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.

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. Can be fresh or saltwater. Considered wetlands.

R = Riverine. Riverine is tidal and non-tidal moving water contained within a channel. Can be fresh or saltwater.  Considered wetlands.

M = Marine.  Marine is open ocean water overlying the continental shelf and associated coastline.  Considered saltwater.  Considered wetland.

L = Lacustrine.  Lacustrine is water bodies situated in topographic depressions or dammed channels lacking vegetation and greater than 20 acres in size.  Can be fresh or saltwater.  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 = Forested. Woody vegetation over 20 feet in height.

SS = Scrub-Shrub. Woody vegetation less than 20 feet in height.

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.

Wetland Category
Reference Guide

Flats & Beaches:
Classification - E2US, E2FL, E2BB, PUS, M2US, M2BB, M2FL, R1US, R1FL, R2US, R2FL, R3US,R3FL, R4US, R4FL, L2US
Map Marker -

Wetland areas that are intertidal (exposed at low tides, covered at high tides) with less than 30% of the surface covered with vegetation. Tidal mud flats, sand bars, beaches, and shorelines represent most of the flats and beaches category.
Forested Wetlands:
Classification - E2FO, PFO
Map Marker -

Woody vegetation over 20 feet in height, occupying wet soil and/or wet surface conditions. These areas remain wet for extended periods during the growing season.

Fresh Marsh:
Classification - PEM, R1EM2, R2EM2, L2EM2
Map Marker -
Emergent vegetation that is herbaceous hydrophytic species. Marsh species have adapted to predominately non-tidal freshwater conditions and covers more than 30% of the surface. Freshwater marsh is found in low-lying frequently flooded areas, with the water remaining on or near the surface for extended periods of time during the growing season. Vegetation is present for most of the growing season and maintains the same general appearance from one year to the next.

Mosses - Lichen:
Classification - PML
Map Marker -
Moss-Lichen Wetland Class includes areas where mosses or lichens cover substrates and where emergents, shrubs, or trees make up less than 30% of the areal cover. Moss-Lichen dominated wetlands are typically found in northern latitudes and are characterized by soils that are saturated by water from snow and ice meltwater.

Open Water:
Classification - POW, PUB, R1UB, R2UB, L1UB, L2UB, L1OW, L2OW, M1UB, M1OW, M2UB, M2OW, E1UB, E1OW, E2UB, E2OW, R1OW, R2OW, R3UB, R3OW, R1RB, R2RB, R3RB, M1RB, E1RB, L1RB, L2RB, PRB
Map Marker -

Area covered by water. Water is tidal or non-tidal. It is considered fresh water if saline content is less than 0.5 parts per thousand. It is considered salt water if saline content is greater than 0.5 parts per thousand. The category includes rivers, bayous, creeks, intermittent streams, inland ponds and lakes, and delta distributary channels, sloughs, bays, sounds, and interior ponds into marsh.

Reef:
Classification - M1RF, M2RF, E1RF, E2RF
Map Marker -
Reefs are characterized by elevation above the surrounding substrate and interference with normal wave flow usually forming ridge-like or mound-like features. They are primarily below the water surface, but parts of some reefs may be exposed at low tides. The most common reef formers are corals, oysters, and tube worms.

Salt Marsh:
Classification - E2EM, PEM, R1EM2, R2EM2, L2EM2
Map Marker -
Emergent vegetation that is herbaceous hydrophytic species. Marsh species have adapted to tidal saltwater conditions. Saltwater marsh includes low-lying frequently flooded and less frequently flooded high marsh. Vegetation is present for most of the growing season and maintains the same general appearance from one year to the next.

Streambed:
Classification - R1SB, R4SB, E2SB
Map Marker -
Streambed includes the bed of a stream channel that is occupied by water intermittently during periods of abundant water availability. The streambed is in the Riverine System and all channels of the Estuarine System or of the Tidal Subsystem of the Riverine System that are completely dewatered at low tide. The streambed substrate may vary greatly depending on the gradient of the channel, the velocity of the water, and the sediment load and be comprised of bedrock, rubble, cobbles, gravel, sand, mud, non-persistent vegetation, or organic materials.

Submerged Floating Aquatics:
Classification - M1AB, M2AB, E1AB, E2AB, R1AB, R2AB, R3AB, L1AB, L2AB, PAB
Map Marker -
Wetlands and deepwater habitats dominated by plants that grow principally on or below the surface of the water for most of the growing season in most years. They are best developed in relatively permanent water or under conditions of repeated flooding. The plants are either attached to the substrate or float freely in the water above the bottom or on the surface.

Seagrasses: Submerged saltwater flowering plants attached to the bottom found in estuarine or marine environments along shallow coastal areas and in protected bays and lagoons. Depth of seagrasses are limited by water clarity because they require light

Wetland Scrub-Shrub:
Classification - E2SS, PSS
Map Marker -
Areas dominated by woody vegetation less then 20 feet tall. The vegetation includes true shrubs, young trees, and trees or shrubs that may be stunted because of environmental conditions. Wetlands scrub-shrub are flooded for extended periods during the growing season. This type of woody vegetation is invasive into slightly higher elevation areas within the marsh.