Bringing Back the Logjams
Stream restoration is booming, but it's a tricky business
Long before humans set foot in North America, colossal logjams clogged the continent's largest rivers. Jumbles of giant fallen trees extended for miles along rivers such as the Mississippi, the Red, and the Willamette. Some jams endured for so long that century-old forests grew on top. But starting in the late 1800s, pioneers and the Army Corps of Engineers cleared the massive tangles, opening the West to river navigation and settlement.
After years of such herculean efforts, scientists are now saying that a logjam is a good thing, and they are putting them back. By building artificial jams, researchers at the University of Washington hope to kick-start the recovery of endangered Puget Sound chinook salmon. The project is part of a nationwide surge in stream restoration, from the proposed $7.8 billion restoration of the Everglades to reviving tiny suburban creeks.
Food and shelter. Gradually, scientists came to realize that logjams play a critical role in healthy streams, such as shading the water so it remains at good spawning temperatures. Currents flowing through the logs scour deep pools for fish to hide from predators, and the decaying logs serve as a source of nutrients for plants and fish prey.
In the summer of 1998, Tim Abbe, a University of Washington fluvial geomorphologist who studies stream dynamics, trucked fallen trees up to 90 feet long to Washington's Stillaguamish River and built five jams. "Like open-heart surgery, it's really gruesome while it's going on," says Abbe. "You've got some of the biggest bulldozers Caterpillar makes in the stream bed, trying to lift the trees as fast as possible and get out quick." Despite Abbe's description, the finished products appear amazingly natural. "People say it looks just like a pile of wood," says engineer Tracy Drury, who works with Abbe. "And I say, that's exactly the point." Snorkeling expeditions this month have revealed pools beneath the jams sheltering chinook waiting to spawn.
The Stillaguamish experiment is part of a wave of river rehabilitation washing over the country. America's rivers, once slick with industrial wastes and choked with garbage, have improved markedly, thanks to the Clean Water Act of 1972. By the 1980s, mayors from Fort Lauderdale to Baltimore to New Orleans were building bike paths and shopping districts on old industrial sites. Now, conservation groups and local governments are looking to restore the health of river ecosystems by bringing back native plants and improving wildlife habitat. Grass-roots interest is exploding; membership in the conservation group American Rivers has grown from about 500 groups five years ago to more than 3,000 today, and hundreds of local groups are taking on volunteer projects. Even the federal government, which funds many local projects, has joined the party. The Corps of Engineers, once devoted to replumbing entire watersheds in the name of flood control, plans to restore seasonal flows in the Missouri River to improve wildlife habitat and may even breach dams on the Snake River in Washington.
While scientists applaud the increased interest, they say many restoration projects are so poorly designed that they end up harming rivers instead. In Maryland, for example, the State Highway Administration bulldozed the naturally straight Deep Run River into looping meanders in an effort to improve fish habitat. The first big rains melted the meander banks. "We have high standards for who we consider to be qualified to mess around with people's bodies in medicine," says Dave Montgomery, a fluvial geomorphologist at the University of Washington, "but we haven't hit that state of valuing rivers enough to require similar expertise." Scientists are just beginning to understand how tinkering with a stream can affect everything from wildlife habitat to bank erosion and water quality. And since most restoration funds are earmarked for construction, few groups can afford to monitor the effects of their projects. The lesson: caveat restorer.
This story appears in the September 6, 1999 print edition of U.S. News & World Report.
advertisement
