mike Dunleavy issued a preemptive disaster declaration to speed emergency response.
“By issuing this declaration before the flood occurs, we can position state resources and personnel in advance to support local and tribal governments in their efforts to protect lives, homes, and essential services,” Dunleavy said in a statement. “Our goal is to act early to reduce impacts and preserve community safety.”
Meteorologist Andrew Park issued a blunt warning to residents and mariners:
“It’s very dangerous right now. Stay away if you can. Keep your eyes peeled for big trees.”