To effectively manage natural resources within watersheds, it is often necessary to
establish vegetated buffer zones to protect aquatic systems from land use activities that
occur in uplands. The majority of inland Corps of Engineers civil works projects are
constructed along streams and rivers that have adjacent riparian corridors.

There is increasing interest in the value of riparian areas as corridors and buffer strips
on Corps lands, especially as potential wildlife habitat. These landscape features
typically comprise a very small proportion of the landscape, but they provide essential
habitat for a variety of plants and animals. Many riparian buffer zones and corridors on
Corps lands are badly in need of restoration and management. However, Corps project
managers currently have only limited information and few guidelines on design criteria.
This article describes work to develop technical guidelines for restoring and managing
riparian buffer zones and corridors. The potential benefits-with regard to water quality
and many important ecological functions-are significant. Riparian buffer zones remove
nonpoint source pollution from adjacent land-use practices, such as agriculture, and
also provide critical wildlife habitat

Background

A variety of activities affect riparian habitats on Corps lands, including project
construction and operation, agriculture, and recreation. The operation of projects for
flood control, water supply, navigation, and hydropower exerts considerable stress on
the riparian habitats at many Corps projects. These projects often modify natural flows
and flooding regimes and divert ground and surface waters, thus producing substantial
alterations to the riparian zone. Water-based recreation may also cause problems in
some areas. Corps projects are also influenced by surrounding land uses, including
agriculture, livestock grazing, timber harvest, industry, and urbanization. The adverse
impacts of these activities are often detrimental to riparian and aquatic habitats,
especially where protective buffer strips are not retained or established and
subsequently managed as part of the project plan. These conditions can lead to long-
term degradation of water quality, wildlife and fish habitat, and recreation resources,
thus eliminating many economic benefits that could have been achieved through better
guidelines.

Potential Benefits of Buffer Zones

Buffer zones are usually viewed for their potential benefits to water quality, and
numerous studies have addressed the influence of buffer zones on reducing nonpoint
source pollution in watershed runoff. However, recommended design criteria are highly
variable, and relatively few studies have addressed the compatibility of recommended
buffer strip widths for water quality with other important ecological functions.
For example, buffer zones can function as corridors for migration and dispersal of
animals if they are long enough to provide connections of disjunct habitats.
Buffer zones can also provide habitat for plants and animals if enough area is available
to meet life-history needs. Riparian zone width is often positively related to faunal
species richness and density and is an important consideration in management of
riparian ecosystems. The abundance of neotropical migrant birds in eastern riparian
zones is often positively correlated with width of riparian habitat.

Common Questions

Questions often asked regarding restoration and management of buffer zones and
corridors include the following:

What spatial attributes and dimensions (length, width, total area, configuration,
continuous versus fragmented area) and vegetation characteristics (dominants, species
diversity, vertical and horizontal layering) are required to provide a functional riparian
buffer zone system from a broad ecological perspective?

Should buffer strips connect habitats to provide conservation corridors for wildlife? If
so, how? Would these corridors be beneficial to wildlife or only create movement lanes
for predators?

How do various land uses and activities affect the quality and integrity of riparian
zones? What is the cumulative effect of these activities on riparian systems?

What is the value of riparian zones to threatened, endangered, and other sensitive
plant and animal species? Are special designs needed to protect these species?

What are the most environmentally desirable and cost-effective means of restoring
degraded riparian corridors and buffer zones?

What plant species are most appropriate for establishment or improvement of buffer
zones?

Research Objectives

A 3-year research project on corridors and buffer zones was initiated during fiscal year
1997 at the U.S. Army Engineer Waterways Experiment Station (WES) as part of the
Ecosystem Management and Restoration Research Program (EMRRP).

The goal of this research is to develop technical guidelines from current literature and
field studies that will allow Corps personnel to make decisions for riparian buffer zone
and corridor designs based on the most accepted scientific criteria.

Specific Research Objectives

Determine the suitability of these landscape features to provide various project needs
(for example, fish and wildlife habitat improvement/creation, river and stream
conservation, erosion control, noise abatement/visual screening, and reduction of
nonpoint source pollution).

Identify measurable physical, biological, and ecological variables and integrate them
with current design criteria.

Apply these designs to improve planning for and management of buffer strips on Corps
lands.

Richard A. Fischer and Chester 0. Martin, U.S. Army Engineer Waterways Experiment
Station, Vicksburg, MS