29 January 2014

The Keystone Canyon avalanche in Alaska, and its large ice-dammed lake

Posted by dr-dave

The Keystone Canyon avalanche

I do not usually cover snow and ice avalanches in my blog, but the recent Keystone Canyon avalanche, and other avalanches on the Richardson Highway in Alaska, requires that I make an exception.  The largest of many avalanches occurred on Monday at Keystone Canyon as a consequence of the recent combination of exceptional temperatures and high levels of precipitation through the winter (Jeff Masters has a blog post about the meteorology of this event).  It appears that there were actually two large avalanches at Keyston Canyon, one natural and one caused by blasting to try to remove the remaining unstable snow.  The net effect of this has been to block the Richardson Highway, the only road to the town of Valdez (population 4,000) people.  The best view of the avalanche deposit is a video from a helicopter that flew over the site:

Unfortunately I know nothing about the processes of clearing an avalanche from a road, especially one that is trapping a large, deep lake behind it, but I am sure that this will be very challenging.  This news report suggests that the plan will be to allow the lake to drain naturally before starting to clear the snow and ice, and other reports suggest that the lake level is falling.  Anchorage Daily News is reporting today that clearing of the other avalanches on the road has started, but that because of the impounded water at Keystone Canyon there is no estimated date upon which the road will be fully reopened.

Images of the Keystone Pass avalanche

Anchorage Daily News also has a gallery of images of the Keystone Canyon Avalanche. I think the best impression of the scale can be gained from this view, taken by the Alaska Department of Transportation and Public Facilities:

Keystone Canyon avalanche

Whilst this image shows the magnitude of the task facing the work crews:

Keystone Canyon avalanche

Alyeska Pipeline Company

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And on a lighter note, it is hard not to smile at this warning sign on the flooded road.  No kidding!

Keystone Canyon avalanche

Alaska Department of Transportation and Public Facilities

 

Acknowledgements

Thanks to Lee Allison, Greg Springer, Bryan O’Sullivan, Andrew Giles, Lockwood DeWitt and others for help with this post.