The dramatic trade-off “reactivated the flood plain,” in engineer-speak. It also highlighted limitations in the long-term strategy of hemming in rivers with levees and dams, then pushing farms and towns up against the river walls.
“For decades we’ve treated levees as the only line of defense” against floods, said Andrew Fahlund, senior vice president of American Rivers, which advocates for healthy waterways. “They ought to be the last line of defense.”
In a move that echoes the approach taken by the Netherlands, which has long wrestled with such problems, a nascent movement made up of activists and city leaders victimized by flooding is pushing for “natural river defenses.” They want to set the rivers free, if just a little.
Cities and counties are buying up homes and farms and relocating residents to restore flood plains and wetlands. They’re moving levees back from the water’s edge. And they’re ditching steep concrete channels in favor of gently sloped green spaces.
Oft-flooded Napa, Calif., calls its $400 million project the “living river.” Confronted in the 1970s with a Corps plan to turn the downtown riverbank into a concrete channel, citizens said no. Instead, in 1998, voters said yes to relocating 13 bridges, buying out some 100 homes and businesses and restoring 900 acres of wetlands.
The project, now about two-thirds complete, according to Mayor Jill Techel, dug the city’s Veterans Memorial Park into a bowl for holding floodwaters. The wine-tasting destination’s downtown now features a tiered trail that doubles as a spillway for the Napa River when it swells.
Nonetheless, the town flooded again on New Year’s Eve 2005. Although the project was incomplete, Techel said, the town drained in 24 hours instead of the usual two to three days. The new wetland area “was a sponge,” she said. “It took all that water.”
And in Pierce County, Wash., the Puyallup River — which has flooded 15 times over the past 20 years — will soon spread out a bit more. Engineers have started pushing back levees, mile by mile. The straightened, channelized river could no longer handle the increased snowmelt from Mount Rainier, said county engineer Dennis Dixon. “After 100 years, we’re seeing that’s not quite working.”
Meanwhile, Cedar Rapids, Iowa, has been buying out 1,300 homes and 100 businesses in a flood plain inundated by the town’s “800-year-flood” of 2008, said Mayor Ron Corbett. “We’re really moving people out of harm’s way,” he said, to establish a 220-acre “floodable greenway.”