How 'glacial outburst' flooding was averted in Alaska's capital city
The danger is over for residents of Alaska's capital city of Juneau, who were urged to evacuate on Aug. 13 as the nearby Mendenhall River, engorged by water from a glacial outburst caused by a melting glacier, surpassed record flood levels.
Emergency barriers built to protect Mendenhall Valley and Juneau, a city of about 32,000 people in the Alaskan panhandle, were successful, Paste BN reported. Most of Juneau's residents live in the valley.
Two miles of HESCO barriers were installed along the river in June to mitigate summer flooding from the Mendenhall Glacier. Glacial flooding is driven by climate change, according to the National Oceanic and Atmospheric Administration.
The flood threat did not affect a planned summit between President Donald Trump and Russian President Vladimir Putin, scheduled on Aug. 15 at a military base near Anchorage, more than 500 miles away.
What happens when a melting glacier causes flooding?
This is how a glacial outburst sent water toward the Mendenhall Valley, threatening Juneau.
The Mendenhall Glacier is a river of ice about 12 miles long and 1.5 miles wide. It’s moving from the Juneau Icefield in the Coast Mountains down the Mendenhall Valley to Mendenhall Lake, about 12 miles from Juneau.
The glacier acts as a dam for nearby Suicide Basin, a lake-sized bowl that holds rainwater and annual snowmelt. As the glacier melts, it releases a large amount of water from the basin in what's called a glacial outburst. That water reaches Mendenhall Lake a day or two later and then enters the river, which could have flooded Juneau.
Major flooding was prevented
According to the Alaska Climate Adaptation Science Center, the amount of flooding in the Mendenhall Valley was determined by:
◾The amount of water in Suicide Basin.
◾The rate at which the water flows beneath Mendenhall Glacier and into Mendenhall Lake.
◾How the level of Mendenhall Lake rises.
Barriers prevented flooding, but city officials asked evacuated residents to remain outside the area until notified it's safe to return. Water levels were predicted to drop rapidly following the crest, Paste BN reported.
Where in Alaska will Trump and Putin meet?
Trump and the Russian president will meet at Joint Base Elmendorf-Richardson, a 13,000-square-acre U.S. military base in Anchorage, a White House official confirmed to Paste BN.
The two leaders are expected to discuss Russia’s three-year war in Ukraine.
CONTRIBUTING Trevor Hughes, Jeanine Santucci, Swapna Venogopal Ramaswamy
SOURCE Paste BN Network reporting and research; Reuters; NASA Earth Observatory; juneau.org, juneauflood.com, NOAA, National Weather Service
This story was updated to add a new graphic profiling the HESCO barriers.