Case Studies

Westfield State Impervious Surface

Background

Our new index, the Intercardinal Aggregation Index (ICAI) can be used to determine the aggregation of impervious surfaces. In this case study, I will implement the ICAI on the impervious surface layer for Westfield State University.

Westfield State University (WSU) is located in Westfield, Massachusetts in the western portion of the state. An aerial image of Westfield State University's main campus can be viewed in Figure 1.

Figure 1. Aerial view of Westfield State University's main campus.

If we were to view the impervious surface (on a 1 meter grid) of Westfield State, our impervious surface grid would look like Figure 1.2. The data for the impervious surfaces of Massachusetts can be found here.

Figure 1.2. Impervious surface raster layer of Westfield State University.

The general procedure to get ICAI results for your impervious surface raster include:

    1. Download the impervious surface layer and clip the appropriate area for analysis.
    2. Select only the attribute class that you wish to perform the analysis on (i.e., the impervious surface).
    3. If necessary, use the aggregate tool to re-size the raster.
    4. Run the Intercardinal Aggregation Index on your raster.

The Importance of Grid Size

Step 3 is an essential step that mustn't be overlooked. The results of the ICAI (as well as the AI) are largely dependent on the grid size, which oftentimes needs to be adjusted to see meaningful results. For instance, a 1 meter grid will typically yield results that are very aggregated. This is because there are so many pixels (with shared adjacencies) that an inaccurate depiction of the aggregation of the raster will result. Likewise, if your grid size is too large, one will also see in accurate depiction of the aggregation. Therefore, you must pick a grid size that is appropriate for your raster. Different grid sizes for this case study can be viewed in Figure 1.3.1 - 1.3.3.

Figure 1.3.1. WSU impervious surface on a 1 meter grid.

Figure 1.3.2. WSU impervious surface on a 5 meter grid.

Figure 1.3.3. WSU impervious surface on a 10 meter grid.

Results

After performing the ICAI analysis on the 1m, 5m, and 10m grid sizes, I had an output of the following results:

UMass Amherst Impervious Surface

Similar to the last analysis that was conducted (above), we can implement the ICAI on the impervious surface layer of UMass Amherst, whose aerial view of the main campus is displayed in Figure 2.1.

Figure 2.1. Aerial view of the UMass Amherst campus.

The same procedures for the analysis was conducted as in the analysis for the Westfield State impervious surface layer, and we tested the ICAI on the same three grid sizes - 1 meter grid, 5 meter grid, and 10 meter grid, and are shown in Figures 2.2.1 - 2.2.3.

Figure 2.2.1. UMass Amherst impervious surface, 1 meter grid.

Figure 2.2.2. Umass Amherst impervious surface, 5 meter grid.

Figure 2.2.3. Umass Amherst impervious surface, 10 meter grid.

After using the Intercardinal Aggregation Index geoprocessing tool, we came to the following conclusions.

ICAI for the Beaches of Dennis, MA

Intercardinal Aggregation Index

We can implement the Intercardinal Aggregation Index (ICAI) to determine how aggregated particular sections of beaches are. This analysis was done for the sections of beach along the Dennis, Massachusetts coastline. Out outtake image showing the location of Dennis, MA is shown in Figure 3.1.1 and Figure 3.1.2.

Figure 3.1.1. Figure 3.1.2.

There are two main coastlines of Dennis, MA - the first is the coastline which includes the Atlantic Ocean; the second is the coastline which exposes the land to the Cape Cod Bay. While there are many different beaches which are categorized by their names and regions (e.g., Corporation Beach, Mayflower Beach, etc.), for this analysis, I simply separated the beaches into four main sections, which have been separated by natural geographic features, namely either rivers or inlets. For the purposes of this analysis, I have named these sections of beaches:

    1. Atlantic Coast (West)
    2. Atlantic Coast (East)
    3. Bayside Coast (West)
    4. Bayside Coast (East)

These beaches are shown on the map in Figure 3.2.

Figure 3.2. Map of Dennis, Massachusetts.

Results

After following the same steps in the last case study, I came to the following conclusions in regards to each section of beach:

Aggregation Index

A similar analysis for the same sections of beach has been performed by me in a previous case study in my GARP 0344: Advanced GIS course (Fall 2015). Results of this analysis can be found here.