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Design Recommendations for Riparian Corridors and Vegetated Buffer Strips

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INTRODUCTION Riparian zones occur as transitional areas between aquatic and upland terrestrial habitats. Although not always well-defined (Fischer et al. 2000), they generally can be described as long, linear strips of vegetation adjacent to streams, rivers, lakes, reservoirs, and other inland aquatic systems that affect or are affected by the presence of water. Riparian zones typically comprise a small percentage of the landscape, often less than 1 percent, yet they frequently harbor a disproportionately high number of wildlife species and perform a disparate number of ecological functions when compared to most upland habitats. Riparian zones have been widely recognized as functionally unique and dynamic ecosystems only within the past 25 years. Even more recently, these areas have become a major focus in the restoration and management of landscapes (Knopf et al. 1988, Naiman, Dcamps, and Pollock 1993). Unfortunately, many riparian zones in North America do not function prope
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ERDC TN-EMRRP-SR-24 1
Low Moderate High
Complexity
Low Moderate High
Value as a Planning Tool
Low Moderate High
Cost
Design Recommendations for
Riparian Corridors and Vegetated
Buffer Strips
by Richard A. Fischer
1
and J. Craig Fischenich
1
April 2000
1
US Army Engineer Research and Development Center, Environmental Laboratory, 3909 Halls Ferry Rd., Vicksburg, MS 39180
INTRODUCTION
Riparian zones occur as transitional areas
between aquatic and upland terrestrial habitats.
Although not always well-defined (Fischer et al.
2000), they generally can be described as long,
linear strips of vegetation adjacent to streams,
rivers, lakes, reservoirs, and other inland
aquatic systems that affect or are affected by
the presence of water. Riparian zones typically
comprise a small percentage of the landscape,
often less than 1 percent, yet they frequently
harbor a disproportionately high number of
wildlife species and perform a disparate
number of ecological functions when compared
to most upland habitats. Riparian zones have
been widely recognized as functionally unique
and dynamic ecosystems only within the past
25 years. Even more recently, these areas
have become a major focus in the restoration
and management of landscapes (Knopf et al.
1988, Naiman, Décamps, and Pollock 1993).
Unfortunately, many riparian zones in North
America do not function properly (e.g., they are
degraded to the point that they do not protect
water quality or provide the resources needed
to make them suitable as wildlife habitat or as
Figure 1. Characteristics of vegetated
riparian buffer strips influence water
quality, wildlife, and recreational
opportunities (photo courtesy of the U.S.
Army Corps of Engineers).
movement corridors). This degradation also
negatively affects many of the other important
functions and values these landscape features
provide.
WHAT IS THE DIFFERENCE
BETWEEN BUFFER STRIPS AND
CORRIDORS?
There is considerable confusion in the literature
regarding both wetlands and riparian zones
(Fischer et al. 2000). At the heart of this
confusion is the proper distinction between
vegetated buffer strips and corridors. Riparian
zones are most commonly referred to as
vegetated buffer strips (e.g., riparian buffer
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strips) or as wildlife movement corridors (e.g.,
riparian corridors). These titles relate to the
principal intended or recognized purpose of the
riparian zones. Understanding the similarities
and differences between these two terms, and
having a clear idea of one’s objectives, can
have major implications for how one might
attempt to manage a riparian ecosystem.
These terms are defined below:
Riparian Buffer Strip. A linear band of
permanent vegetation adjacent to an aquatic
ecosystem intended to maintain or improve
water quality by trapping and removing various
nonpoint source pollutants (NPSP) (e.g.,
contaminants from herbicides and pesticides;
nutrients from fertilizers; and sediment from
upland soils) from both overland and shallow
subsurface flow. Buffer strips occur in a variety
of forms, including herbaceous or grassy
buffers, grassed waterways, or forested
riparian buffer strips. A buffer strip may provide
habitat for a variety of plants and animals if
sufficient land area is retained to meet the life-
history needs of those species. Buffer strips
may also function as movement corridors if
they provide suitable connections between
larger blocks of habitat (see below).
Riparian Corridor. A strip of vegetation that
connects two or more larger patches of
vegetation (i.e., habitat) and through which an
organism will likely move over time. These
landscape features are often referred to as
“conservation corridors,” “wildlife corridors,”
and “dispersal corridors.” Some scientists have
suggested that corridors are a critical tool for
reconnecting fragmented habitat “islands.”
WHY ARE BUFFER STRIPS AND
CORRIDORS IMPORTANT?
The management and restoration of riparian
corridors and vegetated buffer strips is
becoming an increasingly important option for
improving water quality and conserving wildlife
populations. There is solid evidence that
providing riparian buffers of sufficient width
protects and improves water quality by
intercepting NPSP in surface and shallow
subsurface water flow (e.g., Lowrance et al.
1984, 1986; Peterjohn and Correll 1984; Pinay
and Decamps 1988). In the absence of proper
buffer strips, there is a greater requirement for
water treatment plants and other expensive
restoration techniques (Virginia Department of
Forestry 1998).
Buffer strips also clearly provide habitat for a
large variety of plant and animal species,
shade aquatic habitats, and provide organic
matter (e.g., leaves) and large woody debris
that is critical for aquatic organisms. Their role
as movement corridors for wildlife species is
not quite as clear, but they have become a
popular tool in efforts to mitigate fragmentation
and conserve biodiversity. They have been
proposed, and in some cases documented, to
be habitat components that promote faunal
movement, enhance gene flow, and provide
habitats for animals either outright or during
disturbance in adjacent habitats (e.g., clearcut
in upland). However, some scientists suggest
that corridors are being used too frequently and
at the expense of purchasing and conserving
larger blocks of unfragmented habitat.
Vegetated riparian zones in urban areas, often
called “greenbelts” or “greenways,” are
protected open spaces (usually along stream
valleys and rivers) that are managed for
conservation, recreation, and nonmotorized
transportation. They provide numerous social
benefits and are a focus of many community
enhancement programs. Greenways can
provide a community trail system for outdoor
recreation activities, such as hiking, jogging,
bicycling, rollerblading, horseback riding, cross-
country skiing, or walking. Greenways can also
stimulate the economy by providing an array of
economic and quality-of-life benefits.
Numerous studies demonstrate that linear
parks not only can improve the quality of life in
communities, they can increase nearby
property values that in turn increase local tax
revenues (McMahon 1994).
STATE OF THE SCIENCE
Many land managers throughout the country
are in need of improved design criteria when
planning for riparian corridor restoration and
management, and they need information on
how various land uses influence riparian
vegetation, fauna, and water quality. Although
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the value of riparian buffer strips is increasingly
being recognized, information available to
make sound management decisions for
enhancing some of the functions that riparian
zones can provide is presently limited (Fischer
et al. 1999). Criteria for determining proper
dimensions of buffer strips for some functions
is not well-established and recommended
designs are highly variable. Economic, legal,
and political considerations often take
precedence over ecological factors, and most
existing criteria address only reduction or
elimination of NPSP (Lowrance et al. 1984,
1986; Peterjohn and Correll 1984; Pinay and
Decamps 1988). However, water quality
enhancements are only one of many functions
performed by riparian buffers (Budd et al. 1987;
O’Laughlin and Belt 1995). Because of the
lack of information relating riparian zone
characteristics to other specific functions,
management prescriptions (e.g., width
recommendations) are frequently based upon
either water quality considerations or anecdotal
information. There is little regard for the full
range of effects these decisions may be having
on habitat, flood conveyance and storage,
recreation, aesthetics, and other riparian
functions.
