Riparian ecosystem creation and restoration: a literature summary

Riparian ecosystems generally compose a minor proportion of surrounding
areas, but typically are more structurally diverse and more productive in plant
and animal biomass than adjacent upland areas. Riparian areas supply food,
cover, and water (especially important in the arid West) for a large diversity
of animals, and serve as migration routes and forest connectors between habitats
for a variety of wildlife, particularly ungulates and birds.

Because riparian ecosystems often are relatively small areas and occur in
conjunction with waterways, they are vulnerable to severe alteration. Riparian
ecosystems throughout the U.S. have been heavily impacted by man's activities.
Riparian ecosystem creation and restoration have been used as mitigation for
project impacts from highway, bridge, and pipeline construction; water
development; flood control channel modifications; industrial and residential
development; agriculture; irrigation; livestock grazing; mining; and accidental
habitat loss.

Creation of a riparian ecosystem in| a more mesic upland area (e.g.,
‘grassland or cropland) adjacent to a river requires appropriate water supply and
grading the topography to suitable elevations to support plantings of riparian
vegetation. Restoration involves returning the ecosystem to pre disturbance
conditions and typically implies revegetation. Removing exotic vegetation or
restoring water supplies to pre disturbance level also may be involved.
Enhancement of riparian ecosystems commonly refers to improving existing
conditions to increase habitat value, usually by increasing plant or community
diversity to increase value for wildlife. Managing a riparian ecosystem
typically involves enhancement techniques. However, creation and restoration
projects often involve use of techniques considered more management-oriented
(e.g., fencing to prevent cattle grazing until planted vegetation of a created
or restored wetland is established).

Protection of an existing riparian ecosystem from impact should be of
utmost importance during planning and construction phases of development
projects. If loss or damage is unavoidable, wetland creation or restoration
can be used as mitigation. Compared to other wetland types (e.g., coastal
wetlands), projects and techniques involving creation or restoration of riparian
ecosystems are not well documented. For example, only 8% of the records in the
WCR Data Base contained information on riparian ecosystems, whereas 31% of the
records contained information on coastal emergent or forested ecosystems. To
provide a source of currently available literature, riparian information from
92 records (primarily published papers or reports) in the U.S. Fish and Wildlife
Service's (FWS) Wetland Creation-Restoration (WCR) Data Base (Schneller-McDonald
et al. 1988) was used to develop a literature summary of creation and restoration
of riparian ecosystems.

The summary provides an overview of the status of riparian ecosystems in
the U.S., a discussion of several riparian functions, and a review of some
techniques used for planning, implementing, monitoring, and measuring project
success of creation-restoration efforts. Case studies of various creation or
restoration projects are used to demonstrate these techniques and to report some
results of their use. Several well-documented case studies are discussed in
detail to illustrate more extensive efforts to plan, implement, or monitor
riparian ecosystem creation-restoration projects.

For the purpose of this report, riparian ecosystems are defined as
landscapes adjacent to drainageways of floodplains that exhibit vegetation, soil,
and hydrologic mosaics along topographic and moisture gradients that are distinct
from the predominant landscape surface types. Major plant communities are
described under palustrine system in Cowardin et al. (1979).

Literature from the WCR Data Base was used to provide a summary of riparian
ecosystem creation-restoration literature. Thus, information concerning natural
systems is not included unless discussed in these articles. This focus allows
the reader to compare relative information available on riparian ecosystem
creation-restoration efforts. However, this focus also results in limited
information in some sections of the report (e.g., Status of Riparian Ecosystems
in the U.S.).

Individuals involved in riparian ecosystem creation-restoration efforts
are encouraged to thoroughly examine available literature on natural and altered
systems. Brinson et al. (1981) provide a comprehensive review and synthesis of
the ecology and status of riparian ecosystems. Over 500 articles are cited in
their 124-page report. Chapters include the following topics: status of
riparian ecosystems in the U.S., ecological functions and properties of riparian
ecosystems (e.g., geomorphology, primary productivity, nutrient cycling,
hydrology), importance of riparian ecosystems to fish and wildlife, and
considerations in valuation (ecologic and economic) of riparian ecosystems.
Brinson et al. (1981) also discuss management of riparian ecosystems. Riparian
ecosystem management literature was not included in the WCR Data Base, unless
the article also discussed creation or restoration.