Juneau glacier flooding leaves residents looking for long-term solutions

JUNEAU — Floodwaters from the Mendenhall River rushed under Sam and Amanda Hatch’s home last August at then record-levels. After the water receded, their house sank several inches into the saturated soil, shifting its foundations.

As they rebuilt, the Hatch family decided to elevate their house by four feet on piers to avoid flooding in the future. Scraping together deals and favors, Sam Hatch said the whole process cost around $135,000. It was completed a month ago, he said.

Just in time.

For a second straight year, a massive basin to the side of the Mendenhall Glacier burst last week, sending billions of gallons of water rushing downstream. Hundreds of houses were inundated, causing significant damage. But not the Hatch home.

“We’re glad we did it, and it fixed a lot of problems for us,” Sam Hatch said on Wednesday.

Immediately after Tuesday’s flooding, Juneau officials estimated that more than 100 homes had been inundated by Suicide Basin draining rapidly. Deputy Juneau city manager Robert Barr said Friday the estimate had been revised to over 300 homes affected by the flood.

Earlier in the week, Gov. Mike Dunleavy and U.S. Sens. Lisa Murkowski and Dan Sullivan toured the flood-impacted areas. They said after a second straight year of devastating floods that longer-term mitigation measures need to be considered.

On streets near the Hatch household, yards were still full of trash and ruined housewares on Friday. Forty Alaska National Guardsmen deployed to help clear debris, joining local volunteers who scrambled to clean up Friday as sunny weather in Juneau turned to spitting rain.

Sam and Amanda Hatch appeared to have solved the problem of flooding at their home, but they felt no satisfaction witnessing the devastation wrought on their neighbors.

“Nobody wants to be right about this,” Sam Hatch said.

Lifting a house by four feet was a novel solution to a problem now facing hundreds of Mendenhall Valley residents: How do you avoid devastating floods that could occur each summer for the foreseeable future?

Longer-term fixes

Suicide Basin is located roughly two miles from the foot of the Mendenhall Glacier, a popular tourist destination that looms over the Mendenhall Valley, where the bulk of Juneau residents live.

Human-induced climate change has caused Alaska’s glaciers to recede dramatically. Suicide Basin, once covered in ice, now fills with rain and meltwater each summer at a rate of roughly 1,900 gallons per second, said Jason Amundson, professor of geophysics at University of Alaska Southeast.

The basin has been a hazard for Juneau residents since 2011, but its scale is hard to fathom. It’s as long as four cruise ships sitting end to end, said Eran Hood, a professor of environmental science at UAS. The basin is roughly a third of a mile wide, he said, and hundreds of feet deep.

There is bedrock on three sides — the fourth side is the Mendenhall Glacier itself. Amundson said modeling suggests that water bores a tunnel through the glacier each summer to find an outlet. Once it does, the basin rapidly drains, which can cause the Mendenhall River to rise dramatically. Each winter, the tunnel appears to reseal, ready for the basin to fill up again, Hood said.

A time lapse camera shows how the ice-capped basin has filled with water since April. Steadily, ice and water rises hundreds of feet over months, before it drops dramatically on Aug. 5 — emptying the enormous body of water in a few frames.

Last year’s then-record flooding saw roughly 14 billion gallons of water rapidly released into the Mendenhall River. Amundson said preliminary estimates are that 16 billion gallons of silty water rushed into the river this week, which would fill more than 32,000 Olympic-sized swimming pools.

Hydrologists are unable to predict how big of a glacier outburst flood will occur from Suicide Basin one year to the next — it could be devastating, it could be unnoticeable, Hood said. Suicide Basin is likely the best monitored glacial outburst flood on Earth. But even still, no one knows the full extent of the risk, he said.

“What is the largest flood you could possibly get out of the basin? The answer is, we don’t know,” he said.

Local Juneau officials are focused on the immediate needs of helping affected residents clear and repair their properties, but conversations are expected to turn soon to potential long-term flood mitigation methods.

“I think someone just needs to do a careful assessment and see what makes the most sense, right?” Amundson said.

Since the 2023 flood, scientists have heard ideas: Bombing the glacier. Siphoning off water. Building a tunnel through a mile or two of bedrock for a more controlled release of water. Both scientists stressed they aren’t engineers, but Hood and Amundson said none of those options seem feasible.

