Alaska’s capital, Juneau, is on high alert as authorities warn of potentially record-breaking floods caused by a sudden water release from the Mendenhall Glacier, located about 19 km from the city and a popular tourist destination.

The flooding began Tuesday morning, when massive amounts of rainwater and snowmelt—accumulated in a basin behind an ice dam—burst out, flowing into Mendenhall Lake and River. The National Weather Service estimates that water levels will peak today, Wednesday, between 8 a.m. and noon, reaching 5.12 meters—surpassing the record set in the past two years.

Residents evacuate amid urgent warnings glacial lake will flood city https://t.co/3y0cZw6edU pic.twitter.com/jhnyXmpAHQ

— The Independent (@Independent) August 13, 2025

The phenomenon has occurred every summer since 2011, when a smaller glacier in the area retreated due to climate change, creating a basin that fills in spring and summer and then drains abruptly. Both 2023 and 2024 saw record years in succession, with last year’s flood reaching 4.9 meters and damaging nearly 300 homes.

Dire warnings from experts
Local authorities, in cooperation with federal and state agencies, have installed about 10,000 giant Hesco sandbags over a 4 km stretch, aiming to protect 460 properties from floodwaters up to 5.5 meters. However, experts warn that even these measures may be insufficient in the event of an extreme release.

According to the University of Alaska and the Alaska Climate Adaptation Science Center, a major outburst could release up to 15 billion gallons of water—the equivalent of 23,000 Olympic swimming pools. During last year’s flood, the Mendenhall River’s flow reached half the volume of Niagara Falls.

The study of a permanent solution, such as building a levee, is still in the early stages by the U.S. Army Corps of Engineers, with residents expressing frustration at the slow pace of progress. Scientists warn that sudden flooding events will likely continue for at least another 25 to 60 years, as long as the glacier continues to act as a natural dam for the basin.