Pacific Coast Towns Rethink Tsunami ‘Vertical’ Evacuation Options

By | August 29, 2011

When the next devastating earthquake strikes off the Northwest coast, it is expected to send a tsunami so fast that it could leave coastal communities with perhaps 20 minutes to escape the surge of water.

For small towns like Long Beach, which sits on a long spit just above sea level, the wave’s speed will leave minimal options for getting away: People can literally run for the hills, but the first elevated areas are more than a mile to the east, difficult to reach and likely unknown to tourists. Or people can try to drive, cramming roads that could be ravaged by the quake and follow the ubiquitous blue evacuation signs — assuming they still exist.

“If you have a major earthquake, God only knows which way those signs are going to point,” said Long Beach city administrator Gene Miles.

Recognizing the ominous options they currently face and the Japan tsunami that displayed the potential destruction, some areas along the Northwest coast are working on plans to build massive hills or structures that could be used to escape the tsunami’s reach. The so-called vertical evacuation sites have been adopted in parts of Japan but have never been pursued in the United States.

Communities in Washington, working with state officials and university researchers, have identified a series of about 40 potential evacuation sites and are now working on more for areas on the Olympic Peninsula. Officials in Bay City, Ore., have discussed the possibility of a site in a low-lying area. Crescent City, Calif., plans to use an existing assisted living facility — the tallest building in town — to shelter people who can’t get to higher ground in the event of a sudden tsunami.

For those looking at building new sites, here’s one glaring problem: The ideas are expensive. Miles estimates that his plan to build a 40-foot berm — about as high as the tallest buildings in town — would cost $250,000. The reinforced earthen mound would sit near a school and close to the city center, allowing people to scale the hill and wait out the destruction on top.

Only 1,392 people live in the town, although it fills with vacationers during the summer.

Costs were a factor in the decision by Cannon Beach, Ore., officials to back away from a proposal to rebuild its city hall to withstand a tsunami and refuge people in upper levels. Now officials there are in early discussions about the possibility of creating some sort of evacuation platform, said Mayor Mike Morgan.

Scientists believe it is only a matter of time before the next mega-quake strikes at the Cascadia Subduction Zone just off the Northwest coast. Those quakes, which can send tsunamis straight onto shore, strike every 400 to 500 years _ with the last one happening about 300 years ago.

The earthquake would likely last about five minutes and trigger perhaps six feet of land subsidence along the coast. Rushing in from just 50 miles offshore, the tsunami could arrive within 20 minutes.

Oregon’s Department of Geology is in the process of reassessing the potential devastation that a tsunami could inflict on the coast. New maps recently produced for the small city of Bandon illustrate potential damage from the surge.

Some people who would be on the waterfront in Bandon would have nearly a mile to travel to reach high enough terrain. And, since the tsunami’s inundation would grow deeper as it crashes into higher ground, scientists project that evacuees in certain locations may need to get to an area 100 feet above sea level to be safe.

Officials in Bandon still believe the hillsides are the greatest refuge and are not looking at building any vertical structures. That’s the case in many communities along the Oregon coast that have hilly, amphitheater-style backdrop that can be used for escape.

Ian Madin, the chief scientist at the Oregon Department of Geology, said the vertical evacuation sites could be useful in some communities but that steep terrain makes them unnecessary in many areas. He cautioned that the Japan earthquake and tsunami should not trigger a panic that leads to pointless spending on costly projects.

“You’re not going to solve the problem in six months, and the odds are that you will have decades to prepare,” Madin said. “I hate to see people stampeded into rash decisions.”

Washington state also has a rugged coastline, but it includes more lowlands that are vulnerable. That’s part of the reason behind Project Safe Haven, a coordinated analysis of evacuations between federal, state, local and tribal officials.

Leaders behind the effort believe several population areas along the Washington coast _ including parts of South Beach, Westport and the Tokeland peninsula _ are not close enough to natural evacuation spots.

John Schelling, who leads the earthquake program at the Washington Emergency Management Division, said the towers, berms and buildings under consideration each have pros and cons _ from costs to accessibility to usability during regular living. But he said the plans that communities are adopting will help set the stage for making a funding pitch in the future.

Some of the early stages of the planning came after the 2004 Indian Ocean tsunami. Schelling said this year’s disaster brought a renewed focus and helped to engage citizens.

“The Japan event really reinvigorated tsunami planning and preparedness efforts,” Schelling said.

Topics Catastrophe Natural Disasters Washington Oregon Earthquake Japan

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