Latest prediction is Suicide Basin will be full Aug. 14, heavy rain tomorrow will ‘spike’ water level
- Mark Sabbatini
- Jul 9
- 3 min read
Updated: Jul 9
Water level as of Wednesday nears 1,250 feet; city and state agencies say alert and response preparations well underway
Suicide Basin will be full on Aug. 14 at the current fill rate, about a week later than when record flood levels occurred during the past two years, according to an update this week by the National Weather Service Juneau.
The update published Monday at the weather service’s official Suicide Basin monitoring website states the water level as of that day was 1,224 feet. The level was 1,247 feet on the same date a year ago and 1,332 feet in 2023.
"Water levels have risen about 28 feet in the last week," the update notes. The overflow level of the ice dam is 1,371 feet, so "if the rate of rise in the basin remains around 4 feet per/day, this would result in a full basin in 37 days, around August 14th."
"The inflow rate into the basin can change through the summer due to periods of above normal temperatures along the ice field and rain events," the update notes.
Heavy rain is forecast for Juneau on Thursday, which is likely to affect the basin levels, said Ryan O’Shaughnessy, emergency manager for the City and Borough of Juneau, during a Local Emergency Planning Committee meeting Wednesday.
"With the atmospheric river coming in tomorrow I think we’ll see a spike over the next couple of days," he said.
The weather service forecast calls for rain to continue through at least next Tuesday, with high temperatures in the 60s and lows around 50. Those temperatures are roughly average for July in Juneau, compared to colder-than-average temperatures in recent months that resulted in a lower water level in Suicide Basin.
"These differences in water levels from 2024 and 2023 to current levels are due to the cold spring/early summer time temperatures," the monitoring website’s update notes. "Freezing levels remained 3000 to 4000 feet through the spring and early summer time but are now around 7000 feet. These high freezing levels will continue to melt off snow and ice on the icefield and the water input into the basin."
Glacial outburst floods from Suicide Basin have occurred annually since 2011, but record releases of water the past two years have damaged more than 300 homes and caused extensive infrastructure damage. Experts are predicting such flooding is likely to continue annually due to factors related to climate change.
O’Shaughnessy said the city is working with state, tribal and other agencies on the details of this year’s preparation and response plan.
"We do intend to declare a local emergency as soon as there is a credible threat,” he said.
That declaration will result in evacuation plans being set in motion and alerts being sent as necessary to residents — with a signup portal at CBJ’s website determining the type and content of those alerts.
"We’ve been shouting from the rooftops every chance we can: ‘Please sign up for alerts,’" O’Shaughnessy said. A test of those alerts is scheduled next week.
Free distribution of sandbags is also scheduled July 19 and 26 (both Saturdays) at Dimond Park.
If an evacuation-level flood occurs, CBJ is coordinating with the American Red Cross of Alaska’s Juneau Office to set up a shelter at the former Floyd Dryden Middle School, O’Shaughnessy said.
Preparations are also being made for bridge monitoring and debris removal by the Alaska Department of Transportation and Public Facilities, said Christopher Goins, the department’s Southeast regional director, during Wednesday’s meeting.
Monitoring the bridges across the Mendenhall River on Egan Drive and Back Loop Road will take priority over debris removal, although he said the foundation of both are sufficiently deep that the risk is more to people at the edges than the bridges being washed away.
• Contact Mark Sabbatini at editor@juneauindependent.com or (907) 957-2306.
