Alaskan Glacier Outburst Causes Historic Flooding Crisis in Juneau for Third Consecutive Year

A massive release of water and debris from Suicide Basin, a glacial lake connected to the Mendenhall Glacier near Juneau, Alaska, has led to dangerous conditions downriver and flooding concerns for the third consecutive August.

On Tuesday, a glacial outburst from Suicide Basin released an enormous amount of water and debris, resulting in hazardous conditions along the river leading towards Juneau throughout Wednesday. The Mendenhall River, which runs alongside the western edge of the city, surpassed its previous record high level of 15.99 feet on Wednesday morning after rising over 7 feet within a day.

The Mendenhall Glacier and its attached Suicide Basin form when parts of the glacier melt and retreat, creating a large reservoir that fills with rain, snow, and ice during the summer months. As the basin becomes too full, it eventually overflows, releasing water into nearby Mendenhall Lake before surging down the river.

The river reached a new record high of 16.65 feet on Wednesday morning, according to weather service reports, significantly higher than the previous record crest set last August. While the river levels began dropping shortly after, major flooding continues in the afternoon until water levels return closer to normal by Thursday.

Meteorologist Andrew Park with the weather service in Juneau warned residents to stay away from the river due to the high level of debris – including trees – present in the water. Flooding was reported in Mendenhall Lake on Tuesday evening, with over three feet of water accumulating in some areas.

Last year’s glacier outburst caused the river to reach 15.99 feet, resulting in severe flooding affecting more than 100 homes in Juneau. City officials described the flood severity as “unprecedented.” This year’s river level surpassed last year’s by a full foot.

Juneau has installed a flood barrier along the affected area, with approximately 1,000 residents and businesses residing there. While water was seeping through some of the barriers as of Wednesday morning, they had not been breached yet.

Officials urged evacuation for those living in the inundation area on Tuesday night. No mandatory evacuation orders were in effect as of Wednesday morning.

Republican Senator Lisa Murkowski warned on Tuesday that this situation could become life-threatening if residents are told to evacuate. Alaska Governor Mike Dunleavy issued a preemptive disaster declaration on Sunday to better coordinate emergency response efforts for the outburst.

Juneau, with a population of around 33,000 according to the US Census Bureau, is surrounded by coastal waters to the west and south. The city has experienced an increase in glacial lake outbursts since 2011, with the frequency and severity worsening each year since 2023.

These events are attributed to climate change caused by fossil fuel pollution, which is causing glaciers, like those in Alaska, to thin or melt completely. Rising temperatures have significantly reduced the size of the Mendenhall Glacier and its Suicide Basin, increasing the annual risk of glacial lake outburst flooding.

Studies have shown that between 10 and 15 million people worldwide are vulnerable to the impacts of such flooding events, with an increase in both the number and size of glacial lakes anticipated to boost the frequency of these flooding incidents in the future.