Seaside becomes tsunami test model

Story Posted: Fri, Aug 10, 2007

OSU laboratory to study effects of big waves hitting North Coast community

By PAMELA ROBEL
The Daily Astorian

CORVALLIS - Seaside has been reduced to blue, red and yellow buildings at the O.H. Hinsdale Wave Research Laboratory at Oregon State University.

The lab has constructed a small model of downtown Seaside to study the effects of a tsunami. Currently, the effects of tsunami waves on the model of Seaside are merely observations since the lab is conducting two other studies in the same pool. At the December conclusion of a study examining how tsunamis shift sand along coastlines, being conducted by a Princeton University researcher, in December, the miniature Seaside will take front-and-center.

When that changeover occurs researchers will begin a project that is likely to continue for years to come and will encompass everything from numerical models to wave heights, to the amount of water that will remain after a significant event, to possible places of safety. The large-scale project will cover a number of items and scenarios but will require patience from the residents of Seaside as well as that of the researchers, because conclusions will be difficult to come to.

The project

Solomon Yim, a professor of Civil Engineering with expertise in Structural Engineering and Hydrodynamics and a part of the Network for Earthquake Engineering Simulation (NEES), is the primary investigator on the Seaside project. He says he is looking forward to beginning work on the tsunami project.

"It's an interesting project," said Yim. "Right now the work is still very preliminary."

The lab was approached by a Canadian production company interested in making a television show to study the effects of a tsunami on the Canadian coast. O.H. Hinsdale Wave Research Laboratory Director Dan Cox suggested focusing on a city in Oregon because OSU is a state university.

Seaside was chosen rather than other Oregon coastal cities for a few reasons. A report had been released with wave heights for a 500-year event in the Seaside area and the terrain of Seaside is relatively flat and easy to reproduce in model form.

"The models are expensive to create and so we were looking for underlying bathymetry that would be beneficial for other researchers," said Cox.

Cox also said that the civil infrastructure of Seaside, as well as the city's tsunami awareness, made it a desirable location to study. "Seaside is sort of the model community for preparedness," said Cox.

According to Yim, the efforts of the lab are focused upon the work of a Princeton researcher at the moment and while the sand research is conducted, those dedicated to the Seaside project observe the way the generated waves affect the model in the wave pool.

The model of Seaside takes into account some of the large buildings - color-coded in blue - along the shore, the Prom, the "single-story shops" in downtown, represented by red blocks, idealized two-story residential houses painted yellow and the topography of the area, including the downward slope of land away from the beach. All of the macro-detail included in the current model gives researchers an opportunity to examine the big picture before narrowing their focus.

"The Seaside beach was easy to model," said Yim. "The topography is interesting with the hotels, residential houses and 6-foot seawall. You don't see this elsewhere."

Once the Seaside becomes the focus of the pool, the lab will "examine almost all possibilities" from "realistic waves and scenarios" to "tsunami 'proofing'" techniques. The Seaside footprint will be kept in the pool for quite some time, according to Yim, and will be developed in more detail as time goes on.

"It will be a very dynamic project," said Yim. "I think it will take a minimum of five years and, in terms of long-term research, could be researched for up to 20 years."

As the primary investigator of the project, Yim says he has set personal goals for himself based on wanting to verify his own numerical models of tsunamis but, even in the midst of this, he is trying to keep an open mind because of the similarities between other coastal cities and Seaside. Yim is hoping that other researchers from around the nation and world will descend upon the Seaside project and apply what is learned to those other cities similar to Seaside.

"This is just the beginning," said Yim.

Some of those other researchers may include a group of students participating in Research Experience for Undergraduates through the University of Notre Dame. The students from the University of Arizona, Whitman College, the University of Michigan, Brown University, Notre Dame and the University of Pittsburgh, along with Program Director Tracy Kijewski-Correa were in Seaside Aug. 2 to study its geology.

"The characteristics of Seaside are similar to Thailand," said Kijewski-Correa. "The advantage Seaside has over Thailand is alarms."

The geology studies of Seaside included core soil samples to measure how often tsunamis occur in the area. Along with the research in Seaside, the group flew to Thailand Aug. 3 to conduct more research.

"Clearly, I think, we need to realize we're at risk and we need to get over the 'it's them, not us' mentality," said Kijewski-Correa.

The wave maker

Pseudo-tsunamis are being produced by the largest wave maker in the world.

These waves are generated by a series of 29 paddles that can be set to move as one single wall or as individual sections. The movements of the paddles can be manipulated to create four distinct wave types: Regular, irregular, tsunami and multidirectional. There is also the option for a "user defined" wave based upon a researcher's aim. There are also considerations for wave sets, with the ability to create multiple waves with 0.5 seconds to 10 seconds between each wave.

"The lab's hallmark is the precision and repeatability of the wave-maker," said Cox.

Each paddle is pushed by a compact 20-horsepower motor that can create a wave that rolls through the 160-foot long pool at 6.6 feet per second. There is consistently 3.3 feet of water in the pool as a basis for the generation of waves.

The "idealized waves" can be observed from above, thanks to a catwalk spanning the width of the pool that can be moved the length of the pool.

Construction of the pool and wave maker began in 2000 and were finished in 2003 with the help of a $5 million grant from the National Science Foundation and the NEES to create a tsunami research basin. With the funding of that grant and others, the pool will continue to research tsunamis until at least 2014.

Along with visual observations of the waves in the pool, there is also numerical and computer modeling being employed to study the speeds, depths and other aspects of tsunamis.

"It's a hybrid of numerical and physical modeling," said Cox.

According to Cox, the lab is trying to address several issues regarding tsunamis in the Cascadia Subduction Zone, the zone in which the North Coast is located. The zone begins roughly 70 miles offshore and extends to below the Cascade Mountains and spans from southern British Columbia, Canada, to Northern California.

"The good news is as compared to the San Andres Fault this is a deeper fault and (the earthquake) lasts for about five minutes," said Pat Corcoran, an outreach specialist specializing in coastal natural hazards with the OSU extension office, in explanation of the Cascadia Subduction Zone. "The earthquake is relatively easy on people but extremely hard on buildings. The immediate danger after the earthquake will be fires."