Flooding in Mendenhall Lake and River may begin soon as levels in Suicide Basin drop

The National Weather Service in Juneau has issued a special weather statement indicating that water levels have started to drop in Suicide Basin, a glacial lake that’s dammed by the Mendenhall Glacier.

Hydrologists and meteorologists who are monitoring basin activity believe this drop was caused by water spilling over the top of the ice dam. Cameras and water gauges deployed to monitor the basin alerted them that water levels started dropping on Wednesday evening.

That doesn’t necessarily indicate that the basin is draining yet, but residents along the Mendenhall Lake and River should begin to prepare for flooding. 

“Once we do see water hit Mendenhall Lake, with the USGS lake gauge, we will probably be issuing a flood warning,” said hydrologist Aaron Jacobs.

Glacial outburst flooding occurs annually when water in Suicide Basin drains into Mendenhall Lake and River, but last year’s flood reached record levels with a peak of 15 feet, causing flooding and major erosion along the banks of the Mendenhall River. Two homes were completely swept away and dozens more were damaged.

People can learn more about this year’s potential flood impacts on the National Weather Service webpage. Scrolling down to the “Gauge Location” section and selecting “Activate MNDA2 FIM Gauge” creates a map of areas in the Mendenhall Valley that might experience flooding.

The latest updates on Suicide Basin and glacial outburst flooding are posted on the National Weather Service monitoring page.