Researchers examining effectiveness of stream restoration
Are costly projects bringing back habitat and hydrologic function or merely cosmetic?
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From the way it looks, Muddy Creek would seem to deserve its name. The Maryland stream is decidedly murky, with an orange tint to its slow-moving water.
That’s not necessarily a bad thing. This tributary of the Rhode River near Edgewater underwent an extreme makeover earlier this year, and it’s still adjusting to being dramatically altered by a $1 million stream restoration project that raised its bed, widened its banks and added some meanders and pools to its channel.
Whether the creek has been “restored,” or just rehabilitated, remains to be seen. Its condition is being closely monitored by scientists at the Smithsonian Environmental Research Center, on whose sprawling campus the project was performed.
“This looks like a wetland on Mars,” remarked Tom Jordan, a senior scientist at SERC, as he surveyed the unusual hue of one marshy pool. But he noted later that the stream “has just been hugely disturbed, so we expect to see some anomalous behavior. We don’t know how long it is going to persist. These are the kind of things we want to find out.”
The Smithsonian’s Muddy Creek research project is one of a series of studies under way to try to answer questions — and resolve disputes — about the efficacy of stream restorations. That’s critical, because such projects have become a favored tool of state and local governments across the Chesapeake Bay region as they strive to meet federal mandates to reduce sediment and nutrient pollution fouling the estuary.
Environmental consultants and engineers who do stream restoration projects, and some scientists who’ve studied them, have been at odds for years about how much good they do in trying to bring back water bodies degraded by development.
Streams supply drinking water, and they furnish freshwater to the Bay. But their ecological value goes far beyond that, as they provide food and habitat for myriad plants and animals, from bacteria to bugs, to frogs and fish. In healthy streams, those organisms use up many of the nutrients that wash into streams. Streams also carry away unused nutrients and sediment, while also trapping some along the way.
But centuries of land alteration, from clearing forests and farming to building roads, homes and shopping malls, have dramatically altered those complex ecosystems, turning many into little more than drainage ditches, or sometimes, concrete-lined culverts. According to the state-federal Chesapeake Bay Program, 57 percent of the streams in the six-state watershed are in poor or very poor condition.
In recent decades, there’s been growing interest by government agencies, engineering firms and environmental groups in restoring degraded waterways. The methods for doing that can be dramatic and sometimes controversial, with bulldozers felling dozens of trees and reshaping stream channels. Skeptics, including some scientists, question the value of such projects, whether they hold up over the long term and provide real biological or chemical improvements — or whether they are primarily cosmetic.
In an attempt to settle the major differences, the Chesapeake Bay Trust has awarded nine research grants since 2015 to examine the impacts of various techniques used in re-engineering stream channels on water quality and wildlife habitat.
“When questions are raised, we can’t ignore them,” said Jana Davis, the Trust’s executive director. “We have to address them.” While every restoration project is at least slightly different, Davis said, “Hopefully there are some trends. Once we find out what that trend is, we can apply it more widely.”
There’s a lot at stake. A total of 300 miles of stream reaches have already undergone restoration across the six-state watershed, according to Bay Program data. Another 440 miles are targeted for overhauls by 2025. With construction costs on urban stream restorations averaging more than $600 per foot, hundreds of millions have been spent to date, and the final tally seems sure to top $1 billion.
Fixing a legacy of problems
Urban and suburban streams, in particular, often suffered severe erosion as their floodplains disappeared and their watersheds became covered with pavement and buildings. Rainfall that used to soak into the ground is funneled by storm drains into the nearest waterway, where even a brief downpour can turn a burbling brook into a raging flood.
Historically, those streams weren’t narrow ribbons of water, as many appear today. Rather, they were wide, complex corridors in which the waterways were intimately connected with their floodplains and adjacent wetlands. When water levels rose after a storm, they overflowed onto those surrounding areas, where pollutants were absorbed and the downstream rush of water was slowed.
