Residents and local officials in Juneau, Alaska, are preparing for possible flooding from the Mendenhall Glacier after recent measurements showed rising water levels in a nearby basin. This type of event, called glacier outburst flooding, occurs when water pressure forces a sudden release from a basin blocked by ice. It has been a problem since 2011 because of the glacier’s natural ice dam, which stores water from seasonal rain and melting snow. The National Weather Service reported that the basin reached 1,353 feet (412 meters) on Friday, just 15 feet (4.6 meters) below the danger point that could cause a sudden release. In both 2023 and 2024, the Mendenhall River reached record levels, damaging nearly 300 homes in the past year. Research from the University of Alaska Southeast and the Alaska Climate Adaptation Science Center found that large floods can release up to 15 billion gallons of water, equal to almost 23,000 Olympic-size swimming pools.

Authorities have placed about 10,000 temporary barriers along 2.5 miles of riverbank to protect over 460 properties. This is considered a preventive step to reduce damage. Capital City Fire/Rescue warned that debris in high water could create hazardous conditions for people nearby. The U.S. Army Corps of Engineers has started a long-term study, but experts say the threat could last 25 to 60 more years. Some residents have shown frustration over the slow timeline, while researchers call for collaborative planning to protect the Mendenhall Valley from repeated flooding in the future.