Caleb Stevens
Lab 4 (GEOG 482)
2-22-16
Tsunami Zones of Oregon: Why It’s Important to Know
The Oregon Coast is a popular destination for tourists and settlers alike. As more and more people choose to relocate to the 33rd United State, the more attention it receives toward its vulnerability to natural disasters. A main catastrophic event that threatens thousands of Oregon residents is the possibility of a major tsunami striking the coast. Oregon lies just east of the Juan de Fuca/ Pacific plate subduction zone, which is due for a major earthquake within the next 50 years, geologists predict. Such an earthquake would cause a tsunami and, depending on the severity of the seismic event, would most likely cause major damage to the communities and towns along the Oregon coast. The more information we can gather about the possible tsunami zones and affected areas along the coastline will better prepare us for when the event does occur. Things like elevations, slopes, roads clear of the tsunami zones, and population densities can give us an educated assumption of how a future tsunami could unfold in a given city. By conducting these studies, we can determine where is the best location to set up relief spots and shelters for people who may lose their homes. GIS, and more specifically Multi‐Criteria Evaluation, is an extremely vital tool when it comes to these analyses because it can take into consideration multiple factors that will play a role in the areas overall safety and accessibility, and by taking separate factors and having the ability to apply relatable functions to said factors, we can determine spatially what areas are most ideal for tsunami relief.
The methods used to conduct this analysis relied heavily on a few pieces of data that were available. These few datasets could then be combined to calculate ideal locations for tsunami relief areas. Digital elevation models were used to calculate the slope of the area being studied. By deriving the slope and steepness of the local terrain, we are able to eliminate a lot of location right off the bat. Since these areas with high slope in the coastal mountain ranges will be susceptible to landslides after a seismic event, these areas need to be avoided at all cost. Another useful dataset was provided by DOGAMI and allowed us to map the areas along the coast known as “Tsunami Zones”. It essentially is a buffer of the water bodies along the coast that would most definitely swell and cause flooding in the event of a tsunami. Census information was also used to calculate the population densities of the selected areas. This is helpful in mapping where the relief zone should be because the higher the population density, the higher the need for disaster relief and therefore, a relief shelter should be where the most people are located. Finally, roads that were clear of the tsunami zone were used, provided by ODOT. Because transportation around the area affected is essential (for medical emergencies, supply distribution, etc.), roads that would not be condemned by the tsunami were viewed as more desirable and played a factor into where the relief location was located. By using these characteristics of the local area, we can create models which can be used and implemented in other areas around the world where similar data is available to the user who is trying to conduct such research and preparedness.
(Screen shots of GIS Model used in calculating the most ideal tsunami relief location.)
The first map is an overview of the state of Oregon and the areas of vulnerability to tsunamis mapped in white, known as the “tsunami zones” of the coastal region. By using State land and county information, paired with the tsunami zone shapefile, we can calculate the potential amount of land that would be covered by a tsunami if it were to strike. A similar operation is used in calculating the amount of State highways would be directly affected by a tsunami. And lastly, by using US Census information on each county and city that contains land on the coast, we are able to calculate the amount of civilians that would be affected directly by the tsunami zone provided by DOGAMI. The table below displays the overall land, highways, and populations that are currently residing on land within the “tsunami zone”.
(Map 1)
A closer look at the area of Coos Bay, Oregon was conducted and areas of recommendation for a tsunami relief zone were determined. By calculating the ideal conditions on a scale from 1 to 10 (10 being the most ideal, 1 being the least), of the areas slope, nearness to but not within the tsunami zone, population density, and nearness to unscathed highways, we were able to map the most desired locations to place a tsunami relief shelter (See map 2 for Desired locations within Coos Bay area). The point starred on map 3 is an area with high population density, is on a highway that is out of the tsunami zone yet leads to the center of town, has a very low slope, and is close to but not within the tsunami zone. This location is ideal because of its close proximity to those affected by the tsunami, yet is far away enough for it to be a safe place. The Bi-Mart that is located within this ideal zone also contains a large parking lot where shelters could be installed if need be.
(Map2)
(Map3)
CONCLUSION:
The research conducted yielded satisfactory results in the fact that it built a successful model that can be implemented wherever tsunami relief zones need to be determined/mapped. Different weights for each characteristic in the model can be altered and edited in order to pertain more to the specific location of focus. The more spatial methods and research that are conducted such as this, the better understanding and preparedness communities will have in areas of natural disaster risk like the Oregon coast. By assessing the towns slope, population density, affected roads, and distance from the tsunami zone, we were able to map the most ideal locations to conduct tsunami relief in a time of despair and need for those affected.
Sources:
http://www.oregon.gov/DOGAMI/Pages/index.aspx
http://www.cityofseaside.us/emergency-preparedness/earthquake-and-tsunami-preparedness