As watersheds develop and floodplains vanish, problems cascade into streams. They are forced to carry more — and faster flowing — water, whose erosive powers dig deep channels with steep banks. Surges in runoff following storms, now confined to narrow channels, begin eating away at the banks, unleashing tons of additional sediment that instead of settling on floodplains, smothers aquatic habitats downstream. Temperatures, as well as water flows, fluctuate wildly, making streams uninhabitable, except for only the most-tolerant species.
Restoration advocates say re-engineering stream channels can help mimic the functions once provided by expansive flood plains, reducing bank erosion and cutting down on a major source of water-clouding sediment to the Bay. The practices can also curb the flow of phosphorus and nitrogen, the two nutrients that feed the Bay’s algae blooms and its fish-stressing “dead zones,” proponents say.
But some scientists say many stream restoration techniques don’t work equally well everywhere, that some projects have only limited environmental benefits, and that there’s not been enough long-term monitoring to tell if the upgrades hold up over time.
“I’m glad there’s actually some science” looking at it, said Tom Schueler, executive director of the Chesapeake Stormwater Network, a Maryland-based nonprofit. Schueler co-chaired a panel of experts tasked by the Bay Program with quantifying how much credit to give stream restoration projects for reducing sediment and nutrient pollution to the Bay and its tributaries.
“Before the Bay Trust did this,” Schueler said, “it was just two sides that had some philosophical disagreements — bitter disagreements — and facts and some science were being thrown around.”
Those in the business of carrying out such projects say they welcome the scrutiny.
“If we don’t do the right kind of monitoring, the steam restoration industry is headed for a huge backlash when (people) realize how much money is being spent on it,” said Jim Gracie, president of Brightwater Inc., an environmental consulting firm that’s been doing restoration work for three decades.
Gracie said he’s glad the Trust has partnered with the state Department of Natural Resources to provide a “pooled” monitoring fund for conducting more extensive tracking of selected restoration projects’ performances.
“We need to be able to defend what we’re doing because it’s the right thing to do,” Gracie said, adding that something must be done to curtail the harm done by stormwater runoff from existing communities.
“Stream restoration research has been done in fits and starts over the years, but applied, serious applied research, has really taken off in the last handful of years,” said Scott Macomber, president of the Maryland Stream Restoration Association.
Macomber, who’s with a Hunt Valley stormwater consulting firm, acknowledged that “in a way the practice [of restoration] did get out a little bit more ahead of the science.” But now, with a growing number of projects seeking to take advantage of the nutrient and sediment reduction credit the Bay Program grants them toward meeting Chesapeake cleanup requirements, “everyone wants to make sure those rates are realized after implementation.”
Erik Michelsen, head of watershed protection and restoration for Anne Arundel County, said local officials like him need more information as they plan more and more of these projects. Arundel does more than most — it projects spending roughly $175 million over the next four years on stream restoration.
“There’s a lot of money being spent on monitoring,” Michelsen said, “to check the box on various permit requirements. But there’s almost a consensus that a lot of the money being spent on that is not well-spent and not being used to collect data that’s necessarily comparable or (collected) in a scientifically meaningful way.” Now, he said, more people are asking, “Is there a way to spend the same amount of money and get better results?”
Stream restoration professionals say their methods and materials have evolved over the years as they’ve learned from the growing number of projects being performed.
“We do things differently today than certainly we did five years ago, and 10 and 15 years ago. I think we’re getting better,” said Mark Secrist, who heads a stream restoration team in the Chesapeake Bay office of the U.S. Fish and Wildlife Service. Many of the projects the federal agency works on are geared toward creating or recreating habitat for fish such as brook trout, a notoriously finicky species that demands cool, clear, nearly pristine streams.
New techniques are being tried, such as “natural channel design,” which seeks to stabilize an eroding stream by understanding how it has responded to development and other manmade changes in its watershed. Another method involves removing so-called “legacy” sediments, by excavating sediment that’s built up over centuries along a stream. That buildup disconnected the stream from its historic wetlands and floodplains, which used to capture sediment and nutrients and slow the downstream movement of water.