Although riparian buffer strips are being planted
along thousands of streambank miles
throughout the country, the benefits of variable
buffer strip designs (e.g., width, length, type of
vegetation, placement within the watershed)
are effectively unrecognized. There have been
few systematic attempts to establish criteria
that mesh water quality width requirements with
conservation and wildlife values; specifically,
the ability of these buffer strips to function as
habitat or as corridors for wildlife dispersal
between habitats in highly fragmented
landscapes. Even less information is available
relating riparian vegetation characteristics to
hydraulic, sediment transport, and bank
stability conditions of streams.
The exact specifications for connectivity
1
provided by wildlife corridors are not well-
1
In this case, connectivity refers to a measure of the
extent to which riparian zones provide for biological and
ecological pathways that sustain plant and animal species
throughout a region.
known. Most connectivity-related research has
been done in predominately agricultural and
forested landscapes, not riparian systems.
Furthermore, it is difficult to extrapolate from
individual species connectivity requirements to
general rules. However, it is known with
certainty that connectivity is important for the
survival of some plant and animal populations.
WHAT ARE THE GENERAL
DESIGN CONSIDERATIONS?
Unfortunately, there is no “one-size-fits-all”
description of an ideal riparian buffer strip.
First and foremost, the primary objectives of a
buffer strip should be determined. Various
objectives might include protection of water
quality, streambank stabilization, downstream
flood attenuation, or provision of wildlife habitat
or movement corridors. In general, the ability
of buffer strips to meet specific objectives is a
function of their position within the watershed,
the composition and density of vegetation
species present, buffer width and length, and
slope. Some benefits can be obtained for
buffers as narrow as a few feet while others
require thousands of feet.
Placement with Watersheds. The spatial
placement of buffer strips within a watershed
can have profound effects on water quality.
Riparian buffers in headwater streams (i.e.,
those adjacent to first-, second-, and third-order
systems) have much greater influences on
overall water quality within a watershed than
those buffers occurring in downstream reaches.
Downstream buffers have proportionally less
impact on polluted water already in the stream
(Alliance for the Chesapeake Bay 1996). Even
the best buffer strips along larger rivers and
streams cannot significantly improve water that
has been degraded by improper buffer
practices higher in the watershed. Many Corps
projects occur along the higher order streams
and rivers and have little or no control over
water quality resulting from land-use practices
higher in the watershed. However, buffer strips
along these larger systems tend to be longer
and wider than low-order systems, thus
potentially providing significant wildlife habitat
and movement corridors.
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GIS can aid in determining where the most
benefit can be accrued from placing buffers on
a landscape. Knowledge of soils and valley-
floor types provides important information
regarding types of channels and riparian
processes likely to be present in a given area
(Hemstrom 1989). Because interactions
between aquatic, riparian, and terrestrial
ecosystems are a function of valley-floor
morphology, digitized GIS data on valley-floor
morphology aids in delineation of specific areas
where erosion potential is high (e.g., where
streams flow through alluvial deposits) or low
(e.g., through bedrock). Thus, critical areas for
buffer strips can be identified before significant
impacts occur.
How Wide and How Long? Most of the focus
on buffer design is the needed width, but the
vegetation assemblage, layout, and length are
also key design parameters. Buffer width, as
defined herein, is measured beginning at the
top of the bank or level of bankfull discharge.
Width recommendations for buffer strips are
either fixed or variable in nature. Fixed-width
buffer strip recommendations tend to be based
on a single parameter or function. They are
easier to enforce and administer by regulatory
agencies but often fail to provide for many
ecological functions (Castelle, Johnson, and
Conolly 1994). Variable width buffer strips are
generally based on a variety of functions and
usually account for site-specific conditions by
having widths adjusted along the length of the
strip depending on adjacent land use, stream
and site conditions (e.g., vegetation,
topography, hydrology), and fish and wildlife
considerations (Castelle, Johnson, and Conolly
1994). Protection of water quality is often the
most common consideration during buffer strip
design recommendations. Although many
buffer strip width recommendations tend to be
arbitrary or based on anecdotal information, the
scientific literature is replete with
recommendations for maintaining or improving
water quality in a variety of different settings
(e.g., various soil types and different slopes)
(Table 1).
Wildlife habitat and movement corridors in
riparian zones are also an important
consideration when determining widths.
Appropriate designs for species conservation
depend on several factors, including type of
stream and taxon of concern (Spackman and
Hughes 1995). Recommended widths for
ecological concerns in buffer strips typically are
much wider than those recommended for water
quality concerns (Fischer et al. 1999; Fischer
2000) (Tables 2 and 3). Table 4 organizes
buffer/corridor widths recommended in the
literature in terms of functions, and Table 5
provides suggestions for general corridor
restoration and management.
Management for long, continuous buffer strips
adjacent to aquatic systems should be a higher
priority in most cases than fragmented strips of
greater width (Weller, Jordan, and Correll
1998). Continuous buffers are more effective
at moderating stream temperatures, reducing
gaps in protection from NPSP, and providing
movement corridors for wildlife. Unfragmented
buffer strips are also important as habitat. For
example, Gaines (1974) found that yellow-
billed cuckoos in California most often occur
where the riparian vegetation exceeds 300 m in
length and 100 m in width.
National and Regional Approaches.
Recognizing the importance of riparian
buffers and corridors, many Federal, state and
local agencies have established riparian
restoration and preservation programs. As part
of the 1996 Farm Bill, the National Resources
Conservation Service (NRCS) started the
National Conservation Buffers Initiative to
encourage landowners in agricultural and other
urban and rural settings to install buffer strips
primarily to improve the quality of our Nation’s
waters. The goal of the initiative is to restore 2
million miles (up to 7 million acres) of
conservation buffers by the year 2002. The
NRCS has set minimum and maximum widths
that landowners can enroll in these programs
ranging from a minimum of 30 ft (9m) for some
herbaceous filter strips up to a maximum of 150
ft. (45 m) for forested riparian buffer strips. A
variety of programs are available to landowners
under the Farm Bill, including the continuous
Conservation Reserve Program (CRP) sign-up,
Environmental Quality Incentives Program
(EQIP), Wildlife Habitat Incentives Program
(WHIP), Wetlands Reserve Program (WRP),
Stewardship Incentives Program (SIP),
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Table 1. Recommended Widths of Buffer Zones and Corridors for Water Quality
Considerations
Authors State Width Buffer Type Benefit
Woodard and Rock
(1995)
Maine >15m Hardwood buffer The effectiveness of natural buffer strips is
highly variable, but in most cases, a 15m
natural, undisturbed buffer was effective in
reducing phosphorus concentrations adjacent
to single family homes
Young et al. (1980) >25m Vegetated buffer 25m buffer reduced the suspended sediment
in feedlot runoff was reduced by 92%
Horner and Mar
(1982)
>61m Grass filter strip
Vegetated buffer
strip
Removed 80% of suspended sediment in
stormwater
Lynch, Corbett, and
Mussalem (1985)
>30m 30-m buffer between logging activity and
wetlands and streams removed an average of
75 to 80% of suspended sediment in
stormwater; reduced nutrients to acceptable
levels; and maintained water tempertures
within 1
B
C of their former mean temperature.
