July 26, 2005

Reaching Safe Ground

Continued from page 1

By David Wolman

Although the tsunami simulator emphasizes communications, there's no limit to the layers of data it can simulate. It could include architectural designs that predict if structures will stand or be damaged, what bridges could survive a wave impact, the importance of the time of day, or even the likelihood that people will hear a warning, but not heed it. Furthermore, the model incorporates not only vehicular movements but also foot traffic.

"This is something they're really focusing on in Japan: getting beyond dependence on automobiles for evacuation," says Crawford. In geographically similar areas, such as the narrow, low-lying peninsula of Long Beach, Washington, this approach would be critical, as well, since a tsunami there would likely take out major roads and bridges.

In fact, Crawford says officials in Washington, Oregon, and northern California stand to benefit greatly from such a social science model. For instance, it has already helped Crawford and other planners figure out where to locate safe "assembly areas" that evacuees could quickly reach by foot.

"What this computer simulation does is allow us to take inundation maps and models showing wave arrivals, combine them with information about infrastructure, and then take into account the social science as well," says Crawford. "Running these models gives a fairly close prediction of whether we can evacuate our people in time and what the collateral damage would be."

The simulations are not perfect, admits co-researcher Yeh: "We still can't simulate flow of details like the flow of water between just a few houses or by a certain road. We're also trying to make a casualties model more accurate."

Further, modeling human behavior -- especially during a natural disaster -- requires some assumptions that can limit the accuracy of any model. "We hear from the social scientists that on 9/11, there was spontaneous organization of evacuation across the Hudson [River]," says Yeh. "This is remarkable because the assumption is that people would be acting chaotically. Yet it looked as if they had done practice drills."

In the case of a tsunami, it's possible some people will still head to the beach out of curiosity, despite knowing about the danger. "How can we predict this stuff? It's not simple," says Yeh. "At least these simulations can give some quantifiable ideas about what may happen."