Lesson 10: Find a Landslide

Elk City, Idaho, February 18, 2016

http://www.idahostatesman.com/news/state/idaho/article61300727.html

http://kutv.com/news/nation-world/video-massive-landslide-blocks-idaho-highway-hundreds-trapped-in-town

Watch from about 1:45 on for the exciting stuff. (Warning: there is some swearing)

This is a landslide that happened in Elk City, Idaho last February. From what I read, debris made its way to the road fairly frequently and transportation employees would clear it off. However, when they went to work this day, the slope was still visibly moving. As you saw in the video, it started out pretty slow, but still visible, then it got very fast. This landslide cut off the only road in and out of the small town of 250 people, leaving them stranded. Later, an emergency road was opened up for a short period of time. 

I think this would be classified as a transitional slide mass movement. It appears to move down a flat surface, maybe a bedding plane. It is not viscous enough to be a flow and to me looked too smooth to be a This landslide happened in the winter, so it may have been triggered by the extra weight of snow. However, after reading about the history of the area (events like this, but on a smaller scale have happened before), my best guess is that there was no major trigger and the slope materials had just weakened over time to the point that the strength fell below what was needed for stability.



Additionally, I thought it was interesting how it started out kind of slow, but then quickly gained speed as more and more land fell. The main landslide happened in under a minute. It was a very eye opening thing to see how nature can chip away at something slowly and cause it to culminate in a huge change to the landscape. I've included a diagram as well as the cross section I did for the group assignment.

One of the big problems being faced with this landslide was there was nowhere to put the debris. I would recommend some sort of materials pit be commissioned nearby seeing how this area has a history of landslides. To prevent/mitigate further landslides, I would recommend covering the most susceptible areas with impermeable membranes so water cannot penetrate the land and weaken it. There are different materials available to do this. This would require some research and surveying though to identify the most susceptible areas. Overall, it seems like a landslide is very likely to happen again in this area if nothing is done.