Glacial outburst floods aren't a new phenomenon in Alaska, but climate change is scrambling the geography of risk.

For the third consecutive year, a wave of water gushed out of an Alaskan glacial lake, threatening the state’s capital city of Juneau. But, flood barriers installed by the city managed to prevent disaster from unfolding in the picturesque port town despite record-breaking water levels this week.

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.