This lab is the culmination of the whole semester long project. At the end of this lab, I will have a suitability model showing where frac sand mines would be appropriate and where they wouldn't be. Most of this lab will be modeling different rasters and using the raster calculator tool to add up all of our suitability/risk models so that we can see where mines could be located so that they have minimal impact upon the environment and the people.
Study Area:
I haven't touched much on Trempealeau County throughout the semester so here is a little background on this unique county. Trempealeau County (Figure 1) is situated along the Mississippi River in West Central Wisconsin. The county seat is a small town called Whitehall and the total population of the county is 28,816. Trempeauleau County is situated in what many people call, the Driftless Area (Figure 2). This is an area of Wisconsin that was unglaciated 12,000 years ago and as a result has a very different topography then the rest of the state. Many rivers flow through this country and have created deep valleys and large bluffs that so many people come to see along the Mississippi River. Since Trempeauleau is within the Driftless Area, it has some very old geologic layers that contain a high quality sandstone that is just the right shape and size (also rounded and sorted) for frac sand. This is what has made this county a topic of interest when it comes to the boom of sand mines around the state.
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| Figure 1: Outline of Trempealeau County showing some of the bigger cities/towns |
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| Figure 2: Map of Wisconsin showing the Driftless Area shaded in Pink in the Southwestern Corner |
Methods:
The workflow for this lab is creating various sets of raster's and reclassifying them so we can use the raster calculator tool to determine where the best locations are in the county for Frac Sand Mines. For the suitability model I created it within model builder and used the following rasters:
Geology Raster
Land Use Land Cover
Railroads
Slope
Water Table Depth
To get all of these rasters ready for the calculation I had to prepare them. For some I had to run a tool that converted them from a vector file to a raster file, for all of them I had to reclassify them into a raster that gave each cell a value from 1 to 3, with 3 being the most suitable for a mining location. Once I normalized all the rasters into something that was consistent throughout, they were ready for the raster calculator. Figure 3 below shows the flow model of this process that took quite a while.
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| Figure 3: A data flow chart of the sand mine suitability model |
The end result of this model was a raster that had a range of values from 0 to 15 with 15 being the most suitable. You can see from Figure 4 below that quite a bit of the county would be considered suitable, with emphasis on the valleys in the western part of the county. This is partly because the rail terminals are in the western part of the county and that provides easy and quick transportation of all that sand.
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| Figure 4: Final Map showing where in the county it would be the most suitable to establish a sand mine |
Discussion/Conclusion
You can see from the maps above the power of raster modeling. You can take a relatively large area and do many different analyses on it and once your all done, combine them together to get a overarching view of many different variables. It takes time however to do this as it is not easy trying to troubleshoot many different rasters, all from different providers and make them ready for final analysis. It would be much easier if it was already prepackaged and wrapped in a bow and all you had to do was press RUN. That is pretty much what I have now, if I were to perform this on another county, I would be able to just add different data sets and tweak a few parameters and wala, a brand new sand mine suitability map for the county of your choice, all thanks to the data flow model and model builder. Knowing how to start and finish this process is essential, especially for anyone that will use your data later on. You cant document your workflow any better than by using model builder and that can save yourself and others a lot of time down the road. Time is Money, so we should all enjoy that!
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