Ghaffarzadeh,
Robinson, and
Cruse (1992)
>9m Grass filter strip Removed 85% of sediment on 7 and 12%
slopes
Madison et al.
(1992)
>5m Grass filter strip Trapped approximately 90% of nitrates and
phosphates
Dillaha et al. (1989) >9m Vegetated filter
strip
Removed an average of 84% of suspended
solids, 79% of phosphorus, and 73% of
nitrogen
Lowrance et al.
(1992)
>7m Nitrate concentrations almost completely
reduced due to microbial denitrification and
plant uptake
Nichols et al. (1998) Arkansas >18m Grass filter
strips
Reduced estradiol (estrogen hormone
responsible for development of the female
reproductive tract) concentrations in runoff into
surface water by 98%.
Doyle et al. (1977) >4m Grass filter
strips and
forested buffers
Reduced nitrogen, phosphorus, potassium, and
fecal bacteria from runoff.
Shisler, Jordan, and
Wargo (1987)
Maryland >19m Forested
riparian buffer
Removed as much as 80% of excess
phosphorus and 89% of excess nitrogen
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Table 2. Recommended Widths of Corridors and Vegetated Buffer Strips for Vegetation,
Reptiles and Amphibians, Mammals, Fish, and Invertebrates
Authors State Width Benefit
Spackman and
Hughes (1995)
Vermont >30m Needed to capture >90% of vascular plant species
Brosofske et al.
(1997)
Washington >45m ...buffers at least 45m wide on each side of the stream are
needed to maintain an unaltered microclimatic gradient near
streams (but could extend up to 300m in other situations)
Reptiles and Amphibians
Burbrink, Phillips,
and Heske (1998)
Illinois 100-
1000m
Wide (>1000m) areas of riparian habitat did not support greater
numbers of species of reptiles and amphibians than narrow
(<100 m) areas
Rudolph and
Dickson (1990)
Texas >30m “We recommend retaining streamside zones of mature trees at
least 30 m wide and preferable wider when forest stands are
harvested. Zones this wide will benefit amphibians, reptiles, and
other vertebrates.”
Semlitsch (1998) Eastern U.S. >165m To maintain viable populations and communities of
ambystomatid salamanders, attention must be directed to the
terrestrial areas peripheral to all wetlands; maintaining the
connection between wetlands and terrestrial habitats will be
necessary to preserve the remaining biodiversity of our
remaining wetlands.
Buhlmann (1998) South
Carolina
>135m
Aquatic turtles (e.g., chicken turtle [Deirochelys reticularia]) may
spend a greater proportion of a year in terrestrial habitat (e.g.,
buffer strips adjacent to wetlands) than in the wetland where
they would have been predicted to occur
Mammals
Dickson (1989) Texas >50m The minimum width of streamside management zones that will
maintain gray squirrel (Sciurus carolinensis) populations is about
50m.
Invertebrates
Erman, Newbold,
and Roby (1977)
California >30m Maintained background levels of benthic invertebrates in
streams adjacent to logging activity
Fish
Moring (1982) >30m Increased sedimentation from logged, unbuffered stream banks
clogged gravel streambeds and interfered with salmonid egg
development. Buffer strips at least 30m wide allowed eggs to
develop normally
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Table 3. Recommended Minimum Widths of Riparian Buffer Strips and Corridors for Birds
Minimum
Authors Location Width Benefit
Darveau et al.
(1995)
Canada >60m There was evidence that 50-m-wide forested buffer strips
were required for forest-dwelling birds. Bird populations
may decline in strips before regeneration of adjacent
clearcuts provide suitable habitat for forest birds
Hodges and
Krementz (1996)
Georgia >100m Riparian strips >100 m were sufficient to maintain functional
assemblages of the six most common species of breeding
Neotropical migratory birds
Mitchell (1996) New
Hampshire
>100 m Need >100m-wide buffers to provide sufficient breeding
habitat for area sensitive forest birds and nesting sites for
red-shouldered hawks
Tassone (1981) Virginia >50 m Many Neotropical migrants will not inhabit strips narrower
than 50 m
Triquet,
McPeek, and
McComb (1990)
Kentucky >100 m Neotropical migrants were more abundant in riparian
corridors wider than 100 m; riparian areas <100 m wide
were inhabited mainly by resident or short-distance
migrants
Spackman and
Hughes (1995)
Vermont >150 m
Riparian buffer widths of at least 150 m were necessary to
include 90% of bird species along mid-order streams
Kilgo et al.
(1998)
South
Carolina
>500 m
Although narrow bottomland hardwood strips can support
an abundant and diverse avifauna, buffer zones at least
500m wide are necessary to maintain the complete avian
community
Keller, Robbins,
and Hatfield
(1993)
Maryland;
Delaware
>100 m
Riparian forests should be at least 100 m wide to provide
some nesting habitat for area-sensitive species
Gaines (1974) California >100 m
Provide riparian breeding habitat for California yellow-billed
cuckoo populations
Vander Haegen
and deGraaf
(1996)
Maine >150 m
Managers should leave wide (>150 m) buffer strips along
riparian zones to reduce edge-related nest predation,
especially in landscapes where buffer strips are important
components of the existing mature forest
Whitaker and
Montevecchi
(1999)
Canada >50 m 50-m-wide riparian buffers only supported densities <50%
of those observed in interior forest habitats
Hagar (1999) Oregon >40m Although riparian buffers along headwater streams are not
expected to support all bird species found in unlogged
riparian areas, they are likely to provide the most benefit for
forest-associated birds species if they are >40 m wide
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Table 4. General Riparian Buffer Strip Width Guidelines
Recommended
Function Description Width
1
Water Quality
Protection
Buffers, especially dense grassy or herbaceous buffers
on gradual slopes, intercept overland runoff, trap
sediments, remove pollutants, and promote ground
water recharge. For low to moderate slopes, most
filtering occurs within the first 10 m, but greater widths
are necessary for steeper slopes, buffers comprised of
mainly shrubs and trees, where soils have low
permeability, or where NPSP loads are particularly
high.
5 to 30 m
Riparian Habitat
Buffers, particularly diverse stands of shrubs and trees,
provide food and shelter for a wide variety of riparian
and aquatic wildlife.
30 to 500 m +
Stream
Stabilization
Riparian vegetation moderates soil moisture conditions
in stream banks, and roots provide tensile strength to
the soil matrix, enhancing bank stability. Good erosion
control may only require that the width of the bank be
protected, unless there is active bank erosion, which
will require a wider buffer. Excessive bank erosion may
require additional bioengineering techniques (see Allen
and Leach 1997).
10 to 20 m
Flood Attenuation
Riparian buffers promote floodplain storage due to
backwater effects, they intercept overland flow and
increase travel time, resulting in reduced flood peaks.
20 to 150 m
Detrital Input
Leaves, twigs and branches that fall from riparian forest
canopies into the stream are an important source of
nutrients and habitat.
3 to 10 m
1
Synopsis of values reported in the literature, a few wildlife species require much wider riparian corridors.
