The legal definition provided by the US Army Corps of Engineers (USACE):
Those areas that are inundated or saturated by surface 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)).
In layman’s terms:
A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play many roles in the environment, principally water purification, flood control, carbon sink and shoreline stability. Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life.
Integral Wetland Solutions biologists are wetland experts that help you reach your goals.
Most wetlands are not visibly wet with standing water. Nevertheless, the resulting biodiversity on seemingly dry soil holds clues to the wetland’s status that must be understood and interpreted correctly by an experienced biologist, to ensure a safe path through your permitting process.