Exercise 8: Raster Modeling

Goals

The goals of this assignment were to use various raster tools to build models for both sand mining suitability as well as sand mining impact in the form of environmental and cultural risk in Trempealeau County, WI. In this exercise we were required to:

• Build a sand mining suitability model
• Build a sand mining risk model 
• Overlay the results of the two models to find the best locations for sand mining with minimal environmental and community impact

Data Sources Used

• Trempealeau County Geodatabase
• UWEC mgisdata
• NLCD geology raster

Methods

The first part of the assignment was revolved around creating a suitability model for mining locations in Trempealeau County. There were five different criteria which were used to create the final suitability model. These criteria were, railroads, land cover, slope, water table, and geologic criteria. When creating these separate models, we had to use many different spatial analyst tools in order to create a raster the properly showed the data we were looking for. The specific criteria for each suitability model will be shown in an Excel spreadsheet labeled Figure 2. Figure 1 below, shows the model used to create the suitability model. Some of the tools that were used in creating these models were, Euclidean distance, Reclassify, Polygon to Raster, Topo to Raster. Euclidean distance was used to show distances from different points of interest. Reclassify was used to simplify our ranking system from more suitable to less suitable. Polygon to raster was used to convert polygon features to a raster that we could then use in our suitability model. Topo to raster was used once to convert a topographic map to a raster.

Figure 1. shows the model that was created to execute all of the tools used to create the suitability model.

Figure 2. This table shows what the ranking system for each suitability category was.

In the next section of part one, we were to create a similar model but instead of suitable land, we wanted to map potential areas where there could be environmental or social impacts. For this environmental impact model, we assumed that things like residential areas, schools, farmland, and rivers were all important things to make sure that the mine couldn't impact negatively. We were also told to add another feature that we thought would be bad if the mine negatively impacted. I chose to add trails because generally, trails are a nice recreational area that are generally supposed to look and feel peaceful. Most of the same tools were used. Figure 3 below, shows the model that was created to execute all of the tools to see the potential areas of environmental impact. Figure 4. shows the ranking system that was used to determine what areas were potentially going to be effected. 

Figure 3 shows the model that was used to execute the tools necessary to create the environmental impacts maps.

Figure 4. shows the table that explains the ranking system used to create the environmental impacts model.

Results

The final results for this assignment were very interesting. All of the individual models that we created were combined into final models using raster calculator. Figure 5 below shows the final maps created when creating the suitability model. Figure 6 below shows the final maps created when making the environmental impacts model. Finally Figure 7 shows a raster calculator result from combining the suitable land and the environmental impacts. 

Figure 5. Suitability models and the final combined map. Ranking follows the table in the methods section. Red is not suitable land and blue is more suitable land. 

Figure 6. Environmental impact areas and the combined impacts map. Red areas represent areas that would create more environmental or social impacts were a mine to be put there. Blues represent areas that would be more environmentally friendly based on the data that was used. 

Figure 7, The final overlay map that combines the suitable land area and the environmental impacts map. Blue areas represent more ideal areas to put a mine and the red and orange areas indicate spots that would not be ideal for a sand frac mine.

Conclusion

Exercise 8 was a very interesting way to end the GIS 2 class. Working with rasters provided a lot of interesting information and I feel like a learned how to interpret areas in a different way. Before this assignment, I didn't realize the amount of tools that could be run on rasters. This was both a challenging and rewarding assignment to showed us again that things do not always go as planned when working in GIS. I feel like this assignment really challenged my critical thinking and provided me with new skills in ArcMap. The end findings showed that there were a decent amount of areas where a mine could be placed without having too much of an impact on Trempealeau County.