SREL Reprint #2483

Restoration of a severely impacted riparian wetland system - The Pen Branch Project

Christopher Barton1, Eric A. Nelson2, Randall K. Kolka3, Kenneth W. McLeod4, William H. Conner5,
Michelle Lakly6, Douglas Martin2, John Wigginton7, Carl C. Trettin1, Joe Wisniewski8

1Center for Forested Wetlands Research, USDA Forest Service, SREL - Drawer E, Aiken, SC 29802, USA
2Savannah River Technology Center, Westinghouse Savannah River Company, USA
3Department of Forestry, University of Kentucky, USA
4Savannah River Ecology Laboratory, University of Georgia, USA
5Baruch Forest Science Institute, Clemson University, USA
6Institute of Ecology, University of Georgia, USA
7School of Forestry, Auburn University USA
8Wisniewski and Associates Inc, USA

Introduction: The Savannah River Swamp is a 3020 ha forested wetland on the floodplain of the Savannah River and is located on the Department of Energy's Savannah River Site (SRS) near Aiken, SC (Fig. 1). Historically the swamp consisted of approximately 50% baldcypress-water tupelo stands, 40% mixed bottomland hardwood stands, and 10% shrub, marsh, and open water. Tributeries of the river were typical of Southeastern bottomland hardwood forests. The hydrology was controlled by flow from four creeks that drain into the swamp and by flooding of the Savannah River. Upstream dams on the Savannah River have caused some alteration of the water levels and timing of flooding within the floodplain (Schneider et al., 1989).
Major impacts to the swamp hydrology occurred with the completion of nuclear production reactors and one coal-fired powerhouse at the SRS in the early 1950s. Water was pumped from the Savannah River, through secondary heat exchangers of the reactors, and discharged into three of the tributary streams that flow into the swamp. Flow in one of the tributaries, Pen Branch, was typically 0.3 m3 s-1 (10-20 cfs) prior to reactor pumping and 11.0 m3 s-1 (400 cfs) during pumping. Elevated flows continued from 1954 to 1988 at various levels. The sustained increases in water volume resulted in overflow of the original stream banks and the creation of additional floodplain. Accompanying this was considerable erosion of a deep silt layer on the newly formed delta. Heated was was discharged directly into Pen Branch and water temperature in the stream often exceeded 65°C. The nearly continuous flooding of the swamp, the thermal load of the water, and the heavy silting resulted in complete mortality of the original vegetation in large areas of the floodplain (Fig. 2). . . .

SREL Reprint #2483

Barton, C., E. A. Nelson, R. K. Kolka, K. W. McLeod, W. H. Conner, M. Lakly, D. Martin, J. Wigginton, C. C. Trettin, and J. Wisniewski. 2000. Restoration of a severely impacted riparian wetland system - The Pen Branch Project. Ecological Engineering 15:S3-S15.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).