Residents in Alaska capital clean up swamped homes after an ice dam burst and unleashed a flood

Residents in Alaska's capital cleared out waterlogged homes Wednesday after a lake dammed by the picturesque Mendenhall Glacier gave way, causing the worst flooding in the city yet from what has become a yearly phenomenon.

At least 100 homes and some businesses were damaged by rapidly rising floodwaters in the overnight hours Tuesday, according to initial estimates. In some areas, cars floated in chest-high water as people scrambled to evacuate. The waters receded by Wednesday, and the river level was falling.

The flooding happened because a smaller glacier nearby retreated more than a decade ago — a casualty of the warming climate — and left a basin that fills with rainwater and snowmelt each summer. When the water creates enough pressure, as happened this week, it forces its way under or around the ice dam created by the Mendenhall Glacier, enters Mendenhall Lake and eventually makes its way to the Mendenhall River.

Since 2011, the phenomenon has at times flooded streets or homes near Mendenhall Lake and Mendenhall River, and last year floodwaters devoured large chunks of the riverbank, inundated homes and sent at least one residence crashing into the raging river.

But this week's flooding was unprecedented and left residents shaken as they tried to dry out furniture, important papers and other belongings in the sun Wednesday and filled trash containers with sodden insulation and carpeting.

While the basin was created by glacial retreat, climate change plays almost no role in the the year-to-year variations in the volume of the flooding in Juneau, said Eran Hood, a professor of environmental science at the University of Alaska Southeast who has studied the Mendenhall Glacier for years.

The glacial flooding, however, is a reminder of the global risk from bursting snow-and-ice dams — a phenomenon called a jökuhlaup, which is little known in the U.S. but could threaten about 15 million people around the world.

The city of about 30,000 people in southeast Alaska is reachable only by plane and by boat and is already struggling with a housing shortage that could limit the temporary accommodations available for flood victims. Juneau also has limited rental car agencies for those whose vehicles were swamped.

Resident Alyssa Fischer said her father woke her up early Tuesday via Face Time and told her to get out of her house as floodwaters surged. She helped him move his cars to higher ground, as well as her pet quail and ducks, before evacuating with her 4- and 8-year-old children to a shelter at the local middle school.

On Wednesday she was relieved that damage to her property was limited to a crawl space and the garage. But she worries about the future and doesn't feel safe.

“This seems to be a big issue, and I don't think it will lessen,” Fischer said.

The Mendenhall River crested early Tuesday at 15.99 feet (4.9 meters), a new record, topping the level during last year's flood by over a foot, and the water reached farther into the Mendenhall Valley, officials said. The city said the high water even reached some homes outside expected flood areas. The valley is roughly a 15 to 20 minute drive from downtown Juneau.

The National Weather Service said late 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 urged residents in the area to have an evacuation plan and to spend Monday night elsewhere, and it also opened an emergency shelter.

No injuries were reported. Gov. Mike Dunleavy issued a disaster declaration to aid the response and recovery.