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Table 5. General Recommendations for Corridor Restoration and Management
1
Think at a watershed scale when planning for or managing corridors. Many species that
primarily use upland habitats may, at some stage of their life cycle, need to use corridors for
habitat, movements, or dispersal.
Corridors that maintain or restore natural connectivity are better than those that link areas
historically unconnected.
Continuous corridors are better than fragmented corridors.
Wider corridors are better than narrow corridors.
Riparian corridors are more valuable than other types of corridors because of habitat
heterogeneity, and availability of food and water.
Several corridor connections are better than a single connection.
Structurally diverse corridors are better than structurally simple corridors.
Native vegetation in corridors are better than non-native vegetation.
Practice ecological management of corridors; burn, flood, open canopy, etc. if it mimics
naturally occurring historical disturbance processes.
Manage the matrix with wildlife in mind; apply principles relative to the native plant and
animal communities in the area.
1
Craig Johnson, Utah State University, Presentation made at National Conservation Buffers Workshop, San Antonio,
TX, January 1998.
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Figure 2. Depiction of a three-zone buffer approach developed for the Chesapeake Bay
Watershed. This approach may be applicable to most forested riparian buffer strips in North
America (from Welsch 1991).
and Emergency Watershed Protection Program
(EWP). Information on these programs can be
found on the Internet at
http://www.nhq.nrcs.usda.gov/OPA/Buffers.html
The Chesapeake Bay watershed has been the
focus of a large restoration effort to improve
water quality within the watershed. As part of
this initiative, a three-zone riparian buffer was
developed to assist with planning, design, and
long-term management of forested riparian
buffer strips (Welsch 1991). This approach
provides a framework through which water
quality, habitat, and other objectives can be
accomplished. Figure 2 depicts the relative
positions of the three zones. The width of each
zone is determined by site conditions and
objectives, as discussed below.
Zone 1. This zone begins at the stream edge
and is the area that provides streambank
stabilization and habitat for both aquatic and
terrestrial organisms. Primary functions of this
zone include provision of shade, and input to
the stream or river of detritus and large woody
debris from mature forest vegetation.
Vegetation in this zone also helps reduce flood
effects, stabilize streambanks, and remove
some sediments and nutrients. Vegetation
should be composed of native, non-invasive
trees and shrubs of a density that permits
understory growth; it should also tolerate
frequent inundations. The width of this zone
typically varies between 15 and 25 ft (5 and 8
m) or more.
Zone 2. This zone extends upslope from Zone
1 from a minimum of 10 ft
(3 m) up to several hundred feet, depending on
objectives, stream type, soil type, or
topography. The objective in this zone is to
provide a managed riparian forest with a
vegetation composition and character similar to
natural riparian forests in the region. Species
of vegetation used in this zone should be
reasonably flood- and drought-tolerant. The
primary function of Zone 2 is to remove
sediments, nutrients, and other pollutants from
surface and groundwater. This zone, in
combination with Zone 1, also provides most of
the enhanced habitat benefits, and allows for
recreation and aesthetic benefits.
The cost of installing and managing a buffer
strip is a strong concern to some land
managers, as it is often viewed as a loss of
productive land. However, these opportunity
costs can be offset by including practices such
as periodically harvesting trees in this zone for
sawtimber or pulp, growing nuts, berries, and
fruits for commercial purposes, or leasing lands
out for hunting (Washington County Soil and
Water Conservation District 1999). Periodic
selection harvests within this zone likely
Zone 1 Zone 2 Zone 3
Zone 3 Zone 2 Zone 1
Zone 1 Zone 2 Zone 3
Zone 3 Zone 2 Zone 1
Zone 1 Zone 2 Zone 3
Zone 3 Zone 2 Zone 1
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release the growth of smaller trees that will
absorb nutrients from the soil at a higher rate
than the more mature trees.
Zone 3. This zone typically contains grass or
herbaceous filter strips and provides the
greatest water quality benefits by slowing
runoff, infiltrating water, and filtering sediment
and its associated chemicals. The minimum
recommended width of Zone 3 is 15 ft (4.5 m)
when used in conjunction with Zones 1 and 2,
or 35 ft (10.6 m) when used alone. The
primary concern in this zone is initial protection
of the stream from overland flow of NPSP such
as herbicides and pesticides applied to lawns,
agricultural fields, and timber stands. Properly
designed grassy and herbaceous buffer strips
may provide quality habitat for several upland
wildlife species, including the northern
bobwhite (Colinus virginianus), which has
experienced significant population declines
during the last 2 decades.
Buffer Composition. Generally speaking,
vegetation used for buffer projects should
consist of a mix of trees, shrubs, and
herbaceous plants that are native to the region
and well-adapted to the climactic, soil, and
hydrologic conditions of the site. The relative
effectiveness of different vegetation types at
meeting specific objectives within a buffer strip
is listed in Table 6. A botanist familiar with
local flora should be enlisted to select those
species most likely to meet project objectives,
as well as ensure that plants are placed in the
proper zone in the floodplain (e.g., those that
thrive with frequent inundation at the edge of
the stream versus those less tolerant of
flooding further from the stream). The
composition of the natural riparian community
in adjacent locations can be a good guide and
is often used as a starting point for the
revegetation design.
Establishing diverse vegetation, either directly
or through succession, is desirable for a variety
of reasons. A relatively large number of
species means an array of environmental
tolerances is represented. As the project site
experiences fluctuations in various
environmental conditions over time, such as
water level, temperature, and herbivory, some
plants or species will not survive, but others
may thrive. A diverse array of plant species is
essential to a riparian system's ability to
provide and to sustain a number of functions.
Various plant species association and
hydrological conditions provide required
habitats for different life-history phases of
animals, such as feeding, winter cover, and
breeding (Heitmeyer et al. 1984, Frazer et al.
1990). Vegetation diversity in a buffer can be
increased in numerous ways by:
a. Planting an array of different species in
different amounts.
b. Planting a variety of growth forms such as
herbaceous ground cover, shrubs, saplings
and tree species, or emergents.
c. Planting species with a variety of life
histories (e.g., annuals, short-lived or
long-lived perennials).
d. Providing a range of site conditions (e.g.,
through elevational changes, creation of
habitats with varying aspects/orientations)
to support a diverse range of plant species.
Plans for acquiring plants must be made well in
advance of the project implementation
(sometimes 1 to 2 years). The availability of
plants of the appropriate species, size, and
quality is often a limiting factor in the final
selection and plant acquisition process. Some
native plant species are very difficult to
propagate and many desirable species are not
commonly available through commercial
suppliers. As a general rule, it is advisable to
specify as many species as possible and
require the use of some minimum number of
these species. Table 7 provides guidance for
the minimum percentage of any one tree
species in a revegetation plan.
ERDC TN-EMRRP-SR-24
12
Table 6. Relative Effectiveness of Different Vegetation Types for Providing Specific Benefits
Vegetation Type
Benefit Grass Shrub Tree
Stabilizes bank erosion
Traps sediment
Filters nutrients, pesticides, microbes
sediment-bound
soluble
Provides aquatic habitat
Provides wildlife habitat
range/pasture/prairie wildlife
forest wildlife
Provides economic products
Provides visual diversity
Prevents bank failures
Provides flood conveyance
Medium
High
High
Medium
Low
High
Low
Medium
Medium
Low
High
High
Medium
Low
Low
Medium
Medium
Medium
Low
Medium
Medium
Low
Medium
Low
Low
Medium
High
Low
High
Medium
High
High
Low
Modified from Dosskey, Schultz, and Isenhart (1997).
