U.S. Department of Agriculture: Forest Service -- National Agroforestry Center
Document Type
Article
Date of this Version
2013
Citation
International Journal of Forest Engineering, 2013 Vol. 24, No. 1, 76–90, http://dx.doi.org/10.1080/19132220.2013.793056
Abstract
A forested headwater watershed in West Virginia was monitored to examine changes to in-stream turbidity following the construction of a 0.92 km (0.57 mi) haul road. Due to the design of the study, most of the sediment that entered the stream following road construction was known to result from the stream crossings and approaches to the crossings. Stream-water samples collected daily and sequentially during stormflow from 1999 through 2005 were used to interpret the effects of stream-crossing construction on turbidity and suspended-sediment concentrations (SSC). Daily and stormflow turbidity and SSC values increased as a result of the construction. Average sediment loads (kg per storm) and total annualized sediment loads (kg per year) also increased significantly, both by a factor of about 1.8. Sediment delivery to the stream was caused by mechanical introduction of soil during stream-crossing culvert installation and fill-slope construction in the crossing approaches, and by erosion of those areas due to delays in vegetation re-establishment. Inputs from stream-crossing construction affected the overall sediment regime of the stream; the turbidity-discharge hysteresis changed from the normal clockwise pattern to a counter-clockwise pattern for about seven months. As the crossing fills and approach fill slopes became re-vegetated, they stabilized, and annualized sediment loads declined. However, at the end of the study, sediment exports remained above pre-disturbance levels.