Hydrologic characterization of two prior converted wetland restoration sites in eastern North Carolina

Wetland losses resulting from conversion to agriculture and other land uses has generated considerable interest in wetland restoration. Increased federal and local regulations have mandated that wetland areas must be protected, and when loss is unavoidable, mitigation and restoration efforts are required. Establishing appropriate hydrologic functions will inherently influence wetland restoration success. This research involved a three-year field study to develop guidelines for restoring wetland hydrologic function to drained agricultural fields. Two field sites (9.2 ha and 10.4 ha) located in Beaufort and Craven Counties, North Carolina, were instrumented and monitored to evaluate the effectiveness of the restoration treatments used. Experimental treatments included two levels of water table management (high outlet control at 15 cm above average land surface and low outlet control at 15 cm below average land surface) and two types of surface contouring (smooth and rough) to control runoff. The restoration treatments imposed at the Beaufort County site created a range of wet conditions. The high water table management, rough microtopography treatment displayed the most consecutive and total number of days with the water table less than 30 cm deep, while the low water table management, smooth microtopography treatment displayed the driest conditions. The restored wetland status of the Craven County site was marginal. Due to both lateral seepage and seepage around the water control structures, the intended levels of water table management at the Craven County site could not be maintained. Roughing of the soil surface reduced the amount of outflow from restoration treatments by approximately 30% compared to the smooth microtopography treatments. Rough microtopography also reduced peak outflow rates and increased the duration of outflow events.