Each summer in the mountains above Juneau, Alaska, meltwater from the massive Mendenhall Glacier flows into mountain lakes and into the Mendenhall River, which runs through town.

A huge basin of rainwater and snowmelt dammed by Alaska’s Mendenhall Glacier has started to release, sending a potentially record surge of flooding toward parts of Juneau.

These floods, which began more than a decade ago, have become increasingly destructive in recent years and now pose a persistent summertime threat. This time, Alaska’s capital city fortified itself against the floodwaters.