Thursday, July 5, 2012

Visualizing Elevation Change: Mountaintop Removal Mining

Here at SkyTruth, we are always looking for new ways to visualize the environmental impact of human activity, so we've been playing with LiDAR (Light Detection and Ranging) data and digital elevation models (DEMs). We thought it would be interesting, and potentially useful, to create a profile of the terrain of a mine before and after mining activity.  I've started with the controversial Spruce No.1 mountaintop removal coal mine in Logan County, West Virginia as my test subject.

Topography of the Spruce No.1 mine in Logan County, WV, in 2010.

Google Earth imagery showed that significant mining activity had occurred between 2003 and 2011.  I retrieved a digital elevation model (DEM) of the mine location that shows what the topography looked like  in 2003, from the WV GIS Technical Center.  This elevation dataset was created from aerial survey photography that was flown in 2003.  I then downloaded LiDAR data that was collected over the area in 2010 from WV View and converted the LiDAR to a DEM using ArcGIS.  Next, I calculated the difference in elevation between the two DEMs; in other words, the change in elevation over that 7-year period.

In the slide show below, I have provided hill shades of the DEMs to better visualize the difference. I color coded the areas affected by mountaintop removal (blue) and the areas affected by valley fill (yellow) and overlaid the color coded DEM over the hill shades of the mine in 2003 and 2010. I have also created a profile graph of the elevation along two cross sections before and after mining activity. After analyzing all these results, I have found that 7.4 million cubic meters of rock was removed by way of mountain top removal mining and 9.8 million cubic meters of rock has filled what once was a valley.  (Why the difference?  The fill has a lot of gaps and spaces, so it's not as compact as the original, mined bedrock.)

                 

8 comments:

  1. This is great technology. One thing to consider with this representation and the elevation profile created with before and after MTR. The reclamation will change the final grade to much different that what is pictured in this comparison. I would recommend looking at areas mined and reclaimed from 2003 to 2010 as those would show a true representation of permanent land form change.

    ReplyDelete
  2. Thanks Billy. Some of the cut areas might get slightly modified - that's where the coal was removed - but the main thing that won't change is the valley fills, where overburden has been dumped into the adjacent stream valleys. That will be steeply graded and planted with vegetation to stabilize it, but the original valley topography will not be restored.

    The thick pile of fill alters the hydrology of the stream, making it shorter and steeper, which makes it more prone to flash-flooding. And rainwater percolating through the fill chemically interacts with unweathered minerals in the mass of fresh crushed rock that makes up the bulk of the fill, raising the levels of total dissolved solids and the conductivity of the stream water, and mobilizing toxic metals such as selenium that pose a threat to downstream water users and aquatic critters: http://blog.skytruth.org/2010/08/coal-mining-skytruth-work-helps-link.html

    ReplyDelete
  3. Hello.
    I would like to translate this article to spanish for my students. Is it possible?
    Thanks in advance.
    Jaime

    ReplyDelete
  4. Jaime - Google Translate (http://translate.google.com/) works fairly well. Try this: http://tinyurl.com/8wbep5m

    ReplyDelete
  5. No, I could translate without problems from english, I don't like google translator, but I would like to translate your article to spanish language and I would like to use your pictures, of course, I must write that "you" are the authors, the link to your english article, etc.
    Do you have some legal restriccion or something like this?
    Thank you

    ReplyDelete
  6. You are free to publish a translation of our article with attribution. Please share a copy of your translation with us prior to publication.

    Thank you

    -David

    ReplyDelete
    Replies
    1. Could you give me your email for send the translation?

      Delete
    2. Please email to: info@skytruth.org

      Thanks!

      Delete