SEASIDE —After a summer of work, U.S. Highway 101 south of Seaside should be better able to cope with flooding problems – and a 364-acre parcel of wetlands will return to its natural state.

Henderson Environmental Design has completed its work on the Necanicum River Wetland Mitigation Bank project after spending the past three months reshaping the parcel of land between Circle Creek Campground.

Supporters say the flood mitigation project is a rare win-win for those concerned with both managing roads and restoring the area’s native wildlife.

“It’s been a good project,” said David Neys, Astoria district manager for the Oregon Department of Transportation. “It allows us to contribute to the wetlands mitigation bank.”

ODOT’s wetlands mitigation bank functions like a carbon offset, where every project that infringes or destroys wetlands must be offset by a project that restores or maintains them.

In this case, ODOT’s desire to find a wetlands mitigation project and Clatsop County’s interest in reducing flooding on a stretch of Highway 101 near Beerman Creek on the south edge of Seaside allowed them to collaborate with the North Coast Land Conservancy on its ongoing project to restore the adjacent parcel of land to its natural state.

“One of the fringe benefits was that we were able to establish a historic wetland for the conservancy over the next two, three, four, five years,” said Larry McKinley, Northwest area manager for ODOT. “The second fringe benefit was to reduce flooding.”

Though restoring the conservancy’s parcel – which had been farmland before the conservancy purchased it – to its natural wetlands state will be an ongoing process, drivers on Highway 101 should see the impact of the project as soon as the rainy season hits.

Though the wetlands mitigation project will not stop the highway from flooding entirely, it will significantly reduce the amount of water on the roadway by allowing the water to drain naturally onto the wetlands.

This water diversion also should allow even lower-profile cars to drive down this portion of Highway 101 without incident.

“It’s meant to reduce the duration and intensity of flood events,” McKinley said. “Hopefully it will clear quicker and might not even cross, but the intensity will be much less.”

According to Neys, ODOT generally begins restricting driving in the area when the water hits 11 or 12 inches; it occasionally hits a depth of 2 feet. A study of the plan indicates that it could reduce the water depth by about a foot.

Water inundation on this stretch of highway has been a persistent problem for ODOT and area drivers.

“It happens every winter, and it’s happened for years,” Neys said. “If we get a lengthy rain event after a lot of moisture ... some of those events will close the road entirely.”

Seaside Mayor Don Larson knows firsthand about the problems.

“How do you get people to the hospital from the south? How do you get emergency vehicles through?” he asked. “It’s just stopped people.”

Larson is also impressed by how well the various municipalities and organizations have collaborated.

“It’s been a wonderfully accepted community effort,” he said.

Because the berms had been built up to hold off the Necanicum River and maintain the land for farming, when heavy rains hit, the water had nowhere to go but across the highway. The highway side of the Necanicum River is markedly lower.

“The way it flooded was way flashier, said Katie Voelke, executive director of the conservancy. “It used to be very locked into a channel.”

Once these channels filled, they flooded the highway rapidly. By lowering the riparian berms, ultimately removing 15,600 cubic yards of dirt, the water can now flood onto the 99-acre parcel of land nearest the Necanicum. Henderson has hydro-seeded the area with an herbaceous layer, a shrub layer and a tree layer.

“We’re trying to vegetate such a large area,” said Brad Livingston, wetland program coordinator for ODOT. “The idea is trying to get a lot of cover in.”

As the seeds take root and the plants proliferate, the parcel will be able to absorb more water. Approximately 100 nurse logs and root balls have also been anchored to the land, allowing for greater habitat complexity.

“We’re trying to mimic the Sitka spruce habitat,” said Livingston.

The revitalized habitat should attract native wildlife, and ODOT and the conservancy have also created fish habitats by placing trees that local logging operations were unable to use in streams abutting the parcel. The logs are kept in place by 8,000-pound boulders.

All in all, the land will not only soak up and disperse water thereby diminishing flooding, it will revert to its prepasture natural state.

“Yes, it’s like a reservoir,” Voelke said. “But it’s also an ecosystem.”

As the seeds take root, the water saturates the soil and native plants return, Voelke hopes that the restored wetlands will become a place for the community to encounter nature as it was centuries ago.

“We’ve always had a plan and a vision toward opening this to the community,” she said.

Though the wetlands mitigation project will not stop the highway from flooding entirely, it will significantly reduce the amount of water on the roadway by allowing the water to drain naturally onto the wetlands.

 

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