National Wetland Inventory
Classification
Reference
Guide
The labels on the National Wetland Inventory Maps are based on a hierarchical classification scheme of System, Subsystem, Class, Subclass, Water Modifier, and Special Modifiers. In WETMAAP, to keep it simple, we are concerned with only the System and Class level identifiers.
| System | Class | Water Modifier |
| E | 2 | EM | 1 | P | x |
| Subsystem | Subclass | Special Modifier |
E = Estuarine. Estuarine is tidal, saline content greater than 0.5 parts per thousand. Considered salt water. Considered wetlands.
P = Palustrine. Palustrine is tidal or non-tidal (mostly non-tidal) with a saline content less than 0.5 parts per thousand. Considered fresh water. Considered wetlands.
U = Upland. Upland is too dry to be considered wetlands.
AB = Aquatic Bed. Seagrass, lily pads, water hyacinth, etc. Because they vary in location and extent from one year to the next. This is considered to be open water.
OW = Open Water
UB = Unconsolidated Bottom. Water covers the surface all the time. Considered as open water.
EM = Emergent Vegetation. Herbaceous vegetation
US = Unconsolidated Shore. Exposed sand or mud at low tide or low water stages. Not vegetated.
FL = Flats. Exposed sand or mud at low tide or low water stages. Not vegetated.
BB = Beaches and Bars. Exposed or flooded sand or mud at low tide or low water stages. Not vegetated.
FO or F = Forested. Woody vegetation over 20 feet in height.
SS = Scrub-Shrub. Woody vegetation less than 20 feet in height.
R = Range. Vegetation dominated by herbaceous plants. Unimproved, fallow, or mowed grass dominated area.
A = Agriculture. Improved pasture and cropland. Planted crops or grass.
U = Urban. Developed areas for residential, industrial, and commercial uses.
B = Barren. Not vegetated. Not developed.
RF = Reef. Primarily below the water surface features formed by coral, oysters, and worms.
ML = Moss - Lichen. Areas where substrate is covered by moss - lichen vegetation.
SB = Streambed. Bed of a stream channel that is occupied by water intermittently.
To see the corresponding WETMAAP to NWI Classification categories