At least 100 homes were damaged by flooding from a lake dammed by Juneau’s Mendenhall Glacier, which has become a perennial threat to surrounding areas.
The lake formed in a basin that was left behind by the retreat of a nearby glacier. It fills with rainwater and snowmelt during spring and summer and builds up so much pressure at a certain point that it overflows through channels formed beneath the Mendenhall Glacier.
Since 2011, the phenomenon has several times caused flooding of roads or homes near Mendenhall Lake and the Mendenhall River.
Last year, a two-story house was swept away by raging floodwaters that also damaged a condo building, prompting some residents to reinforce river banks near their properties.
The damage on Monday night was less dramatic but more widespread. Local leaders passed an emergency resolution saying hundreds of homes were affected, including some outside potential flood zones.
Deputy City Manager Robert Barr said Tuesday that officials were still trying to determine the extent of the damage.
“I would say there are over a hundred homes right now,” he wrote in an email. “I’m not sure about hundreds. Either one is possible right now.”
The National Weather Service said the Mendenhall River reached 15.99 feet (4.9 meters) on Tuesday morning, higher than the 14.97 feet (4.6 meters) during last year’s massive flood that washed out large parts of the river.
This year’s flooding inundated the Mendenhall Valley even more. “There was a lot of water in the valley, on the streets, in people’s homes,” Barr said. He said at one point some streets were under 3 to 4 feet (0.9 to 1.2 meters) of water, possibly more.
However, he said that erosion has reduced compared to last year.
No injuries were reported. Governor Mike Dunleavy issued a disaster declaration to aid in response and recovery efforts.
The water level of the river fell rapidly on Tuesday.
The weather service said last week that water levels in the basin had reached the top of the glacier and warned people to prepare for flooding.
The city urged residents to make evacuation plans and spend Monday night elsewhere. The city opened an emergency shelter, and about 40 people stayed there overnight, Barr said.
He credited increased monitoring by agencies and use of technology for providing more time to prepare this year.