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Types of Wetlands in America's WETLAND


(visit [8/27/02])

These definitions and characteristic descriptions are taken almost verbatim from Wetlands Training Institute (1991).

DEFINITION:  Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.  Wetlands generally include swamps, marshes, bogs, and similar areas.



1.  Vegetation:  The prevalent vegetation consists of macrophytes (the normal large plants one sees easily) that are typically adapted to areas having hydrologic and soil conditions described above.  Hydrophytic (water adapted) species, due to morphological, physiological, and/or reproductive adaptations, have the ability to grow, effectively compete, reproduce, and/or persist in anaerobic (no available oxygen) soil conditions.  Indicators of vegetation associated with wetlands are variable, but the strongest case exists when more then 50% of the dominant species are Obligate Wetland Plants (OBL - virtually always occur [.99%] in wetlands), Facultative Wetland Plants (FACW - plants that occur >67%-99% of the time in wetlands), or Facultative Plants (FAC - plants with a similar likelihood [33%-67%] of occurring in wetlands and nonwetlands).

2.  Soils:  Soils are present and have been classified as hydric (associated with water), or they possess characteristics that are associated with reducing soil conditions.

3.  Hydrology:  The area is inundated either permanently or periodically at a mean water depth of 6.6 ft, or the soil is saturated to the surface at some time during the growing season of the prevalent vegetation.



The following wetlands classification is adapted from Cowardin et al. (1979).

Palustrine Wetlands  

All non-tidal freshwater wetlands containing trees, shrubs, emergents; also, such habitats where tidal driven salinity is below 0.5 ppt.  Non-tidal wetlands lacking these plant characteristics and being less than 20 acres in size are also palustrine.  Includes the following types of Palustrine Wetlands:

Bottomland hardwoods - Basically, the alluvial plains of rivers, characterized by a mixture of trees and other vegetation that can tolerate occasional flooding (gum, oak, ash, maples, hackberry, holly, bays, magnolia, elderberry, etc.).

Bottomland hardwood (note the palmetto plants) in Alexandria, LA.


Swamps:  Areas that are usually flooded and have woody vegetation.  In the south, the characteristic species include Bald Cypress (Taxodium disticum) and Tupelo gum (Nyssa aquatica) (hence "cypress-tupelo swamps").  Their natural salinity is very near 0 ppt (means 0 parts of salt per thousand parts of water; as an example, ocean waters are 35-39 ppt).

A swamp scene from Jean Lafitte National Park.  Note the alligator in the foreground.

View of a Cypress swamp in coastal Louisiana.  The tree in the foreground is a twisted tupelo gum.


Cypress knees in a swamp.  Their function is to add support to the tree in a watery environment.

Tupelo Gum also have “knees” that lend support.

Marsh:  Areas with standing water for part of the year that also contain non-woody standing vegetation.

Freshwater marsh - Marshes having a salinity range of 0-2 ppt with very high plant species diversity (at least 89 species of plants representing >0.01% of the total).  Typical resident plants include Cattail (Typha), Water Lilies (Nymphaea, Nymphoides, and Nuphar), Sedge (Scirpus), and many, many more.


Flotant marsh (quaking prairie) - A type of marsh, usually found in freshwater or intermediate situations, composed of thick, floating mats of vegetation with open water beneath.  


Flotant marsh looks like all marsh, except it can support the weight of a human.


As flotant marshes age, they gradually change their look and nature.  The Photo above has cypress trees and wax myrtle bushes rooted in it, but they are still floating and not rooted in the bottom.  Gradually, they will root in the bottom and the flotant marsh will no longer exist.


Intermediate marsh - Marshes having a salinity range of 2+-10 ppt with high plant species diversity (about 51 species of plants representing >0.01% of the total).  Visually, these marshes exhibit a mix of freshwater and brackish marshes, having Wiregrass (Spartina patens) and such plants as Cattail (Typha), Water Lilies (Nymphaea, Nymphoides, and Nuphar), Sedge (Scirpus), etc.

Intermediate marsh in Cameron Parish.

Intermediate marsh from about 400 ft.

Brackish marsh - Marshes having a salinity of 10+-20 ppt with moderate plant species diversity (about 36 species of plants representing >0.01% of the total).  The characteristic plant is Wiregrass (Spartina patens) (usually more than 50% of the total vegetation).

Brackish marsh in Lafourche Parish (from about 400 ft).


[see Estuarine Wetlands section below for the final type of marsh - saline, or salt]

Bogs - Peat-accumulating wetlands that receive most of their water from precipitation and exist where a high water table waterlogs the soil.  Precipitation leaches out the nutrients and the bogs are acidic.  Have acid adapted plants, especially sphagnum moss.

There are no bogs in the Louisiana coastal plain.  They are common above Lake Pontchartrain and elsewhere.

Lacustrine Wetlands  

Basically, lakes and ponds characterized by sparse vegetation.  Wetlands that are situated in a depression or dammed channel; lacks shrubs, trees, or other emergent plants with greater than a 30% areal coverage; and cover a total area of 20 acres or more.  Salinity is always less than 0.5 ppt.  Includes lakes, reservoirs, playa lakes (intermittent), and low-salinity tidal lakes.


Riverine Wetlands  

Basically, rivers, streams, bayous, etc. with sparse vegetation.  All freshwater wetlands contained within a channel.  Subject to the nature of the channel (bottom type, slope, source of water, etc.).  Includes rivers, creeks, bayous, canals, and the like.  Salinity is less than 0.5 ppt.  When plants are present, they are often rooted in the bottom (water lilies, algae) and are most abundant in eddys along the margins.


Estuarine Wetlands  

Tidally influenced bodies of water and their adjacent wetlands that are semi-enclosed by land but are at least periodically open to the sea at one end and have freshwater flowing into the other.  Subject to salinity fluctuations depending on the amount of freshwater received from adjacent river(s) and the amount of sea water from the adjacent sea.  

Specific zones:

Open estuary:  The open water portion.  Salinity may range from fresh near the mouths of rivers and bayous to very saline near the open sea.

Lake Pontchartrain fits this category best.

Saline (salt) marsh:  Marshes having a salinity of >20 ppt (frequently full sea water: 35 ppt) with low plant species diversity (about 13 species of plants representing >0.01% of the total).  The characteristic plant is Oyster grass (Spartina alterniflora) (usually more than 60%, not infrequently 100%, of the total vegetation).  Black Rush (Juncus romerianus) may also be abundant, as is Pickleweed (Salicornia sp.) and Batis (Batis maritima).

[Though part of the Palustrine Wetlands, the other types of marsh feed the Estuarine Wetlands and may be found nearby.] 

Salt marsh on Timbalier Island, LA, at low tide.

                    Salt marsh in St. Augustine, FL.  Note how uniform salt marshes are.

Salt marsh near Grand Isle, Louisiana.  Note that most is Oystergrass (in the front), with darker stands of Black Rush.  This is typical of salt marsh.


Marine Wetlands

The open sea over the continental shelf.  Subject to waves, currents, and tides.  Salinity is typically 30+ ppt (sea water is 35 ppt).  Vegetation includes algae and phytoplankton.

Description: Oil from BP Deep Horison SE Venice 5-2-10 RAT 14.jpg

This image is an oil slick taken a couple of days after the BP Macondo blowout.