Environmental Engineering Reference
In-Depth Information
2.2.2.2.1 Riparian Zone
The riparian zone is the interface between land and a stream or river. The riparian is the transitional
area of the river corridor between the river and upland areas and is deined by Webster's as “relating
to or living or located on the bank of a natural watercourse (as a river) or sometimes of a lake or a
tidewater.” But, deinitions vary and include (Fischer et al. 2001, 2002):
“Associated with water courses. Riparian may refer to vegetation associated with large rivers
or with small, even intermittent drainages such as arroyos” (Dick-Peddie and Hubbard 1977).
“Riparian areas are three-dimensional ecotones of interaction that include terrestrial and
aquatic ecosystems, that extend down into the groundwater, up above the canopy, outward
across the loodplain, up the near-slopes that drain to the water, laterally into the terrestrial
ecosystem, and along the water course at a variable width” (Ilhardt et al. 2000).
“A distinct ecological site, or combination of sites, in which soil moisture is suficiently in
excess of that otherwise available locally, due to run-off and subsurface seepage, so as to
result in an existing or potential soil vegetation complex that depicts the inluence of that
extra soil moisture” (Anderson 1987).
“As ecotones, they encompass sharp gradients of environmental factors, ecological
processes and vegetative communities. Riparian areas are not easily delineated but are
composed of mosaics of landforms, communities and environments within the larger land-
scape” (Gregory et al. 1991).
“Environs of freshwater bodies, watercourses, and surface-emergent aquifers (springs,
seeps, and oases) whose transported waters provide soil moisture in excess of that oth-
erwise available through local precipitation to potentially support the growth of mesic
vegetation” (Warner and Hendrix 1984).
“Land inclusive of hydrophytes and/or with soil that is saturated by ground water for at
least part of the growing season within the rooting depth of potential native vegetation”
(Brosofske 1996).
“Riparian areas are transitional between terrestrial and aquatic ecosystems and are distin-
guished by gradients in biophysical conditions, ecological processes, and biota (Figure 2.21).
They are areas through which surface and subsurface hydrology connect waterbodies with
their adjacent uplands. They include those portions of terrestrial ecosystems that signii-
cantly inluence exchanges of energy and matter with aquatic ecosystems (i.e., a zone of
inluence). Riparian areas are adjacent to perennial, intermittent, and ephemeral streams,
lakes, and estuarine-marine shorelines” (National Research Council 2002).
So, why is the deinition of a riparian zone important? The deinition may impact management
decisions and it also has regulatory implications. For example, is a riparian zone a wetland? If so, and
particularly if the contiguous river is navigable, there is a body of law intended to protect the ripar-
ian zone, such as under Section 404 of the CWA. Under this section, anyone wanting to discharge ill
material into “waters of the United States” must obtain a permit from the COE. However, the National
Research Council (2002) indicated that “riparian areas generally do not satisfy regulatory and other
deinitions of 'wetland,' and thus are not encompassed by regulatory programs for wetland protection.”
In general, no federal statute provides direct protection for riparian zones. Certain federal laws do
require an evaluation of the adverse effects that would be caused by federal actions, along with the
consideration of less environmentally damaging alternatives, and although not speciically focused on
riparian zones, they may include them as part of the evaluation. Other federal laws, such as the Farm
Bill, provide incentives for moving intensive agricultural practices away from streams by installing
riparian buffers. Other programs promote the development, restoration, or conservation of riparian
buffer zones, such as the National Buffer Conservation Initiative, which is intended to encourage the
use of conservation buffer strips by agricultural producers and other landowners in both urban and
rural settings. The COE considers that although it does not have the authority to directly regulate
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