Yet another approach gaining wider use calls for installing “regenerative stormwater conveyances,” which involves putting weirs or low dams across a stream to slow its flow and cause water to pool. These projects often include reconnecting a deeply eroded stream with portions of its floodplain and creating wetlands. That was the general approach used on Muddy Creek.
Bringing back Muddy Creek
Before its makeover, Muddy Creek had become a deep ditch after decades of erosion caused by the installation of a road culvert in its channel. The pipe compressed the stream’s flow so that in rainy periods, the water jetted out like a huge garden hose, scouring away the highly erodible soils of the coastal plain. The stream’s banks towered over Jordan when he stood at the bottom of the gully.
At the urging of the West/Rhode Riverkeeper, Jordan said, Smithsonian officials decided it was time to try to do something about the sediment and nutrient pollution being generated by Muddy Creek’s eroding banks. They also saw a great opportunity to assess the effects of stream restoration techniques, as the lab’s scientists have been monitoring the creek since the 1970s.
Last winter, nearly 500 yards of the stream’s deep gully got filled in with layers of gravel, sand and wood chips. The channel itself was reworked to wander back and forth across what had historically been the stream’s flood plain, and a series of low rock berms were laid across the bottom — all with the intent of slowing down the flow of water.
In the spring, after construction had been completed, “we had water all over the place,” said Jordan. Instead of a drainage ditch, he added, “it looked more like a series of wetlands, and some wood ducks checked it out, and said ‘hey, this looks like our kind of town.’ ”
On a midsummer visit with no recent rain, the stream had dwindled but not dried up. Frogs plopped into the water and peered out, as a green heron stalked them.
Jordan and his post-doctoral fellow, Josh Thompson, have set up automatic water samplers at either end of the restored stream reach to give them round-the-clock tracking of what’s being washed downstream. The data are too new to reach any conclusions, but results so far show that roughly half of the sediment drops out in the slower-moving water. They’re seeing some reduction in nutrients, too.
It remains to be seen how, or if, the stream regains a robust population of aquatic insects and other invertebrates. A crayfish den or two were visible, but the water itself is too murky to see much. The unearthly color is a byproduct of iron that’s naturally in the soils leaching out into the stream with groundwater, where it oxidizes as it comes into contact with air. Bacteria that feed on the iron also have proliferated, adding to the mix.
“Some people are worried about this aspect of restoration, that there’s too much of this iron oxide formation,” Jordan said. The oxidation and the bacteria are depleting oxygen in the water, making it less hospitable to aquatic creatures, but those conditions may also be helping the creek remove some of the nitrogen that would otherwise flow downstream to the river.
Since the project was finished, restoration contractors, regulators and scientists have trooped to the Smithsonian research center to see it. Jordan and Thompson point out that while the re-engineering of Muddy Creek appears to be succeeding, it had fewer things going against it than many streams that are targeted for reworking. The creek watershed is almost entirely rural and mostly wooded, and the Coastal Plain is relatively flat, making it easier to slow down the flow.
“A lot of these stream restorations are done in watersheds where there’s a lot of impervious surface, and so they’re really flashy” Jordan said. “This one is…a special case,” he added.
Different places, challenges
The Smithsonian team is also monitoring another recently completed stream restoration project near Annapolis that represents the other extreme. It’s a nontidal stretch of Church Creek flowing through the heavily developed Parole area, which is hemmed in by shopping centers and Aris T. Allen Boulevard. The vast majority of rain falling there is quickly piped into the stream, as nearly three fourths of the watershed is covered with pavement and buildings, according to Kirk Mantay, watershed restoration director for the South River Federation. Church Creek is the most impaired tributary of South River, he said.
The stream got some of the same treatment as Muddy Creek, with rocks and boulders laid across its channel to create pools and slow the flow. Stumps of dead trees have been planted, roots up, to add organic matter and habitat. Frogs can be seen in the Parole creek, and Mantay said a recent electro-shock survey found more fish in the stream, including eels, mosquito fish and other hardy species capable of surviving in all but the most degraded conditions.
But in rainstorms, the surge of runoff from surrounding development still turns the creek into a torrent that has rolled boulders downstream. Even in quieter times, its pools are murky and rocks on the bottom are coated with an orange slime, another sign of iron leaching out.
It’s still too early to draw firm conclusions, but stream samplers set up by the Smithsonian team aren’t tracking the same degree of sediment and nutrient removal as at Muddy Creek, according to Jordan and Thompson.
“Some of these things you just can’t fix,” Jordan said.
Mantay said the federation expects only limited pollution reduction at the Church Creek project, but still considers the $700,000 in public funds a worthy investment.
“If this shows a positive impact, even minor, in every category, then that tells me we’re doing a good thing,” he said.
The Smithsonian team plans to add a third restored stream to its study, one that appears to be only moderately degraded compared with the Church Creek stretch. From those three they hope to identify what’s working, what’s not, as well as why in each case. From that, they hope to advise restoration experts and regulators in planning future projects.
“A lot of what’s fueling construction of these is the idea that we can meet our TMDLs by putting in these things,” said Jordan, referring to the “total maximum daily load” pollution control plans that have been established for hundreds of streams across the watershed, and for the Bay itself.
Based on advice from the expert panel that Schueler co-chaired, the Bay Program has assigned water-quality credits for stream restoration projects. But Jordan said that “the data to back up the credits are very slight. There’s really not much. And so we need more. These things are so different one from the other, it’s not like a restoration will do the same anywhere you put it.”
Understanding what works
Other researchers who’ve gotten grants from the Bay Trust are trying to find useful patterns in the outcomes of a growing array of projects.
Solange Filoso, a biogeochemist with the University of Maryland Center for Environmental Science, is reviewing all of the stream restoration projects she’s studied for the last nine years “to really try to determine once and for all what kind of designs are more effective and at what position in the watershed restoration performs better.”
She’s still pulling all of the data together, she said, but as with the real estate business, location appears to matter in planning a restoration project. Those carried out farther up in a watershed appear to be more successful than those done farther downstream, she said. And conversely, if runoff surges upstream are not tempered somehow, they can dump sediment that smothers restored reaches downstream.
“With stream restoration, especially when we go downstream, we are not eliminating the source of the problem,” she said. “Even though you may be able to patch the stream reach that‘s in trouble and it works for a while, it’s not a real solution.”
Michael Williams, a research associate at the Smithsonian Environmental Research Center, said he’s seen cases where completed restoration projects were removing sediment and nutrients, but were undermined by a big storm or a new development that increased runoff from the watershed.
“These things oftentimes require a lot of tweaking,” he said.
Filoso said her research has found that nitrogen and even phosphorus removal varies considerably in restored stream reaches. In one project she studied, the nitrogen in the water was chemically transformed from one type to another, but not really removed. And in some cases, she’s also seen evidence that restoration may capture sediment, but actually boost the amount of chemically reactive phosphorus in the stream.
“So this idea of ‘restoring is better than nothing,’ I’m not sure,” she said.
Part of the issue with defining stream restoration success may be in the use of the term itself. Some practitioners and scientists alike agree that it’s often misleading to talk of “restoring” a stream, when it’s not really being put back to the way it was centuries, or even decades, ago. Some projects may improve water quality, but other benefits may be limited, such as restoring habitat and populations of aquatic insects, fish and other wildlife — especially for more sensitive species.
Other scientists say that while there’s evidence restorations can improve water quality, a more holistic approach to dealing with runoff is needed to benefit stream ecosystems.
“I think it needs a two-pronged approach,” said Josh Thompson, the SERC post-doc, first to manage runoff from the watershed with things like green infrastructure and low-impact development, and then to focus efforts on fixing problems in the stream itself. “Certainly there’s no easy way of managing this problem. It’s not going to be solved overnight,” he added. “I think people recognize that.”
But if the current effort continues, Thompson said he believed that “together, with other good researchers…we’ll have enough data from all these different studies to really say what the benefits are and what can be improved.”
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