Record glacial flooding swept away two homes in Alaska’s capital

The water surrounding the 3,000-year-old Mendenhall Glacier, which draws tourists from around the world, is now threatening the city.

Flooding from the glacier has been happening every summer since 2011, but this weekend’s overflow smashed previous water level records by nearly three feet. “It really exceeded our expectations,” said National Weather Service meteorologist Andrew Park, adding that it is “pretty devastating for the community.”

Scientists are still learning a lot about the decade-old phenomenon, he said.

Violent flooding from the basin above the glacier began on a perfectly dry day in 2011. Park said meteorologists and hydrologists were at first baffled as to why the river was rushing when there had been no rain. But then they found that a basin above the Mendenhall Glacier was creating enough pressure to push its water through the glacier and into Mendenhall Lake, Park said, causing an entirely new flooding threat to the community.

Every year, the basin fills until the pressure causes the water to look for a path out.

“Water finds a way,” Park said. “It finds the weakest point.”

Since 2011, he said, scientists have studied the basin to monitor the situation around these annual releases — but this year’s outburst was historic. The Mendenhall Lake gauge crested about 11:30 p.m. local time Saturday night at a level of 14.97 feet, he said, which smashed the previous record of 11.99 feet set in July 2016.

The lake’s level as of 10:15 a.m. local time Sunday was 8.96 feet with levels receding, per NWS data.

Park said it isn’t clear if this phenomenon can be blamed on climate change.

“This is still a recent phenomenon,” Park said, later adding, “there’s going to be a lot of eyes on this.”

Scientists have said that although no weather event is caused solely by mankind’s influence, the frequency of extreme weather is increasing because of human-influenced climate change. Cities around the world are having to adjust to the new normal caused by extreme weather.

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So what changed this year to create such fierce flooding? “We don’t know the answer to that yet,” Barr said.

When asked how many homes were flooded, he said it was in the dozens.

“Dozens is a big number for us,” said Barr, who helps run the city of about 32,500 residents.

There will be ripple effects from the flooding, too, he added. An unknown number of homes that run on oil had their fuel tanks swept away. Barr said the city contacted the Coast Guard and state environmental agencies for help.

“They’re aware and they are helping us think through, if there’s any sort of spill, a protection response,” he said.

City officials declared a local state of emergency midday Sunday, as crews work to safeguard roads and bridges affected by the flooding.

The torturous part for residents, scientists and city leaders is that it seems the flooding will now happen in Juneau every year — but the severity will remain a mystery until only shortly before the waters come rushing.

“There’s not much we can do from a prevention point of view,” Barr said.