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Southern Exposure: Nature wins in a landslide

By R.J. Marx

The Daily Astorian

Published on December 12, 2016 12:01AM

Oregon Department of Geology and Mineral Industries In this state map, darker area indicate “very

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U.S. Rep. Suzanne Bonamici visited Circle Creek and Boneyard Ridge in late November to see the floodplain restoration project.

Lyra Fontaine/EO Media Group

U.S. Rep. Suzanne Bonamici visited Circle Creek and Boneyard Ridge in late November to see the floodplain restoration project.

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SEASIDE — We spend so much time responding to the extraordinary demands of tsunami prep that we don’t consider the more traditional threats. After all, tsunamis only happen every 244 years.

Seaside Fire and Rescue Chief Joey Daniels told me that while training for tsunamis and mega-quakes was important, the day-to-day operations of the department focused on more common occurrences like  landslides and floods.

City Council President Don Johnson urged residents this fall to not only consider tsunamis, but remember storms that come “even more frequently.”

“Prepare for the Big One, but be ready for the other ones coming through,” Johnson said this fall.

I’m still haunted by the call I received about one year ago from Astoria’s Kari Stedman, who with her aunt, Marilyn Keno, was caught in rising waters in front of Dennis’ 7 Dee’s last year. As soon as they hit the water, the engine stalled and water began filling the vehicle. Stedman escaped by climbing out a window and onto the roof of the Ford Taurus before wading through two feet of water to free Keno. Both were treated for hypothermia and post-traumatic stress.

I never drive past that spot in the rain without thinking about it.


The flood of ’96


A heavy rain can still shut down a major road like U.S. Highway 101, and it did so on Thanksgiving Day.

Oregon’s Statewide Planning Goal 7 states stream and river crossings must be designed to allow for clearance above flood levels and flood-prone roads and bridges identified and mapped.

Nature doesn’t always play along.

While Seaside’s hills are underlain by mudstone bedrock or volcanic rock, which rarely has landslides, heavy rains can trigger debris and mud flows like those witnessed in Seaside in February 1996. “The Great Flood of ’96” forced the evacuation of 22,000 people in Oregon and 7,000 in Washington. Snow, freezing temperatures and then a subtropical jet stream flooded saturated ground.

A bridge collapse south of U.S. Highway 26 near the Nehalem River left families trapped after a 40-foot concrete center span was washed away by a massive logjam led to a bridge collapse.

It took eight hours for rescuers to hike into the hills to get around mudslides and reach trapped families. Roads were marked to signal planes. One home was lost to fire after power came on. Standing water, wet building materials and furnishings led to dire warnings from the state health department.

“People are just beginning to come out of their initial shock,” the county’s former emergency manager Ed Hauer told the Seaside Signal two weeks after the floods.

For families who lost homes and belongings, “They don’t know where to go from here,” Hauer said.

Some roads remained underwater for days, while slides and deterioration closed many smaller roads.

At the storm’s peak, 167 roads closed throughout the state. Northwest Oregon highways faced more than $44 million in damages, and drew rescue support from the National Guard, Coast Guard and local responders.

Car engines, refrigerators and major appliances were carried off in the floodwaters.

“Even my false teeth floated away,” Hamlet’s Larry Sage told the Signal.


Making strides


Landslides are ranked as one of the most significant natural hazards in the state, causing millions of dollars in damage annually, geologist Brad Avy wrote in a 2016 report from the Oregon Department of Geology and Mineral Industries, the state agency known as DOGAMI.

While DOGAMI has made “great strides” in mapping landslides, forecasters still can’t tell us the possibility a slide will occur or its intensity.

Not all hillsides are slide prone. But if you see ground movement, evacuate immediately.

“It may start very slowly and be hard to detect,” said Althea Rizzo, geologic hazards coordinator for the state Office of Emergency Management said. “Know the routes to safe ground.”

Better and more accurate maps have led to identification of previously unknown slides. “It will take time to make the necessary preparations,” Rizzo said. “It may be necessary to harden routes against slides.”

Think about how much worse it would have been if North Coast Land Conservancy hadn’t embarked on its Circle Creek floodplain restoration project in 2013. To restore the floodplain, the land conservancy and its partners — including Clatsop County and the Oregon Department of Transportation — excavated sections of a berm that was built along the Necanicum River, leaving certain areas to maintain older trees.

Lyra Fontaine reported that the berm removal allowed water from the Necanicum River to naturally flood the Circle Creek floodplain, instead of the adjacent Highway 101. After the first year of the project, analysis showed that the restoration prevented road closure at least three times that winter. Since the 2013 berm removal, “we’ve had significantly less flooding both in frequency and severity,” the Oregon Department of Transportation reported.

When the highway was closed elsewhere during last winter’s big rainstorm, it was passable by Circle Creek.


The forecast


So far, this year’s flood watches and landslide threats shut down trails in the state’s Coast Range, the central and south Willamette Valley and the south Washington coast.

“People, structures and roads located below steep slopes in canyons and near the mouths of canyons may be at serious risk,” DOGAMI Communication Director Ali Ryan Hansen said in advance of November’s Thanksgiving storms.

Dangerous places include canyon bottoms, stream channels, bases of steep hillsides and road cuts or other areas where slopes of hills have been excavated or over-steepened. Be especially careful in places where slides or debris flows have occurred in the past.

As I write this, Ecola State Park and Indian Beach Trail are closed after heavy rains undid temporary repairs to Indian Beach Trail.

Visitors to Saddle Mountain State Natural Area are forewarned by the Oregon Recreation and Parks Department that winter weather may cause the road to become impassable. “Use caution and always let someone know where you are going,” they advise.

In 2005, the same department forecast a 25-year period of La Niña, which means that the Oregon Coast is entering a period with more extreme storms and likely greater impacts from coastal erosion.

That was 11 years ago, with about 14 more to come.

But who’s counting?

R.J. Marx is The Daily Astorian’s South County reporter and editor of the Seaside Signal and Cannon Beach Gazette.



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