Weather Service issues flood watch as Juneau awaits glacial outburst

Lake, river heights are expected to peak about midnight Friday morning

The hydrograph at Mendenhall Lake began turning upward Wednesday morning as water from Suicide Basin began entering the lake. (Screenshot)

The hydrograph at Mendenhall Lake began turning upward Wednesday morning as water from Suicide Basin began entering the lake. (Screenshot)

The National Weather Service has issued a flood watch for Mendenhall Lake and Mendenhall River as Suicide Basin drains into the lake.

According to the watch notice, issued at 8:48 a.m. Wednesday, flooding is expected to begin Thursday and peak around midnight Friday morning.

At 9 a.m. Wednesday, the hydrological gauge at Mendenhall Lake measured a stage of 6 feet. Flood stage is 9 feet. The flood is expected to crest at 12 feet when it hits its peak.

If that happens, it would be a new record, topping the old mark set in July 2016 by another Suicide Basin-driven flood.

The Weather Service is cautioning that not much is known about this particular flood, which means the height of the crest and its timing is uncertain.

While glacial outburst floods from Suicide Basin have been occurring regularly for the past eight years, this year’s cycle was interrupted when a chunk of ice a fifth of a mile long splashed into the basin.

That event appears to have blocked normal drainage channels, and now the basin is emptying only because it overtopped its icy dam. The water is now eroding that dam, allowing more to escape and flow downward.

Aerial photographs and videos show the water flowing from the basin — which is in an eastern side lobe of the Mendenhall Glacier — and along the boundary between the glacier and the rocky cliffs that define its border. The water flows into (and presumably beneath) the glacier at some point before Mendenhall Lake. Subglacial channels are carrying the water to the lake.

Impacts of this year’s flooding will be determined by the ultimate height of the flood. When the lake stage reaches 9.1 feet, water will cover West Glacier Spur Road between Skaters’ Cabin and the West Glacier trailhead, according to the Weather Service. At 9.4 feet, homes along View Drive will see their yards flooded. At 10 feet, Mendenhall Campground will be flooded. At 11 feet, View Drive will be flooded, and some homes will experience significant flooding.


• Contact reporter James Brooks at jbrooks@juneauempire.com or 523-2258.


More in News

Coast Guard aircrews medevaced two people from Dry Bay Airstrip, approximately 30 miles Southeast of Yakutat, Alaska, after their plane crashed, May 25, 2022. (Courtesy photo / Coast Guard District 17)
Three medevaced after plane crash near Yakutat

All four aboard were injured, three critically so.

The author’s appreciation for steelhead has turned into something like reverence considering what’s happening to populations in the Lower 48 and Canada. (Jeff Lund / For the Juneau Empire)
I Went to the Woods: Silent steel

“You forget most of what ends up in the freezer, but those steelhead, they stick with you.”

Senate President Peter Micciche, R-Soldotna, seen here in this June 16, 2021, file photo, announced Wednesday he will not seek relelection in the Alaska State Senate, where he has served since 2013. (Peter Segall / Juneau Empire file)
Senate president says he won’t run again

“Honor and a privilege.”

Hoonah’s Alaska Youth Stewards helped make improvements to Moby and water the plants in summer 2021. (Courtesy Photo / Jillian Schuyler)
Resilient Peoples & Place: Moby the Mobile Greenhouse cultivates community

It presents opportunities to grow food knowledge and skills.

It's a police car until you look closely and see the details don't quite match. (Juneau Empire File / Michael Penn)
Police calls for Thursday, May 26, 2022

This report contains public information from law enforcement and public safety agencies.

Gavel (Courtesy photo)
Alaska Supreme Court orders use of interim map for elections

The decision came just over a week before the June 1 filing deadline for the August primaries.

A male red-winged blackbird displays his showy red patches and calls to a rival male (Gina Vose photo)
On the Trails: Birds and beetles at Kingfisher Pond

Something is almost always happening at Kingfisher Pond.

Most Read