JUNEAU, Alaska – An outburst of flooding from a lake dammed by Juneau’s Mendenhall Glacier damaged at least an estimated 100 homes in what has become a perennial hazard for nearby neighborhoods.
The lake formed in a basin that was left behind when a nearby glacier retreated. It fills with rainwater and snowmelt during the spring and summer and at a certain point builds enough pressure to force its way out through channels it carves beneath Mendenhall Glacier. Since 2011, the phenomenon has at times caused flooding of streets or homes near Mendenhall Lake and Mendenhall River.
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Last year, a two-story home was swept away by raging floodwaters that also undermined a condo building, prompting some residents to reinforce the riverbank near their properties. Monday night's damage was less dramatic but more widespread: Local leaders adopted an emergency resolution saying hundreds of homes were affected, including some outside expected flood areas.
Deputy City Manager Robert Barr said Tuesday that officials were still trying to get a handle on the extent of the damage.
“I would say over a hundred homes right now,” he wrote in an email. “I’m less certain about multiple hundreds. Either still possible.”
The National Weather Service said the Mendenhall River crested early Tuesday at 15.99 feet (4.9 meters), higher than the 14.97-foot (4.6-meter) crest from last year's ferocious flood, which devoured huge chunks of riverbank.
This year's flooding reached farther into Mendenhall Valley. There was “a lot more water in the valley, on the streets, in people's homes,” Barr said. Some streets at one point had 3 to 4 feet (0.9 to 1.2 meters) of water, possibly more, he said.
However, there appeared to be less erosion than last year, he said.
No injuries were reported. Gov. Mike Dunleavy issued a disaster declaration to aid the response and recovery.
The river level dropped quickly Tuesday.
The weather service late last week said the water level in the basin had reached the top of the glacier and warned people to prepare for flooding.
The city also had urged residents to have an evacuation plan and to spend Monday night elsewhere. The city opened an emergency shelter, and about 40 people were there overnight, Barr said.
He credited increased monitoring by agencies and use of technology with helping provide more preparation time this year.