Merriam-Webster Dictionary (online)

“Riparian - Relating to or living or located on the bank of a natural watercourse (such as a river) or sometimes of a lake or tidewater.”

United States Agencies

U.S. Department of Agriculture Natural Resource Conservation Service (USDA-NRCS, 2005)

“Riparian areas are ecosystems that occur along watercourses or water bodies. They are distinctly different from the surrounding lands because of unique soil and vegetation characteristics that are strongly influenced by free or unbound water in the soil. Riparian ecosystems occupy the transitional area between the terrestrial and aquatic ecosystems. Typical examples would include floodplains, stream banks, and lake shores.”

U.S. Forest Service (USFS, 2000)

“Riparian areas are geographically delineated areas, with distinctive resource values and characteristics, that are comprised of the aquatic and riparian ecosystems, floodplains, and wetlands. They include all areas within a horizontal distance of 100 feet from the edge of perennial streams or other water bodies…. A riparian ecosystem is a transition between the aquatic ecosystem and the adjacent terrestrial ecosystem and is identified by soil characteristics and distinctive vegetation communities that require free and unbound water.”

Bureau of Land Management (BLM, 1999)

“A riparian area is an area of land directly influenced by permanent water. It has visible vegetation or physical characteristics reflective of permanent water influence. Lake shores and stream banks are typical riparian areas. Excluded are such sites as ephemeral streams or washes that do not exhibit the presence of vegetation dependent upon free water in the soil.”

U.S. Fish and Wildlife Service (FWS, 1998)

“Riparian areas are plant communities contiguous to and affected by surface and sub-surface hydrologic features of perennial or intermittent lotic and lentic water bodies (rivers, streams, lakes, or drainage ways). Riparian areas have one or both of the following characteristics: (1) distinctively different vegetative species than adjacent areas, and (2) species similar to adjacent areas but exhibiting more vigorous or robust growth forms. Riparian areas are usually transitional between wetlands and upland.”

U.S. Environmental Protection Agency (EPA) and National Oceanic and Atmospheric Administration (NOAA) Coastal Zone Management Act (EPA, 1993)

“Riparian areas are vegetated ecosystems along a water body through which energy, materials and water pass. Riparian areas characteristically have a high water table and are subject to periodic flooding and influence from the adjacent water body. These systems encompass wetlands, uplands, or some combinations of these two land forms. They will not in all cases have all the characteristics necessary for them to be classified as wetlands.”

Society for Range Management and Bureau of Land Management ( Anderson , 1987)

“A riparian area is a distinct ecological site or combination of sites in which soil moisture is sufficiently in excess of that available locally, due to run-on or subsurface seepage, so as to result in an existing or potential soil-vegetation complex that depicts the influence of that extra soil moisture. Riparian areas may be associated with lakes, reservoirs, estuaries, springs, bogs, wet meadows, muskegs and intermittent and perennial streams. The distinctive soil-vegetation complex is the differentiating criteria.”

Arizona agencies and organizations

Tonto National Forest (Grove, 2005)

“Riparian areas - Land areas which are directly influenced by water. Usually have visible vegetative or physical characteristics showing this water influence. Stream sides, lake borders, or marshes are typical riparian areas.” The definition is from the glossaries of both the Tonto National Forest Plan (1985) and its Environmental Impact Statement (EIS).

Arizona Riparian Council (ARC, 1994)

“Riparian is defined as vegetation, habitats, or ecosystems that are associated with bodies of water (streams or lakes) or are dependent on the existence of perennial, intermittent or ephemeral surface or subsurface water drainage.”

Significant Publications

Lowrance et al., (1985)

“Riparian areas - Complex assemblage of plants and other organisms in an environment adjacent to water. Without definite boundaries, it may include streambanks, floodplain, and wetlands, ... forming a transitional zone between upland and aquatic habitat. Mainly linear in shape and extent, they are characterized by laterally flowing water that rises and falls at least once within a growing season.”

Ilhardt et al., (2000)

“Riparian areas - Functionally defined as three-dimensional ecotones of interaction that include terrestrial and aquatic ecosystems, that extend down into the groundwater, up to above the canopy, outward across the floodplain, up the near slopes that drain to the water, laterally into the terrestrial ecosystem, and along the water course at a variable width.”

National Research Council (NRC, 2002)

“Riparian areas - Transitional between terrestrial and aquatic ecosystems and are distinguished by gradients in biophysical conditions, ecological processes, and biota. They are areas through which surface and subsurface hydrology connect water bodies with their adjacent uplands. They include those portions of terrestrial ecosystems that significantly influence exchanges of energy and matter with aquatic ecosystems (i.e., a zone of influence). Riparian areas are adjacent to perennial, intermittent, and ephemeral streams, lakes, and estuarine–marine shorelines.”

Ffolliott et al., (2004)

“Riparian areas - Situated in the interfaces between terrestrial and aquatic ecosystems, located along the banks of rivers and perennial, intermittent and ephemeral streams and around the edges of lakes, ponds, springs bogs and meadows.”

Operational Definition

Chattahoochee-Oconee National Forests (2004)

“Riparian areas - Associated with the aquatic ecosystem and that portion of the terrestrial ecosystem that is substantially affected by the presence of surface and ground water. Consists of perennial streams, natural ponds, lakes, wetlands, and adjacent lands with soils, vegetation and landform indicative of high soil moisture or frequent flooding. Have variable widths that are determined by ecologically significant boundaries rather than arbitrary distances. The extent of riparian areas is determined on-the-ground using features of soil, landform and vegetation. No one feature is used alone to delineate these ecosystems. Characteristics include: Soils - soils with poor drainage or a high water table during the growing season. Landform - the 100-year floodplain [relatively flat areas including the area subject to 1 percent 9100 year recurrence) or greater chance of flooding in any given year). Vegetation - the presence of hydrophytic (water-loving) vegetation, classified as obligates or facultative riparian species.”