Storms have yet to cause a major landslide on U.S. Highway 101 this winter, but it is the time of year when road crews expect to see some damage.

If you’re new to the state Department of Transportation’s district office in Astoria and low on the totem pole, it’s likely you’ll pull night duty this winter, and one of the night shift’s primary tasks is to patrol the coastal highway, visiting trouble spots and sweeping fallen rock out of the roadway.

The highway, like U.S. Highway 30 or U.S. Highway 26 that cut through dynamic landscapes, is constantly at the mercy of the weather. Small rockfalls and landslides are chronic in some spots.

“It’s very unpredictable for the most part, but what we can predict is that they do happen,” said Lou Torres, a spokesman for the Department of Transportation.

Highway 101 — or the Oregon Coast Highway — was built in the 1920s in response to growing demand for a highway along the coast. The roadway piggybacked off an early need for emergency preparedness after World War I.

But the highway is caught in a network of ongoing slides related to erosion by high wind and waves and heavy rainfall during winter storms in January and February.

Development — such as the construction of the highway itself — has, in some places, exacerbated the natural movement of land. A portion of Highway 101 in Curry County is periodically closed by landslides, issues that began in 1938 when the road was constructed, according to the Oregon Department of Geology and Mineral Industries.

Landslides

Last April, a landslide sent about five dump trucks-worth of material across Highway 101 near Hug Point several miles south of Cannon Beach. The slide closed the highway for several hours. Though it happened in the middle of the day, no injuries or accidents were reported.

In fact, injuries from rock and landslides on Highway 101 are rare, as far as state officials are aware. Certainly, though, slides have caused serious damage to vehicles, said Mark Buffington, manager for the Department of Transportation’s office in Astoria.

In some places in Clatsop County, the highway carves between hillsides. Motorists drive through areas where a rock wall looms on one side and a sloped outcropping rises and falls on the other. This method of construction left certain spots open to landslides, mudslides and rockfall.

There’s a 10-mile stretch in the southern portion of the county and farther south, closer to Tillamook, where crews are constantly picking up rock or moving mud.

“As long as we have what we have now … we’ll always deal with that,” Torres said. “Between gravity and the intense rainfall that we get, when you add that together, you’ll always have a problem.”

In general, mitigation work is costly. Recent work on a short section in the Clatskanie Bluff area off Highway 30 just over the Clatsop County line cost around $2.3 million. These project costs were on the high end, but repair work still can cost several hundred thousand dollars or more.

State road crews routinely deal with slides and rockfall on a stretch of Highway 30 near Clatskanie in neighboring Columbia County. A major slide in the area over a decade ago crushed homes and shut down the highway. The Associated Press later revealed that information predicting the landslide dangers was shelved to avoid clashes with land developers. People who lived in the area were not aware of the risk.

‘Cleanup, scaling and screening’

What kind of repairs are done depends on the soil, the type of rock and the vegetation.

The Department of Transportation’s district office oversees roughly three and a half counties with a maintenance budget of about $10 million a year. The budget is specific to regular issues like brush maintenance, new asphalt or pothole patching, Buffington said. Surprise rockfalls aren’t figured into the spending plan.

Over the years, the state’s method of addressing issues on Highway 101 in Clatsop County has remained roughly the same. There’s the familiar fix of installing a kind of hanging chain-link fence-type screen over the rock face, a common sight along the coastal highway in some places.

“Cleanup, scaling and screening,” Buffington said.

“The biggest challenge is not knowing when and where rocks are going to fall on the highway,” he said. “Sometimes it is predictable since it is a regular trouble spot, and other times, it is a completely new rockfall.”