Losing function through wetland mitigation in central Pennsylvania, USA

Area of Science:

• Environmental Science
• Ecology
• Hydrology

Background:

• The Clean Water Act mandates wetland mitigation for dredging and filling impacts.
• Current mitigation assessment often relies on vegetative cover and acreage, inferring function rather than directly measuring it.

Purpose of the Study:

• To compare the functional capacity of created wetlands with natural reference wetlands using hydrogeomorphic (HGM) functional assessment models.
• To evaluate the success of wetland mitigation efforts in central Pennsylvania.

Main Methods:

• Utilized hydrogeomorphic (HGM) functional assessment models to measure structural variables in created and natural wetlands.
• Compared functional capacity between created wetlands and two sets of natural reference wetlands (impacted site geomorphic setting and similar floodplain setting).

Main Results:

• Created wetlands in a floodplain setting differed significantly from natural ridge-side slope reference wetlands in seven of ten assessed functions.
• Functional differences persisted even when compared to natural floodplain wetlands, primarily due to unnatural hydrologic regimes and landscape characteristics.
• The created wetlands did not meet the criteria for successful wetland mitigation.

Conclusions:

• Hydrogeomorphic (HGM) functional assessment models are crucial for accurately evaluating wetland mitigation success.
• Wetland mitigation efforts require careful consideration of geomorphic setting, hydrology, and surrounding landscape characteristics.
• Current wetland mitigation practices may not adequately ensure the restoration of ecological functions.