Enhancement of Disturbed Upper Coastal Plain Stream Systems: Establishing Restoration Criteria and Strategies for a Stream Mitigation Bank

Stream restoration refers to activities that are taken to correct or improve previous alterations that have destroyed, diminished, or impaired the character and function of stream systems. Restoration generally involves the conversion of an unstable, altered, or degraded stream channel to its natural or referenced condition, with consideration given to recent and/ or future watershed conditions. This process may include restoration of the stream's geomorphic dimension, pattern and profile, and/or biological and chemical integrity in order to achieve dynamic equilibrium (physically and/or biologically). Enhancement refers to activities that are initiated to improve an aspect of an impaired stream system, but recovery to that of the natural or reference condition is not feasible or practical. The Savannah River Site (SRS) is representative of Upper Coastal Plain landforms, watersheds, and tributaries of the Savannah River watershed (Kilgo and Blake 2005). Prior to the 1950's land use and stream impacts on the SRS were similar to other lands along the Sand Hills fall line between the Piedmont and Coastal Plain (Smock and Gilinsky 1992). Agricultural activities increased runoff and sedimentation, particularly along steep embankments adjacent to the streams and near the headwaters (USDA 1951, Trimble 1974), and grazing and logging altered the riparian areas along nearly every tributary (White 2004). Stream fluvial morphology and structure were impacted by creating channels and dams, or altered through removal of debris (Brooks and Crass 1991). Macrophyte substrates may also been removed indirecdy by these activities, which potentially altered prey-predator relationships that ultimately effected community structure. Introduced species of aquatic organisms such as fish (Marcy et al. 2004) and plants (e.g. cattails) have had limited impact; however the potential exists for other invasive species, such as nutria, zebra mussels, and aquatic plants to invade these systems. These land use legacies are representative of a wide range of historical impacts and degradation processes to stream systems that occurred in the region Oacobson et al. 2001). Subsequent to the establishment of the SRS, reforestation of the farms and cut over areas has resulted in a predominant forest cover, reducing non-point discharges and facilitating natural stream recovery. However, construction activities and industrial development prior to the implementation of Clean Water Act standards, likely increased channel sedimentation and runoff to streams from hardened surfaces, or exacerbated erosion in headwaters, such as around F-Area (Kilgo and Blake 2005). In addition, on-SRS some channels were reconfigured direcdy (e.g. Beaver Dam Creek) to accept high volume industrial water releases, or indirecdy restructured by the discharge of reactor water (Indian Grave's Branch and Fourmile Branch). Reduction in fire at wetland/ riparian interface zones has also altered the natural communities and resulted in loss of habitat (e.g. switch cane). Finally, regional air quality problems, such as mercury emissions from coal power plants and industrial mills, have resulted in accumulation of contaminates within these aquatic systems (http://www.ned.doe.gov/coal/E&WR). Similar to urbanization effects (Crawford and Lenat 1989), tnost of these activities would have had negative impacts on aquatic communities. Observations frotn numerous watershed studies have shown that the negative impacts are linear for macro-invertebrate and fish indicators (Karr and Schlosser 1978, Booth and Reinelt 1993). The SRS implemented a Wedand Mitigation Banking and Restoration Program in the late 1990's, primarily focused on depression wedands, such as Carolina Bays (US COE 2001, Barton 2003). The Bank is being used to offset unavoidable impacts from Closure projects and other industrial missions. Soil and Groundwater Closure projects have proposed remediation alternatives that involve treatment and remediation of waste along seeps or streams, which can direcdy impact the aquatic communities and associated riparian zones (Ed McNamee, pers. comun.). The opportunity exists to restore portions of the SRS streams degraded by pre-1950 land uses, or by subsequent pre-compliance industrial activities that could off-set expensive project by project mitigation. This activity will also support SRS natural resource stewardship goals (US DOE 2005). However, major challenges exist.