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Environmental and economic concerns lead Virginia Tech scientists to study stream restoration

   

Students and faculty members in Virginia Tech’s Department of Biological Systems Engineering are developing methods to improve streams nationwide and train the next generation of environmental professionals while they work to reverse the effects of degradation on Stroubles Creek, a small “headwater” stream that flows through Blacksburg, Va.

Local citizens, the Town of Blacksburg, and Virginia Tech researchers developed a watershed management plan for Stroubles Creek after routine environmental testing showed that the stream was in crisis.

“Monitoring by the Virginia Department of Environmental Quality showed that the benthic macroinvertebrates — the insects that live on the bottom of a stream and are good indicators of water quality — were suffering from water pollution,” says Theresa “Tess” Wynn, assistant professor and a lead faculty member in Virginia Tech’s Stream and Wetland Ecological Engineering Team. “Because certain macroinvertebrates are particularly sensitive to pollution, you know you have a problem when those insects are not present.”

According to the U.S. Environmental Protection Agency, more than 40 percent of assessed waters in the United States are impaired, mostly from non-point source pollution. Urbanization and agricultural production are contributing factors, both throughout the country and for Stroubles Creek.

The department, part of the College of Agriculture and Life Sciences and the College of Engineering, conducted a study on Stroubles Creek to diagnose the source of its water-quality issues. This study, which determined that excess sediment from Blacksburg construction and the stream channel itself polluted the stream, produced a total maximum daily load (TMDL) for Stroubles Creek — that is, it specified the maximum amount of sediment the stream can tolerate without violating state water-quality standards. Gene Yagow of the Center for Watershed Studies at Virginia Tech led this study.

Although this stream is fairly small, repairing it may have a big impact. Because streams flow into rivers and other large waterways, improving the small streams also improves entire watersheds. In fact, small “headwater” streams such as Stroubles Creek account for roughly 80 percent of the total stream length within a typical watershed.

Economic factors also supplement the environmental motives for this research. A 2005 study on U.S. stream restoration practices revealed that since the 1990s the country has spent an average of $1 billion each year on stream restoration. Most of these restoration efforts involve expensive form-based design that frequently requires the entire stream channel be reshaped and held in place by large stone structures.

Multifaceted approach turns Stroubles Creek into an outdoor laboratory

With the help of W. Cully Hession, associate professor, and their students, Wynn is using a two-year grant from the Virginia Department of Conservation and Recreation to split a 1.3-mile section of the main channel and a tributary into three sections to examine the effectiveness of common approaches to stream restoration.

Each segment of the stream will undergo a different type of restoration:

• In the first segment, the researchers will prevent cattle from trampling the stream bank, a major source of erosion if left unchecked over a long period of time. Researchers want to better understand the effect of livestock access on stream bank stability and stream health, as well as the benefits of simply removing livestock access to the stream channel.
• Researchers are reshaping the stream bank and planting woody vegetation in the second segment. Hession has spent more than a decade studying the effects of trees on stream channels and has found that trees, unlike grasses, are ideal for healthy streams in the eastern United States. “Streamside forests are important for stream health,” adds Hession. “Research shows that trees along streams provide many benefits, such as shading, food, improved habitat, and increased bank strength.”
• The third segment will undergo natural channel design, also called form-based design. The most expensive of the three approaches, this involves rebuilding the stream channel to re-create a functional floodplain and reduce shear stress on the stream bank during flooding.

Wynn and Hession will study changes in the channel form and health that result from the three stream restoration practices, with the goal of determining cost-effective ways of improving unhealthy streams. This three-pronged effort aims to reduce sediment, nitrogen, phosphorus, and bacteria from the Stroubles Creek Basin and to turn the stream into an outdoor laboratory and classroom.

Wynn and Hession can bring their students to learn about stream channel morphology and health but they also invite outside researchers and stakeholders to learn about stream restoration practices and their effectiveness. In fact, Stroubles Creek will be featured at the upcoming 2008 conference of the American Ecological Engineering Society to be held at Virginia Tech in June 2008.

• To learn more, read “Bringing New Life to an Eroding Stream” in the 2008 edition of Innovations, the flagship publication of Virginia Tech’s College of Agriculture and Life Sciences.
• For more information on this topic, e-mail Michael Sutphin  or call (540) 231-6975.