Bringing New Life to an Eroding Stream
A plan to restore Stroubles Creek may offer a model for improving streams across the country
In 1908, the Town of Blacksburg, Va., was only a few square blocks. Virginia Tech, then called Virginia Polytechnic Institute, consisted of a handful of buildings and agricultural fields. Stroubles Creek, a freshwater stream that emerges from natural springs on the northern part of town, flowed nine miles through the town and the middle of campus with little disturbance before discharging into the New River.
Today, a century of urbanization and agricultural development has led to the deterioration of Stroubles Creek, which now joins hundreds of other streams across the country classified as “impaired” under the Clean Water Act. In fact, the U.S. Environmental Protection Agency reports that more than 40 percent of assessed waters in the United States are impaired, primarily because of non-point source pollution. Theresa “Tess” Wynn, assistant professor of biological systems engineering, hopes not only to reverse the degradation of this small, 14,000-acre watershed in Blacksburg but also to find better ways to improve streams
throughout the country.
“The United States is spending approximately $1 billion each year on stream restoration, but much of this is form-based design that often doesn’t work and doesn’t consider the long-term implications of land use and climate change,” Wynn explains.
The reasons to improve stream restoration techniques are not solely economic, though. Because streams flow into rivers and other large waterways, improving the small streams also improves the entire watershed. Roughly 80 percent of all stream miles within a watershed are small “headwater” streams. These streams are heavily affected by events taking place on the land around them. Environmental concerns such as this not only motivate Wynn’s research but also provide a starting point for it.
“Concerns about Stroubles Creek began when monitoring by the Virginia Department of Environmental Quality showed that the benthic macroinvertebrates – little insects that live on the bottom of a stream and are good indicators of water quality – were suffering from water pollution,” Wynn says. “Because certain macroinvertebrates are particularly sensitive to pollution, you know you have a problem when these insects disappear.”
Gene Yagow and Brian Benham with the Center for Watershed Studies at Virginia Tech and the Department of Biological Systems Engineering conducted a study of Stroubles Creek that determined the source of the water-quality problem was excess sediment
from construction in Blacksburg and the stream channel itself. This study produced a total maximum daily load (TMDL) that specified the maximum amount of sediment Stroubles Creek can tolerate without violating state waterquality standards.
Yagow and Benham worked with Wynn; Tamin Younos, director of the Virginia Water Resources Research Center; and a committee of concerned local citizens, government staff, andVirginia Tech faculty to develop a plan for improving the health of Stroubles Creek. “We all know that urbanization plays a key role in the degradation of Stroubles Creek,” Wynn says. “During storms, water travels from asphalt pavement directly to the stream, bypassing the natural storage the soil provides. This increased flow rips the channel apart.”
The boom in agricultural development near Stroubles Creek over the past century has also added to the problems it faces. “Imagine a 1,000-pound dairy cow trampling along a stream bank,” Wynn says. “The amount of pressure the cow is putting on the bank in pounds per square inch will erode the stream even further over time.”
These issues are not unique to Stroubles Creek, but theapproach that Wynn and her colleagues are taking is. Usingan almost $200,000, two-year grant from the Virginia Department of Conservation and Recreation, they will split 1.8 miles of the main channel and a tributary into three sections and apply different stream restoration techniques to each one to examine the effectiveness of common techniques. This restoration effort aims to reduce 242 tons of sediment per year, as well as significant amounts of phosphorus and nitrogen from the Stroubles Creek Basin.
“In the first section of the creek, we are removing the cattle to find out how taking just cattle out of the equation will improve stream health,” Wynn began. “In the second, we will reshape the stream banks and plant woody vegetation, and in the third, we will use what researchers in the streamrestoration community call natural channel design.”
This last approach, which is also known as form-based design, is the most expensive and involves rebuilding the channel to re-create a functional floodplain and reduce the sheer stress on the stream bank. “We are trying to make a more active floodplain to reduce the force on the stream bank during flooding,” she says, emphasizing that flooding is a beneficial and natural part of the life of a stream. “A
floodplain is like a relief valve. What we are doing is making the Stroubles Creek floodplain rougher by planting more trees and the like.”
Trees are ideal for healthy streams, at least in the easternUnited States. “We believe grasses are not as effective at reducing stream-bank erosion because they lay down during flooding and do not have as extensive or as rigid a root system as woody plants,” Wynn adds.
W. Cully Hession, associate professor of biological systems engineering, has spent the last 12 years studying not only the effects of channel morphology on aquatic ecosystem health but also the effects of trees on stream channels. “Streamside forests are important for stream health,” he says. “The research shows that trees along streams provide many benefits, such as shading, food, improved habitat, and increased bank strength.”
Hession has been involved in the Stroubles Creek project in a study on methods to measure stream-bank erosion rates and the amount of sediment added to streams from eroding channels. In collaboration with Wynn, he is studying how traditional technologies used to monitor stream erosion rates, such as erosion pins, compare with more advanced methods, such as ground-based laser surveying equipment that can map a stream bank by the millimeter.
The stream-restoration research at Virginia Tech involves a variety of other high-tech field equipment, including data loggers, automated samplers, water-quality sensors, a 3-D acoustic Doppler flow meter, and a submerged jet test device. In the Department of Biological Systems Engineering’s Water Resources Lab, a new 16-foot experimental stream channel allows Wynn, Hession, and their graduate students to research how the structure of stream banks, obstacles within them, and vegetation affect water flow and erosion in a controlled setting. They use this equipment to study a range of issues related to stream restoration such as innovative ways to
reduce pollution from urban areas, new sensors for measuring water quality, and techniques for improving stream and wetland restoration design practices.
In many ways, Stroubles Creek has become an excellent outdoor laboratory and classroom that can be used to fulfill Virginia Tech’s missions of research, teaching, and outreach. “There is a push in academia to look at fundamental processes and do process-based stream-restoration designs,” Wynn says. “We are applying this to our stream-restoration work in hopes of finding a more effective and economic way of improving stream channel health.”
For more information about the Stroubles Creek restoration project and similar research, check out the Stream and Wetland Ecological Engineering Team website at http://twosweet.bse.vt.edu/.