Threatening Floods Expected in Juneau: Third Consecutive Year of Record-Breaking Glacial Outbursts
A catastrophic flood event is imminent in Juneau, Alaska, with potentially record-breaking levels anticipated for the third consecutive August due to a sudden outburst from Suicide Basin, a glacial lake.
Official announcements issued on Tuesday confirm that flooding is expected along Mendenhall Lake and River through Wednesday, following the occurrence of a glacial outburst at Suicide Basin. Residents in the 17ft lake level inundation zone have been advised to evacuate the area until flood waters subside.
Glacial lake outbursts are caused when melting snow, ice, and rain rapidly drain from a lake that has accumulated behind a glacier, much like draining a full bathtub by pulling out its plug. The current incident involves the Mendenhall Glacier and Suicide Basin, which border the western region of Juneau, approximately 10 miles away from the city center.
The National Weather Service has issued a flood warning for the area, indicating that the Mendenhall River—which runs along the western side of the city—will rise significantly on Tuesday and Wednesday. The river is projected to peak at around 16.6 feet on Wednesday afternoon, surpassing the record level set in August 2022.
Last year’s glacial outburst caused the Mendenhall River to surge to 15.99 feet, resulting in severe flooding that impacted over 100 homes in Juneau. Officials described the flood as unprecedented, with the river level in 2024 surpassing the one reached during the early August 2023 glacial flood by a full foot.
In response to this year’s event, Juneau has installed a flood barrier along the affected area. The region houses approximately 1,000 residents and businesses, though no mandatory evacuations have been implemented at present. Authorities are urging everyone in the inundation area to evacuate before river levels peak.
Senator Lisa Murkowski issued a warning on Tuesday, stating, “This is likely to become a life-threatening situation. If you are told to evacuate, stop what you are doing and immediately go to an emergency shelter or another safe location.”
In anticipation of the impending disaster, Alaska Governor Mike Dunleavy has preemptively declared a state of emergency to facilitate more efficient emergency response efforts. According to his statement, “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.”
As of Tuesday afternoon, the Mendenhall River was close to reaching moderate flood stage—Level 3 of 4—immediately following the onset of the glacial outburst. Major flood stage—Level 4 of 4—is forecasted to commence early Wednesday afternoon and continue until around midnight, local time, before water levels begin to recede on Thursday.
With a population of approximately 33,000, according to the US Census Bureau, Juneau is surrounded by coastal waters to the west and south. Glacial lake outbursts have become an annual occurrence in Juneau since 2011, with the events becoming increasingly severe each year since 2023.
These incidents are a direct result of climate change due to fossil fuel pollution. The Arctic, including Alaska, is warming at twice the global rate as temperatures rise, causing glaciers like those in Alaska to thin or melt entirely. Over time, part of the once icy expanse of Suicide Basin has been replaced by an earthen divot that fills up like a bathtub each summer, setting off the sequence of events leading to these outbursts.
The increasing loss of ice cover in the Mendenhall Glacier and its Suicide Basin creates an annual glacial lake outbreak hazard as ice is replaced by liquid water.