Part 4—Analyze Tsunami Risk for Coastal Oregon

Step 1 – Launch AEJEE and Adjust Layers

  1. Launch AEJEE by double-clicking its icon on your desktop or by clicking its icon in the dock (Mac) or Launch Bar (Win).
  2. Choose File > Open..., and navigate to the file, TsunamiRunup_Part3.axl, that you saved at the end of Part 3. Select it and then click Open.

  3. Move the new layer, OR Coast contour 5m, in-between the Tsunami Inundation Area and Plate Boundary Types layers.

Step 2 – Turn on the Oregon Tsunami Events and Investigate the Relationship between Coastlines and Tsunamis

In this step, you will investigate whether tsunami run-up events occur more frequently on steeply-sloped or more gradual, beach-like, shorelines.

  1. Turn on the Tsunami RunUp layer and investigate the relationship between coastal topography and tsunami events. Note: you may decide that you need to change the color of the tsunami run-up events for more contrast; magenta is a good choice.
  2. Use the Pan pan tool and Zoom Zoom in / Zoom Out tools to move around the map. When you are done exploring, you should be able to describe the types of shorelines that seem more tsunami-prone.
  3. Zoom back to the extent of the state of Oregon.
    Note: A quick way to accomplish this is to turn on and make active the Oregon Border layer and click the Zoom to Active Layer Zoom to Full Extent layer button.

Step 3 – Query the Oregon Coast Contour Layer to Locate Populated Areas that are at Risk

Where are the most vulnerable towns in Oregon? First, find the populated places then compare those places to the coastal contours.
  1. Turn on and make active the Oregon Place Names layer.
  2. Click the Query Builder button Query builder button .
  3. In the Query Builder window, find the places whose designation (DESIG) is populated place (ppl). You can either make selections in the Select a field: and Values: lists or manually entering this query statement: (DESIG = 'ppl' ) in the query field. Click Execute. Note: Since there are over 100 results, it is not necessary to display the query results in the query box.
  4. Take a moment to observe the pattern of population in Oregon, shown as yellow dots on this map. Are there more populated areas by the coast or inland? What other questions do these population patterns raise?
  5. Next, locate the areas of the Oregon coast that are at a low elevation level, and therefore the most tsunami-prone.
    • Turn on and make active the OR Coast contour 5m layer.
    • Click the Query Builder button Query builder button .
    • Select a field: "elevation" whose values are greater than or equal to 0, and less than or equal to 25 by manually typing this equation into the query field (elevation >= 0 and elevation
    • Click Execute.
  6. Once the selection is complete, return to the map. You will need to zoom, pan, and adjust layers to investigate this selection more carefully.
  7. Use the Identify tool identify button to learn the height above sea level of each of the selected contour lines. This tool is a quick way to gather information from an Active layer. Make the Oregon Coast contour 5m layer active, then select the Identify tool and click on the contour lines that are highlighted in yellow. The line will flash briefly and an Identify Results window will open.

  8. In general, many beachfront towns seem vulnerable to a tsunami in this range (0-25 meters).
  9. Turn off the Oregon Place Names layer.

Step 4 – Turn on the Tsunami Inundation Line Layer and Compare it with the 20-meter Tsunami Contour

Three measurements are important when preparing for a tsunami: the run-up refers to the vertical height of a wave as it comes ashore; the wave height measures the vertical height of the wave before it comes onshore; and the inundation distance is the measured horizontal distance a tsunami stretches onshore from the coastal edge.

In this case, the Tsunami Inundation Area is a calculated height above sea-level. This line takes into account both the topography and the bathymetry of a region. The line highlights areas that could potentially be flooded by a major tsunami. Scientists from the Oregon Department of Geology drew the boundary line in 1995. It is used in coastal development decisions, such as where to build a hospital or other important public building.

  1. Turn on the Tsunami Inundation Area layer and compare it with the contour lines that you highlighted in the last step.
  2. How do the contour lines compare to the Tsunami Inundation Area?
  3. Turn off the OR Coast Contour 5m and Tsunami Inundation Area layers.

Step 5 – Locate the Town of Seaside, Oregon and use the Query Builder to find Tillamook Head

Recall that a large tsunami devastated the nearby town of Cannon Beach in March 1964. Seaside is the focus of our Case Study. Both of these towns are located near Tillamook Head. According to scientific research, one of the reasons that Seaside is at high risk of tsunami inundation is due to Tillamook Head, a large rock outcropping located south of the city. In the event of a tsunami, waves would pile up against this large outcrop concentrating their energy on Seaside.

  1. Begin by turning on the Seaside Schools layer to locate the town of Seaside. Zoom into Northwest Oregon. Hint: it is easier to see the town if you turn off the OR Coast Contour 5m layer.
  2. Where exactly is Tillamook Head? Use the Query Builder to locate this topographic feature along the Oregon coast.

  3. Turn on and make active the Oregon Place Names layer. This layer contains names and locations of over 41,000 features in Oregon. By querying this dataset, you can find both natural and man-made locations. (Hint when querying: be patient, as this is a large dataset for AEJEE to handle.)
  4. Begin by changing the symbol of the Oregon Place Names layer to green squares in the Properties of the layer.
  5. In the Query Builder window type in the query statement: (NAME = 'Tillamook Head') and click Execute. AEJEE will search the database and locate the feature. Close the query builder window to see Tillamook Head displayed on the map. Zoom in to the area of Tillamook Head and Seaside. Turn the OR Coast contour 5m layer on again. Seaside Schools, Tsunami Run-up Events, and Oregon Coast Contour 5m are displayed on the map. Notice that there have been several tsunami run-up events in this area.

    Note: The map below has been zoomed in and some layers have been turned off to simplify the map. To turn off the selections that you made earlier, select the OR Coast contour 5m layer and click the Clear all Selections Clear Selections button.

    tillamook head highlighted

Step 6 – Save your Project and Quit AEJEE

  1. Save your project with a new name, such as "Tsunami_runup_Part4".
  2. Quit AEJEE.