In theory, it makes sense: Find a polluted stream that has been straightened like a farm ditch or corralled into a concrete culvert. Dig the stream a new, winding channel that slows the water's flow, with pools for fish and banks planted with vegetation to hold the soil together.
This is what stream restorers in North Carolina and elsewhere have been doing for about 20 years, often at public expense.
But studies of what seemed a logical solution to the destruction of streams by road builders and developers have found that the work is doing little good.
"We waste huge amounts of money to go in and create the structure in the channel," said Mathias Kondolf, a professor of environmental planning and geography at the University of California. He and other researchers think it would be better to let streams naturally create their own channels.
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The federal Clean Water Act is the reason that streams and wetlands must be restored in equal proportion to those development damages. Stream restoration alone is now a billion-dollar-a-year industry in the United States.
Many states have programs that provide these restoration projects on behalf of developers. Others leave it up to developers to do their own work or to hire someone to do it.
For its scope and ease of access, North Carolina's Ecosystem Enhancement Program is considered a national model. The program charges developers a fee based on the amount of damage their projects will cause streams and wetlands. It then becomes the state's responsibility to get the offsetting restoration work done.
The program and its predecessors have spent $196 million on 239 stream restorations. Of those, 176 have been built; the rest are in design or construction
And there's sure to be plenty more. North Carolina has seen an explosion in population and is second only to Alaska in miles of streams, one study found.
The growth in roads, shopping centers and subdivisions, in fact, has produced hundreds of opportunities to return streams and wetlands to their "natural" state. But a debate about the environmental benefits pits scientists who are collecting water quality data against engineers who have championed the restoration projects and are paid to design them.
As far back as Colonial times, streams have been straightened and wetlands drained for agricultural or commercial development.
But there's a problem here, rooted in substances that predate the Colonies: North Carolina modeled some of its restoration projects after Colorado's, a state with rocky soil. Much of North Carolina is sand and clay.
Clay erodes easily under water and also hardens in dry conditions, speeding up the flow of stormwater runoff and making it hard for plants to survive.
Such a lack of science behind the restoration work concerns state environmental officials. In October, they announced plans for a science advisory group, including experts in environmental research, to assist the Ecosystem Enhancement Program. In 2009, the program laid off its sole researcher, Kevin Miller, who now works for the U.S. Bureau of Land Management.
Ignoring the research
A leading researcher in stream restorations is Emily Bernhardt, a Duke University ecology professor.
Three years ago, Bernhardt presented her research team's analysis of four stream restorations in the Triangle, including three of the state program's best. The team examined oxygen content, stream temperature, pollutant levels and insect activity to assess the streams' water quality and then compared them with three of the Triangle's most degraded streams.
The findings: The water quality of the restored streams was worse, despite an investment of roughly $1 million. The restorations had removed trees, which took away the shade and made the streams warmer.
Bernhardt remembers state program leaders listening politely. They didn't ask for a copy of her report.
"They thanked me for coming in, they asked interesting questions, but they didn't do anything about the information," she said.
Bernhardt's study, funded in part by the state, is one of several in North Carolina that have found that restored streams provide little improvement in water quality. A growing number of reports across the country and in Europe reach the same conclusions, researchers say.
A 2006 N.C. State University study looked at 13 stream restorations across North Carolina, periodically counting insects and other visible stream-dwelling invertebrates. The creatures are reliable indicators of water quality because of their sensitivity to pollutants.
The study found that, for most sites, the populations decreased over time, though it said conditions could eventually improve.
Last year, a UNC Asheville presentation showed that five restored streams in the western part of the state had no increase in insect life compared with unrestored, polluted streams.
Sediment to Falls Lake
One reason these projects have so little effect lies in the work involved.
Restoration is a task performed with trackhoes, dump trucks and bulldozers. They dig channels, remove trees, grade floodplains and haul in boulders and smaller rocks to try to hold the stream in place.
This kind of major surgery can release tremendous amounts of sediment, which compresses the banks and floodplain so that stormwater is unlikely to be absorbed. The removal of shade trees raises a creek's water temperature. None of this improves water quality.
A recent UNC-Chapel Hill study looked at how construction affected a restored section of Ellerbe Creek running through Durham's Northgate Park. The study found that the project sent a large amount of sediment into the channel that was pushed downstream as storms hit.
Ellerbe Creek is one of the Triangle's most polluted streams. It feeds Falls Lake, which is already troubled by too much sediment. Falls Lake is Raleigh's primary water supply.
From the marina that Amy Poole and her husband run on the lake, close to where nitrogen-rich Ellerbe Creek feeds into it, she sees and smells the effect. Algae has coated the surface with a green scum; hundreds of dead catfish finger lings once washed up against the marina's docks. Hard rains push clay silt out of the creek, turning the lake a dull red.
