PACIFIC COUNTY — What happens in the minutes and hours after the Cascadia Subduction Zone ruptures along the state’s outer coast is shown in alarming new simulations released Aug. 26 by geologists at the Washington State Department of Natural Resources.
These scientific models in the form of free online videos provide a scary preview of towering ripples in the ocean coming ashore one after another following a magnitude 9.0 earthquake. Yet they also offer hope, in form of more time to escape for some. And they build a case for constructing a series of evacuation towers in vulnerable areas.
“Tsunamis have struck Washington’s coast many times over our geologic history. It’s a question of when, not if, the next one will hit,” Commissioner of Public Lands Hilary Franz said. “These videos are designed to give the communities that would be most impacted by tsunamis a visualization of what areas are likely to face the most damage so they can make sure their residents, businesses and institutions are secure and resilient.”
The latest simulations zero in on the Long Beach Peninsula and other areas of Pacific County, along with Grays Harbor.
Washington residents are accustomed to expecting a series of tsunamis after a Cascadia Subduction Zone (CSZ) rupture. The most recent occurred in January 1700, a fact established by University of Washington Geologist Brian Atwater about 25 years ago, partly based on evidence found in Pacific County. Followup studies found these megathrust quakes happen every 300 to 600 years. There have been about 40 earthquakes on the subduction zone in the last 10,000 years.
Still, our evolving understanding of this threat holds surprises, according to the DNR simulation and Pacific County Emergency Management Agency Director Scott McDougall.
“We know the [initial] wave will reach the Long Beach area and outer coast in 20 minutes,” Director McDougall stated. “It is going to go up the river to Chinook in 30 minutes, and it takes a bit longer to back around into Baker Bay near Ilwaco in about 40 minutes. Tokeland’s about 35 minutes. South Bend is about 90 minutes, and Bay Center is about 40 minutes.”
McDougall continued, “those waves are going to continue to be generated for about 12 hours. The first wave is not going to be the highest. If you watch the simulation, you will see that the higher waves come later in the process.”
DNR also provided some information on maximum wave amplitudes and expected inundation. The area near Klipsan Beach saw the highest water level.
“At North Cove about 27 feet,” McDougall said. “At Ocean Park about 36 feet. At Long Beach, about 36 feet. It also provided some inundation depths for previously dry land. Pacific Pines State Park in Ocean Park, about 42 feet. About 10 feet at South Bend High School.”
McDougall continued, “there was one that surprised me at the shoreline beyond 201st Lane on the peninsula — kind of the Klipsan Beach area. There is some shoreline there that could see the water get as high as 53 feet.”
While DNR advises that the videos are not designed to aid “site-specific decision-making,” they take many factors into account to provide the best estimate of tsunami flooding along the coast. Things like the tide cycle and undersea terrain will affect exactly what happens.
It’s also important to note that although the tsunamis generate the most attention, the megathrust quake that sets them off will be destructive in its own right, dwarfing anything experienced in the Pacific Northwest in generations. Even cities far from the CSZ like Seattle and Portland are expected to suffer serious damage.
There might be more time
The simulation does show that some residents might have something they didn’t believe they had before — time. Due to the event’s length, the landscape through which the seawater travels and when levels rise has become more transparent. Maximum inundation is expected to take nearly four to five hours after the earthquake.
“Even the people who live within the area of inundation may have time to get to that high ground area,” McDougall said. “Every step inward you take, every step upward you take puts you closer to safety.”
Away from the beaches, Raymond, South Bend, and locations further up the Willapa River will mostly deal with escapable flooding.
“It is going to be limited to the riverbank area,” McDougall said. “It isn’t going to be this massive wall of water. I think that there were people who thought this massive wall of water would come in and wash away everything. The bulk of Raymond, South Bend and Bay Center won’t be affected.” McDougall said this is due primarily to Willapa Bay absorbing a lot of the wave and surge energy.
Dire need for vertical evacuation towers
According to McDougall, some pedestrian evacuation routes could require upwards of 110 minutes to reach high ground. This means some peninsula residents will have few options as depicted in the DNR simulation. The only good solution, according to McDougall and other agencies, is construction of a system of vertical evacuation towers.
Determining how many is mainly dependent seasonal fluctuations in the number of people on the peninsula. In the winter months, when tourism isn’t as busy, the peninsula’s population is around 10,000. Over significant summer holidays like July 4 and Labor Day, there are several times more people present. The planning aims for a capacity to elevate 50,000 to 75,000 out of harm’s way.
“We figure [we need] anywhere from 23-29 vertical evacuation towers,” McDougall said. “The pricing on that is going to depend on the type of tower that is selected. We are talking roughly $3 million a structure.” The overall cost is estimated to be between $69 million and $87 million, depending on how many towers are built.
Broad-based community buy-in
Money is the major roadblock for building any vertical evacuation tower, McDougall said. This is particularly true of grants that require a partial local match. His solution is to appeal to the private and public sectors for balanced help.
“Would I like to see public money used to build these structures? Absolutely,” McDougall said. “But I think the private sector is going to have to start asking themselves ‘Do we want to protect the people staying in our facilities, do we want to protect our employees, do we want to look at developing privately funded vertical evacuation structures?’”
He continued, “it is going to have to be a public and private [sector] partnership. I don’t expect the private sector to pick up all the costs of this. I also don’t believe it’s reasonable to expect that the public sector will pay off the costs of this as well.”
McDougall expects that Federal Emergency Management Agency grants could pay approximately 75% of the costs for the vertical evacuation towers. This would leave the county to somehow pay the remaining 25% match, estimated to be at least $17.25 million in total, or $750,000 per tower.
“I will do everything I can to empower this kind of construction,” McDougall said. “But ultimately [these] are community-level decisions and I can only drive so hard to make them come to fruition. I’m not trying to pass the buck, but I can’t drive these things by myself. So there has to be broad-based community buy-in for these things to happen.”
There has been some talk at the capitol in Olympia that the legislature has been looking at ways to assist with funding, but the covid-19 outbreak has thrown all financial planning into disarray.
Building consensus and agreement
Whenever a post is published on Facebook regarding a coastal earthquake and its potential destruction, almost like clockwork comments of “I’ll just kiss my butt goodbye” or “Ain’t nothing I can do, so I’ll just die” flood the posting. These pessimistic reactions are something McDougall has long contested.
“There is everything we can do,” McDougall said. “It could potentially happen tomorrow, and I get that, but we also potentially could see it happen in 50 years. Can we prepare for something that is going to happen tomorrow? Unlikely. Can we prepare for something that might be 50 years away? Absolutely.”
He continued, “Unfortunately for a lot of people who live in [these communities], something that happens 50 years from now is not their concern, and there is not a sense of urgency. It’s a very complex situation. We are going to have a hard time building consensus and agreement, but I will do whatever I can do to build that.”
See tinyurl.com/WA-Tsunami-Simulations to see the new videos.