Be prepared for possible flooding along Mendenhall River corridor

Water from Suicide Basin, located in the Mendenhall River drainage, started pouring over the top of the Mendenhall Glacier Monday afternoon, and is making its way to Mendenhall Lake and Mendenhall River. Though it’s unknown what will happen in the next few days, the City and Borough of Juneau wants community members to be aware of what’s going on and to be prepared for possible flooding.

“The water is going over the left side of the Mendenhall Glacier for a couple hundred yards and then goes underneath the glacier. We’re not seeing significant runoff on the lake gauges yet, but as this water goes over the top of this ice dam, it’s going to cut the ice dam down lower and lower, increasing the runoff,” CBJ Emergency Program Manager Tom Mattice said. “We don’t know if this will trigger a normal jökulhlaup, but we assume there’s going to be more and more water coming down out of Suicide Basin. The basin has more water in it right now than it did in 2016, so if a normal jökulhlaup happens today, we could have record flooding. That being said, this event could happen much slower than a normal jökulhlaup; nobody really knows. We’re waiting and seeing.”

The United States Geological Survey is the lead agency on the issue, and the National Weather Service measures the Mendenhall Lake water level and shows predictions: https://water.weather.gov/ahps2/hydrograph.php?wfo=pajk&gage=mnda2

Here are tips on how to prepare and stay safe:

• Juneau residents living along the Mendenhall River corridor should have Go Bags ready and an evacuation plan in place. Keep in mind each person’s specific needs, including medication. Plan for alternate accommodations in the event of flooding.
• Be extra careful on or around Mendenhall Lake and Mendenhall Glacier. In the event of flooding, stay away from the river bank, flooded areas, and bridges going over Mendenhall River.
• Stay informed by regularly checking the Mendenhall Lake level and listen for flood alerts on the Emergency Alert System. Capital City Fire/Rescue is monitoring the situation and providing updates as needed on its Facebook page.

For more information, contact Emergency Program Manager Tom Mattice at 586-0419 or [email protected].