Alaska declares state disaster emergency as ‘glacial lake outburst’ floods homes, roads
Photos of those neighborhoods show homes turn into islands, as driveways and roads became immersed, and vehicles with floodwater high enough to reach the windshield.
FILE: Record flooding occurs along Mendenhall River in Alaska
Glacier-dammed outburst flooding occurred in Alaska on Saturday leading to record-breaking flooding along the Mendenhall River. Aug. 2023.
JUNEAU, Alaska – Alaska Gov. Mike Dunleavy declared a state disaster emergency on Tuesday as the Mendenhall River reached record levels and flooded neighborhoods in Mendenhall Valley.
Located in north Juneau, those neighborhoods experienced extensive property damage, displacing many of its residents, according to City and Borough of Juneau officials.
Photos of flooded Alaska neighborhoods show homes turned into islands, as driveways and roads became immersed, and vehicles with floodwater high enough to reach the windshield.
![Flooded neighborhood.]()
Image 1 of 5Flooded neighborhood. (Alaska Division of Homeland Security and Emergency Management)
![Flooded neighborhood.]()
Image 2 of 5Flooded neighborhood. (City and Borough of Juneau)
![Flooded parking lot.]()
Image 3 of 5Flooded parking lot. (City and Borough of Juneau)
![Rising Mendenhall River.]()
Image 4 of 5Rising Mendenhall River. (City and Borough of Juneau)
![Road in a neighborhood is closed due to flooding.]()
Image 5 of 5Road in a neighborhood is closed due to flooding. (City and Borough of Juneau)
The City and Borough of Juneau issued an evacuation order on Monday night and created an emergency shelter for residents displaced by the flooding.
No deaths or injuries have been reported, according to the Alaska Division of Homeland Security and Emergency Management.
"I am grateful no one has been injured or killed by this morning’s outburst flood," Dunleavy said. "Emergency responders and managers have done an outstanding job keeping their residents safe,"
Dunleavy added that he has directed all Alaska agencies to support the community affected by the flood event.
What caused the Mendenhall River flooding?
Vehicles inundated.
(Sen. Lisa Murkowski / FOX Weather)
The flooding event was caused by a confluence of factors.
First, the Mendenhall River, which runs next to the flooded neighborhoods, rose to record levels when it crested at 15.99 feet at 3:15 a.m. local time. For reference, the major flood stage for the Mendenhall River is 14 feet.
HOW FLOODWATER CAN MAKE YOU VERY SICK
This water level rise happened due to a phenomenon known as a "glacial lake outburst" that occurred upstream, specifically in the Suicide Basin and Mendenhall Glacier.
Map showing locations of Mendenhall Valley, Mendenhall River, Mendenhall Lake, Mendenhall Glacier and Suicide Basin.
(Climate.gov / FOX Weather)
Suicide Basin, a depression in the earth created by a receding Suicide Glacier, collects rain and meltwater from the glacier over the year, the NWS Juneau said. That water is then kept in place by the Mendenhall Glacier as it serves as a natural dam.
HOW ICE TRANSFORMS THE LANDSCAPE
Oftentimes, when the basin fills with water, a channel forms through a lower level of the Mendenhall Glacier to release the water downstream into Mendenhall Lake, which feeds the Mendenhall River.
FILE: Mendenhall Glacier.
(City and Borough of Juneau / FOX Weather)
This inflow of water is what caused the Mendenhall Lake to rise to nearly 10 ft and the Mendenhall River to rise to record levels and flood neighborhoods.
NWS Juneau officials said the river level will fall out of the major flood stage. As of late Tuesday morning, the river level was measured to be nearly 12 feet and continues to drop.
Record-setting glacial lake outbursts
Flooded neighborhood.
(Alaska Division of Homeland Security and Emergency Management / FOX Weather)
NWS Juneau officials said flooding along Mendenhall River and Mendenhall Lake due to glacial lake outbursts from Suicide Basin has happened multiple times each year since 2011.
In the summer of 2023, a glacial lake outburst set a record when it caused the Mendenhall River to crest near 14.82 feet at 12 a.m. on Aug. 6.
One year to the date by a few hours, the glacial lake outburst this week broke the record.