Lesson Report 3: Analyzing Spatial Data in a GIS. by Diana Jo Lau

Transcription

1 Lesson Report 3: Analyzing Spatial Data in a GIS by Diana Jo Lau Introduction On April 27, 2011, a tornado outbreak occurred in the State of Alabama and Mississippi. The tornado in Tuscaloosa-Birmingham, AL resulted in 63 deaths, 1500 people injured, and total damages exceeding one billion dollars. The tornadoes were classified as the Enhanced Fujita (EF) scale at intensities form 1 to 5, the latter being the most intense. This project will analyze the closes relief sites to the affected areas and determine which affected area needs the most emergency relief. Lesson Objectives To use the spatial analysis functions such as overlay and buffering in ArcToolbox. To combine features and attributes using the intersect function. To create buffer zones using linear distance or field property. To create thematic maps to describe the data analyzed. Project Criteria 1. To locate public facilities close to the affected areas that represent candidate emergency relief sites. 2. To locate the affected area that needs the most emergency relief. Results and Discussion The GIS data was downloaded from the link provided in Lesson 3. The data was already projected to NAD83 UTM Zone 16N in units of meters (King, Walrath, & Zeiders, ). Shapefiles were created as tables were joined to its respective layer. The shapefiles were created to keep the join permanent and allow its attribute table to be editable. A buffer zone based on field was created for the tornado destruction path, in the figures below the areas in between the Response Relief Zones indicate the tornado destruction buffer. A buffer zone based on field was created to identify the destruction based on the tornado's size. A one mile relief zone out of the tornado destruction buffer was mapped and called Response Relief Zone, this buffer type is categorized as linear, because it measures a fixed distance along a path (this case the tornado path). To narrow the search of candidate sites (hospitals, churches and schools) attribute and spatial queries were performed (see Figure 3), and finally an overlay (intersection) between the relief zones and counties was performed to identify the areas of relief zones by counties. In the Emergency Relief Zones attributes table, a new field was created to categorize the population density with the affected areas; with this field a scale from 1 to 5 was created in order to indicate the most to least affected area. To calculate the relief priority, a value of 1 was added to the EF scale and the result was multiplied by population density. Since an EF scale can be 0, the value of 1 was added to avoid a result of zero (0) when multiplied by population density. This analysis yield to results for Criteria 1, see Figures 1 and 2.

2 The analysis for Criteria 2 was performed using Census Tracts. The same procedure for the analysis of Criteria 1 was applied using data of Census Tracts downloaded from the Lesson 2 Try This! section. Figures 3 and 4 indicate the relief response zones by census tracts for Tuscaloosa County and Jefferson County, respectively. Figure 1 Relief Priority Zones in counties affected by the tornadoes in Alabama. The most affected zone is identified in dark red (1) in the Relief Priority Zones scale. The pink (5) color shows the areas least affected by the tornadoes.

3 Figure 2 Candidate Facilities for Emergency Relief in counties affected by the tornadoes in Alabama. Hospitals, schools and churches are depicted within the relief priority zones that would serve as an emergency relief facility.

4 Figure 3 Attributes Table of Candidate Relief Sites. This table show 997 records that include all hospitals, churches and schools located in the relief priority zones.

5 Figure 4 Candidate Facilities for Emergency Relief by Census Tracts in Tuscaloosa County in Alabama. A close-up of Tuscaloosa County depicts the census tracts and relief priority zones in greater detail. The relief priority zones scale helps identify the most affected zone in red (1) and the least affected zone in bright yellow (5).

6 Jefferson Tuscaloosa Figure 5 Candidate Facilities for Emergency Relief by Census Tracts in Jefferson County in Alabama. A close-up of Jefferson County depicts the census tracts and relief priority zones in greater detail. The relief priority zones scale helps identify the most affected zone in red (1) and the least affected zone in bright yellow (5).

7 Conclusion As seen in Figures 1 and 2 the counties in Alabama most affected by the tornadoes were Tuscaloosa and Jefferson. Other counties with high relief priority zone include Limestone, Madison, Marshall, and St. Claire. Based on the relief priority zones by census tract analysis it is clear that these two counties were the most affected because of its population density. A limitation for this analysis is that transportation to relief sites is not taken into account, in addition, it is uncertain if the candidate sites still exist after the tornadoes, specially the schools and churches. References King, E., Walrath, D & Zeiders, M ( ). Problem-Solving with GIS, Lesson 3, /Part 1, Section b. The Pennsylvania State University World Campus Certificate/MGIS Programs in GIS. Retrieved March 13, This document is published in fulfillment of an assignment by a student enrolled in an educational offering of The Pennsylvania State University. The student, named above, retains all rights to the document and responsibility for its accuracy and originality.