Evaluation of Shoreline Plantings for Wetland Mitigation at Coddle Creek Reservoir in Piedmont North Carolina

Abstract

Wetland mitigation provides a method of compensating for loss of vital wetlandfunctions while allowing unavoidable wetland degradation. Coddle Creek Reservoir,located in northwest Cabarrus County, North Carolina, has been developed as a drinking water reservoir for nearby municipalities experiencing dramatic populationincreases. Approximately 356 acres of shoreline plantings were installed to mitigatewetland losses associated with development of the reservoir. Recently, considerable controversy has developed over mitigation projects and their effectiveness in replacingwetland functions. The objective of this study was to evaluate the mitigation plantings atCoddle Creek Reservoir by comparing them to naturally developed shoreline vegetation at a nearby reservoir. Results will be used for long-range management of vegetation atCoddle Creek as well as future reservoir construction projects.Vegetation, soil, and hydrologic data were collected at Mountain Island Lake to determine natural community development along reservoir shorelines. Natural successionhas created distinct community types progressing from the Mountain Island Lake shorelineupslope along an elevational (moisture) gradient. Project design at Coddle CreekReservoir delineated three specific planting zones to mimic natural community developmentalong a moisture gradient. Results of this study suggest that design and initialestablishment of vegetation zones at Coddle Creek Reservoir closely resemble the naturalzonation of vegetation adjacent to Mountain Island Lake. A narrow fringe of wetlandvegetation occurs along the reservoir shoreline that progresses upslope into a zone of transitional vegetation that blends into the upland zone that dominated prior to reservoirconstruction. This wetland zone is most limited by the amount of wetland soils presentadjacent to the reservoir. The extent of wetland soil conversion is strongly correlated to the slope of the site.