The North Carolina Division of Coastal Management (DCM) has developed a coastal area wetlands conservation plan which relies on adequate knowledge of the location and extent of wetlands by watershed in coastal NC. After reviewing existing data, DCM determined that none of the data could be used exclusively as a wetlands inventory for the conservation plan. Therefore, DCM has developed wetland mapping methods using geographic information systems (GIS) and existing spatial data to accommodate a limited time schedule and large land area. Three primary spatial data layers provide information that are assembled into the DCM wetlands data. These layers are the National Wetlands Inventory (NWI), county soils (DSL), and classified land use/land cover from TM satellite imagery. In addition, an update was performed using a more recent version of land use/land cover data. The NWI and DSL data are 1:24,000 scale, vector data. The imagery is 30 meter resolution, filtered and unfiltered, raster data. Extracting the most relevant information from each of these layers allows DCM to produce the best information about the location and extent of Coastal Plain wetlands available today. DCM's classification scheme is based on both vegetative cover and hydrogeomorphic character. Wetland classes currently recognized by DCM are: Salt/Brackish Marsh, Estuarine Shrub-Shrub, Estuarine Forest, Maritime Swamp Forest, Freshwater Marsh, Pocosin, Bottomland Hardwood, Swamp Forest, Headwater Swamp, Hardwood Flat, Pine Flat, Managed Pineland, Human Impacted In addition, modifiers may be applied to any of these categories indicating that they have been partially drained, cleared of vegetation, or recently cutover. An automated Arc/Info model considers the NWI classification and the imagery classification in assigning a wetland type to each polygon. Soil types are used to determine whether or not marginal areas are considered to be wetlands, including managed pine areas. Once the automation is complete, an interactive session allows the user to assign wetlands to classes specific to their position in the landscape. A hydrographic data layer is used in addition to the layers mentioned previously to more easily interpret the landscape position and hydrogeomorphology (HGM) of the wetlands. For example, a temporarily flooded, hardwood area may be classified as bottomland hardwood or hardwood flat, depending on its location: adjacent to a stream or within an interfluvial divide, respectively. Finally, each wetland is assigned to an HGM class of riverine, flat/depressional, headwater or estuarine. In addition to automated and manual processing, and a limited amount of field verification is performed.
These data were created to assist local, state, and federal government agencies and others in making resource management decisions and in land use planning.
Because of overall data filesize, the statewide dataset was clipped by riverbasin. coverage filesizes: (by riverbasin, in megabytes): Cape Fear (/cpf_wets) - 131 Chowan (/cho_wets) - 21.6 Lumber (/lbr_wets) - 54.1 Neuse (/neu_wets) - 91.7 Pasquotank (/pas_wets) - 35.6 Roanoke (/roa_wets) - 24.1 Tar-Pamlico (/tar_wets) - 58.1 White Oak (/wok_wets) - 31.9
publication date
These data are advisory in nature. They are not a substitute for an on-site determination of jurisdictional wetlands. Although every effort was taken to ensure the accuracy and validity of wetland location and extent, these data contain inherent errors and limits. Surfaces mapped from remotely sensed data have certain degrees of error and accuracy limits. The actual boundaries may differ from those shown in these data. Wetlands smaller than one acre often are overlooked at this scale and may not be included in these data. There also may be cases in which regulatory agencies' determinations of the existence or lack of wetlands differ from these data. While every effort has been made to ensure that these data are accurate and reliable within limits of the current state of the art, DCM cannot assume liability for any damages caused by inaccuracies in the map of supporting data. DCM makes no warranty, express or implied, nor does the fact of distribution constitute such a warranty.
A comprehensive accuracy assessment of these data was performed by DCM using funds provided by the Environmental Protection Agency. Random field points were collected by DCM staff and compared to this data set. For more information see the DCM publication "An Accuracy Assessment of GIS Wetland Mapping in the Coastal Counties of North Carolina".
These data were originally processed by USGS 7.5 minute quadrangle and by county. Upon completion of all quadrangles and all counties, each quadrangle was dissolved by the attributes included here and all quadrangles were joined together using the Arc/Info "mapjoin" command. Digital data and hard copy maps were checked extensively for consistency and completeness by GIS analysts and wetland specialists on DCM's staff. There may be inconsistencies in these data along county boundaries. This is due mainly to the fact that the soils data used for development of this data set was mapped by county and was not edge-matched or otherwise made consistent at county boundaries.
These data represent areas within the 20 coastal counties which fall under the jurisdiction of the Division of Coastal Management and an additional 17 counties within the NC Inner Coastal Plain. These data are not a substitute for an on-site determination of jurisdictional wetlands. Wetlands smaller than one acre are often overlooked at this scale and may not be included in these data.
