The Mendenhall River, located near Alaska’s capital, surged to unprecedented levels on Wednesday morning following glacial explosions that sent water rushing downstream into nearby communities. This prompted residents to evacuate to elevated areas.
As reported by the National Weather Service in Juneau, the river reached a height of 16.65 feet, marking it as the largest recorded glacial lake explosion event to date.
To give some context, last year’s incident occurred from August 3 to August 6, with the river recorded at 15.99 feet.
Prior to the flooding, local authorities had advised those living in the 17-foot flood zone to evacuate to higher ground until the situation was deemed safe with “all clear” alerts broadcasted through emergency radio systems.
The Red Cross also set up shelters in local gymnasiums to accommodate evacuated residents until conditions improved.
Several facilities, including the Mendenhall Valley Public Library and various parks and recreational centers, shut down in anticipation of flooding.
Travel was disrupted as well; flooding forced the closure of multiple roads, including Mendenhall Loop Road. Officials stated that the closure would remain until water levels fell below 12 feet and safety inspections could be conducted.
The Federal Aviation Administration also imposed temporary flight restrictions in the region to ensure safe aerial monitoring and response.
The National Weather Service issued a flood warning for the Mendenhall River prior to the anticipated rise in water levels.
They predicted the river would range between 16.25 feet and 16.76 feet, with expectations trending towards the upper end of that scale.
Officials pointed out that the water itself is hazardous, but the presence of debris could exacerbate the situation. Mariners were cautioned that the river was carrying numerous trees and other obstructions.
Andrew Park, a meteorologist at the Juneau NWS office, emphasized the dangers, urging people to avoid the river. “If you enter that water, you’re not going to leave it,” he warned.
The Suicide Basin, adjacent to the Mendenhall Glacier above Juneau, has seen annual flooding events since 2011. The last significant release occurred on October 20, 2024.
What is a glacial lake explosion flood?
Glacial Lake Explosion Floods (GLOFs) are distinct from typical floods caused by heavy rainfall or thunderstorms. According to the USGS, these floods can emerge when ice-covered basins filled with water lead to an excess of pressure that opens drains beneath glaciers, releasing large amounts of water downstream.
Such events are unpredictable and have caused substantial loss of life and damage worldwide. There’s uncertainty about how the risks related to these lakes might evolve as climate change progresses and glaciers continue to recede.