Table 7. Species Diversity Guidelines for Trees
Number of Trees Maximum % of Any One Species
10 to 19 50%
20 to 39 33%
40 or more 25%
Other factors that determine species
percentages within a plant selection are:
a. Desired ultimate composition of the plant
community.
b. Function within the plant community (i.e.,
overstory, understory, shrub, groundcover,
herbaceous).
c. Dominance in the plant community.
d. Growth characteristics and compatibility
with other species.
e. Aggressive, fast-growing species such as
elderberry (Sambucus spp.) and poplar
(Populus spp.) should be proportioned and
managed to reduce conflict with slower
growing species.
f. Slower-growing species, such as
wintergreen (Gaultheria spp.) and spruce
(Picea spp.) may require a higher
ERDC TN-EMRRP-SR-24 13
percentage to be successful in the
development of the plant association.
g. Some species may not be appropriate for
the initial planting phase. These include
many of the herbaceous understory plants,
such as ferns, and others that demand a
micro-environment that can only develop
over time.
The planting distance between woody species
(trees and shrubs) should account for
anticipated maintenance practices. If
maintenance is necessary, planting trees and
shrubs in well-spaced rows makes
maintenance activities, such as mowing or
mulching, much easier. Care should be taken
to offset the rows of trees and shrubs so as to
form a diamond pattern. Tree rows should
generally be spaced about 6 to 10 ft (2 to 3 m),
and shrubs about 3 to 6 ft (1 to 2 m). Within the
row, spacing should be 3 to 6 ft (1 to 2 m) for
small shrubs, 5 to 8 ft for large shrubs, 6 to 10
ft (2 to 3 m) for evergreens, and 8 to 12 ft (3 to
4 m) for deciduous trees. If the riparian zone
will not be maintained with equipment, there is
no need to plant in rows and a more
natural-appearing planting arrangement should
be utilized.
Other considerations influencing plant spacing
are:
a. The competitive strength of the plants at
the end of the plant establishment period.
b. Weed control. Densely spaced vegetation
hinders weeds from establishing.
c. Species that need support from
surrounding plants in order to compete and
develop into a functional plant association.
Examples are snowberry
(Symphoricarpos), wild rose (Rosa spp.),
Salal (Salal spp.), leatherleaf (Mahonia
spp.), and Spiraea (Spiraea spp). The
initial plant spacing should be based on
closure of the planting after approximately
three years. The plants will form a thicket
over time. This plant layer is important for
weed control in its supportive role in the
plant community.
d. Species that form groupings or groves
should be spaced to support the
development of individual plants that form
the desired cluster.
e. Climax trees should be spaced to resemble
the distribution in the natural plant
community.
f. Pioneer species should be spaced to
quickly perform their function in the plant
succession scheme without causing
undesirable competition with desirable
plants. Consider a management program
that includes periodic removal of plants that
have outlived their function.
In grassy buffers, the use of a mixture of native
cool- and warm-season grasses planted in a
heterogeneous pattern is recommended. This
will not only assist in protecting water quality
but will also provide wildlife habitat benefits.
The inclusion of warm-season grasses
provides many wildlife benefits that cool-
season grasses alone cannot provide, such as
abundant nesting cover for upland game
species. In addition, many non-game species
such as field nesting songbirds can find
protection in the thick canopy this grass
provides. Warm-season grasses grow in a
dense manner, and resist collapse from snow
and ice (they also provide a degree of winter
cover when little or no snow cover exists).
Finally, warm-season grasses are good seed-
producers, creating abundant food for wildlife.
The authors have begun to compile woody and
herbaceous vegetation commonly found in
riparian systems, including the floodplain zone
where they typically are found, and the region
of the country where they occur. This will be
published as a future ERDC technical note.
APPLICABILITY AND
LIMITATIONS
The ability of a riparian buffer strip to provide
various functions (e.g., attenuate floods, protect
water quality, provide habitat or wildlife
movement corridors) depends on such factors
as width, length, degree of fragmentation, and
type, density, and structure of vegetation
ERDC TN-EMRRP-SR-24
14
present. Objectives may also be constrained
by land ownership, extent of potential for
growth of riparian vegetation, soil type, slope,
or past land-uses.
In all cases, buffers wider than 10 m should be
promoted for optimizing a range of multiple
objectives for water quality, stability, and
habitat functions. However, widths of 100 m or
more are usually needed to ensure values
related to wildlife habitat and use as migration
corridors. Increasing widths to encompass the
geomorphic floodplain is likewise desirable to
optimize flood- reduction benefits. If only a
narrow forested buffer strip is possible, it
should at least be wide enough to sustain a
forest or shrub community that will adequately
stabilize the streambank from erosion. These
recommendations apply to either side of the
channel in larger river systems and to total
width for lower-order streams. Recommended
widths in this report are intended to provide a
starting point for land managers to make
decisions regarding design of buffer strips in
their own area. Proper widths for various
objectives may vary significantly by region and
depend on a variety of ecological and physical
factors.
ACKNOWLEDGEMENTS
Research presented in this technical note was
developed under the U.S. Army Corps of
Engineers Ecosystem Management and
Restoration Research Program. Technical
reviews were provided by Messrs. Chester O.
Martin and Jerry Miller, both of the
Environmental Laboratory.
POINTS OF CONTACT
For additional information, contact the authors,
Dr. Richard A. Fischer (601-634-3726,
fischer@wes.army.mil) or Dr. J. Craig
Fischenich, (601-634-3449,
fischec@wes.army.mil), or the manager of the
Ecosystem Management and Restoration
Research Program, Dr. Russell F. Theriot (601-
634-2733, therior@wes.army.mil). This
technical note should be cited as follows:
Fischer, R. A., and Fischenich, J.C.
(2000). "Design recommendations for
riparian corridors and vegetated buffer
strips," EMRRP Technical Notes
Collection (ERDC TN-EMRRP-SR-24),
U.S. Army Engineer Research and
Development Center, Vicksburg, MS.
www.wes.army.mil/el/emrrp
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... Para diseñar una faja filtro que tenga la capacidad de reducir correctamente la entrada de contaminantes en el río Serpis, es esencial definir su anchura y composición de especies vegetales. Para ello se ha recurrido a diferentes fuentes bibliográficas típicas en el ámbito de las fajas filtro en las que se recomiendan las características de dichas infraestructuras verdes según la finalidad perseguida (Wenger, 1999, Fischer & Fischenich, 2000, Jontos, 2004. El diseño de las fajas filtro se inició con la elección de especies. ...
... El diseño de las fajas filtro se inició con la elección de especies. De acuerdo con Jontos (2004) y Fischer & Fischenich (2000), las especies herbáceas perennes son las formaciones vegetativas que se deberán plantar en las fajas filtro, ya que son más efectivas en la mejora de la calidad del agua al presentar una alta capacidad de filtración de nutrientes, microbios y pesticidas presentes en los sedimentos. El control de las formas solubles de los nutrientes y pesticidas es más reducido, aun así, son las herbáceas las que mayor control ejercen sobre dichas formas. ...