Accuracy varies depending on source scale and/or resolution of the data layer from which each wetland polygon is derived.
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Three primary spatial data layers provide information that are assembled into the DCM wetlands data. These layers are the National Wetlands Inventory (NWI), county soils (DSL), and classified land use/land cover from TM satellite imagery. In addition, an update was performed using a more recent version (1996) of land use/land cover data. The NWI and DSL data are 1:24,000 scale, vector data. The imagery is 30 meter resolution, filtered and unfiltered, raster data. An automated Arc/Info model considers the NWI classification and the imagery classification in assigning a wetland type to each polygon. Soil types are used to determine whether or not marginal areas are considered to be wetlands, including managed pine areas. Imagery is used primarily to determine the extent of managed pine areas, as well as areas where vegetation has been removed and recently cutover areas. Once the automation is complete, an interactive session allows the user to assign wetlands to classes specific to their position in the landscape. A hydrographic data layer is used in addition to the layers mentioned previously to more easily interpret the landscape position and hydrogeomorphology (HGM) of the wetlands. For example, a temporarily flooded, hardwood area may be classified as bottomland hardwood or hardwood flat, depending on its location: adjacent to a stream or within an interfluvial divide, respectively. Finally, each wetland is assigned to an HGM class of riverine, flat/depressional, headwater or estuarine. In addition to automated and manual processing, a limited amount of field verification is performed.
Area of polygon
Software computed
Perimeter of polygon
Software computed
Internal feature number
Software computed
Feature identification number
User Defined
DCM Wetland Type (by DCM numeric value)
Defined by DCM based on automated or manual processing of
Non-wetland; could be upland, water, or tidal flat
Combination of all data layers
Salt/Brackish Marsh
Primarily NWI data layer
Freshwater Marsh
Primarily NWI data layer
Estuarine Shrub/Scrub
Primarily NWI data layer
Pocosin
Primarily NWI and soils data layers
Bottomland Hardwood
Primarily NWI data layer
Swamp Forest
Primarily NWI data layer
Hardwood Flat
Primarily NWI data layer
Pine Flat
Primarily NWI and soils data layers
Managed Pineland
Primarily Landsat and soils data layers
Estuarine Forest
Primarily NWI data layer
Maritime Swamp Forest
Primarily NWI data layer
Headwater Swamp
Primarily NWI data layer (Primarily from manual rather than automated classification)
Partially Drained Salt/Brackish Marsh
Primarily NWI data layer Note: All drained modifiers result primarily from automated classification of NWI data.
Partially Drained Freshwater Marsh
Primarily NWI data layer
Partially Drained Estuarine Shrub/Scrub
Primarily NWI data layer
Partially Drained Pocosin
Primarily NWI and soils data layers
Partially Drained Bottomland Hardwood
Primarily NWI data layer
Partially Drained Swamp Forest
Primarily NWI data layer
Partially Drained Hardwood Flat
Primarily NWI data layer
Partially Drained Pine Flat
Primarily NWI and soils data layers
Partially Drained Estuarine Forest
Primarily NWI data layer
Partially Drained Maritime Forest
Primarily NWI data layer
Partially Drained Headwater Swamp
Primarily NWI data layer
Human Impacted
Primarily NWI and Landsat data layers
Cleared Estuarine Shrub/Scrub
Primarily NWI and Landsat data layers
Cleared Pocosin
Combination of all data layers
Cleared Bottomland Hardwood
Primarily NWI and Landsat data layers
Cleared Swamp Forest
Primarily NWI and Landsat data layers
Cleared Hardwood Flat
Primarily NWI and Landsat data layers
Cleared Pine Flat
Combination of all data layers
Cleared Estuarine Forest
Primarily NWI and Landsat data layers
Cleared Maritime Forest
Primarily NWI and Landsat data layers
Cleared Headwater Swamp
Primarily NWI and Landsat data layers
Cutover Estuarine Shrub/Scrub
Primarily NWI and Landsat data layers
Cutover Pocosin
Combination of all data layers
Cutover Bottomland Hardwood
Primarily NWI and Landsat data layers
Cutover Swamp Forest
Primarily NWI and Landsat data layers
Cutover Hardwood Flat
Primarily NWI and Landsat data layers
Cutover Pine Flat
Combinatio of all data layers
Cutover Estuarine Forest
Primarily NWI and Landsat data layers
Cutover Maritime Swamp Forest
Primarily NWI and Landsat data layers
Cutover Headwater Swamp
Primarily NWI and Landsat data layers
Hydrogeomorphic Classification
NC Division of Coastal Management
Riverine HGM classification
Manual classification based on wetland type and/or proximity to streams
Flat/Depressional HGM classification
Manual classification based on wetland type and/or proximity to streams
Headwater HGM classification
Manual classification based on wetland type and/or proximity to streams
Estuarine HGM classification
Manual classification based on wetland type
DCM Wetland Type (character field containing actual type rather than number)
See w-type attribute above
