United StatM
Environmental Protection
Agancy
Offica of Water (WH-556F).
Office of Wattands, Ocaana,
and Watersheds (A-104 F)
EPA843-F-93-001 j
March 1993
WETLANDS FACT SHEET* 9
Definition and Delineation
Definition
Since the 1970's, the U.S. Army Corps of
Engineers (Corps) and the US. Environmental
Protection Agency (EPA) have used the same
definition of wetlands for regulatory purposes:
Wetlands an anas that an inundated or satu-
rated 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 anas.
Basically, wetlands are areas where the
frequent and prolonged presence of water at or
near the soil surface drives the natural system -
the kind of soils that form and the plants that
grow, and the fish and/or wildlife communities
that use the habitat Swamps, marshes and bogs
are well-recognized types of wetlands, but there
aremanyimportantspecific wetland types, such
as vernal pools, playas and prairie potholes, that
have drier or more variable water regimes than
those well-recognized by the general public.
Field Indicators
When the upper part of the soil is satu-
rated with water at growing season tempera-
tures, soil organisms consume the oxygen in the
soil, and conditions unsuitable for most plants
quickly develop. Such conditions also cause the
development of soil characteristics (e.g., color
and texture) that are diagnostic of so called
"hydric soils". The plants that can grow in such
conditions are called "hydrophytes" (e.g., marsh
grasses). Together, hydric soilsand hydrophytes
FOR MORE INFORMATION: Call the EPA
Wetlands Hotime» at 1-800-832-7828
are useful field indicators of the presence of
wetlands and are essential for field identifica-
tion of wetlands.
The actual presence or absence of water
itself (Le., by ponding, flooding, or soil satura-
tion), however, is a less reliable indicator of the
presence of wetlands. Except for wetlands
flooded by ocean tides, the hydrology of wet-
lands fluctuates as a result of rainfall patterns,
snowmelt, dry seasons and droughts. Some of
the most well-known wetlands, such as the Ev-
erglades and Mississippi bottomland hardwood
swamps, are often dry. Conversely, many up-
land areas are very wet during and shortly after
wet weather. Such natural fluctuations must be
taken into account when identifying areas sub-
ject to federal wetlands jurisdiction. Similarly,
the effects of upstream dams, drainage ditches,
dikes, irrigation and other modifications must
also be considered.
Delineation Manual
EPA and the Corps are currently using
the 1987 Corps of Engineers Wetlands Delinea-
tion Manual to delineate wetlands for the Clean
Water Act Section 404 permit program. Section
404 requires a pernit from the Corps or autho-
rized State for the discharge of dredged or fill
material into the waters of the United States,
including wetlands. The 1987 Manual will re-
main in use pending review of public omments
on the 1991 proposed Manual and the ongoing
National Academy of Sciences study of wet-
lands delineation.
The 1987 manual organizes field indica-
tors into three categories- soils, vegetation, and
hydrology- and has evidence thresholds, or cri-
teria, for each category. With this approach, an
area that meets all three criteria is considered a
wetland.
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