Can lidar images help identify slopes most at risk from slides?

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by GLENN FARLEY / KING5 News

Bio | Email | Follow: @GlennFarley

KING5.com

Posted on May 27, 2014 at 6:14 PM

Updated Tuesday, May 27 at 8:08 PM

SEATTLE -  First there was the Oso slide in March that killed 42 people and leaves another missing. On Sunday a massive landslide 40 miles east of the city of Grand Junction leaves three ranchers missing.  What is up with these slides, and what can be done to prevent them?

In Mesa County, Colorado rescuers who had been trying to find the ranchers on the lower portion of the slide were pulled off as concerns grow about the slides stability and the threat from future slides as the land above the slide zone is cracked and a newly formed depression is allowing the build up of water in a sort of lake.

The slide happened as part of a large plateau called the Grand Mesa, that's historically seen slides.  The area around Oso, Washington has also seen slides before, and lidar images taken with lasers from a plane show ancient slides.

"I think what we actually should be talking about is 'lidar-ing' the entire country in landslide prone terrain, as part of the basic infrastructure for hazard planning,"  said Dave Montgomery, a geomorphologist and professor at the University of Washington. 

While lidar looks like a black and white photograph, it really isn't.  Think of it as a type of radar that uses infrared light.  Typically flown from a specially equipped airplane, each pulse of light is a data point measuring distance.  And it's that composite of data points that produces the image.  One advantage of lidar say scientists, is that it can strip away vegetation like trees exposing the earth itself.  It's also been used to find earthquake faults. 

But their use for assessing landslides has been limited.  And there is a growing desire within state and Federal government to do more comprehensive lidar mapping of landslide zones.   

"How often do they happen, where do they happen, how far would they go?  And the beauty of lidar is it gives us  much better glasses to answer those kinds of questions."  said Montgomery. 

 

 

 

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