Those who attended a “tsunami rally” in Arch Cape recently will meet again July 24 to discuss how they might be able to permanently store emergency supplies outside the tsunami inundation zone.

The meeting will run from 10 a.m. to noon in the Arch Cape fire station, 79729 U.S. Highway 101.

About 35 attended the rally June 28, filling the fire station to standing-room only. A similar rally isn’t expected to be conducted in Cannon Beach. The city’s emergency preparedness committee voted June 27 not to support a rally for fear it might take attention away from ongoing training that already is being conducted for local residents and business operators, said City Manager Rich Mays.

Those who came to the Arch Cape rally wanted to hear more about the new map released by the state Department of Geology and Mineral Industries showing where a “distant” and “local” tsunami might reach in Arch Cape.

The map isn’t much different than the previous map released in 2007, when research was done as a pilot project by state geology experts, said Peter Ovington, an outreach specialist for the geology department.

However, the new map focuses solely on Arch Cape, instead of including it as an accompaniment to Cannon Beach, as the previous map did.

The Arch Cape map shows assembly areas on the east end of Shannon Lane at Arcadia Beach State Recreation site, on the east end of Buena Vista Drive, at the parking lot of St. Peter the Fisherman Church, east of Walsh Lane, on Clatsop Lane, at Ray Brown Road and Cove Beach Road and at Ray Brown Road and Columbia Street.

Those evacuating a tsunami should meet at those assembly areas to wait for emergency personnel, Ovington said.

The Arch Cape map is one of 10 drawn for Clatsop County. Like the other maps drawn for other areas on the North Coast, it shows where the “worst case” tsunami would go, according to the latest research.

A distant tsunami, caused by an earthquake in Alaska, Japan or elsewhere on the Pacific Rim, could reach close to Carnahan and Pacific roads. In some areas, especially close to the Arch Cape tunnel, it would surge past Pacific Road and even beyond U.S. Highway 101.

On the south side of the tunnel, a distant tsunami could reach just west of Cove Beach Road and might even go to Ray Brown Road north of Clatsop Lane.

A local tsunami, caused by a Cascadia earthquake, would go past the highway nearly everywhere north of the tunnel. Waves could reach as high as 70 feet.

Major portions of Buena Vista Drive, Hemlock Lane, East Ocean Lane and East Shingle Mountain Lane would be inundated by a local tsunami.

South of the tunnel, a local tsunami would go beyond Ray Brown Road and up a significant portion of Clatsop Lane. It would inundate a significant amount of Cove Beach Road and go past the south end of Ray Brown Road.

State geology and tsunami scientists worked for four years to determine where previous tsunamis have occurred and how far they extended over the coast. The researchers were funded by a grant from the National Oceanic and Atmospheric Administration.

They worked with lidar technology, which uses sound waves to provide data on elevations. Lidar can also find where underground land slides have occurred, previously unknown faults and underground streambeds.

By taking core samples of the earth under the ocean and along the coast, researches also could determine how many tsunamis have occurred and where they landed.

In the past 10,000 years , 19 earthquakes have occurred in the Cascadia subduction zone, 50 to 75 miles offshore of the Pacific Coast, from northern California to southern British Columbia. Their magnitude has ranged from 8.7 – considered “small” – to 9.1 – an “extra-extra large.”

An “extra-extra large” earthquake occurred in 7,000 BC and again in 4,000 BC. The last Cascadia earthquake happened in January 1700, and that was a medium sized quake, said Ovington.

Cascadia earthquakes appear to occur every 300 to 500 years, and it has been 313 years since the last one, Ovington said.

The Oregon coast is a geologic “mirror image” of the Japanese coast, where an “extra-extra large” earthquake occurred two years ago, Ovington said. Among several lessons learned from that quake was that the resulting tsunami travels rapidly up river channels and sloughs. Seawalls and forests didn’t hold back the water, which can travel in the middle of the ocean at 500 mph, but slows down somewhat when it reaches shore.

Lianne Thompson, who lives in the Arch Cape area and works as a community organizer for DOGAMI, said people can stop worrying by preparing themselves for the event.

“Take little bites of being prepared consistently and persistently,” she said.

In addition to preparing a “go bag” with essential emergency supplies, people should walk the evacuation routes at their homes and along the rest of the coast. Regular hikes on the trails results in “tissue memory” that could kick in automatically if a tsunami is approaching, especially in the middle of the night, Thompson said.

Taking community emergency response training, studying the recommendations of the American Red Cross or obtaining a ham radio operator’s license are other ways to prepare, she said.

Those attending the rally expressed concern about being isolated for days or weeks after a tsunami or other natural disaster, such as the “Great Coastal Gale” in 2007. Several said they wanted to find out more about the “cache container” program that Cannon Beach began last year.

Cannon Beach bought two 8-foot by 20-foot shipping containers for residents and others to store barrels filled with personal supplies. The containers are on city-owned property just off of Elk Creek Road, east of the highway.

The city plans to open two other container sites in Tolovana Park and on the north side of town in October.

Rich Mays told the group he would discuss the city’s program at the Arch Cape meeting on July 24.

Ovington said the rally had “probably the best outcome” of any of the four rallies conducted on the North Coast.

Clatsop County Commissioner and Arch Cape resident Debra Birkby said she knew why.

“I think the high isolation factor is what’s driving it,” Birkby said.


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