As glaciers recede due to climate change, flooding increases

SARAH MCCAMMON, HOST:

This past weekend, the Mendenhall Glacier near Juneau, Alaska, released a flash flood on a river that cuts through a densely populated part of town. At least two homes collapsed into the river, and dozens of people have been displaced. As Anna Canny with member station KTOO reports, this kind of flooding is a growing issue around the world as glaciers recede due to climate change.

(SOUNDBITE OF WATER RUSHING)

ANNA CANNY, BYLINE: On Sunday, John and Christine Loverink stood a few feet away from what used to be their backyard on the bank of the Mendenhall River. The water was still far above its usual level.

JOHN LOVERINK: It's about 2 1/2 times wider than it's ever been, that I've seen.

CANNY: The night before, the river rose nine feet in a matter of hours with water that had been released from the Mendenhall Glacier. The Loverinks had to evacuate and are now staying with friends.

J LOVERINK: I called her and said, what stuff should I grab?

CHRISTINE LOVERINK: Well, and he's normally, like, calm, cool, collected John. And he was...

J LOVERINK: (Laughter).

C LOVERINK: ...Sounding a little bit panicked, so I knew that things were happening fast down there.

CANNY: The water eroded the bank where the Loverinks' condo building stood. One corner now hangs off a steep drop-off. It's been condemned, along with a handful of other homes in Juneau. More have been damaged by standing water. Flooding from the Mendenhall Glacier has been happening every year since 2011, according to hydrologist Eran Hood with the University of Southeast Alaska. But this year was the first year that flooding significantly damaged homes because the speed of the water was so much faster.

ERAN HOOD: So roughly 50% higher than what we've ever seen. And this record goes back to the 1960s.

CANNY: This type of flooding isn't exclusive to the Mendenhall Glacier. Hood says that even worse events have happened in Iceland, the Andes and the Himalayas. A recent study estimated that 15 million people globally are threatened by these glacial outburst floods. The risks of them are increasing as human-caused climate change drives temperatures higher. As glaciers recede, they can leave behind a depression that can fill with rain or meltwater from the glacier. Those might be dammed by rock or ice. But if that dam suddenly gives way...

HOOD: This results in the really catastrophic floods that can cause, you know, just like a dam failure, a huge wall of water to move downstream.

CANNY: The dam that holds back water at the Mendenhall Glacier is made of ice. Hood theorizes that the cracks in the ice dam must have grown larger than usual in order for so much water to be released at once. On Monday, Juneau's city council voted to declare a local emergency. They plan to request aid from the state and federal level.

For NPR News, I'm Anna Canny in Juneau. Transcript provided by NPR, Copyright NPR.