Coastal North Carolina wetlands are presented by common type. A hydrogeomorphic classification is included as well. The wetlands presented here are broken down into the following categories. A brief explanation of each wetland type follows its name. Salt/Brackish Marsh (w-type 1) Any salt marsh or other marsh subject to regular or occasional flooding by tides, including wind tides (whether or not the tide waters reach the marshland areas through natural or artificial watercourses), as long as this flooding does not include hurricane or tropical storm waters. Coastal wetland plant species include: smooth cordgrass; black needlerush; glasswort; salt grass; sea lavender; salt marsh bullrush; saw grass; cattail; salt meadow cordgrass; and big cordgrass Estuarine Shrub Scrub (w-type 3) Any shrub/scrub dominated community subject to occasional flooding by tides, including wind tides (whether or not the tide waters reach these areas through natural or artificial watercourses). Typical species include wax myrtle and eastern red cedar. Estuarine Forested (w-type 15) A forested wetland community subject to occasional flooding by tides, including wind tides (whether or not the tide waters reach the marshland areas through natural or artificial watercourses). Examples include pine-dominated communities with rushes in the understory or fringe swamp communities such as those that occur along the Albemarle and Pamlico sounds. Maritime Swamp Forest (w-type 16) A forested community characterized by its stunted growth due to the stresses imposed by its proximity to salt spray from the ocean. Typical vegetation includes live oak, red maple and swamp tupelo. Freshwater Marsh (w-type 2) Herbaceous areas that are flooded for extended periods during the growing season. Included are marshes within lacustrine systems, managed impoundments, some Carolina Bays, and other non- tidal marshes (i.e. marshes which do not fall into the Salt/Brackish Marsh category). Typical communities include species of sedges, millets, rushes and grasses that are not specified in the coastal wetland regulations. Also included are giant cane, arrowhead, pickeralweed, arrow arum, smartweed, and cattail Pocosin (w-type 4) Freshwater shrub/scrub communities (i.e. non-Estuarine shrub/scrub) dominated by evergreen shrubs, often mixed with pond or loblolly pines. Typically occur on saturated, acid, nutrient poor, sandy or peaty soils; usually removed from large streams; and subject to periodic burning. Bottomland Hardwood (w-type 6) Riverine forested or occasionally shrub/scrub communities usually occurring in floodplains, that are seasonally flooded. Typical species include oaks (overcup, water, laurel, swamp chestnut), sweet gum, green ash, cottonwoods, willows, river birch, and occasionally pines. Swamp Forest (w-type 7) Very poorly drained riverine or non-riverine forested or occasionally shrub/scrub communities which are semi-permanently flooded, including temporarily flooded depressional systems. Typical species include cypress, black gum, water tupelo, green ash and red maple. Headwater Swamp (w-type 17) Wooded, riverine systems along first order streams. These include hardwood dominated communities with soil that is moist most of the year. Channels receive their water from overland flow and rarely overflow their own banks. Hardwood Flat (w-type 9) Poorly drained interstream flats not associated with rivers or estuaries. Seasonally saturated by high water table or poor drainage. Species vary greatly but often include sweet gum and red maple. Pine Flat (w-type 10) Freshwater, seasonally saturated pine communities on hydric soils that may become quite dry for part of the year. Generally occur in flat or nearly flat areas that are not associated with a river or stream system. Usually dominated by loblolly pine. This category does not include managed pine systems. Managed Pineland (w-type 11) Seasonally saturated, managed pine forests (usually loblolly pine) occurring on hydric soils. Since this category is based primarily on soils data and 30 meter resolution satellite imagery, it is less accurate than the other wetland categories. Human Impacted (w-type 40) Areas of human impact have physically disturbed the wetland, but the area is still a wetland. Impoundments and some cutovers are included in this category, as well as other disturbed areas, such as power lines. Partially Drained Wetland (w-type 21-37) Any wetland system described above that is, or has been, effectively drained (according to the National Wetlands Inventory). Cutover Wetland (w-type 63-77) Areas for which satellite imagery indicates a lack of vegetation in 1994. These areas are likely to still be wetlands, however, they have been recently cut over. Vegetation in these areas may be regenerating naturally, or the area may be in use for silvicultural activities. Note that marshes can not be considered cutover. Cleared Wetland (w-type 43-57) Areas of hydric soils for which satellite imagery indicates a lack of vegetation in both 1988 and 1994. These areas are likely to no longer be wetlands.
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