The objective of this assignment was to get the residents who call the Pacific Northwest home to consider the potential impacts a large scale earthquake could have on their well being. For this assignment we made our focus on the coastal cities of Lincoln County, Oregon. We were asked to perform a series of path distance and Multi-Criteria evaluations and report our findings.
Lincoln County, Oregon is situated in the middle of the State along the Pacific Ocean coastline. It is home to some of Oregon’s most iconic beach towns; the largest cities being Newport and Lincoln City. If history is any indication, then residents of the Pacific Northwest can expect a sizable earthquake in the near future. Tsunamis are being triggered by the nearby earthquakes offshore of Oregon along the Cascadia Subduction Zone, where the North American Plate and the Juan de Fuca Plate meet. This 1,000 kilometer fault stretches from Northern Vancouver Island to Cape Mendocino California. (Pacific Northwest Seismic Network).
It is vital that scientists, geologists and geographers alike continue to study and help the future prediction and planning of earthquakes and tsunamis not only off the Oregon Coast, but the whole Pacific Northwest, Alaskan, and California coastlines. The study of tsunami evacuation through many various methods can help save the lives of tens of thousands of lives along the Oregon Coastline. The Lincoln County coastline region alone is home to about 40,000 residents that are at risk of being affected by an impending tsunami. Many of these coastal residents are over the age of 65, so the need for a fast and efficient tsunami evacuation plan is very important. There are a few things that a successful tsunami evacuation plan must have, a direction that is out of the tsunamis path, an area that is accessible by a large percentage of the residents, and the use of roads and placements of bridges need to be into factor when determining the best evacuation routes and zones.
For the analysis portion of our assignment we heavily relied on the newly introduced method called, Multi-Criteria Evaluation. Also known as a MCE,is used in many aspects around the globe. Most often MCE is used for the development of suitability assessment models for many different global issues. “Determining the suitability of a given spatial area for particular uses is another fundamental step in resources planning. Suitability assessment is a multi-criteria evaluation (MCE) process widely used in a variety of planning and decision-making situations.” (J. Bello-Pineda ET AL.226). For all intents and purposes a Multi-Criteria Evaluation was exactly the method that we needed to implement to find the area of utmost suitability for tsunami evacuations.
The first thing I did to get my process going was to collect all of the necessary data sets and files. I used the University of Oregon’s GIS Data Library to grab the digital elevation model of the Oregon coastline, as well as the Oregon roads shape file, Oregon Counties polygon, Oregon water bodies, Oregon streams, and Oregon Rivers shape files. After clipping the data sets to strictly Lincoln County I was able to start my process of analysis and predicting the pathway in which a 7.0 magnitude tsunami would take. I visited a few sites to research the characteristics of tsunamis, and tsunami history in Oregon’s geological past. the National Oceanic and Atmospheric Administration (NOAA) had excellent information on the science behind tsunamis. I also visited DOGAMI website, Oregon Department of Geology and Mineral Industries for reference to the Pacific Northwest region.
After further research I chose the parameters in which to test the path of the tsunami. I chose that a 7.0 earthquake would generate a tsunami that would go as far inland as 1.5 km, I only chose water bodies that were within 1.5 kilometers of the Pacific Ocean because of this measurement. After creating a buffer of 1.5 km for the water bodies shapefiles, I also created a buffer of 20 meters for all low lying rivers and streams in the region. I chose these exact distances after examining the elevation of the terrain for the rivers and streams safe distances. After creating the buffers of the water bodies I wanted to find out the average distance a resident that lives in one of these coastal towns could travel in the distance it takes for the tsunami to reach landfall. I found out from the DOGAMI tsunami website that a 7.0 earthquake off the Oregon Coast would reach land in 20 minutes. I then figured that the average person could travel 1.25 miles or 2011.68 meters. I had to convert every measurement to meter form because the data that I was using was in this same form of measurement.
After these first steps I created a cost surface layer that represented the cost for travel for the new study area. The new study area being the area that someone could travel in the 20 minute period. After reclassifying and converting all the layers to raster form I was then ready for the Multi-Criteria evaluation. The MCE analysis would take into account the six raster layers that I had previously constructed and with user weight inputs can run a test to find the most suitable area for a tsunami evacuation. Below is a diagram of the various inputs and weights that I ran in Model Builder.
I chose these particular weights because I figured the rivers and streams of the region would not be hit as hard as the water bodies after the tsunami had reached land. Also the Elevation and distance to roads layers were more important in regards to the weighted MCE test. After the test was ran I constructed this map of suitability for the tsunami evacuation areas in Lincoln County.
After I had ran the Multi-Criteria Evaluation, I got a raster data set that I could not understand. I had to reclassify the values in order to find out where the actual suitable areas for evacuation were located. I reclassified the the values in six groups and called it the suitability score or index. A value of zero being the least optimal area of evacuation, and a score of six being the most suitable. I then created the map seen above with the areas on the three most populated towns of Lincoln County with the optimal evacuation zones.
While there are at least one areas of level 6 suitability for the cities of Newport, Waldport, and Lincoln City, I also see some areas of lower suitability such as a score of 3, 4, or 5. These areas are lower in the index because one of the weighted inputs of the Multi-criteria Index was not properly met. For example the tsunami would submerge everything in its 1.5 km pathway that was 20 meters above sea level and below, so some of these indexed sites were lower in elevation than others. Others areas required more than the allotted 20 minute time frame for the residents to safely walk to and would result in a very low score on the index because I had weighted the walking distance at 25% of the weighted amount.
In the end I feel that my work and research in regards to mapping out the optimal tsunami sites was a great success. I now know how to effectively create a Multi-Criteria evaluation that helps solve a real world problem and can be used for future projects and research. The tsunami preparedness on the Oregon Coast should be a top priority here in the State of Oregon, and with research on geological events such as this even at the smaller scale can help add to the literature on proper tsunami evacuation. If I were to do a second tsunami evacuation zone MCE there are definitely a few steps that I would alter, such as converting my study areas and cost distances to that of a larger scale tsunami. I definitely believe in the power of a MCE and its combined use with GIS can have a very positive effect on educating the population on tsunami evacuation and preparedness
Work Cited.
“Cascadia Subduction Zone | Pacific Northwest Seismic Network.” Cascadia Subduction Zone. Pacific Northwest Seismic Network, n.d. Web. 13 Nov. 2015.
Bello-Pineda, J., R. Ponce-Hernández, and M. A. Liceaga-Correa. “Incorporating GIS and MCE for Suitability Assessment Modelling of Coral Reef Resources.” Environmental Monitoring and Assessment Environment Monitor Assessment 114.1-3 (2006): 225-56. Web. 15 Nov. 2015.
Journal Article
“NOAA Tsunami Basics.” NOAA Tsunami Basics. NOAA, n.d. Web. 15 Nov. 2015.
“Oregon Tsunami Clearinghouse / Resource Library.” Oregon Tsunami Information Clearinghouse. DOGAMI, n.d. Web. 15 Nov. 2015.