Saltwater Wetlands
Because the NLCD does not differentiate between freshwater and saltwater wetlands, it was necessary to find a way to distinguish between these two types. According to the Coastal Area Management Act’s Handbook for Development in Coastal North Carolina (3), saltwater wetlands are defined by the Coastal Resources Commission as "any marsh in the 20 coastal counties that regularly or occasionally floods by lunar or wind tides" and which contains one or more of 10 specific plant species (3). The twenty counties in North Carolina that are considered to be coastal are: Beaufort, Bertie, Brunswick, Camden, Carteret, Chowan, Craven, Currituck, Dare, Gates, Hertford, Hyde, New Hanover, Onslow, Pamlico, Pasquotank, Pender, Perquimans, Tyrrell, and Washington. In order to estimate the area of saltwater wetlands in these counties, 20% of the total wetlands in all but three of the coastal counties were converted to saltwater wetlands. In the other three counties, their percentage was estimated using a different percentage because of the large portion of county area near open saltwater. In Dare County 80% of wetlands were converted to saltwater, for Hyde County, 60%, and for Currituck County, 50%. All other wetlands were considered to be freshwater.
Estuaries
Estuaries provide a number of important ecosystem services, such as habitat refugium, waste assimilation and nutrient regulation, making them much more valuable than other areas of open water. However, because the NLCD does not directly distinguish estuaries from other areas of open water, it was necessary to estimate the percentage of open water in North Carolina that can be considered estuarine. For this study, the same conventions that were used to determine saltwater wetlands were used for estuaries, with 20% of all open water in seventeen of the coastal counties converted to the estuary land type and an increased percentage used for the three counties with a high fraction of county area near open saltwater.
Riparian Buffers
In order to identify the area associated with riparian buffers, GIS was used to create a buffer around relevant North Carolina hydrography. The hydrography layer was created by the North Carolina Corporate Geographic Database and was accessed through the UNC GIS Library. Using the buffer wizard in GIS, a 75-foot buffer was created around all rivers categorized as third order or higher. A 75-foot buffer was implemented around such rivers because in Dr. Costanza’s report, rivers of third order were given a 50 foot buffer, and rivers of fourth or fifth order were given a 100 foot buffer. Third order and higher water bodies are used because these water bodies are considered to be more sensitive because of their use and/or proximity to development (JJ2). To simplify, the average was taken and applied to all rivers third order or higher. The total riparian buffer area for the state was calculated, and, for the purposes of this study, it was assumed that riparian buffers were uniformly distributed across the entire state.
Beach and Coastal Shelf
In order to determine beach acreage, an interactive GIS mapping tool provided by the North Carolina Division of Coastal Management (citation) was used to find the length of beachline (in miles) for each of the 20 coastal counties. Each county’s beachline length was then multiplied by 0.10 miles (assumed average beach depth) to determine the beach area for each of the coastal counties. Similarly, the coastal shelf category was created by multiplying the coastline length (in miles) for each of the eight counties with a coastal boundary by a standard width of three miles to find the respective coastal shelf areas. This standard width of three miles was used because it is the width used in Dr. Costanza’s report. The eight counties considered to have a direct coastal boundary for the purposes of this study were Brunswick, New Hanover, Pender, Onslow, Carteret, Hyde, Dare, and Currituck.