JUNEAU, Alaska — Flooding from a lake dammed by Juneau’s Mendenhall Glacier has damaged at least 100 homes, making it a constant hazard for nearby neighborhoods.
The lake formed in a basin left by the retreat of a nearby glacier. It fills with rain and melted snow in the spring and summer, and eventually builds up enough pressure to flow through channels it carves beneath the Mendenhall Glacier. Since 2011, the phenomenon has occasionally caused flooding of streets or homes near Mendenhall Lake and the Mendenhall River.
Last year, a two-story home was swept away by floodwaters that also undermined a condominium, prompting some residents to shore up river banks near their properties. Monday night’s damage was less dramatic but more widespread: Local leaders passed an emergency resolution saying hundreds of homes were affected, including some outside expected flood zones.
Deputy City Manager Robert Barr said Tuesday that officials were still trying to assess the extent of the damage.
“I would say over a hundred houses at present,” he wrote in an email. “I am less sure if there are several hundred. Both are 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 of last year’s ferocious flood, which devoured huge chunks of riverbank.
This year, flooding reached more of the Mendenhall Valley. “There was a lot more water in the valley, in the streets, in the homes,” Barr said. Some streets at one point received between three and four feet of water, possibly more, he said.
However, there appeared to be less erosion than last year, he said.
No injuries were reported. Governor Mike Dunleavy issued a disaster declaration to aid in the response and recovery.
The river level dropped rapidly on Tuesday.
The weather service announced last week that the water level in the basin had reached the top of the glacier and warned people to prepare for flooding.
The city also asked residents to have an evacuation plan and spend Monday night elsewhere. The city opened an emergency shelter, and about 40 people spent the night there, Barr said.
He credited increased agency oversight and the use of technology for allowing more preparation time this year.