Poole remembers how clean the lake looked 30 years ago, when the U.S. Army Corps of Engineers dammed the Neuse River to create it, and she wonders why no one tried to keep it that way.
"It just astounds me that action wasn't put into place at the very beginning," she said. "I don't know why it was allowed to go on for as long as it did."
In urban areas such as the Triangle and Mecklenburg County, stream restorations are particularly challenging. The streams are already confined to narrow floodplains, battered by stormwater runoff during big storms and fouled by leaking sewage treatment systems. Building a new stream channel doesn't eliminate all those problems.
Upstream development further complicates restorations. Designers have to factor in how new subdivisions, shopping centers and highways would affect their projects. If they underestimate the effect, the stormwater surges caused by additional parking lots, roads and rooftops can blast apart newly constructed streams.
That's what happened last year in fast-growing Cabarrus County, where a storm tore up a restored tributary to Coddle Creek shortly after construction concluded. The fix, estimated at $109,000, includes widening the upper part of the restored stream to better handle stormwater surges.
Clay, not rock
After major work, streams often fail to hold their shapes.
Two years ago, environmental scientists Jerry Miller of Western Carolina University and Craig Kochel of Bucknell University looked at 26 stream restorations in the western half of North Carolina. These were streams for which new channels had been dug and reinforced with boulders and rock to control the stream paths.
What they found was that more than a third of the streams had channel failure. Banks and beds were eroding or sediment was filling the channel and choking off fish, insects and other stream life.
Miller and Kochel said it would have better served the environment, and at less cost, if restorers had given many of these streams more land for a wider floodplain so that they could have created their own channels.
That approach would include planting buffers of trees, shrubs and other vegetation along the banks to hold soils together and to absorb pollutants from stormwater runoff. Such a project would also fence out cows, machinery and humans.
Miller said designed streams often fail to account for topography. They conform to a conceptual ideal: the calm, meandering, babbling brook that isn't found in many natural settings.
Dave Rosgen, a hydrologist from Colorado, developed a stream classification system that embraces this ideal, and many people took to it - in part because a winding design produces more linear feet of stream, attractive to those trying to match restoration with environmental damage on a foot-to-foot basis. Rosgen is considered a pioneer in the stream restoration field, but many environmental scientists say his concepts have been applied too broadly.
That's particularly true in North Carolina.
State officials say they have learned the lesson about over-engineered streams and have scaled back some projects as a result. They say they realize that to make Rosgen's methods work here, stream designers should take into account the characteristics of North Carolina's land.
"Colorado is boulder and cobble, while North Carolina is clay and sand," said Mac Haupt, the state program's monitoring supervisor.
Little money to monitor
Rosgen said there is nothing wrong with the techniques that he has developed and used for more than 40 years. He said he has seen them work in every region of the country, including North Carolina.
He said the real issue behind stream restoration failures is a lack of training. Many say they have learned his techniques, but Rosgen often discovers they've learned them second hand.
"What's happening is there's so much demand from people who want their rivers fixed and there's not a lot of detailed, trained people out there," he said.
Haupt and other state restoration officials stand by their work, even though there are more than 30 stream restorations built using Rosgen's principles that have eroding banks and beds. Those problems cost from tens of thousands to hundreds of thousands of dollars to fix.
The state officials say the negative research findings are premature. They point to individual streams that research shows have improved.
And they are unwilling to require data collection that would show whether these restorations are improving water quality. Instead, they check only to make sure that the physical improvements are holding up. The officials want universities to monitor the water, with help from the state.
Jeff Jurek, the state restoration program's project control and research director, said developers and the N.C. Department of Transportation - which pay the most fees into the program - would not want to bear the expense of more extensive evaluations.
"People ... really only want to pay for what the regulators set as the mitigation standards," Jurek said.
The U.S. Army Corps of Engineers and other federal officials who oversee stream and wetland restorations have made a similar argument: Too much monitoring, and the projects become cost-prohibitive to the public and private entities that pay for them.
State regulators at the Division of Water Quality, however, see value in monitoring water quality in the restoration projects. They are developing a new method of data collection that could determine whether the projects help.
Researchers studying stream restorations say not monitoring water quality risks spending tens of millions of dollars on projects that might not help the environment. That money, they say, could be better spent on proven measures such as controlling development, upgrading wastewater treatment facilities, removing leaking septic systems and treating polluted stormwater before it gets into rivers and lakes.
Miller, the Western Carolina professor, likened the situation to someone taking aspirin to battle a fever. It may lower the temperature, but it won't address the illness.
"You are treating the symptom, which in this case is a degraded river and ecosystem," he said. "But you are not getting at the root problem."