To assess how an earthquake might alter the functions of the Bonneville Dam as a site of hydropower generation, recreation, and fish rehabilitation, we conducted the following methods.
- Geologic Hazard Mapping
We situated the Bonneville Dam within the various zones of Cascadia earthquake hazards. For the Oregon data, we used the Oregon Department of Geology and Mineral Industries Statewide Hazard View portal for each of these layers. For the Washington data, we used the Washington State Department of Natural Resources Geologic Hazard Maps. For Washington, we specifically examined the Washington State Seismic Hazards Catalog for the Cascadia (not the Cascadia North) scenario. Using the interactive interface, we examined Cascadia event shaking predictions, landslide inventory, and soil liquefaction for the river banks adjacent to the Bonneville Dam on either side of the Columbia River. As well, we mapped the Cascadia Subduction Zone slab depth across the Pacific Northwest to illustrate the extent of the zone and its increasing depth inland
- Chain of Events Analysis
In order to estimate the management response to an earthquake, we created event trees from information found in “Selecting Analytic Tools for Concrete Dams Address Key Events Along Potential Failure Mode Paths.” The event trees show the decisions that need to be made, in what order they will be made, and the potential outcome of each decision. Event trees outline the decisions that are made following an event, in this case a M9.0 earthquake with an epicenter off the coast of Oregon or Washington. Using the emergency and evacuation information collected in our case studies and background research as well as specific procedural information about the Bonneville Dam (procured from Amy Echols, Deputy Chief, Public Affairs of the U.S. Army Corps of Engineers), we made event trees for Bonneville hydropower, recreation, and fish safety.
Event trees are usually accompanied by a quantitative element to show the probability of the likelihood of a decision. Because of limited information and little transparency in the Bonneville Dam emergency systems, we were not able to create these probabilities.
- Interviews
We knew that it would be necessary to talk to integral staff and administration at the Bonneville Dam in order to further understand how the dam would alter in the event of the earthquake. We called the Emergency Operations Center, the Bonneville Power Administration, and the Oregon Office of Emergency Management. After calling many numbers, we were placed in contact with Amy Echols, Deputy Chief, Public Affairs of the U.S. Army Corps of Engineers. We had a long over-the-phone interview with Amy that aided us greatly in the execution of our research.
We also reached out to Professor Elizabeth Safran, who directed us to important background geologic information which can be found in our situated context.