Residents and authorities in Juneau, Alaska, are preparing for possible flooding from the Mendenhall Glacier after recent measurements indicated rising water levels in a nearby basin. The event, known as glacier outburst flooding, occurs when water pressure forces a sudden release from a basin trapped by ice. This annual threat has persisted since 2011 due to the glacier’s natural ice dam, which holds water from seasonal rain and snowmelt. According to the National Weather Service, the basin reached 1,353 feet (412 meters) on Friday, just 15 feet (4.6 meters) below the threshold that could cause a breach. In 2023 and 2024, the Mendenhall River reached record levels, damaging nearly 300 homes last year. Research by the University of Alaska Southeast and Alaska Climate Adaptation Science Center revealed that large floods can release up to 15 billion gallons of water, equal to almost 23,000 Olympic-size swimming pools.

Authorities have installed about 10,000 temporary barriers along 2.5 miles of riverbank to protect more than 460 properties, an effort described as a proactive measure against potential damage. Capital City Fire/Rescue warned that debris in the river during flood stages could create perilous conditions for anyone nearby. The U.S. Army Corps of Engineers has begun a multiyear study to find a long-term solution, though experts estimate that the threat could persist for another 25 to 60 years. This enduring situation has led to calls for a more expeditious approach, with some residents expressing dissatisfaction over the slow timeline. Researchers emphasized the need for coordinated action to ensure resilience in the face of repeated flooding events in the Mendenhall Valley.