ORTING — As heavy rain threatens to flood rivers this winter, many flood-plain managers are trying to work with nature, rather than against it, to keep waterways from overflowing.
Instead of relying on dikes, levees and other engineered structures to protect communities, some cities and counties are taking a different tack. They’re giving rivers more room to meander by setting back levees and buying up nearby land that can absorb floodwaters. They’re also adding trees and other vegetation and reconnecting rivers to flood plains.
In 2013, the state Legislature set aside $44 million for the Floodplains by Design program, a partnership between the Department of Ecology, Nature Conservancy and Puget Sound Partnership.
Projects in Whatcom, King, Yakima, Kittitas, Wahkiakum and other counties are using that state and other money to reduce flooding, while also improving water quality, restoring fish habitat, preserving farmland and opening up public access.
“Already we’re seeing nothing but great results,” said Ken Wolfe, building official for the city of Orting, 20 miles southeast of Tacoma. “Past practices didn’t pencil out very well. Giving the river back what it used to have is the best way to approach flood control.”
The $18 million levee-setback project along the Puyallup River helped protect the town of 7,000 people from potential flooding last month.
A late November storm pushed the river to a level that, a year or two ago, would likely have flooded city streets or required sandbags, Wolfe said, but the project moved back the levee by up to 400 feet in some places and gave the river more space to spread out. The project also included improved salmon habitat.
Across the country, communities along river corridors are rethinking how to manage flood plains in ways that serve many purposes.
“Rivers are very energetic and dynamic systems,” said Robert Naiman, emeritus professor with the University of Washington who has studied river ecology and watershed management. “If you don’t want to have flooding, you’ve got to allow the rivers to take their own course to a large extent.”
Putting in dikes and levees confines rivers and streams into a narrow channel, Naiman said, adding: “It will work for a little while, but it’s not going to work forever.”
Flood plains are areas that naturally flood, and they act like sponges to hold water. But many have been developed or changed by levees, dams and stream channels, experts say. Rivers that are squeezed between levees, for example, force water to flow faster and rise higher.
Flood plains provide some of the richest habitat for fish and wildlife, but they’re the most heavily developed because people are attracted to living near rivers, said Bob Carey, who directs strategic partnerships with the Nature Conservancy.
“We get a ton of benefits (from floodplains), but those things have been at odds with each other,” Carey said.
Along the Puyallup River, north of Orting, Pierce County officials recently completed a project to reduce flooding and create new salmon habitat. The county created a 2,000-foot side channel this summer, giving the river more room to flow and providing more floodwater capacity.
“We’re poking holes in it, and allowing the river more access,” said Hans Hunger, the county’s capital improvement program manager.. “We’re giving it more room to slow down, dump out gravel, and create more complexity.”
On a recent morning, Hunger and others gave Ecology Department officials a tour of that project. Crews had also placed log jams in the channel to create holding areas for salmon and other fish.
Earlier, the team had toured another project that will conserve nearly 160 acres of farmland, while restoring habitat along a salmon-bearing creek.
There’s been so much interest in the flood plain initiative that the Ecology Department has received $180 million in requests for the next round of potential funding.
“It’s a new way,” said Adam Sant, Ecology’s flood plain project manager, “of thinking about flood plains.”