Residents told to prepare in case glacial outburst flooding begins this weekend

There’s still no indication that Suicide Basin has started to drain, but Juneau’s riverside residents should make an evacuation plan and prep a go-bag in case glacial outburst flooding begins this weekend. 

City officials previously said they planned to roll out a text alert system to notify residents of rising river levels, but Emergency Programs Manager Tom Mattice said that hasn’t happened yet.

“We’ll get out PSAs as soon as it comes live,” he said. “It’s just taking a little longer than we’d hoped.”

The Mendenhall Glacier dams Suicide Basin, a glacial lake that can hold more than 10 billion gallons of water. Right now the basin is close to full, and earlier this week water started to spill over the top of the ice dam.

But flooding in the Mendenhall Lake and River won’t begin until water starts draining out underneath the glacier. 

There’s a lot of uncertainty about when that will happen, and about how fast it will drain, but meteorologists say flooding could happen in the coming days and weeks. 

As of Friday afternoon, the Mendenhall River is running at 5.25 feet, well below flood stage, which begins at 9 feet. The forecast through the weekend and early next week calls for dry weather.

Last year’s outburst flood was the worst on record, undermining foundations and sending two homes into the river.

The City and Borough of Juneau plans to put any emergency notices related to flooding on its Facebook page and website.

The most up to date information can be found on the National Weather Service’s Suicide Basin monitoring page. People can go there to learn more about glacial outburst flooding and how it might threaten their property.