Introduction:
While it may not often cross people’s minds, earthquakes and tsunamis are real threats to the Pacific Northwest coastline. The New Yorker’s “The Really Big One” article hints towards a massive Cascadia earthquake that may occur in the next fifty years where, “In the Pacific Northwest, the area of impact will cover some hundred and forty thousand square miles, including Seattle, Tacoma, Portland, Eugene, Salem, Olympia, and some seven million people. When the next full-margin rupture happens, that region will suffer the worst natural disaster in the history of North America”. In light of the heightened awareness of earthquake and tsunamis, this study focuses on the broad scale impacts of a potential tsunami occurring on the Oregon Coast, as well as a sample model of potential recovery areas in Lincoln County, Oregon.
Methods:
The study was conducted using the following data:
1. “Oregon Tsunami Evacuation Zones- 2013”. DOGAMI. Vector Digital Data. 2013.
2. “Oregon City Limits – 2013”. ODOT. Vector Digital Data. 2013.
3. “Highway Network – 2013”. ODOT, Road Inventory Classification Services (RICS). Vector Data. 2013.
4. “Blocks2010” Census blocks with demographic data from 2010. University of Oregon.
5. County Lines Oregon. ESRI, University of Oregon.
6. Lincoln County Digital Elevation Model, 50m. University of Oregon.
First, broad level impacts were identified. Using Overlay and Clipping tools, the area of city limits impacted by tsunami event, demographic information, and the length of highways impacted by Tsunami were calculated. To calculate the population impacted by a tsunami, the Intersect tool was used, followed by summaries of the modified tabular data. This choice influences the results because it does not clip or divide the areas or demographic data, creating an overestimate in the results.
In order to create a suitability model for identifying possible ‘recovery zones’ in Lincoln County, a conversion of the vector data into raster form is necessary. Within ModelBuilder, both the highway data and the tsunami zone data were converted to raster form using Euclidean Distance tool. All three of these new rasters were standardized converting them all to values of 1-10 with the reclassifying tool and an equal interval classification. The equal interval classification allows for a standardization between the minimum and maximum values of each set, ensuring an equal distribution.
All three of these new standardized rasters were then overlayed using the Raster Calculator Tool:
Results:
The tabular data above represents s county and city-wide impacts of a potential tsunami. The use of the intersect tool influences the results because it does not clip or divide the areas or demographic data, and therefore creates an overestimated output value. In the event of a natural disaster, however, it is better to be over-prepared than inadequately prepared.
Looking at the map, the blue areas represent the potential tsunami impact zone. This reaches farther inland in low elevation areas, especially river deltas. The green areas are the results of the Raster Calculator tool, which combined the standardized elevation data, highway distances, and tsunami proximity raster. These areas are potential locations that would be appropriate to place a disaster relief zones for Lincoln County.
Conclusion:
There are many places along the Oregon Coast and within Lincoln County that can potentially be impacted in the event of “The Really Big One”. This suitability analysis, consistent of three main input factors, can be considered in the event of a tsunami in the near future. There are several locations that would lie in an area of relatively low slope, near a highway, and not within the impact zone. These zones can be used for several disaster relief purposes, including temporary housing, clinics, and aid distribution centers.
References:
Schulz, Katheryn. “The Really Big One”. The New Yorker. Posted July 20, 2015. Web (Accessed Feb 28, 2017). URL: http://www.newyorker.com/magazine/2015/07/20/the-really-big-one