A catastrophic glacial lake outburst has caused the Mendenhall River in Juneau, Alaska, to reach unprecedented levels, damaging over 100 homes. The flood, described by city officials as “unprecedented,” is the result of rapid drainage from a lake held back by the ailing Mendenhall and Suicide glaciers.
Glacial lake outburst floods occur when a lake formed from melting snow, ice, and rain overtops the glacier that contains it, similar to pulling the plug in a bathtub. These events have become more frequent since 2011 due to climate change, which is causing glaciers in the Arctic, including Alaska, to thin or melt entirely. The Mendenhall and Suicide glaciers are prime examples, with the latter’s once icy expanse replaced by a basin that fills each summer.
The latest outburst began on August 1 after an exceptionally wet July, which saw rainfall double the usual amount. The lake at Suicide Basin reached its limit, leading to a rapid overflow. By Monday, city officials alerted residents of potential evacuation. The water level in Suicide Basin dropped more than 400 feet, including a dramatic 350 feet in 24 hours from Monday to Tuesday.
This deluge propelled the Mendenhall River to a record-breaking 15.99 feet on Tuesday morning, over a foot higher than last year’s levels, which also caused significant destruction. The floodwaters extended further into Mendenhall Valley this year, inundating streets and homes. Photos shared by Alaska’s emergency management agency depicted homes engulfed by murky floodwaters high enough to cover vehicles’ hoods.
Some streets saw water levels of 3 to 4 feet. Fortunately, no injuries have been reported, and an emergency shelter accommodated around 40 people overnight. Alaska Governor Mike Dunleavy issued a disaster declaration to support response and recovery efforts.
“I am grateful no one has been injured or killed by this morning’s outburst flood,” Dunleavy stated. “Emergency responders and managers have done an outstanding job keeping their residents safe.”
Floodwaters have now receded, as the glacial lake has emptied and the river level has fallen below flood stage, according to the National Weather Service in Juneau.