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.
Vegetation: 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.
Soil: 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).
Hydrology: 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, rrift 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.