The basin is perched in mountainous and hard-to-reach terrain miles from roads; there would be permitting issues as it’s located on U.S. Forest Service land, and any solution would likely take years to be implemented, they said.

“It’s unlikely that we’ll be able to engineer anything at the basin itself that would allow water to be drained at a rate that would make a difference in terms of the magnitude of the floods,” Hood said.

Around the world, roughly 15 million people live under the threat of glacial flooding. A glacial outburst in the French Alps killed 175 people in 1892. Some mitigation measures have been successfully implemented in Switzerland and France. But those glacial lakes were vastly smaller and much more accessible than Suicide Basin, Hood said.

There could potentially be mitigation measures — such as levees or drainage systems — built downstream at Mendenhall Lake as it feeds into the river toward homes. But Hood said those measures would likely still have huge costs. And at that point, “you’re mitigating the flood” after the basin has drained, he said.

Using back-of-the-envelope math, Hood said around 10,000 to 15,000 cubic feet per second of water might need to be redirected at peak flood levels, which equates to almost 75,000 to 100,000 gallons per second. There is some unpopulated space to the west of the river to direct flood waters, but even that is limited.

“At some point, you have to break through some neighborhoods,” Hood said.

In coming decades, climate change is expected to cause the Mendenhall Glacier to retreat beyond Suicide Basin, eliminating the threat of annual floods. Hood said that could then render hundreds of millions of dollars invested in mitigation efforts as “unnecessary.”

But there is another lake further up the glacier that could cause problems in the future for Juneau, Hood said.

“And so, any engineering solution to this, to me, would have to be at the lake and not at the basin,” he said.

Mapping and insurance

For now, Juneau officials say the best flood mitigation is preparation. An interactive map shows hazard zones in the Mendenhall Valley at different flood levels. But many residents were not aware their homes were at risk. Dozens of people quickly fled the rapidly rising water early Tuesday morning, though no deaths or injuries were reported.

Barr said the map is “cumbersome” and “not intuitive.” A goal this next year is better communicating risks to residents, he said.

Jay and Wendy Menze thought they were prepared for the flooding. In 2023, flood waters reached their driveway. This year, torrents of water rushed through the downstairs of their home. They had gel-filled sandbags that worked for a while. But they couldn’t stop almost two feet of rushing water.

“The water just washed them away,” destroying flooring and appliances, Wendy Menze said.

For next time, Jay Menze said it would be costly to build a wall of sandbags strong enough to stop four feet of moving water at $10 a sandbag.

However, the Menzes did not sound overly concerned. They are unusual in Juneau and Alaska because they have flood insurance.

Emil Mackey, a local insurance agent and a member of the Juneau School Board, said many Alaskans don’t carry insurance for relatively common disasters like wildfires or floods. He referred to it as a “silent insurance crisis.”

“If you have a river or any kind of water body next to your house, you should expect you’re going to be flooded sometime,” he said.

A 2023 state report showed, by one measure, that just 745 Alaska households had flood insurance. “Bad rumors” abound that flood insurance is unaffordable or unavailable, Mackey said.

”And it’s just not true,” he said.

With little or no insurance, residents have been forced to take care of themselves. Last year’s flooding eroded banks of the Mendenhall River, washing away homes and leaving a condominium building hanging precariously over the water. Condo owners spent $1 million to fortify the riverbank after finding they were ineligible for state disaster assistance, KTOO Public Media reported in October. The riverbank held during this year’s flood and no houses washed away.

Mendenhall Valley residents affected by this year’s flooding can apply through Oct. 9 for up to $21,250 in state assistance for house repairs, and another $21,250 for personal property damage. But Juneau officials said last year’s flooding showed that assistance would not be enough for some people.

The Hatch household didn’t get disaster assistance last year — they paid to elevate their house out of pocket. Amanda Hatch suggested the 2023 flood was a wake-up call that was impossible to ignore.

“When you watch water come up and up and up and up and up into your house, you don’t think, ‘Let’s roll this dice again,’” she said.

A feeling now undoubtably shared by hundreds of Mendenhall Valley residents living in the shadow of Suicide Basin, waiting to see when torrents of flood water will threaten their homes again.

ADN photojournalist Marc Lester contributed reporting.