California Wetlands Information System

Defining Wetlands

What Are Wetlands?

Generally, wetlands are lands where saturation with water is the dominant factor determining the nature of soil development and the types of plant and animal communities living in the soil and on its surface. (Cowardin, Classification of Wetlands and Deepwater Habitats of the United States; FWS/OBS 79/31; December 1979)

Wetlands Definition in Law

As legal protection of and scientific attention to wetlands have increased, so have the number of wetland definitions contained in State and Federal law. Most of these definitions vary slightly but share common terms and concepts. Both State and Federal governments, as well as, wetlands advocates, agree that a single, legally accepted definition of wetlands would be helpful to ensure effective wetlands regulation. The current State/Federal system of wetlands regulations and definitions is fragmented and cumbersome.

Governor Pete Wilson acknowledged this predicament in his California Wetlands Conservation Policy (August 1993) and promised that "the State will work toward the adoption of a consistent wetlands definition to address this situation. This definition will, to the greatest extent possible, be consistent with the definition and wetlands delineation manual used by the Federal government. The definition will also recognize California's unique wetlands types, and not apply to prior converted croplands currently exempt from federal regulation."

The following examples address the breadth and variability of the current State and federal wetlands definitions. Please note that the following examples are only selected definitions contained in State and Federal law and should not be considered in whole as a definitive list.

State Definitions

In conjunction with adopting a wetlands policy on March 9, 1987 the California Fish and Game Commission assigned the Department of Fish and Game (DFG) the task of recommending a wetlands definition. The DFG found the U.S. Fish and Wildlife Service (USFWS) wetland definition and classification system to be the most biologically valid. The DFG staff use this definition as a guide in identifying wetlands while conducting on-site inspections for the implementation of its Commission's wetlands policy (See USFWS definition below).

Wetlands found in the "coastal zone" are regulated under the California Coastal Act of 1976 (CCA) and the federal Coastal Zone Management Act (CZMA), and are within jurisdiction of the California Coastal Commission. Under the CCA, wetlands are defined as land within the coastal zone which may be covered periodically or permanently with shallow water and include saltwater marshes, freshwater marshes, open or closed brackish water marshes, swamps, mudflats, and fens. (Pub. Res. Code 30121)

However, further precision in wetlands jurisdiction is provided to the Coastal Commission under the California Code of Regulations. Under these provisions wetlands are defined as:

" where the water table is at near, or above the land surface long enough to promote the formation of hydric soils or to support the growth of hydrophytes, and shall also include types of wetlands where vegetation is lacking and soil is poorly developed or absent as a result of frequent drastic fluctuations of surface water levels, wave action, water flow, turbidity or high concentration of salts or other substances in the substrate. Such wetlands can be recognized by the presence of surface water or saturated substrate at some during each year and their location within, or adjacent to vegetated wetland or deepwater habitats." (14 CCR 13577)
Because San Francisco Bay does not lie within the Coastal Commission's jurisdiction, coastal management of the bay is provided by another State agency, the San Francisco Bay Conservation and Development Commission (BCDC). The primary State law governing the BCDC, the McAteer-Petris Act, does not define wetlands but does outline the BCDC's jurisdiction respective of wetlands.

"Managed wetlands consisting of all areas which have been diked off from the bay and have been maintained during the three years immediately preceding the effective date of the amendment of this section during the 1969 Regular Session of the Legislature as a duck hunting preserve, game refuge or for agriculture." (Gov. Code 66610(b))
While the above examples are either biological or regulatory in nature, other definitions in State law provide for the acquisition, enhancement, and preservation of wetlands. For instance, under the Keene-Nejedly California Wetlands Preservation Act wetlands are defined as:

"...streams, channels, lakes reservoirs, bays, estuaries, lagoons, marshes, and the lands underlying and adjoining such waters, whether permanently or intermittently submerged to the extent that such waters and lands support and contain significant fish, wildlife, recreational, aesthetic, or scientific purposes." (Pub. Res. Code 5812)
Lastly, under California Wildlife Protection Act "wetlands" means lands which may be covered periodically or permanently with shallow water and which include saltwater marshes, freshwater marshes, open or closed brackish water marshes, swamps, mudflats, fens, and vernal pools. (Fish & Game Code 2785)

Federal Definitions

The U.S. Army Corps of Engineers (Corps) used the following regulatory definition of wetlands for developing a field method for determining the jurisdictional boundaries for regulatory purposes. The Corps definition utilizes the "three-parameter test" for permitting and planning purposes. These three parameters are hydrophytic vegetation, hydric soils, and wetland hydrology. Under this definition an area is considered a wetland only if all three conditions are present. The Corps definition states:

The term "wetlands" means those areas that are inundated or saturated by surface water or groundwater 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. (33 CFR 328.3(b); 40 CFR 230.3(t))
The U.S. Fish and Wildlife Service defines wetlands in a different manner. This definition states:

"Wetlands are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. For purposes of this classification, wetlands must have one or more of the following three attributes: (1) at least periodically, the land supports hydrophytes, (2) the substrate is predominantly undrained hydric soil; and (3) the substrate is non-soil and is saturated with water or covered by shallow water at some time during the growing season of each year." (Cowardin, 1979)
The USFWS definition includes, swamps; freshwater, brackish water, and saltwater marshes; bogs; vernal pools, periodically inundated saltflats; intertidal mudflats; wet meadows; wet pastures; springs and seeps; portions of lakes, ponds, rivers and streams; and all other areas which are periodically or permanently covered by shallow water, or dominated by hydrophytic vegetation, or in which the soils are predominantly hydric in nature.


Wetlands may be further defined through classification. In California, wetlands are commonly classified according to the length of time that an area is inundated or saturated by water or the types of plants and animals an area supports. For example, if an area is only saturated or inundated for part of the year it can be classified as a seasonal or perennial wetlands. Likewise, areas that are inundated or saturated throughout the entire year may be referred to as permanent wetlands.

Other classification systems exist however. Cowardin (1979) recognizes the following five major wetland classifications: marine, estuarine, lacustrine, riverine, and palustrine. Marine and estuarine wetlands are associated with the ocean and include coastal wetlands, such as tidal marshes. Lacustrine wetlands are associated with lakes, while riverine wetlands are found along rivers and streams. Palustrine wetlands may be isolated or connected wet areas and include marshes, swamps, and bogs.

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