... Respecto a las dimensiones de la faja filtro, el rango de anchura propuesto por diferentes autores varía entre los 5 y 30 m (Fischer & Fischenich, 2000). Para seleccionar una anchura definitiva acorde con la especie seleccionada, nuevamente con RUSLE2, se modelizaron varios escenarios con fajas filtro de diferentes dimensiones, desde una anchura de 5 m hasta los 30 m. ...
Research
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La contaminación difusa del río Serpis es una de sus principales problemáticas ambientales y que determinan su mal estado ecológico. Esta contaminación es consecuencia del uso excesivo de los compuestos químicos agrícolas (plaguicidas y fertilizantes) que, a su vez, son fácilmente arrastrados hasta el agua como consecuencia de la proximidad existente entre las tierras agrícolas y el cauce. La presente investigación ha tenido como objetivo modelizar las "laderas tipo" existentes en el río Serpis a su paso por la comarca de la Safor mediante el modelo RUSLE2, el cual permite analizar el funcionamiento sedimentológico de las laderas próximas a una masa de agua. Se definieron e identificaron tres tipologías de ladera: ladera cultivada con presencia de una orla de vegetación riparia, ladera cultivada sin presencia de una orla riparia y ladera cultivada en terrazas, comúnmente, sin orla de vegetación de riparia. Para cada una de ellas se han obtenido diferentes resultados relativos a la generación y emisión de sedimentos al cauce; entre los que se encontrarían también parte de los contaminantes que interesa reducir mediante el uso de las fajas filtro. Éstas consisten en bandas de vegetación capaces de reducir la escorrentía y favorecer la sedimentación, evitando así la contaminación del agua. Una vez identificada la tipología de ladera que presenta más resultados erosivos, se han identificado todos los tipos de laderas de la comarca con características similares a la ladera tipo modelizada. Así mismo, se han recopilado las referencias catastrales de un conjunto de 17 parcelas situadas cerca del río, con el objetivo de facilitar una hipotética actuación de rehabilitación en la comarca, priorizando aquellas zonas donde existe mayor emisión de contaminantes al cauce. Los resultados han indicado que cuanto mayor es la dimensión de la faja, menor es la entrada de sedimentos y contaminantes en el cauce. Una faja filtro de 20 m de ancho, podría llegar a reducir un 94 % la entrada de sedimentos al cauce del Serpis, y entre un 80 y un 84 % la entrada de compuestos nitrogenados y fosfatados. La implantación de este tipo de infraestructuras verdes, o basadas en la naturaleza, en las parcelas colindantes al cauce del río Serpis permitirían, además de reducir la llegada de compuestos químicos agrícolas al agua, incrementar la diversidad y riqueza de hábitats y especies en los alrededores del espacio fluvial; objetivos en consonancia con la Estrategia 2030 de la Unión Europea sobre la Biodiversidad.
... The optimal RBZs offer maximum WQI benefits; however, there is no "one-size-fits-all" design of an ideal RBZ [13]. We recommended optimal widths for each of the six baseline RBZ designs. ...
... The variation in average RBZ width (±100% variation) addressed the adjustable nature of the width. It is noted that the fixedwidth RBZ recommendations tend to be easier to enforce and administer by regulatory agencies; however, the fixed-width often fails to provide for a variety of ecological functions compared to the adjustable RBZ width, which is generally adjusted along the length of the RBZ depending on adjacent land use, site conditions (e.g., vegetation, topography, hydrology), fish and wildlife considerations [13], and most importantly, stream water conditions and TMDL goals. ...
... Urban RBZs were found to be the most sensitive of all watersheds. There is no "one-size-fits-all" design for an ideal RBZ [13]; therefore, the RBZ-WQI tradeoffs analyses are recommended to inform the width selection according to TMDL goals, for streambank stabilization, or for provision of wildlife habitat. ...
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Riparian buffer zones (RBZs) provide multiple benefits to watershed ecosystems. We aimed to conduct an extensive sensitivity analysis of the RBZ designs to climate change nutrient and sediment loadings to streams. We designed 135 simulation scenarios starting with the six baselines RBZs (grass, urban, two-zone forest, three-zone forest, wildlife, and naturalized) in three 12-digit Hydrologic Unit Code watersheds within the Albemarle-Pamlico river basin (USA). Using the hydrologic and water quality system (HAWQS), we assessed the sensitivity of the designs to five water quality indicator (WQI) parameters: dissolved oxygen (DO), total phosphorous (TP), total nitrogen (TN), sediment (SD), and biochemical oxygen demand (BD). To understand the climate mitigation potential of RBZs, we identified a subset of future climate change projection models of air temperature and precipitation using EPA’s Locating and Selecting Scenarios Online tool. Analyses revealed optimal RBZ designs for the three watersheds. In terms of watershed ecosystem services sustainability, the optimal Urban RBZ in contemporary climate (1983–2018) reduced SD from 61–96%, TN from 34–55%, TP from 9–48%, and BD from 53–99%, and raised DO from 4–10% with respect to No-RBZ in the three watersheds. The late century’s (2070–2099) extreme mean annual climate changes significantly increased the projected SD and BD; however, the addition of urban RBZs was projected to offset the climate change reducing SD from 28–94% and BD from 69–93% in the watersheds. All other types of RBZs are also projected to fully mitigate the climate change impacts on WQI parameters except three-zone RBZ.
... Natural and human-altered waterways exhibit great variability in the distance that riparian vegetation extends from the edge of channels and floodplains, and the value of 40 m is supported by studies that have examined or proposed riparian buffers of 10 to 40 m (Castelle et al., 1994;Fischer and Fischenich, 2000;Lee et al., 2004;Micheli et al., 2004). Other existing river protection programs use a variety of setbacks or buffers, ranging from 7 to 22 m, including the USDA Conservation Reserve Enhancement Program (10 to 55 m), Massachusetts River Protection Act (15.2 to 61 m), Vermont Small Stream Setback (15.2 m) the Wild and Scenic River Act (75 to 122 m). ...
