GIS II: Raster Modeling

Goals and Objectives

The purpose of this lab was to gain experience using various raster geoprocessing tools to build sand mining suitability and sand mining impact models.  These models took both environmental and cultural risks into account within the study area of Trempealeau County, WI.  

Methods

Frac Sand Mining Suitability Model 

Figure 1: suitability index model

During the first part of this lab, I utilized specified criteria and raster geoprocessing tools to create a suitability index model in ArcGIS (Figure 1).  For each criterion, I determined class breaks and suitability ranks, using the following scale: 3 = High, 2 = Moderate, 1 = Low.  My justifications for my rankings can be found in Figure 2.

The following criteria was used to calculate mining suitability: 

• Geology
• Land Use & Land Cover
• Distance to Railroads
• Slope
• Water Table Depth

Figure 2: suitability ranking justification table

Frac Sand Mining Impact Model 

Figure 3: impact index model

During the second part of this lab, I utilized specified criteria and raster geoprocessing tools to create a impact index model in ArcGIS (Figure 3).  For each criterion, I determined class breaks and suitability ranks, using the following scale: 3 = High, 2 = Moderate, 1 = Low.  My justifications for my rankings can be found in Figure 4.

The following criteria was used to calculate mining impact: 

• Streams*
• Prime Farmland
• Residential Areas
• Schools
• Wildlife Areas

*For streams, I decided to only use Order 2 - 9 (Strahler Stream Order) streams since contamination of larger streams poses a greater risk to surrounding environments.  

Figure 4: impact ranking justification table

Overlay of Models 

Figure 5: best locations model

After creating both a suitability and impact index model, I overlaid these two models using Raster Calculator to ascertain the best locations for frac sand mines in Trempealeau County, WI (Figure 5).  

Viewshed 

Finally, to gain some experience using the Viewshed Tool in Arc Map, I chose to take a look at visibility from a few parks in Trempealeau County, WI. This was a valuable exercise since the Viewshed Tool can be very useful within the fields of military geography and urban planning, among others. 

Results

After running all of my models, I utilized ArcMap to create cartographically pleasing maps depicting my findings. 

Frac Sand Mining Suitability Model 

Figure 6: suitability maps

Frac Sand Mining Impact Model 

Figure 7: impact maps

Best Locations

Figure 8: best location map

Viewshed

Figure 9: viewshed tool map

Discussion

After examining my map detailing the best locations for frac sand mines in Trempealeau County, I determined that the northwestern corner of the county seemed to have both the best suitability and least risk (Figure 8).  It is important to remember, however, that only ten factors were assessed during this lab.  Countless other factors such as commerical areas, major roadways or locations of current mines could influence the final placement of a mine.  Additionally, in-person site inspections should be carried out to make final determinations since models are not completely reliable.  Despite this, my models and final map provide a valuable, albeit general, look at the best locations for sand mines.  

Conclusions

This lab demonstrated that raster geoprocessing tools can be very effective for analysis purposes.  Through utilizing a systematic and logical ranking system, I was able to create useful suitability and impact models, which, when overlaid, produced a best locations map.  I really enjoyed completing this lab since it served as a synthesis of all of the work we have done this semester.  

Sources

Cropland Cover. In United States Department of Agriculture. Retrieved March 15, 2016 from http://datagateway.nrcs.usda.gov/

Trempealeau County Land Records. Retrieved March 15, 2016 from http://www.tremplocounty.com/tchome/landrecords/

United States Department of Transportation. Retrieved March 15, 2016 from http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_atlas_database/index.html

United States Geological Survey. Retrieved March 15, 2016 from http://nationalmap.gov/about.html

Web Soil Survey. In United States Department of Agriculture. Retrieved March 15, 2016 from http://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm