By BECKY BOHRER and MARK THIESSEN (Associated Press)
JUNEAU, Alaska (AP) — The grey, two-story dwelling with white trim toppled and slid, crashing into the river under as dashing waters carried off a bobbing chunk of its roof. Next 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 known 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 around the globe.
“We sat down there and were just watching it, and all of a sudden trees started to fall in,” Amanda Arra, whose home continued hanging precariously over the river financial institution Monday, informed the Juneau Empire. “And that’s when I started to get concerned. 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 through the spring and summer time. Eventually, the water gushed out from below the glacier and into Mendenhall Lake, from which it flowed down the Mendenhall River.
Water launched from the basin has triggered sporadic flooding since 2011. But sometimes, the water releases extra slowly, over quite a lot of days, mentioned Eran Hood, a University of Alaska Southeast professor of environmental science.
Saturday’s occasion was astonishing as a result of the water gushed so rapidly, elevating the river’s flows to about 1 1/2 instances the best beforehand recorded — a lot that it washed away sensors that researchers had positioned to review the glacial outburst phenomenon.
“The flows were just way beyond what anything in the river could withstand,” Hood mentioned.
Two properties had been fully misplaced and a 3rd partially so, Robert Barr, Juneau’s deputy metropolis supervisor, mentioned Monday. There had been no experiences of accidents or fatalities.
Eight buildings, together with people who fell into the water, have been condemned, however some would possibly be capable to be salvaged by substantial repairs or financial institution stabilization, he mentioned. Others suffered lesser harm.
While local weather change is melting the Mendenhall and different glaciers around the globe, its relationship to such floods is difficult, scientists say.
The basin the place the rain and meltwater accumulate was previously coated by the Suicide Glacier, which used to circulation into the Mendenhall Glacier, contributing ice to it. But the Suicide Glacier has retreated because the local weather warms, leaving a lake within the basin dammed by the Mendenhall.
While that half could be linked to local weather change, the unpredictable ways in which these waters can burst by way of the ice dams and create floods downstream shouldn’t be, they mentioned.
“Climate change caused the phenomenon, but not the individual 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 University of Calgary.
More than half of the folks in danger from glacial outburst floods are in simply 4 international locations — India, Pakistan, Peru and China, in keeping with a research revealed this 12 months in Nature Communications.
One of the 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, triggered a surge of water about 330 toes (100 meters) excessive, however nobody was harm.
Because the bottom alongside the Mendenhall River is basically made up of unfastened glacial deposits, it’s particularly inclined 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 (15.2 meters) 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 just got to rip it all out,” Chris Winter mentioned. “I just don’t know what’s going to happen, but we can’t live in our house right 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 family, and they’re gone and nobody’s in Juneau,” she mentioned. “And I don’t know that we’ll be able to sell it.”
___
Thiessen reported from Anchorage. Associated Press author Gene Johnson in Seattle and researcher Jennifer Farrar in New York contributed to this report.
Source: www.bostonherald.com”