Research
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We define the river process corridor (RPC) as the area adjacent to a river that is likely to affect and be affected by river and floodplain processes. Here we present a novel approach for delineating the RPC that utilizes widely available geospatial data, can be applied uniformly across broad and multi-scalar spatial extents, requires relatively low levels of expertise and cost, and allows for modular additions and adaptations using additional data that is available in particular areas. Land managers are increasingly using a variety of delineated river and floodplain areas for applied purposes such as hazard avoidance, ecological conservation, and water quality protection. Currently, the most-used delineation methods rely on historic maps, field surveys, and/or calibrated empirical models. These approaches are examples of what is possible, but they may be time-intensive, may rely on jurisdiction or organization-specific data or data information systems, or may require specific local-user input or hand-drawing. Our approach, the River Process Corridor Modular Assessment Method, offers a rapid, uniform and objective river and floodplain process area delineation method that uses transparent, easily accessible data, and may be used across large areas. it is derived from the sum of five functional process units that together capture the RPC: (i) the Flood Processes Unit, derived from hydraulic modeling to determine areas subject to overbank deposition and erosion, in-channel deposition and erosion, bank erosion, and channel avulsions; (ii) the Landslide and Steep Terrain Processes Unit, based on terrain slope to show locations subject to sediment delivery, bank failures, and other mass wasting proximal to the flood-prone area; (iii) Wetland Processes Unit, based on the U.S. National Wetlands Inventory to show areas where wetland processes occur; (iv) Channel Migration Processes Unit, based on channel location and migration rates to show areas susceptible to lateral channel movement; and (v) Riparian Ecologic Processes Unit. This paper details the assessment approach for each of these units, and provides a summary outline and table for users. To illustrate and evaluate its potential, we apply the approach in three river reaches in mountainous and low-relief watersheds in the northeastern U.S. and compare results with recent geomorphic change, observed in the field and in historic imagery. The River Process Corridor Modular Assessment Method performs very well, capturing 92% of observed landslide areas, 87% of observed floodplain deposition areas, and 100% of channel migration areas. We also provide an example of how additional data available from the State of Vermont could be added in a modular approach. These results indicate the RPC method is successful at providing both an accurate assessment of potential active hazard areas and sensitive environmental areas, and that it also includes a margin of safety that many managers desire. Its modular nature allows for flexible weighting of different metrics to suit specific applications, and piecewise updating as new data or approaches become available. We conclude that maps of the RPC can be useful as an advisory layer to natural resource managers, property owners, planners and regulators to identify areas that may be valuable for ecological conservation or at risk of future damage during floods, or where they might consider allowing natural river processes occur, in order to enhance ecological processes and help attenuate future flood damage elsewhere.
... Riparian forests of the Cerrado provide habitat to a variety of wildlife and plant litter to soils and riverine ecosystems, where litter is a major source of organic matter that often fuels the aquatic food web (Fischer & Fischenich, 2000). In this context, plant litter entering riverine ecosystems through litterfall or laterally from the banks establish a connection between terrestrial and aquatic environments (Gregory et al., 1991;Wallace et al., 1997). ...
Article
Riparian forests play an important role in stream ecosystems, as they support biodiversity, reduce water erosion, and provide litter that fuels aquatic biota. However, they are affected by great array of anthropogenic threats (e.g., fire, logging, and organic pollution), which alter species composition and their physical structure. Although forest recovery after disturbance such as logging can take decades, the legacy of forest clear‐cut logging on key processes in tropical riparian ecosystems is mostly unknown. Here, we investigated how litter inputs (leaves, twigs, and reproductive parts) and storage, key processes for carbon and nutrient recycling and for forest and stream biota, are influenced by riparian vegetation undergoing succession (after 28 years from logging) through the comparison of reference and logged forest sites in the Cerrado biome. Litterfall was overall similar between forest types, but litterfall of twigs was twofold higher at logged than reference sites. Similarly, litter inputs from the bank to the stream (i.e., lateral inputs) and streambed storage were 50–60% higher at logged than reference sites. The higher litterfall observed in logged forests could be related to higher proportion of tree species that are characteristic of primary and secondary successional stages, including fast‐growing and liana species, which often are more productive and common in anthropogenic areas. Our results showed that the legacy impact of clear‐cut logging, even if residual woody vegetation is maintained in riparian buffers, can shift the type, quantity, and seasonality of litter subsidies to tropical streams. This knowledge should be considered within the context of management and conservation of communities and ecosystem processes in the forest‐stream interfaces. Abstract in Portuguese is available with online material. Florestas ripárias têm um papel importante para os ecossistemas de riachos, pois abrigam alta biodiversidade, reduzem a erosão das margens e fornecem matéria orgânica que mantém a biota aquática. No entanto, as florestas ripárias têm sido afetadas por distúrbios antrópicos (incêndios, remoção da vegetação, poluição orgânica), o que altera a composição de espécies e a estrutura física desses habitats. Embora a recuperação da floresta após a remoção da vegetação possa levar décadas, o legado desse distúrbio em processos chave nos ecossistemas ripários tropicais é praticamente desconhecido. Dessa forma, investigamos como processos essenciais para a ciclagem de carbono e nutrientes na floresta e riachos, como o aporte e o estoque de matéria orgânica (folhas, galhos e partes reprodutivas) nos riachos, são influenciados pelo estágio sucessional da vegetação ripária, comparando áreas preservadas com áreas impactadas, onde a vegetação ripária foi removida há 28 anos e estão em processo de sucessão. O aporte de matéria orgânica foi, em geral, semelhante entre as áreas preservadas e impactadas, mas o aporte de galhos foi duas vezes maior nas áreas impactadas do que nas preservadas. Da mesma forma, o aporte de matéria orgânica das margens (aporte lateral) e o estoque no leito do córrego (estoque bentônico) foram 50–60% maiores nas áreas impactadas. A maior quantidade de matéria orgânica observada nas áreas impactadas pode estar relacionada a maior proporção de espécies arbóreas características de estágios sucessionais primários e secundários. Isso inclui a presença de espécies de crescimento rápido e lianas, as quais muitas vezes são mais produtivas e comuns em áreas sob efeito antrópico. Esses resultados evidenciam que o legado do impacto da remoção da vegetação ripária pode alterar o tipo, quantidade e sazonalidade dos aportes e estoque de matéria orgânica em riachos tropicais, mesmo se uma pequena fração da vegetação arbórea for mantida no entorno dos riachos. Esses achados devem ser considerados dentro do contexto da gestão e da conservação de comunidades e processos ecossistêmicos nas interfaces entre florestas e riachos. Palavras‐chave: fluxos de carbono, Cerrado, desmatamento, produtividade vegetal, decomposição de detritos, riqueza de espécies vegetais. Partial removal of vegetation leads to an increase in the flow of organic matter in the forest. Intensification of land use, occurring to satisfy human populations demands, deteriorates their life quality by eliminating riparian ecosystem services. Litter dynamic in riparian forest is an essential knowledge within the context of forest management and conservation.
... The WF model buffer width was applied to account for potential grid cell alignment and/or spatial resolution mismatches between ours and the TRIM source data (NB: the TRIM dataset is based on smaller cell size as minimum horizontal surface accuracy requirements are 10 m for source DEMs). A 150 m buffer width was applied around TRIM data prior to analyses, which is related to the functional role of riparian ecosystems in water flow regulation (Fischer and Fischenich, 2000;GeoBC, 2003). ...
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Sustainably managing multifunctional landscapes for production of multiple ecosystem services (ES) requires thorough understanding of the interactions between ES and the ecological processes that drive them. We build upon landscape connectivity theory to present a spatial approach for assessing functional connections between multiple ES at the landscape scale, and take a closer look at the concept of ES interactions by explicitly representing the mechanisms behind the relationships between ES. We demonstrate application of the approach using existing ES supply mapping data for plant agriculture, waterflow regulation, and landscape aesthetics and map the functional connectivity between them. We find that, when weights of all linkages were amalgamated, areas of high-value connectivity are revealed that are not present on any individual ES supply area or pairwise link maps, which suggests that the spatial focus of planning for optimal service provisioning may shift when functional relationships between several ES are considered. From water flow supply areas, our modeling maps several functional connections that operate over both short and long distances, which highlights the importance of managing ES flows both locally and across jurisdictions. We also found that different land use and land cover types than those associated with ES supply areas may be serving as critical corridors connecting interdependent ES. By providing spatial information on ES connectivity, our approach enables local and regional environmental planning and management to take full consideration of the complex, multi-scale interactions between ecological processes, land use and land cover, and ecosystem service supply on a landscape.
