Pierce Elementary Schools Analysis
This analysis was performed to inform community stakeholders, state and local officials about Pierce County, Washington's 133 public elementary schools. Hypothetical school feeder regions were created using Thiessen Polygons based on the nearest elementary school. If a student lives within these polygons, they will most likely attend the school which lays within that polygon. Elementary schools were categorized and/or ranked by percentile of on three factors:
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Urban vs. Non-Urban
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Area of school grounds
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Impervious surface percentage
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Downloadable version available by clicking the map image.
Image: Minadao School
Classification by School Acreage
School areas, in acres, were classified based on 5 quantile classes. Each class then contains 20% of Pierce Counties public elementary schools.
Here they are symbolized with a green gradient, where dark green polygons contain the schools with the largest area, in acres. Lighter hues depict decreasing school area.
​(Max: 50 acres, Min:1.8 acres, Mean: 10.1 acres)
Classification by Impervious Surface
Identifying Impervious Surfaces
USGS 2011 Percent Developed Impervious raster data was joined with a Pierce County base map to obtain information about the landscape of Pierce County. Surfaces such as concrete roads and parking lots, or roofed structures are impervious to water, and as such are designated impervious surfaces.
Black areas are completely impervious
Surfaces are shaded lighter as they become more pervious.
Hypothetical Feeder Regions
Pierce County public elementary schools were isolated from a larger school polygon set, as private schools, etc tend to draw students from larger areal pools. School polygons were converted to points, and Thiessen Polygons creating using the namesake tool in ArcMap.
These polygons were created such that each polygon is closer to the point that it is associated with than any other point, in this case, school.
Pierce County does not use feeder regions to designate which school students will attend, but due to proximity, these "feeder regions" are likely to contain the areas where students associated with each school live.
Urban vs. Non-Urban Designation
Urban designations were given to elementary schools that were located completely within the 2000 US Census Urban Area Urban Cluster polygons. Non-Urban designations were given to all other schools
Impervious Surface classifications were created with the ArcGIS Spatial Analyst tool. Elementary school area polygons were joined with USGS 2011 Percent Developed Impervious raster data, to yield the percentage of each school’s surface area that was impervious. Impervious surfaces were classified on the same basis as acreage, using 5 quantile classes.
Dark Green designates schools with low percentages of impervious surface, while red designates schools with high percentages of impervious surface.
(Max: 84.6%, Min: 0.0%, Mean: 39.5%, Std. Dev: 15.9)
Putting it all Together: Large, Small & Impervious
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The top 20% of schools occupying the largest acreage were given a large school area designation, while schools with the lowest 20% were designated as small. All other schools were given an average school area designation
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Impervious Surface Ranks were derived by quantile classification, and the 20% of schools with the lowest percentage of impervious surface given a ‘Low’ designation, and the 20% with the highest percentage given a ‘High’ designation. All other schools were designated as average.
Impervious
Surface Rank
School Area
Please enjoy this interactive ArcGis Online web map
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Symbolized feeder region layers are available for each classification
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Additional information about each elementary schools is available by clicking on any of the points, or regions in the region layers.
Resources/References
Cartographer/GIS Analyst: Tracie S. Barry
Contact: barryts@uw.edu
Created: February 10, 2019
Software: ArcMap 10.6.1
Projected Coordinate System:
NAD 1983 HARN StatePlane Washington South FIPS 4602 Feet
Data Sources: UWT GIS, 2000 US Census, USGS National Map Land Cover, Pierce County Open GeoSpatial Portal