Collaborative Research and Watershed Management for Optimization of Forest Road Best Management Practices

The Coweeta Hydrologic Laboratory, USFS Southern Research Station, worked with state and local agencies and various organizations to provide guidance and tools to reduce sedimentation and facilitate restoration of the 1900km2 Conasauga River watershed in northern Georgia and southern Tennessee. The Conasauga River has the most diverse aquatic ecosystem of any river in the region and is currently being considered for designation as a Federal wild and scenic river. The watershed is encircled and dissected by highways and roads, and receives intense recreational, industrial, and agricultural use from the surrounding human population. Unpaved roads have been found to account for more than 80 percent of stream sedimentation in the forested lands of this region. Collaborative efforts of research and management focused on developing sediment yield models, prioritizing road restoration, and reducing sediment yields from roads to streams. Model development facilitated identification of highly erosive roads and prediction of sediment yield reductions following reconstruction of forest roads. We monitored sediment yield and transport from a wide variety of existing forest roads during autumn 2001. We used these data for model validation. We then used the model to characterize roads by erosion susceptibility and to prioritize roads for reconstruction. During the summer of 2002, we completed reconstruction and installation of best management practices along more than 20 miles of forest roads. We monitored sediment yield from these roads through autumn 2002. Simulated estimates of sediment yield from the reconstructed roads were severely limited by the resolution and quality of available data and the sediment transport algorithms employed in the model. Despite a 46 percent increase in rainfall from the pre to post-treatment period, road reconstruction reduced sediment yield by 70 percent. Introduction The Conasauga River Watershed, figure 1, encompasses 1,870 square kilometers of the Blue Ridge Ecosystem in northern Georgia and southeastern Tennessee. This watershed, host to over 90 species of fishes and 42 species of mussels, has the most diverse aquatic ecosystem of any river in the region (Freeman, et al. 1996). The Conasauga, along with neighboring mountain watersheds in this region, provide water for millions of people in Georgia and Tennessee. Recreational usage of the Conasauga is intensive. Thousands of annual visitors use it for kayaking, canoeing, swimming, fishing, hunting, hiking, mountain climbing, mountain biking, swimming and camping. Currently, water quality and aquatic ecology of the Conasauga River are suffering from excessive sedimentation caused by erosion of streambanks, agricultural lands, development, and gravel roads (Freeman, et al. 1996). Erosion from gravel roads accounts for more than 85 percent of the contemporary sediment threatening water quality of streams in this region (Van Lear, et al. 1995). The USDA Forest Service has designated the Conasauga River watershed as one of fifteen Community-Based Watershed Restoration Partnership programs. This has provided resources to protect and improve the quality of land and water resources within the Conasauga River Watershed. As part of this project, the Forest Service located and characterized threats to the headwater streams and the Conasauga River in the national forest lands of the Chattahoochee and Cherokee National Forests (Roghair, et al. 2001). While approximately half of the area is designated as wilderness and provides water of exceptional quality (Ivey and Evans. 2000), stream sedimentation from gravel roads and private land development is degrading water quality and aquatic ecosystems in the Conasauga River (Roghair, et al. 2001; Henley, et al. 2000). The primary means to reduce runoff, erosion, and sedimentation caused by forest roads is through the implementation of road improvement projects, best management practices and, where necessary, closing roads (Sun, et al. 2003). Due to limited resources, it was important that road improvement projects be prioritized. The prioritization was based upon the severity of sediment erosion and transport, sediment impacts on water quality, road usage levels and potential effectiveness of restoration. Our goal was to determine the ability of a watershed-scale erosion model to assess sediment production, delivery to streams, and predict restoration effectiveness. In this study, we determined the ability of such a model to: