Residents urged to prepare as glacial dam release prompts flood warning in Juneau

Flooding in the Mendenhall valley on July 19, 2018, from a glacial dam outburst earlier that week. (Video still by David Purdy/KTOO)

Glacial dam releases — known as a jökulhlaups — have become annual events in Juneau in recent years due to warming temperatures and the retreat of the Mendenhall Glacier. The latest one has prompted a flood warning for the Mendenhall Lake and River.

Water from Suicide Basin has been flowing over the top of an ice dam since Monday, but now a large volume of water is draining under the glacier and will cause the Mendenhall Lake and River to rise rapidly, threatening a nearby campground and homes. It’s anticipated the flood will crest Friday evening, the National Weather Service said.

Officials are advising residents who live along the river to stay away from the river bank and be “prepared to take action.”

The Weather Service issued a flood warning at 8:15 p.m. Thursday through 10 a.m. Saturday morning. Flood stage on the river is 9 feet. The National Weather Service expects the river to crest Friday at about 10.2 feet, but that forecast could change.

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At just over 9 feet, water covers Skaters Cabin Road between the cabin and the West Glacier Trailhead and begins to flow into Mendenhall Campground.

At 9.4 feet, there will be minor flooding along View Drive. At 10 feet, the weather services says the Mendenhall Campground will be under three feet of water in some places.

During past flood events, the City and Borough of Juneau has recommended that residents living along the Mendenhall River corridor have evacuation plans in place and cautioned people to be careful around the lake and glacier and to stay away from flooded areas and bridges over the Mendenhall River.