Regulatory Menu


Wetland Definition

The Corps and the Environmental Protection Agency (EPA) define a wetland(s) as follows: 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.

A major aspect of the program is to determine which areas qualify for protection as wetlands. The Corps’ 1987 Wetlands Delineation Manual is the federal manual for identifying and delineating wetlands. In addition, the Walla Walla District Regulatory office uses the Arid West Regional Supplement and the Mountain West Regional Supplement. For more information on wetland delineations please see Walla Walla District's Guidance for Submittal of Delineation Reports to the Walla Walla District Corps of Engineers.

General Information on Wetlands

Collapse All Expand All
 What is a Wetland?

Wetlands are areas that are covered by water or have waterlogged soils for long periods (14-21 days) during the growing season.  Some wetland types include, but are not limited to, many bottomland forests, freshwater marshes, bogs, wet meadows, potholes and wooded swamps.

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.

If you intend to place dredged or fill material in a wetland or in an area that might be a wetland, contact the local Corps District Office to see if a permit is required. 


 Why are wetlands Important?
As a significant natural resource, wetlands serve important functions relating to fish and wildlife.  Such functions include food chain production, habitat, nesting spawning, rearing and resting sites for aquatic and land species.  They also provide protection of other areas from wave action and erosion; storage areas for storm and flood waters; natural recharge areas where ground and surface water are interconnected; and natural water filtration and purification functions.

Although individual alterations of wetlands may constitute a minor change, the cumulative effect of numerous changes often results in major damage to wetland resources.  The review of applications for alteration of wetlands will include consideration of whether the proposed activity is dependent upon being located in an aquatic environment. 

 Vegetation Indicators

Nearly 5,000 plant types in the United States may occur in wetlands.  These plants, known as hydrophytic vegetation, are listed in US Fish & Wildlife Service regional publications.  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 pictorial guides of representative wetland plant types have been published.  If you cannot determine whether the plant types in your area are those that commonly occur in wetlands, ask the local Corps District Office or a local botanist for assistance.

 Soil Indicators
There are approximately 2,000 named soils in the United States 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, including:
   - 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 a gagging station or groundwater well data, such information is limited for most areas and, when available, requires analysis by trained individuals.  Thus, most hydrologic indicators are those that can be observed during field inspection.  Most do not reveal the frequency, timing, or duration of flooding or the soil saturation.

The following indicators provide some evidence of the periodic presence of 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 erect object. 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.