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October 2004
Prepared by the Habitat Committee
Factual Basis
A riparian zone is the area of land adjacent to a river or stream. These zones are not uniform in
size, but vary in width and shape depending on the nature of the landscape. The riparian zone
can be a small stretch of land or may encompass the whole floodplain of a river, where the river
and shallow groundwater supplement the local precipitation. The riparian zone serves many
important functions that are vital to a healthy river system.
Riparian zones function as the transition zone (or ecotone) between uplands and the aquatic
system of the river. This zone acts as a buffer, filtering materials washing into watercourses.
Vegetation in the riparian zone physically stabilizes sediments that comprise the floodplain, thus
reducing the passage of soil and sediment lost from eroding upland areas and preventing
excessive soil erosion and deterioration of the whole riverine system. The riparian zone can also
help prevent fertilizers, pesticides and other natural, applied, or spilled chemicals and nutrients
from running or leaching into the river.
Riparian vegetation reduces downstream sediment loads and improves water quality by trapping
sediment transported during floods. Floodplain vegetation also reduces downstream damage
from flood erosion by causing a flooding river to spread into the floodplain and slow its velocity.
Riparian vegetation helps prevent the river from down-cutting or cutting a straight path, thus
promoting the meandering nature of channels, increasing groundwater recharge, and maintaining
an elevated water table.
The complexity of riparian vegetation depends on the volume and timing of river flows.
Watershed characteristics, precipitation, and other climatic events influence these factors.
Periodic floods, such as spring runoff, influence establishment of riparian plant seedlings. High
flows scour portions of the floodplain and re-deposit sediments, allowing tree seedlings to
germinate and grow on bare sandbars without competition from established plants. Many native
riparian plant species disperse seeds as annual high flows subside. The gradually declining flows
keep flood-deposited soils moist as seedlings put down roots. As plants mature, they continue to
depend on water from the shallow floodplain aquifer or upland runoff.
Structurally complex riparian vegetation communities provide many different habitats and
support a diverse array of animal species. Canopies of plants growing on stream banks also
provide shade to the river, ensuring cool stream water necessary for many aquatic species. The
roots of riparian plants also stabilize and create overhanging banks, which, along with vegetative
deadfall in the stream, provide habitat for fish and other aquatic organisms. Riparian zones are
also the source of organic input to streams (such as leaf litter), providing the fundamental food
source for many aquatic organisms.
Policy Statement
Human activities that directly impact the riparian zone must be managed to protect the riparian
ecosystem. Alteration of riparian land and vegetation for agricultural, grazing, forestry, mining,
development or other purposes should be restricted and restoration processes initiated in order to
maintain functioning riparian zones.
 Establishment and Enforcement of Riparian Buffers
Through federal, state and local regulation, riparian buffer zones should be established for all
rivers and streams, including intermittent and non-fish bearing streams, taking into account the
ecology of the particular watershed. For that reason, buffer widths will vary from river to river.
Land-use laws and regulations, such as those pertaining to development, forestry and agriculture
should be consistent with riparian zone protection including the maintenance of buffer zones.
Land-use laws must be enforced, which requires sufficient enforcement funding.
 Invasive Species Control
Programs providing for the maintenance and restoration of native vegetation in riparian zones
and preventing the invasion of exotic species should be adopted and implemented.
 Dam Operations
Dams should be managed to simulate natural flow regimes essential to healthy riparian zones.
Operations should provide for natural flooding events, and natural seasonal variability.
Increasing base flow releases at appropriate times can also help maintain riparian vegetation that
was established under artificial flows. Rapid, unnatural flow fluctuations below dams, which are
most prevalent at hydroelectric dams, should be eliminated through establishment of ecologically
sound ramping rates.
 Recreation Management
River access sites and other recreation facilities should be located to minimize impact to riparian
zones. Campsites should be located at an appropriate distance from the river to prevent
destruction of riparian vegetation and erosion.
 Riparian Fencing
To prevent livestock destruction of riparian vegetation, riparian zones on grazed lands should be
fenced consistent with the appropriate buffer width for the particular river or stream in question.