THE PRACTICAL APPLICATION OF GEOLOGY TO THE MITIGATION AND REGULATION OF ISOLATED WETLANDS

Wetlands are critically important ecosystems that provide ecological value and water quality functions. Although the importance of the ecological and functional value of wetlands in the landscape is well documented, there are still significant gaps in our knowledge of “isolated” wetlands (IWs), especially in regards to water quality and hydrology. Wetlands are considered isolated if they lack a surface water connection to waters of the United States. Isolated wetlands are particularly vulnerable to losses from development and agriculture because they are often surrounded by developable uplands, are often small in size (less than an acre), and have varying degrees of regulatory protection. This project contributes to a better understanding of the hydrologic connectivity to a nearby downgradient water body.

Eleven isolated wetlands were studied, eight in North Carolina and three in South Carolina. The wetlands, surrounding uplands, and an area near the adjacent receiving streams or surface water bodies were cored extensively to determine stratigraphy. Wells were installed in a transect from the wetland to the downstream water body and water level data was obtained one year beginning March 2010. Aquifer pumping tests were conducted at three of the sites. Results indicate a groundwater connection between the isolated wetland and its receiving surface water body in all cases.

All the wetlands in the study were found to have formed in depressions in the surficial sand aquifer, but there were geologic differences among the wetlands. These differences are expressed hydrologically as perched water tables, partially confined aquifers and systems with layers of varying hydraulic conductivity. It is important to conduct this level of hydrogeologic characterization in order to truly understand an individual IW system. This talk will examine how these stratigraphic differences affect the hydrologic regime of the IWs in this study and how the information gained can be used to improve management decisions and provide better protection for these ecosystems.