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Definition of Wetlands

The Clean Water Act (33 U.S.C. Section 1251 and following) defines "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 generally include swamps, marshes, bogs and similar areas."

In June 2006, the US Supreme Court handed down its decision in a case known as Rapanos-Carabell (PDF) (104 pp, 787K, About PDF), involving the geographic extent of the area which the Federal Government may regulate as “wetlands” under the Clean Water Act of 1972.


With development, the number of acres of wetlands in the mid-Atlantic region had been decreasing. However, with more awareness of the benefits of wetlands (more wildlife habitat and less flooding) the rate of decrease slowed and in the last few years wetland gains have exceeded wetland losses. The gains have been due in large part to wetlands restoration and mitigation.

Nationwide, more than 50% of wetlands have been lost or destroyed in the past century.

How Wetlands Are Regulated

EPA's Wetlands Regulatory Program is based on Section 404 of the Clean Water Act. EPA:

Other federal and state agencies play a role in the protection of waters and wetlands. They include:

The Army Corps of Engineers:

In addition, many states have their own laws that protect waters and wetlands. EPA and the Corps of Engineers work together with our states to streamline the process and reduce the regulatory burden and duplication of effort.

Fun Facts About Wetlands

Headwater wetlands are the source of many of our rivers and streams, often high in the mountains. Headwater wetlands’ origins are groundwater seeps and rain run-off.

Protecting headwater wetlands, protects our downstream water quality and headwater wetlands act as sponges, retaining water, releasing it slowly to help prevent downstream flooding and erosion.

Headwater wetlands are the first to receive and process nutrients, sediments and toxic materials associated with human activities – if  headwater wetlands are drained or filled,  upland runoff will move directly into streams, compromising downstream water quality.

Global climate change is expected to increase the number and intensity of floods and droughts, threaten our water supplies and affect water quality. Protecting headwater streams slows down flood waters,  filters pollutants, retains sediment and provides flow to our larger streams during droughts.

Headwater wetlands and streams maintain a natural discharge regime, moderate sediment transport downstream, retain nutrients and process organic matter that supports our aquatic bugs, amphibians and native fish.

Migratory waterfowl stop and feed in wetlands, marshes, open waters and shallow waters during their seasonal flights – which find their origins in our upstream wetlands.

Although not often displayed on maps, smaller headwater streams may account for more than 70% of the overall stream channel length in the United States.

Although wetlands cover only about 5% of the land surface in the lower 48 states, they are home to 31% of plant species.

Two thirds of all fish consumed worldwide are dependent on coastal wetlands at some stage in their life cycle.

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