 United
States Department of Agriculture -
Forest Service |
 Southern Research Station200 W.T. Weaver Boulevard Asheville, NC 28804 |
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Monitoring Sediment from Forest Roads
Asheville,NC -- As part of the USDA Forest Service Large Scale Watershed Restoration initiative, researchers from the Coweeta Hydrologic Laboratory have been studying the impact of sediment from forest roads on streams in the Chattooga River watershed.
The Chattooga River, designated a Wild and Scenic River in 1974, is nationally known for the rapids that mark its steep descent from North Carolina into Lake Tugaloo on the border between South Carolina and Georgia. One of the last free-flowing rivers in the Southeast, the Chattooga flows through dense, mature forests managed by the Forest Service. The Forest Service maintains roads in the area for both management and recreational uses. Several streams in the Chattooga area have been listed by the Environmental Protection Agency as impaired from sediment that washes down from forest roads.
Coweeta's Barry Clinton is measuring sediment production from four types of forest roads: a two-year-old paved surface, a gravel surface receiving routine maintenance, an improved gravel surface where best management practices (BMPs) have been installed, and an unimproved forest road that receives little maintenance. Clinton ranks the road surfaces using the mean TSS (total suspended solids) concentration-a method to measure sediment-in the runoff from road surfaces. Results so far show that sediment movement from the roads varies according to levels of maintenance and road drainage. The paved surface contributes the least sediment, followed by the improved gravel road, the gravel road receiving routine maintenance, and the unimproved road.
Best Management Practices (BMPs) are techniques designed to prevent or minimize the impacts of forestry activities on water quality. " When we began the Chattooga study, the only BMPs present were on the improved gravel roads," said Clinton. 'Streams down slope from improved gravel roads with functioning BMPs had greatly reduced concentrations of sediment; however, where BMPs failed--either due to lack of maintenance or improper installation--sediment concentrations were similar to those associated with the other gravel surfaces."
Sediment concentration also decreased with the distance water traveled from road to stream. "In order to prevent or reduce the risk of sedimentation to streams and rivers, it is critical to ensure that drainage occurs in locations that are not adjacent to water courses," said Clinton. "Drainage outlets should also be set at frequent enough intervals to keep water volumes at a minimum."
Results from this study and other ongoing water quality research
conducted by Coweeta staff will provide much needed information to land
managers on the vulnerability of water courses to currently existing
forest road systems, and on how the proper installation of BMPs can
mitigate against sediment movement from forest roads.
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