AUGUST 20, 2025 – Last week, Alaska’s Mendenhall Glacier released its yearly glacier lake outburst flood, flowing downstream toward Juneau. In preparation for the potential threat to infrastructure and public safety, the U.S. Army Corps of Engineers provided temporary flood mitigation barriers to the city last winter.
While USACE continues to prepare a technical study to help define the parameters of an enduring flood risk mitigation solution, these barriers provided vital short-term protection to the community along the Mendenhall River by holding back the glacial water released from Suicide Basin and performing well during the peak of the floodwaters.
“As we continue to evaluate the performance of the barriers, I’m confident they prevented a lot of property damage compared to 2024,” said Army Brig. Gen. Joseph “Clete” Goetz, commanding general of the USACE – Pacific Ocean Division.
Originating from the USACE National Flood Fight Materiel Center in Illinois, about 37,800 linear feet of barrier wall, 400 supersacks, 112,000 sandbags and 25,000 linear feet of polyethylene sheeting were shipped to Juneau during the winter and spring of 2025 and strategically installed along the river in two phases.
Phase one was completed in the spring and covered about 2.5 miles between Marion Drive and Rivercourt Way. Phase two will build upon lessons learned at this year’s event and provide coverage to the remainder of the area.
As the lead federal agency for floods, USACE provided technical assistance and advisement to the community throughout the process. Installation of these materials is a challenging process that takes the flood event data of the previous year into consideration, Goetz said.
This information can include high-water marks, topography and ground conditions. Depending on the high-water marks, the height of the barriers varies in each location.
The decision was made to build to the high-water elevation with an additional 4 feet. In some cases, this resulted in a barrier two units high, or 8 feet above the ground.
“The successful deployment of these temporary flood protection barriers is reflective of a total team effort with our stakeholder, tribal and community partners,” said Army Col. Jeffrey Palazzini, commander of the USACE – Alaska District. “The preparation and partnership were on full display during the flood event of the past 24-48 hours.”
As of Aug. 14, the barriers have performed well in response to record high floodwaters in the Mendenhall River Valley. However, further assessment is still needed to determine the full extent of any damage.
The last two years of flooding have been historically high, with water levels at the U.S. Geological Survey Mendenhall River streamgage peaking at 14.97 feet and 15.99 feet in 2023 and 2024, respectively. This week, the river reached a record high, with the largest flow measuring 16.6 feet.
USACE leaders were fully engaged on-site during the event, seizing the opportunity to closely monitor the capabilities of the barriers in real time and meet with stakeholders and community members. Although an enduring solution will take years to fully develop, short-term flood mitigation efforts in Juneau continue to be a high priority at all levels of the organization, USACE officials said.
By Cameron McLeod and John Budnik
U.S. Army Corps of Engineers