Juneau, Alaska, Hit With Another "Glacial Outburst" Flood, But This Time They Fought Back

Barriers this year kept the worst of what has become
the annual glacial outburst flood this week
in Juneau, Alaska. You can see how badly
the houses in this photo would have been
flooded without the barriers. 

 Yearly summer events are often fun.

'The one in Juneau, Alaska is not.  

Once again, as has happened every August lately, parts of Alaska's capitol city are being hit by what is know as a glacial outburst flood. 

Such a flood happens when parts of a glacier melt, and water backs up behind rocks and/or ice. Finally the water breaks through, causing an often destructive flash flood. 

In Juneau, water from the melting glacier fills a hemmed in basin until the pressure grows strong enough to release a torrent of water from the Mendenhall Glacier and down the Mendenhall River into Juneau. 

Per the Washington Post: 

"By Wednesday morning, the floodwaters racing gown from what's called Suicide Basin has risen to record levels, faster than scientists had predicted the day before. 

Juneau officials warned residents to evacuate parts of the city that have been prone to repeated flooding."

It appears the flooding peaked Wednesday morning.    About 1,000 people had evacuated ahead of the flood. 

The Mendenhall River was already at minor flood stage because of heavy rains Sunday and early Monday. Since the river started at an elevated level, the gush of water from the glacier pushed the river Wednesday morning to 16.65 feet, which surpassed the record high level of 16 feet set during last August's glacial outburst.  

Since this has become a destructive, frustrating annual event, Juneau is trying to minimize the damage. 

This year, the city worked with the U.S. Army Corp of Engineers to build a massive wall of Hesco barriers along the river to prevent the destruction seen in the last two years, WaPo reports. 

Hesco barriers are durable cloth bags filled with dirt and sand and reinforce with a metal frame. They were often used by the military in places like Iraq and Afghanistan to fortify bases.  But they can be used as giant sandbags, too.

Early reports suggest the Hesco barriers mostly held, preventing much of the feared damage to homes near the river. Roads and streets were inundated, and some homes might have taken on a little water, but the damage appears to be much less than in the previous two years. 

The Hesco wall is expensive, and included big bills assessed to residents who live in flood zones.  There needs to be a more permanent solution, but the future of these floods is unpredictable. 

 The Juneau glacial outburst floods started in 2011 and have worsened in recent years. Climate change is helping to melt more glacial ice than in years past, so more water is now usually available to cause these August floods.

In August, 2023, the outburst flood destroyed several homes.  That event included dramatic video of a house collapsing into the river.  Last year, at least 300 homes were damaged by the flooding. 

It's possible that the nature of future summer glacial floods could change as more of the glacier melts, or the thawing gets even more intense in future years. Alaska has warmed twice as fast as any other state over the past few decades, and there's no reason why that trend won't continue, as areas closer to the Arctic are warming faster than places closer to the Equator. 

The Mendenhall glacial flooding could in upcoming years find another outlet, or burst out another way instead of blasting down the Mendenhall River in one big swoosh.  

Juneau - and many other parts of the world prone to glacial outburst floods in the age of climate change - need to stay on their toes.