Devastating flood incidents are currently underway across Alaska.
Record Flooding Hits Juneau, Alaska, Due to Mendenhall Glacier Outbursts
Juneau, Alaska's capital, has been hit by record-breaking floodwaters from the Mendenhall Glacier. Many homes in the city, located on the river into which the glacier flows, have been affected.
The flooding is a result of glacier lake outburst floods (GLOFs) originating from Suicide Basin, a lake dammed by the retreating Mendenhall Glacier. This annual phenomenon has intensified with the glacier's retreat, causing significant flooding impacts.
The flooding events began around 2011, coinciding with the rapid retreat of Suicide Basin’s glacier dam and changes in the Mendenhall Glacier’s dynamics. This over-deepened bedrock basin fills annually with rainwater and snowmelt. When water pressure builds sufficiently, it breaches the ice dam, releasing sudden outburst floods downstream, known as jökulhlaups or glacier lake outburst floods (GLOFs).
In recent years, these floods have threatened life, property, and critical infrastructure in Juneau's Mendenhall Valley. Floodwaters can submerge roads, disrupting transportation and requiring evacuation orders for residents within flood zones. In August 2025, emergency warnings urged immediate evacuation to avoid the rapidly rising flood levels.
The flooding not only affects local residents but poses risks to tourism and the natural environment near the glacier, a major attraction for Juneau. Hundreds of homes have been washed away and flooded in recent years.
To mitigate the risks, the U.S. Army Corps of Engineers (USACE) is conducting technical studies and monitoring to understand flood risks, glacier dynamics, and water flow patterns. The U.S. Geological Survey (USGS) also monitors flood levels in real-time, providing data to authorities to inform rapid response and evacuation efforts. City officials have implemented early warning systems and public evacuation communications to reduce risk to life during flood events.
However, because the glacier is expected to act as an ice dam sealing Suicide Basin for another estimated 25 to 60 years, annual flood events and outburst risks are expected to continue for decades. Temporary barriers have been installed this year to protect several hundred homes in the flood zone, aimed at preventing major damage to homes in the flood zone.
Officials have warned of potential flooding in Juneau due to the floodwaters from the Mendenhall Glacier. Residents in the flood zone have evacuated after water began flowing from the glacier's ice dam, with the floodwaters already accumulating on several streets and seeped under barriers designed to protect riverside homes in Juneau.
Sources:
- Alaska Public Media
- AP News
- U.S. Army Corps of Engineers
- U.S. Geological Survey
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