Oregon City’s Quake Simulation Study Shows Road, Bridge Dangers

Researchers at Oregon State University say bridges and roads in the northwestern resort city of Seaside should be prioritized for improvement after a simulation discovered they would have higher mortality rates in an earthquake and tsunami.

Researchers found that the bridge on Broadway Street over Neawanna Creek would result in the most fatalities, The Daily Astorian reported .

“The real issue with Broadway is there is really nowhere else to go. But by the time you get to that bridge you have very little time to do anything else,” said Dan Cox, an Oregon State civil engineer who created the model with Haizhong Wang. “It’s a combination of what options you have and how much time you have to do it.”

The two bridges on 12th Street, the bridge on Sundquist Road and Ocean Vista Drive in the Cove were also flagged for improvement.

The bridges and roads are high priorities to retrofit because of relative proximity to areas where people live and gather, making them some of the most populated evacuation routes, researchers said. They also fall in the path of where tsunami inundation would most likely occur.

Thousands of scenarios were run through the model based on the starting points of 4,500 imaginary people, distributed to resemble where most people would be on a busy, summer day such as on the beach or shopping downtown.

The goal was to provide Seaside with a simulation to support decision-making when it comes to addressing the city’s infrastructure needs, Wang said.

The study also recommended investing resources in building highly resistant vertical structures inside the inundation zone as a more economical choice than spending greater amounts of resources retrofitting multiple bridges.

“After a certain point, your return on investment might not be to fix more bridges, but take those resources and put it toward a vertical evacuation structure,” Cox said. “It might not even be infrastructure. You could possibly use resources in more education, et cetera.”

City Councilor Tom Horning said his ultimate goal following the simulation is to persuade the city to develop a plan that retrofits every bridge.

“Seaside, because of geographic layout and rivers, is one of the most challenging communities on the coast,” Horning said, in reference to evacuating in a tsunami. “There’s a strategy in focusing on population concentrations and prioritizing based on that. But every bridge needs to be done. We don’t want to find ourselves in a Hurricane Katrina situation, where we knew there was something that could be done but didn’t do it.”