Seattle District Header Image

SEATTLE DISTRICT

Home
Home > Missions > Civil Works > Regulatory > Permit Guidebook > Wetlands

Electronic Permit Guidebook

               Click here for permit information 

     Click here for permit information

Wetlands

Collapse All Expand All
Wetland systems have been called many names: bogs, marshes, swamps, ponds, prairie potholes, sloughs, fens, wet meadows, bottomlands and more. 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. Wetlands are areas that are covered by water or have waterlogged soils for long periods of time during the growing season. Plants growing in wetlands are capable of living in saturated soil conditions for at least part of the growing season. The U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency define wetlands as the following: 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. So remember, not all wetlands are exactly the same, not all wetlands are "wet", and not all "wet" areas are wetlands.

Wetlands are among the most biologically productive natural ecosystems in the world. They can be compared to tropical rain forests and coral reefs in the diversity of species they support. There's more life in a healthy wetland than there is in almost any other kind of habitat. Wetlands perform important physical and chemical functions and benefit people in many ways.

1) Wetlands often function like natural tubs or sponges, storing water (floodwater, or surface water that collects in isolated depressions) and slowly releasing it. Trees and other wetland vegetation help slow floodwaters. This combined action, storage and slowing, can lower flood heights and reduce the water's erosive potential. Wetlands thus, reduce the likelihood of flood damage to crops in agricultural areas help control increases in the rate and volume of runoff in urban areas buffer shorelines against erosion.

2) Wetlands are vital to the survival of various plants and animals, including threatened and endangered species. Fish and wildlife use wetlands in many different ways - breeding, feeding, nursing, and more.

  • Many migratory birds rest in wetlands on the way to their winter or summer homes. If you visit a wetland in the fall or spring, you could see hundreds or even thousands of birds.
  • The young of certain animals, like fish and crabs, spend their earliest days in wetlands before moving on to open waters.
  • The vegetation in wetlands provides great hiding areas and there is a rich food supply.
    Many of the animals that visit or inhabit wetlands are endangered. In fact approximately 35 percent of all endangered species live in wetlands.

3) Wetlands are the filters of the water cycle. The intertwining roots, leaves and fibers of the dense plant life remove sediment and pollutants from the slow-moving water. When water runs out of the wetland and returns to a stream, it is once again clean.

4) Wetlands help to maintain water quality by temporarily holding back nutrients and sediment from runoff, allowing many wastes, such as some pesticides, to degrade into less harmful forms.

5) Wetlands help improve water quality, including that of drinking water, by intercepting surface runoff and removing or retaining its nutrients, processing organic wastes, and reducing sediment before it reaches open water.

6) Wetlands trap sediments. As flood waters move through wetlands, silt and sediments settle out. This function helps to prevent streams, lakes, and other bodies of water downstream from getting clogged with a build-up of sediment.

7) Wetlands act as storm breakers. Wetlands protect shoreline areas by breaking the wind and waves from storms.

8) Wetlands are good for the economy. Wetlands furnish a wealth of natural products, including fish, shellfish, timber, wild rice, and furs. In commercial terms, wetland products contribute millions of dollars per year to the nation's economy. In addition to this, an estimated 50 million people spend approximately $10 billion each year observing and photographing wetlands-dependent birds.

9) Wetlands provide recreational opportunities. Wetlands are an attractive area for visiting and provide opportunities for popular activities including hiking, hunting, fishing, bird watching, and boating and canoeing.



Wetlands are identified by looking closely at three characteristics: vegetation indicators, hydrology (water or "wetness") indicators, and soil indicators.  Generally, when wetland plants (certain species used as wetland indicators called hydrophytic vegetation), wetland soils (hydric soils), and a certain degree of wetness (hydrology) prevail, the area is called a wetland; when these things do not prevail, the area is called an upland.

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 coordinate with us to determine whether the area is a wetland. Many wetlands can be easily identified in these general situations. However, in situations where it is unclear if wetland indicators prevail, it is necessary to hire a professional scientist who is experienced at completing wetland delineations.

  • Areas that occur in a floodplain or depressions (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.
  • Areas that have plant communities that commonly occur in areas having standing water for part of the growing season (e.g., cattail marshes, bulrush marshes, and sphagnum bogs).
  • Areas that have soils that are called peats or mucks.
  • Areas that are periodically flooded by tides, even if only by strong, wind-driven tides.

A wetland delineation is a study which identifies the exact boundaries of a wetland.  A wetland delineation must be performed in accordance with the 1987 Corps of Engineers Wetland Delineation Manual and the appropriate Regional Supplement.  A qualified wetland scientist should perform the delineation and prepare a delineation report which conforms with Corps requirements.  You should send the delineation to the Corps of Engineers so that the Corps can determine if the boundaries are accurate and can be used for the purposes of obtaining a permit from the Corps.  Listed below are important manuals and documents needed to complete a delineation:

Plants are the most obvious indicator of a wetland. Wetland plants called "hydrophytes" (hydro = water, phyte = plant). Wetland plants grow in water or in a substrate that at least periodically is deficient in oxygen due to excessive water content. Hydrophytes have certain adaptations that allow them to thrive in inundated or saturated soils where non-hydrophytes (upland plants) cannot. Most obvious of the wetland plant adaptations have to do with capturing and transporting oxygen. Listed below are websites which provide further detailed information on wetland plants:

Wetland soils, called hydric soils, have characteristics that indicate they were developed in conditions where oxygen in the soil is limited by the presence of water in soil (saturation) for long periods of time during the growing season. In these situations, the wetland soil becomes so saturated with water that it cannot hold much, if any, oxygen. The prolonged presence of water, and the lack of oxygen, cause chemical changes that affect the color of the soil. By observing color characteristics of a soil sample, soil scientists can determine if it is a hydric soil and how long or how frequently an area has been wet.  Listed below are documents and websites which provide detailed information on hydric soils:


The presence of water (hydrology) at or near the surface for a designated amount of time, is an indicator of a wetland. Water in Washington's wetlands come from several sources: precipitation in the form of rain or snow, tidal action, flood events, and ground water. Most hydrologic indicators can be observed during a typical field inspection. Evidence of wetland hydrology may also be provided by gaging station or groundwater well data, but such information is limited for most areas and, when available, requires analysis by a trained individual. Listed below are documents and websites providing resources to help you determine wetland hydrology on a site: