Juneau on Alert: Record Glacial Outburst Flood Prompts Evacuations

JUNEAU, Alaska — In a race against a record-breaking natural phenomenon, officials in Juneau, Alaska, have issued an evacuation advisory for residents in flood-prone areas as a glacial outburst flood begins to unfold. The event, which is an annual occurrence but is predicted to be the largest on record, is putting homes and infrastructure along the Mendenhall River at risk.

The floodwaters originate from Suicide Basin, a side basin of the massive Mendenhall Glacier. Each year, as the summer sun melts snow and ice, the basin fills with water. When the pressure becomes too great, the water finds a path under or around the glacial ice dam, releasing a sudden, powerful torrent into Mendenhall Lake and the Mendenhall River.

According to the National Weather Service, the basin reached capacity and began spilling over on Sunday. By Tuesday, water had started to escape the ice dam, with the peak of the flooding expected sometime today, Wednesday, August 13. The Mendenhall River is forecasted to crest at a new record height of between 16.3 and 16.8 feet, surpassing the previous record of 15.99 feet set just last year.

In response to the imminent threat, the City and Borough of Juneau, in a joint effort with Tlingit & Haida and other state and federal agencies, has activated a unified command. Governor Mike Dunleavy has also issued a state disaster declaration to expedite the deployment of resources.

City officials have been working to mitigate the potential damage, including the installation of a temporary levee made of approximately 10,000 "Hesco" barriers—essentially giant sandbags—along a 2.5-mile stretch of the riverbank. This measure is intended to protect more than 460 properties. However, residents are still being urged to evacuate as a precaution, and a shelter has been set up at the Floyd Dryden Gymnasium.

While some residents are heeding the evacuation advisory, others are choosing to stay and monitor the situation, with some having built their own protective berms. The unpredictability of these events and the potential for water to flow around the temporary barriers have led to a mix of anxiety and vigilance within the community.

The U.S. Army Corps of Engineers is beginning a multi-year study to find a more permanent solution, but for now, residents are on high alert. Researchers predict that these glacial outburst floods will continue to occur for the next several decades as climate change accelerates the melting of the Mendenhall Glacier, highlighting the ongoing and evolving risks faced by communities living near retreating glaciers.