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.

One of Alaska's most populated cities is bracing for potentially catastrophic flooding as a basin dammed within the Mendenhall Glacier has started to release water.

When the peak of the annual glacial outburst flood hit early Wednesday morning in Juneau, newly installed flood barriers stacked along the Mendenhall River largely prevented flooding of the nearby residential area.