Bursting Ice Dam in Alaska Highlights Dangers of Glacial Flooding


The grey, two-story dwelling with white trim toppled and slid, crashing into the river beneath as speeding waters carried off a bobbing chunk of its roof. Subsequent door, a apartment constructing teetered on the sting of the financial institution, its basis already having fallen away as erosion undercut it.

The destruction came to visit the weekend as a glacial dam burst in Alaska’s capital, swelling the degrees of the Mendenhall River to an unprecedented diploma. The bursting of such snow-and-ice dams is a phenomenon referred to as a jökuhlaup, and whereas it’s comparatively little-known within the U.S., researchers say such glacial floods may threaten about 15 million folks world wide.

“We sat down there and had been simply watching it, and impulsively bushes began to fall in,” Amanda Arra, whose home continued hanging precariously over the river financial institution Monday, advised the Juneau Empire. “And that’s after I began to get involved. Tree after tree after tree.”

The flooding in Juneau got here from a facet basin of the awe-inspiring Mendenhall Glacier, which acts as a dam for the rain and melted snow that accumulate within the basin in the course of the spring and summer time. Finally, the water gushed out from beneath the glacier and into Mendenhall Lake, from which it flowed down the Mendenhall River.

Water launched from the basin has brought on sporadic flooding since 2011. However sometimes, the water releases extra slowly, over plenty of days, mentioned Eran Hood, a College of Alaska Southeast professor of environmental science.

Saturday’s occasion was astonishing as a result of the water gushed so shortly, elevating the river`s flows to about 1 1/2 occasions the best beforehand recorded, a lot that it washed away sensors that researchers had positioned to review the glacial outburst phenomenon.

“The flows had been simply manner past what something within the river may face up to,” Hood mentioned.

Two properties had been fully misplaced and a 3rd partially so, Robert Barr, Juneau’s deputy metropolis supervisor, mentioned Monday. There have been no experiences of accidents or fatalities.

Eight buildings, together with people who fell into the water, have been condemned, however some would possibly have the ability to be salvaged by substantial repairs or financial institution stabilization, he mentioned. Others suffered lesser harm.

Whereas local weather change is melting the Mendenhall and different glaciers world wide, its relationship to such floods is sophisticated, scientists say.

The basin the place the rain and meltwater accumulate was previously coated by the Suicide Glacier, which used to stream into the Mendenhall Glacier, contributing ice to it. However the Suicide Glacier has retreated because the local weather warms, leaving a lake within the basin dammed by the Mendenhall.

Whereas that half could be linked to local weather change, the unpredictable ways in which these waters can burst via the ice dams and create floods downstream will not be, they mentioned.

“Local weather change brought on the phenomenon, however not the person floods,” Hood mentioned.

The variability within the timing and quantity of such floods makes it onerous to organize for them, mentioned Celeste Labedz, an environmental seismologist on the College of Calgary.

Greater than half of the folks in danger from glacial outburst floods are in simply 4 international locations __ India, Pakistan, Peru and China, in accordance with a examine revealed this yr in Nature Communications.

One of many extra devastating such occasions killed as much as 6,000 folks in Peru in 1941. A 2020 glacial lake outburst flood in British Columbia, Canada, brought on a surge of water about 330 toes (100 meters) excessive, however nobody was harm.

As a result of the bottom alongside the Mendenhall River is basically made up of free glacial deposits, it`s particularly vulnerable to erosion, Hood mentioned. The harm may have been a lot worse if the flood coincided with heavy rains, he mentioned.

Chris and Bob Winter constructed their home about 50 toes off the Mendenhall River in 1981. It flooded for the primary time in 2014, an occasion that prompted them to lift their home 3 toes. It flooded once more on Saturday with about 3 inches of standing water, sufficient to soak the carpets, subflooring and drywall.

“You simply received to tear all of it out,” Chris Winter mentioned. “I simply don’t know what’s going to occur, however we will’t reside in our home proper now.”

She mentioned her largest concern is that they’re each of their mid-70s and can most likely have to maneuver south in some unspecified time in the future.

“We raised our household, they usually’re gone and no one’s in Juneau,” she mentioned. “And I don’t know that we’ll have the ability to promote it.”

Thiessen reported from Anchorage. Related Press author Gene Johnson in Seattle and researcher Jennifer Farrar in New York contributed to this report.

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