Jurisdictional wetlands -- those that are regulated by the U.S. Army Corps of Engineers (Corps) under Section 404 -- must exhibit all three haracteristics: hydrology, hydrophytes, and hydric soils (US ACOE 1987). It is important to understand that some areas that function as wetlands ecologically, but exhibit only one or two of the three characteristics, do not currently qualify as Corps jurisdictional wetlands and thus activities in these wetlands are not regulated under the Section 404 program. Such wetlands, however, may perform valuable functions.
Another federal agency, the U.S. Fish and Wildlife Service defines wetlands as: lands that are 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, and that have one or more of the following attributes:
At least periodically, the land supports predominantly hydrophytes; the substrate is predominantly undrained hydric soil; and, 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 et al. 1979).
This definition differs from the EPA and U.S. Army Corps of Engineers definition used for jurisdictional wetlands which requires that all three attributes (hydrophytes, hydric soils, and hydrology) be evident. The 1987 Corps of Engineers Manual on wetland delineation does not consider unvegetated aquatic sites such as mudflats and coral reefs or vegetated shallow water to be wetland areas, whereas the Cowardin classification does (US ACOE 1987).