SEASIDE, Ore. — The partial removal of a berm last summer along the Necanicum River is being deemed a success by project partners after the recent heavy rainfall caused the river to spill over in areas south of Seaside on Monday.
Water from the river inundated the historic flood plain to the west instead of causing U.S. Highway 101 to be impassable, which winter storms had routinely done in the past.
The Oregon Department of Transportation briefly closed the highway near the junction with U.S. Highway 26 Monday morning because water on the road reached as high as 12 inches. But that flooding is considered to be unrelated to the section routinely plagued further north, near the Circle Creek Campground, which had only a skim of water on the highway.
“That is an area that always flooded first and cleared last, so the duration of this flood event was reduced greatly,” said Larry McKinley, ODOT area manager for the region.
McKinley said most of the water that crossed the highway was south of Rippett Lane. That section of highway flooding was unusual, he said, and indicates just how much rain fell.
“That only happens when we have huge rain events,” said Katie Voelke, executive director of the North Coast Land Conservancy, a project partner. “What we know is if it floods at the junction, that’s when it is the worst.”
The flood mitigation project got underway in June and focused on taking out sections of a man-made berm that was created in the 1960s to protect pastureland from flooding.
About 15,000 cubic yards of dirt were removed during the excavation project. Riparian shrubs along the river were transported to other areas within the Circle Creek Habitat Reserve to continue being part of the ecosystem. The 364-acre site belongs to NCLC, which will plant native shrubs and trees as part of its plan to restore the land to its former state.
Clatsop County, ODOT and NCLC partnered to complete the more than $700,000 project in September. The Port of Astoria and nearby cities also collaborated. In 2011, a hydrological study was conducted and funded by ODOT and local governments to determine how to fix the problematic flooding that often results from a combination of precipitation and high tide.
Because the water had nowhere to go west, winter rainstorms would cause the river to flood out over the highway. This time the water went in the intended direction as a result of the project.
“It held up very well,” McKinley said. “This was a very large rain event — so it was really tested.”
“It was never intended to be a cure-all, but part of a solution to a major problem so we’re real pleased with it,” said Ed Wegner, Clatsop County Public Works director.
Clatsop County, working with a hydraulic consultant, is collecting data on the project’s effectiveness.
“In a number of weeks we’ll be able to say more exactly what those rains would likely have caused in terms of inches on the highway,” said Voelke.
Early this week, as water was receding, Voelke said shorebirds and seabirds began to congregate on the flooded land. By reopening this flood plain, different kinds of wildlife are using the habitat.
“Really thousands of birds flock in,” she said. “Where they usually are, it’s too harsh during these storms, so it’s kind of a neat example of how you need all these connections because the environment isn’t stagnant.”
Voelke said that protection of the highway was a beautiful success, but also the way the valley of Circle Creek was completely flooded and spread all the way to the base of Tillamook Head.
The NCLC will be planting 10,000 cedars, spruces and hemlocks at Circle Creek Habitat Reserve this spring as well as 2,000 wetland plants. Contractors will be doing most of the planting, but the organization will also seek volunteers in the coming months.