Suicide Basin is overtopping; flood release expected in one to six days

‘Finalize preparations and evacuation plans,’ CBJ advisory warns; initial forecast calls for flood to peak at 16.1 to 16.55 feet

The Mendenhall River, Lake and Glacier are seen from an aerial view on July 27, 2026. (Photo courtesy of Sonny Mauricio, Alaska Department of Transportation and Public Facilities)

By Mark Sabbatini

Juneau Independent

An alert that Suicide Basin is full and a glacial lake outburst flood is expected in one to six days was issued by the City and Borough of Juneau at 8:39 a.m. Tuesday.

"Finalize preparations and evacuation plans," the emergency advisory sent to cell phones notes.

The city’s emergency flood response webpage states, "No evacuation advisory is being issued yet, but conditions are being closely monitored." An evacuation advisory map and more information about how to prepare for evacuation or flooding are at bit.ly/JuneauFloodReady.

"Starting at 12:30 p.m. on August 11, printed evacuation preparation notices are being distributed to all homes located within the 2026 evacuation advisory area map shown on the CBJ website," an update published at CBJ’s website midmorning Tuesday notes. A non-emergency public flood information hotline providing information about sheltering, transportation, current conditions, and other questions is at 907-500-0890.

Another alert will be issued when the release occurs, according to CBJ. Mendenhall River’s flood stage usually peaks within a day or two, depending on conditions and release rate.

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See also: How to prepare for this year’s glacial lake outburst flood

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The Suicide Basin monitoring website, in an update Tuesday morning, states "Suicide Basin’s water level is full and starting to overtop the ice dam…with the current elevation at around 1345ft."

"The Mendenhall Lake and River are below normal water levels at this time, around 4ft on the lake gauge," the update notes. "For comparison, last year before the outburst flooding event the Mendenhall Lake was reporting near 9ft(minor flood stage) due to effects from (an) atmospheric river."

Last year’s flood crested at a record level of 16.65 feet. The evacuation advisory area has roughly doubled compared to last year based on updated assessments of potential risk.

A chart shows the water level in Suicide Basin as the alert was issued on Tuesday, Aug. 11, 2026. (Mark Sabbatini / Juneau Independent)

KTOO, which is livesteaming river cameras and other flood coverage, reported Tuesday morning that the initial flood forecast this year is a peak flood level of 16.1 to 16.55 feet, according to Aaron Jacobs, the senior service hydrologist at the National Weather Service Juneau.

HESCO barriers along much of the Mendenhall River and about 40 pumps have been set up to mitigate flood impacts. Officials stated an initial installation of barriers last year prevented damage to about 90% of homes in the flood zone, although there was some seepage and damage to the barriers.

The initial barriers have been repaired and raised. A second phase of barriers extending the semipermanent levee was installed this year.

• Contact Mark Sabbatini at editor@juneauindependent.com or (907) 957-2306.