US Army Corps of Engineers
Baltimore District


What are wetlands?

Wetlands are defined 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 transitional areas between open water and dry land and are often found along bays, lakes, rivers and streams. Some are drier than others and may have standing water or saturated soil conditions only during part of the year. Examples include bottomland forests, swamps, bogs, marshes, wet meadows and seasonal wet woods.

Why are wetlands important?

Besides performing important water quality functions such as filtration, wetlands provide food and habitat for an abundance and diversity of life unrivaled by most other types of environments. Along with open water, they are breeding, spawning, feeding, cover and nursery areas for fish and are important nesting, migrating, and wintering areas for water fowl and other wildlife.

Wetlands also serve as buffer areas to protect shorelines and stream banks from erosion and storm surges, and act as natural water storage areas during floods and groundwater recharge areas. In addition, wetlands assimilate, recycle, filter and remove pollutants from water.

Why do wetlands need to be identified?

Section 404 of the Clean Water Act requires the Corps authorizations for the discharge of dredged or fill material into waters of the United States, including Jurisdictionalal wetlands. Activities in wetlands for which permits may be required include, but are not limited, to placement of fill material, land clearing involving relocation of soil, road construction, shoreline erosion control, mining, and utility line or pipeline construction.

Recognizing Wetlands

The U. S. Army Corps of Engineers uses three characteristics to determine if an area is a wetland: vegetation, soil and hydrology. Unless an area has been altered or is a rare natural situation, indicators of all three characteristics must be present for an area to be a wetland. Additional Guidance is provided in the Corps’ 1987 Wetlands Delineation Manual (must be viewed in Adobe Acrobat Reader) with guidance. This manual is maintained and updated by the Corps' Waterways Experiment Station (WES) in Vicksburg, MS.


Wetland vegetation consists of plants that require saturated soils to survive as well as plants that gain a competitive advantage over others because they can tolerate prolonged wet soil conditions. Over 5,000 plant types in the United States may occur in wetlands. For example: cattails, bulrushes, cordgrass, sphagnum moss, bald cypress, willows, mangroves, sedges, rushes, arrowheads and water plantains usually occur in wetlands. Also, wetland vegetation may sometimes exhibit physical adaptations, which indicate the presence of water. The adaptations include shallow root systems, swollen trunks or roots growing from the plant stem or trunk above the soil surface.


Soils that occur in wetlands are called hydric soils. Hydric soils have characteristics that indicate they were developed in conditions where soil oxygen is/or was limited by the presence of water for long periods of the growing season. By examining the soil, one can determine if hydric indicators are present.

Hydric soils:

  • contain predominantly decomposed plant material (peat or muck)
  • have a bluish gray or gray color at 10 to 12 inches below the surface layer
  • have dark and dull (brownish black or black) soil as the major color have the odor of rotten eggs
  • may be sandy and have dark stains or streaks of organic material in the upper layer (3 to 12 inches below the surface)


Wetland hydrology refers to the presence of water, either above the soil surface or within the soil, but near the surface (12 to 18 inches below the soil surface, depending on the soil type). For a sufficient period of the year, to deprive the soils of oxygen and significantly influence the plant types which occur in the area. Gauging station or ground water well data provides the most reliable evidence. However, there are field indicators that provide evidence of the periodic presence of inundation or soil saturation.

Some include:

  • Standing or flowing water
  • Waterlogged soil
  • Water marks on trees
  • Drift lines, which are piles of debris oriented in the direction of water movement
  • Debris lodged in trees
  • Thin layers of sediment deposited on leaves or other objects.

These layers of sediment often become consolidated with small plant parts to form crusts on the soil surface. You should ask the Corps office to determine whether an area is a wetland if it has any of the following conditions:

  • The area is flooded or ponded, and occurs in a floodplain or has low spots or is poorly drained such that water is present just below or collects above the soil surface for part of the growing season?
  • The area has plant communities that commonly occur in areas having standing water for part of the growing season?
  • The area has peat or mucky soils or is soft enough that it compresses under foot?
  • The area is periodically flooded by tides?

CAUTION: Wetlands may not be obvious for particular wetland types or at all times of the year.

What to do:

If you plan to perform work or deposit fill material in a waterway or areas where you observe definite indicators of any of the characteristics of a wetland, you should seek assistance from either the local Corps District Office or an expert at making wetland determinations. The appropriate Corps District Office must make the final determination of whether an area is a wetland and whether the activity requires a permit. This office will accurately define the boundary of any wetlands/waterways on your property, and will provide instructions for applying for a permit if necessary.


If you need to know the boundaries of Corps Jurisdictional on your property for waterways and/or wetlands, the Corps will prepare a delineation for small parcels; i.e., less than 1/2 acre (for mom and pop type situations).  For large tracts and all commercial lands, a qualified consultant should map the boundaries according to the directions found under the Jurisdictional Determinations portion of this web site (click on the gold button on the left side of this page).  Once this mapping is complete, it should be submitted to the Corps with a request for confirmation.