What is a Wetland?

The U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency (EPA) define wetlands as 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 are areas that generally include swamps, marshes, bogs, and similar areas.  

Wetlands are areas that are covered by water or have waterlogged soils for long periods (14-21 days) during the growing season. Plants growing in wetlands are capable of living in saturated soil conditions for at least part of the growing season. Wetlands such as swamps and marshes are often obvious, but some wetlands are not easily recognized, often because they are dry during part of the year or "they just don't look very wet" from the roadside.

Some of these wetland types include, but are not limited to, many bottomland forests, pocosins, pine savannahs, bogs, wet meadows, potholes and wet tundra. Information is given here to help you determine if you have a wetland. If you intend to place dredged or fill material in a wetland or in an area that might be a wetland, contact your local Corps Regulatory Office to see if a permit is required.

Why is it necessary to consider whether an area is a wetland?

Section 404 of the Clean Water Act requires that anyone interested in depositing dredged or fill material into "waters of the United States, including wetlands," must receive authorization for such activities. The Corps of Engineers has been assigned responsibility for administering the Section 404 permitting process. The final determination of whether an area is a wetland and whether the activity requires a permit, must be made by a Corps Regulatory Office.

Activities in wetlands which may require a permit include, but are not limited to:

 •  Placement of fill material

 •  Ditching activities when the excavated material is side-cast

 •  Levee and dike construction

 •  Mechanized land clearing

 •  Land leveling

 •  Most road construction

 •  Dam construction

How can wetlands be recognized?

The Corps of Engineers uses three characteristics of wetlands when making wetland determinations: vegetation, soil and hydrology. Each characteristic is discussed below. Unless an area has been altered or is a rare natural situation, wetland indicators of all three characteristics must be present during some portion of the growing season for an area to be classified as a wetland.

There are some general situations in which an area has a strong probability of being a wetland. If any of the following situations occur, you should ask the local Corps office to determine whether the area is a wetland.

  • Area occurs in a floodplain or otherwise has low spots in which water stands at or above the soil surface during the growing season. Caution: Most wetlands lack both standing water and waterlogged soils during at least part of the growing season.
  • Area has plant communities that commonly occur in areas having standing water for part of the growing season (e.g., cypress-gum swamps, cordgrass marshes, cattail marshes, bulrush and tule marshes and sphagnum bogs).
  • Area has soils that are called peats or mucks.
  • Area is periodically flooded by tides, even if only by strong, wind-driven, or spring tides.

Many wetlands can be readily identified by the general situation stated above. For the boundary of these areas and numerous other wetlands, however, it is unclear whether these situations occur. In such cases, it is necessary to carefully examine the area for wetland indicators of the three major characteristics of wetlands. Indicators of these characteristics, which may indicate that the area is a wetland, are described below:

Vegetation Indicators

Nearly 5,000 plant types in the United States may occur in wetlands. These plants, known as hydrophytic vegetation, are listed in the Corps' 2012 National Wetland Plant List (NWPL). The NWPL and other information concerning the NWPL can be found on the Corps Headquarters Regulatory web page under the listing of Technical and Biological Resources.

However, you can usually determine if wetland vegetation is present by knowing a relatively few plant types that commonly occur in your area. For example, cattails, bulrushes, cordgrass, sphagnum moss, bald cypress, willows, mangroves, sedges, rushes, arrowheads and water plantains usually occur in wetlands.

Other indicators of plants growing in wetlands include trees having shallow root systems, swollen trunks (e.g., bald cypress, tupelo gum) or roots found growing from the plant stem or trunk above the soil surface. Several Corps offices have published pictorial guides of representative wetland plant types.

If you cannot determine whether the plant types in your area are those that commonly occur in wetlands, ask the local Corps Regulatory Office or a local botanist for assistance.

Soil Indicators

There are approximately 2,000 named soils in the U.S. that may occur in wetlands. Such soils, called hydric soils, have characteristics that indicate they were developed in conditions where soil oxygen is limited by the presence of saturated soil for long periods during the growing season. If the soil in your area is listed as hydric by the Natural Resources Conservation Service (NRCS), the area might be a wetland.

If the name of the soil in your area is not known, an examination of the soil can determine the presence of any hydric soil indicators, such as:

  • Soil consists predominantly of decomposed plant material (peats or mucks).
  • Soil has a thick layer of decomposing plant material on the surface.
  • Soil has a bluish gray or gray color below the surface, or the major color of the soil at this depth is dark (brownish black or black) and dull.
  • Soil has the odor of rotten eggs.
  • Soil is sandy and has a layer of decomposing plant material at the soil surface.
  • Soil is sandy and has dark stains or dark streaks of organic material in the upper layer below the soil surface. These streaks are decomposed plant material attached to the soil particles. When soil from these streaks is rubbed between the fingers, a dark stain is left on the fingers.

Hydrology Indicators

Wetland hydrology refers to the presence of water at or above the soil surface for a sufficient period of the year to significantly influence the plant types and soils that occur in the area. Although the most reliable evidence of wetland hydrology may be provided by gaging station or groundwater well data, such information is limited for most areas and, when available, requires analysis by trained individuals. Most hydrologic indicators can be observed during field inspection, but do not reveal the frequency, timing, or duration of flooding or soil saturation.

Indicators of periodic flooding or soil saturation:

  • Standing or flowing water is observed on the area during the growing season.
  • Soil is waterlogged during the growing season.
  • Water marks are present on trees or other vertical objects. Such marks indicate that water periodically covers the area to the depth shown on the objects.
  • Drift lines, which are small piles of debris oriented in the direction of water movement through an area, are present. These often occur along contours and represent the approximate extent of flooding in an area.
  • Debris is lodged in trees or piled against other object by water.
  • Thin layers of sediments are deposited on leaves or other objects. Sometimes these become consolidated with small plant parts to form discernible crust on the soil surface.