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.

Residents in some parts of Juneau prepared to evacuate ahead of what could be a record surge of flooding as rainwater and snowmelt in a huge basin dammed by Alaska’s Mendenhall Glacier started to flow downstream toward the capital city.

Newly installed river barriers held back record levels of flooding and prevented widespread damage in Alaska’s capital city on Wednesday, after an ice dam at the nearby Mendenhall Glacier released a huge surge of rainwater and snowmelt,