Wrangell Sentinel -

The destruction came as a glacial dam burst in Alaska’s capital city on Aug. 5, swelling the Mendenhall River to an unprecedented degree. The bursting of such snow-and-ice dams is a phenomenon called a jökuhlaup, and while it’s relatively little-known in the U.S., researchers say such glacial floods could threaten about 15 million people around the world.

“We sat down there and were just watching it, and all of a sudden trees started to fall in,” said Amanda Arra, whose house still hung precariously over the riverbank two days after the flooding.

The river flooding in Juneau came from a side b...