Restoration of hydrologic and biogeochemical functions in bottomland hardwoods
The degraded state and loss of ecological functions in many bottomland hardwood swamps and riparian wetlands in the United States are directly related to severe alteration of hydrologic flows in streams, with a concomitant loss of hydric soil conditions due to a significant drop in water table levels in adjacent wetlands. To test modern geomorphologic approaches to stream and wetland restoration we created SWAMP (Southern Wetlands Assessment Park) on Sandy Creek in the piedmont of North Carolina. At this research site in 2004 we restored 600 meters of stream and approximately 3 hectares of bottomland hardwood wetlands in the forested downstream portion of a 500-hectare urban watershed. The Duke Forest/Sandy Creek Wetland Restoration Project goals are to test the affects of alternate hydrologic states on wetland habitat and function as well as improve water quality of Sandy Creek before its confluence with New Hope Creek and eventual flow to Jordan Reservoir. This paper: (1) describes the development and performance of an analytical, event-based, rainfall-runoff model for flood frequency and nutrient export prediction for urban watersheds, (2) presents ground water responses to hydrologic restoration, and (3) assesses water quality and biogeochemical changes within the system. Results from our Nonlinear Reservoir Model (NLRM) indicate that this simple model captures the hydrologic dynamics of the system remarkably well, accurately predicts flooding in the study area, and thus provides a means for assessing the success of future restoration efforts aimed at reducing nutrient export.
