PORTLAND — On Monday morning, Johnson Creek began to swell.
By midday, it had crested, then breached. Through the night and into Tuesday, panicked residents along its banks rushed to build sandbag fortresses around their flooding properties.
This isn’t abnormal for the people in Portland, Gresham and Milwaukie who live near the creek. It’s the reality of living in an active floodplain — the drawback of spending most days along a softly gurgling creek in the midst of an urban area.
“It’s sort of the nature of the system,” said Thaddeus Miller, a Portland State University assistant professor who has advised Portland city leaders on how to deal with Johnson Creek. “If you don’t have houses there, it’s no big deal. But it’s a nice area and it’s attractive to settle there.”
Miller, one of a handful of researchers to receive National Science Foundation sponsorship to help cities prepare for weather extremes tied to climate change, said the type of weather that led to this week’s flooding will become more common as the world heats up.
But with proper planning, city leaders can reduce the impact these drenching storms have on residents, even as the high waters become more frequent.
The Portland Bureau of Environmental Services has steadily worked toward that goal since completing a 2001 plan aimed at alleviating the creek’s regular floods.
In part, they’re working to undo the misguided tactics of the past. Parts of the creek were forced into channels lined with rock, while floodplain wetlands were filled in to make room for development. When pounding rainstorms came, the water had nowhere to go but up.
“It’s really easy to forget how important wetlands are, until things like this happen and you see them just completely full,” said Maggie Skenderian, the city’s Johnson Creek watershed manager.
The city has completed nine projects to reduce flooding along Johnson Creek, with several more slated for completion in the next few years.
The biggest project involved buying properties in the floodplain near Foster Road and clearing the land to give the river room to swell. It created enough space to fill the 63-acre area with 2 feet of water.
“That’s why Foster Road didn’t flood sooner than it did yesterday, and why the flooding extent wasn’t larger,” Skenderian said.
But it doesn’t protect residents along the rest of the 26-mile creek. Upcoming projects, including one on the west side of Interstate 205 near Lents and another near the Beggar’s Tick Marsh, will aim to restore more wetlands and floodplains to create additional space for water.
Miller said local leaders and residents might one day need to decide whether the streamside living that Johnson Creek residents enjoy is idyllic enough to withstand the flood evacuations and property damage.
“It may mean moving to give the creek more space,” he said.
The city operates a program to buy up properties from willing sellers along the creek, but “it’s very hard to just have people relocate,” Skenderian said. An estimated 170,000 people live within the creek’s watershed, though only a fraction of that number faces frequent flooding.
In the absence of such a costly and time-consuming approach, Miller said, local and state leaders could do more to lessen the impact of Johnson Creek’s floods by helping residents prepare for them and respond when they hit.
This could come in the form of funds money to help low-income residents retrofit their homes to withstand high water or make repairs after floods damage their property.
“Unless you want to channelize it like the L.A. River, flooding is part of what the system does,” Miller said.
