Water: Nonpoint Source Success Stories
Maryland: Section 319 Success Stories, Vol. III
|State Water Quality Site|
Paired Watershed Study Tests BMP Performance
Maryland Department of Natural Resources
Forestry, Wildlife & Heritage Div.
Regional Watershed Forester
|Primary Sources of Pollution:|
|Primary NPS Pollutants:|
|paired watershed study|
|stabilized stream temperature|
|reduced suspended solid concentrations|
|improved benthic macroinvertebrate populations|
Forests cover about 2.7 million acres of Maryland, representing 40 percent of the state's total land area. Forest health is inextricably linked to healthy streams and a robust Chesapeake Bay. But many forest harvest activities, including poorly designed haul roads, skid trails, landings (loading areas), and stream crossings, can lead to significant inputs of sediment to stream channels, resulting in degradation of water quality and impacts on living resources. The removal of trees adjacent to streams can also cause elevated stream temperatures, reducing habitat quality for fish and benthic macroinvertebrate populations.
To assist loggers and landowners in meeting environmental requirements, the Maryland Department of the Environment and the Department of Natural Resources (DNR) have developed a number of forestry programs. Sediment control plans are required before undertaking major earth-disturbing activity; best management practices (BMPs) and streamside buffer zones are required when logging in nontidal wetlands; and a special "Timber Harvest Plan" must be approved before any timber may be harvested within 1,000 feet of the Chesapeake Bay. DNR's aggressive Stream Releaf Program even has a goal of establishing 600 miles of riparian forest buffer restoration plantings by the year 2010!
Although studies show that most Maryland loggers follow timber harvest BMPs, there have been no studies in the state reporting the effectiveness of these BMPs in protecting water quality under local conditions. Using 319 funding, a 4-year study was designed to test the hypothesis that forest harvest operations have no long-term significant impacts on stream benthos, temperature, and suspended sediment if forestry BMPs are implemented.
Two small forested watersheds, located on Sugarloaf Mountain in Frederick County, Maryland, were monitored from August 1995 until July 1999 as part of a paired watershed study to evaluate the effectiveness of Maryland's BMPs for timber harvest operations. One watershed, designated the "treatment" watershed, underwent a controlled level of timber harvesting with strict adherence to BMPs, while the "control" watershed remained unharvested.
A wide range of BMPs were installed in the treatment watershed, including a 20-foot-long portable timber bridge, a 21-inch-diameter stream-crossing culvert, streamside forest buffer (streamside management zone), drainage out-sloping, broad-based dips, rolling dips, grade breaks and water bars, and the use of geotextile and stone for haul road stabilization. The logging contractors also complied with the BMPs by following marked skid trails and performing postharvest stabilization of roads, landings, and skid trails where required. On slopes over 10 percent, roads, main skid trails, and landings were seeded, limed, fertilized, and mulched.
Timber was harvested in 1997 on 73 acres of the treatment watershed, using a variety of silvicultural prescriptions. Monitoring of baseflow and stormflow suspended sediment samples, temperature, and benthic macroinvertebrates continued until July 1999.
The results of this study indicate that the BMPs were effective in preventing significant impacts on stream water quality, biology, and habitat. There was no significant difference in total suspended solid concentrations or yields due to the harvesting activities. The harvesting also did not significantly affect stream habitat, benthic macroinvertebrate populations, or stream temperature. Most BMPs performed as intended, and none allowed observable sediment input into waterways. Logger awareness and training were also critical to effective use of BMPs because implementation and installation are ultimately under the loggers' control.