Compensatory stream and wetland mitigation in North Carolina: an evaluation of regulatory success.

Data from a probability sample were used to estimate wetland and stream mitigation success from 2007 to 2009 across North Carolina (NC). "Success" was defined as whether the mitigation site met regulatory requirements in place at the time of construction. Analytical results were weighted by both component counts and mitigation size. Overall mitigation success (including preservation) was estimated at 74 % (SE = 3 %) for wetlands and 75 % (SE = 4 %) for streams in NC. Compared to the results of previous studies, wetland mitigation success rates had increased since the mid-1990s. Differences between mitigation providers (mitigation banks, NC Ecosystem Enhancement Program's design-bid-build and full-delivery programs, NC Department of Transportation and private permittee-responsible mitigation) were generally not significant although permittee-responsible mitigation yielded higher success rates in certain circumstances. Both wetland and stream preservation showed high rates of success and the stream enhancement success rate was significantly higher than that of stream restoration. Additional statistically significant differences when mitigation size was considered included: (1) the Piedmont yielded a lower stream mitigation success rate than other areas of the state, and (2) recently constructed wetland mitigation projects demonstrated a lower success rate than those built prior to 2002. Opportunities for improvement exist in the areas of regulatory record-keeping, understanding the relationship between post-construction establishment and long-term ecological trajectories of stream and wetland restoration projects, incorporation of numeric ecological metrics into mitigation monitoring and success criteria, and adaptation of stream mitigation designs to achieve greater success in the Piedmont.

A proposed methodology to determine accuracy of location and extent of geographically isolated wetlands.

Wetlands can provide significant environmental benefits such as assimilation of pollutants, flood water storage, groundwater recharge, and fish and wildlife habitat. Geographically isolated wetlands (IWs) can provide the same benefits as other wetlands, but are particularly vulnerable to losses from urbanization and agriculture since they are isolated, often smaller, and not equal to other wetlands in regulatory protection. There is a need for a reliable assessment of the total number and area of IWs. Access to this information can provide the foundation to monitor IW loss, and can assist in understanding the ecological effects of such loss as well as help to address regulatory shortcomings. A probability sampling survey methodology that balances statistical considerations, expert opinion, and operational considerations is discussed for assessing the accuracy of IW maps. A simulation exercise was used to illustrate how the proposed sampling methodology will produce reliable results in map accuracy assessment. A wetland map for the Lockwood Folly River watershed, in Brunswick County, NC, was created using historical and recent data and used as the sampling frame in the simulation exercise. An updated wetland map for the same watershed, showing exact locations of wetlands, was used to provide "ground-truth" observations based on wetland delineations approved by the U.S. Army Corps of Engineers. Survey-based accuracy estimates were calculated by comparing site classification differences obtained by using both the original and updated wetland maps.