A video provided by the National Weather Service office in Juneau, Alaska, shows scientists flying above the Mendenhall Glacier on Tuesday, Aug. 12, before the glacial lake outburst flooding.
JUNEAU, Alaska – Evacuations are underway in parts of Alaska’s capital of Juneau after a glacial outburst sent water rushing down the Mendenhall River and into communities across the region.
“A glacial outburst has occurred at Suicide Basin,” officials said in a Facebook post. “The basin is releasing and flooding is expected along the Mendenhall Lake and River late Tuesday through Wednesday.”
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This image provided by the National Weather Service (NWS) office in Juneau, Alaska, shows locations likely to be impacted by glacial lake outburst flooding.
(National Weather Service / FOX Weather)
Officials have recommended that residents within the 17-foot lake level inundation zone evacuate the area until the water recedes and an “All Clear” message is sent via the wireless emergency alert system.
Officials said a Red Cross shelter was set up for residents at Floyd Dryden Gymnasium.
This animated image shows water levels dropping within Suicide Basin in Alaska after a glacial lake outburst between Aug. 9 through Aug. 12.
(NOAA)
Facilities along the Mendenhall River, including the Mendenhall Valley Public Library, Diamond Park Field House, Diamond Park Aquatic Center and all nearby fields, were closed on Tuesday because of the dangerous situation.
Travel has also been impacted because several roads in the region have been closed due to flooding, including Mendenhall Loop Road (Back Loop Bridge).
“The closure will remain in effect until water levels recede below 12 feet and bridge engineers complete a safety inspection,” officials said.
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This graphic shows the Flood Warning in effect in parts of Juneau, Alaska, following a glacial lake outburst.
(FOX Weather)
The Federal Aviation Administration (FAA) also issued a temporary flight restriction (TFR) around the area.
“This TFR creates controlled airspace to ensure safe aerial operations for geo-hazard monitoring, flood response, and potential evacuations,” the Alaska Department of Transportation & Public Facilities said.
Newsportual Weather Service (NWS) office in Juneau issued a Flood Warning for the Mendenhall River and said that as of early Wednesday morning, the river was over 15 feet and was continuing to rise.
This graphic shows where the glacial lake outburst flooding is occurring in the Mendenhall Valley in Alaska.
(FOX Weather)
“Our forecast right now, we’re starting to think that we’re going to crest, we were messaging 8 a.m. though 12 p.m., we’re thinking our crest might be closer to 8 in the morning and might be closer to the higher end of the spectrum,” NWS Juneau Meteorologist Andrew Park said in an update.
Forecasters said the river was expected to crest between 16.25 feet and 16.75 feet, and now they think the crest could be closer to the higher end.
While water on its own is dangerous, officials are now warning of debris in the water that could make the situation even worse.
The NWS said mariners should be aware that numerous trees and other debris was in the water and is being washed downstream.
“There is a lot of debris in the river. Please stay away from the river. It’s very dangerous right now,” Park continued. “If you get in that water, you’re not going to make it out of there. So, please, remain away from the river.”
Suicide Basin is a side basin of the Mendenhall Glacier above Juneau. Since 2011, the NWS said Suicide Basin has released glacial lake outburst floods that caused inundation along Mendenhall Lake and River annually with a record flooding event taking place on Aug. 6, 2024.
According to the NWS, the record crest was 15.99 feet.
The latest release occurred on Oct. 20, 2024.
What is a glacial lake outburst flood?
FILE – This photo shows a flooded parking lot in Alaska after glacial lake outburst flooding.
(City and Borough of Juneau / FOX Weather)
A glacial lake outburst flood (GLOF) isn’t like the typical type of flooding that occurs from torrential rain and thunderstorms.
According to the USGS, glacial lakes form in small side valleys that have lost ice and then become dammed by the glacier in the main valley or dammed by rocks and debris.
Over time, as the ice-free basins fill with water, the USGS said, lakes reach a breaking point where water pressure opens up a drain underneath the glacier that releases the water downstream, which can result in a GLOF.
“These events are unpredictable and have caused significant loss of life and infrastructure worldwide,” the USGS said. “Furthermore, it is unclear how these lake hazards may change as temperatures rise and glaciers continue to melt.”
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