This document analyzes factors that contribute to the spread of invasive species in Thurston County, Washington. It examines traffic counts along roads and stream order to determine hotspots for invasive species transportation. The analysis found that the northeast area of the county, which has higher traffic concentration on roads and connects to higher order streams, is most at risk. This is because this area allows for quicker spread of invasives along roads and streams that can then transport them more widely, even to other states. Challenges in the analysis included lack of attribute data and counts to perform more in-depth testing.

1. Invasive Species Analysis
Weighing Traffic Counts and Stream Order to
Determine Likelihood of Invasive Species Spread
By Kathryn Barnes

2. Problem
Invasive species are a constant problem to natural
ecosystems
★ Disrupts nitrogen cycle
★ Crowd out native species
★ Spread non-native diseases, fungi, etc.

3. Location: Thurston County
The county has documented invasive species in the area
since 1975 till 2014
Determining which species to target first has not been
established

4. Sources for Data
★ WSDOT GeoData Distribution Catalogue
★ Washington State Department of Natural Resources
★ Thurston County Noxious Weed Control Agency-web
site and ArcGIS layer search

5. Methods
Begin with a simple base layer
★ One that allows for a general, topographical identification of the area
★ Add weed, rail, road, and stream layers
★ Add Thurston County general parameters

6. Combination Methods
Convert to raster based on certain qualities
★ Roads
○ Feature to raster
○ Based on quantities
■ Traffic Density
★ Streams
○ Feature to raster
○ Based on quantities
■ Stream Order
★ Noxious Weeds
Selections based on location
★ Must be within Thurston County parameters
★ Done to stream, weed, road, and railroad features

7. Analysis Result
An eclipsed area of interest in relation to stream order (those of higher
depositional frequency) and traffic density (areas of higher traffic) was
determined

8. Why this area?
Despite there being other areas of interest, specifically to the southeast of the
targeted, ellipsed area, the sole purpose of this project was to determine
areas that are ‘hotspots’ for invasive specie transportation; high movement
and cleared areas

9. What does this mean?
Focus must be paid to the areas specifically with higher traffic concentration, in
the northeast of the map. These higher concentration roads have the ability
to spread invasives quicker than other areas with less dense roads.
Likewise, the traffic content in this area heading southwest will hit a higher
order stream area. If invasives make it to this area, the streams here have
the ability to pass them at a higher rate, thus circulating them faster.
The locomotion of invasives isn’t entirely confined to the area of Thurston
County. Within these higher impact areas as demonstrated by this project,
people traveling through Washington to areas like Oregon or Idaho have the
ability to pick up these undesirable hitchhikers.

10. Difficulties During the Project
Most of the project time was spent in trial and error, attempting to figure out
what analysis pattern to carry out via ArcToolbox
Some of the Arc Toolbox functions that would be appropriate for functions
expected in this project turned out to be quite the opposite; unusable
Of course, some of the shapefiles had to be changed due to absence of
attribute data
Lastly, because of the lack of counts within department data such as the DNR
and DEQ, it was rather difficult to run decent tests in order to determine an
in depth analysis

11. Thank you!
Contact Info
Kathryn Barnes
Department of Geography
Western Michigan University
kathryn.i.barnes@wmich.edu