Emergency Management Authorities Urge Evacuation in Juneau Amid Rising Threat of Glacial Flooding Driven by Climate Change
Emergency management officials in Juneau, the capital city of Alaska, are urging many residents to evacuate due to an increasingly dangerous threat of glacial flooding. This seasonal risk, intensified by the impacts of climate change, has prompted urgent warnings as the Mendenhall River continues to rise rapidly and could potentially overflow its banks.
According to local authorities, water levels in the Mendenhall River are expected to reach their peak at approximately 4 p.m. local time (Alaska Standard Time) on August 13, which corresponds to 8 p.m. Eastern Time. In preparation for this anticipated crest, emergency teams had already completed the installation of nearly two miles of temporary flood barriers last month, aimed at protecting the Mendenhall Valley. This area is especially critical because it houses the majority of Juneau’s population, which totals around 32,000 permanent residents.
Areas of Juneau Advised to evacuate
In an official alert issued on August 12, the City and Borough of Juneau strongly advised residents to evacuate areas most at risk of being flooded. “Residents are advised to evacuate the potential flood inundation area,” the announcement stated. “Do not go near the river.” Governor Mike Dunleavy has also taken proactive measures by declaring a state of emergency ahead of time, citing extensive damage caused by similar “glacial outburst floods” in both 2023 and 2024 as justification for the declaration.
As of midday on August 12, the river’s water level had surged to approximately 10 feet—double its usual depth of around 5 feet. This increase pushed it into the “moderate” flood stage, according to data from the National Weather Service (NWS). The highest water level ever recorded was 16 feet, a record set during last year’s flooding event, and current forecasts suggest that this year’s event might even exceed that level.
Last year’s glacial outburst released an estimated 14.6 billion gallons of water, which is the equivalent of filling more than 22,000 Olympic-sized swimming pools. The consequences were devastating: homes and basements were flooded, critical infrastructure was damaged or destroyed, and buildings located close to the riverbanks collapsed under the force of the water.
Cause of Juneau Flood
These floods originate from a phenomenon known as a “glacial outburst flood,” which occurs when a natural ice dam holding back water in a glacial lake suddenly fails. In Juneau’s case, this dam is associated with Suicide Basin, a side basin of the Mendenhall Glacier. The summer heat melts the ice at an accelerated pace, causing the basin to release large volumes of water in a short time. Scientists have pointed to climate change as a key driver of this accelerated melting. Alongside this, altered precipitation patterns and warmer overall temperatures are contributing to the growing frequency and intensity of such events.
Suicide Basin and the Mendenhall Glacier are not only scientific concerns but also prominent tourist attractions, easily accessible from the city. According to the National Weather Service, the first recorded outburst from Suicide Basin occurred in 2011, and such events have become more common since then. Recognizing the growing threat, city officials—supported by federal agencies—have installed flood defenses along the riverbanks in the most vulnerable areas. While these new barriers are engineered to withstand extreme flooding, officials are erring on the side of caution by recommending evacuations to ensure public safety.
Climate data underscores the urgency. Over the past several decades, Alaska has experienced warming at approximately twice the rate of the rest of the United States. The state’s average annual temperature has increased by 3.1 degrees Fahrenheit over the last 100 years, according to the National Centers for Environmental Information. This rapid warming trend is accelerating the melting of glaciers and increasing the likelihood of extreme weather and flooding events across the region.
In light of these conditions, residents of Juneau are being asked to prioritize safety and heed evacuation orders while authorities continue to monitor the situation closely and implement protective measures.