... These permanent vegetation areas are located within and between agricultural fields and the watercourses that they drain. These buffers are intended to intercept and slow runoff, thereby providing water quality benefits, reducing the nutrients loads (Fischer and Fischenich 2000). In addition, in many settings, they are intended to intercept shallow groundwater moving through the root zone below the buffer. ...
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Cyanobacterial harmful algal blooms (CyanoHABs) are increasingly being reported worldwide owing to several reasons, including widespread eutrophication and enhanced scientific monitoring. Catchment and water management, organisations, industry, farmers and local governments are all confronting the effects of climate change, which stimulate the growth of cyanobacteria and affect the efficacy of adaptation measures in water systems. To tackle climate change and CyanoHABs growth, actors at different levels require both 'top-down' and 'bottom-up' assessments to help them in formulating and implementing adaptation measures. Potential solutions must also be assessed locally to limit associated adverse effects, in particular, negative effects on water quality. Thus, having a better understanding of the synergies, conflicts and trade-offs between adaptation practices and climate-change effects on CyanoHABs makes a valuable contribution to a more integrated climate policy and the effective climate-proofing of our water bodies. This article examines adaptation practices focused on tackling CyanoHABs occurrence in a changing climate. It fills an important gap between a major environmental problem and potential solutions. The practices and measures advanced as a result of the analysis can be used by persons with different expertise and skill levels for improving the relevant institutional frameworks and policies to protect their local water bodies.
... The agricultural lands in the seminatural patches are mostly under urban-growth pressure. As a necessary precaution, a robust hedgerow system to support these areas would protect these transitional landscapes and support their connectivity to the natural environment (Fischer and Fischenich 2000;Lindenmayer and Fischer 2006). When designed carefully, agricultural lands can work as buffer zones in the landscape. ...
Article
Scenario-based land-use planning depends on choosing from among a range of inputs to a calibrated model to explore the corresponding range of future outputs and impacts—but how are these inputs chosen? This case study examined how a landscape ecology approach could better shape scenario development for a SLEUTH (slope, land use, exclusion, urban, transportation, and hillshade) model application toward achieving possibly more ecologically sustainable scenarios and, therefore, future landscapes. Our methodology relied on two main steps––developing landscape-ecology-led growth scenarios and using SLEUTH to model their impacts on urban growth and land-use change. As a case study, we applied the model to Sariyer, Istanbul, for the year 2045, where transportation infrastructure changes portend significant implications for the future landscape. Even though there are many works on urban growth in the international literature, there has been only limited investigation of the effects of urban transportation systems in developing nations and their implications for urban landscapes. This study’s novelty lies in including a landscape ecology approach in the scenario development to enable better integration with modeling and the use of landscape metrics to modify the scenarios and interpret the model outcomes. Our research question is: can a joint approach of scenario development using landscape ecology principles (associated with landscape metrics) and SLEUTH modeling accurately forecast the impacts of landscape ecology and ecosystem services on human and urban systems? We conclude that a landscape ecology approach does help illuminate future urban-growth behavior led by transportation system development. Landscape ecology can be a medium through which the SLEUTH model can articulate more-comprehensive ecological planning related to the implications of different growth scenarios.
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Riparian buffer zones (RBZs) have been shown to be effective best management practices (BMPs) in controlling non-point source pollutants in waterbodies. However, the holistic sustainability assessment of individual RBZ designs is lacking. We present a methodology for evaluating the holistic sustainability of RBZ policy scenarios by integrating environmental and economic indicators simulated in three watersheds in the southeastern USA. We developed three unique sets of 40, 32, and 48 RBZ policy scenarios as decision management objectives (DMOs), respectively, in Back Creek, Sycamore Creek, and Greens Mill Run watersheds (Virginia and North Carolina) by combining the RBZ—widths with vegetation types (grass, urban, naturalized, wildlife, three-zone forest, and two-zone forest). We adapted the RBZ—hydrologic and water quality system assessment data of instream water quality parameters (dissolved oxygen, total phosphorus, total nitrogen, total suspended solids—sediment and biochemical oxygen demand) as environmental indicators, recently published by U.S. EPA. We calculated 20-year net present value costs as economic indicators using the RBZ’s establishment, maintenance, and opportunity costs data published by the Natural Resources Conservation Service. The mean normalized net present value costs varied by DMOs ranging from 4% (grass RBZ—1.9 m) to 500% (wildlife RBZ—91.4 m) across all watersheds, due primarily to the width and the opportunity costs. The mean normalized environmental indicators varied by watersheds, with the largest change in total nitrogen due to urban RBZs in Back Creek (60–95%), Sycamore Creek (37–91%), and Greens Mill (52–93%). The holistic sustainability assessments revealed the least to most sustainable DMOs for each watershed, from least sustainable wildlife RBZ (score of 0.54), three-zone forest RBZ (0.32), and three-zone forest RBZ (0.62), respectively, for Back Creek, Sycamore Creek, and Greens Mill, to most sustainable urban RBZ (1.00) for all watersheds.
Chapter
The aquatic-terrestrial interface (i.e., riparian buffers) provides essential ecosystem services (e.g., fish habitat, filtration, stabilization, nutrient transport). Despite protection recommendations, many riparian zones have remained highly modified for human use. Assessing spatial-temporal buffer changes offers important freshwater management insights. The aim of this chapter is to illustrate land cover change along riverine buffers of U.S. waterways during the 21st century to-date. Changes are categorized by stream order and land cover classification. Trends in land cover change suggest valuation of riparian zones is increasingly recognized in decision-making, with declining urban sprawl but increasing densification, and increasingly vegetated forests, grasslands, and wetlands.
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We surveyed riparian forest corridors of different widths along the lower Altamaha River in Georgia in 1993 and 1994 to investigate the relationship between forest corridor width and Neotropical breeding bird community diversity and abundance. Species richness and abundance of three of six focal species increased with increasing forest corridor width. We suggest if Neotropical breeding bird communities are a target group, that land managers should consider leaving a 100 m buffer strip along riparian zones.
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Riparian forest strips are usually protected from logging for their buffer effect on aquatic habitats. However, their value to terrestrial wildlife is unknown. From 1989 to 1992, we compared bird abundance and species composition in 5 experimental riparian forest strips (20-m, 40-m, 60-m, and control [>300 m wide], intact strips, and 20-m-wide thinned strips), in boreal balsam fir (Abies balsamea) stands, for 3 years following clear-cutting. Bird densities increased 30-70% (P < 0.05) in all strips the year after cutting and decreased (P > 0.05) thereafter to approximately pretreatment levels. The 20- and 40-m-wide riparian strips had highest mean bird densities, but also the fastest (P < 0.05) decreases thereafter. By the third year after clear-cutting, forest-dwelling species were less (P = 0.01) abundant than ubiquitous species in the 20-m strips. The golden-crowned kinglet (Regulus satrapa), Swainson's thrush (Catharus ustulatus), blackpoll warbler (Dendroica striata), and black-throated green warbler (D. virens) became nearly absent in 20-m strips. The removal of 33% of the trees in some 20-m strips resulted in a <20% decline of bird densities, a moderate effect that combined with the greater effect of strip narrowness. There was evidence that 60-m-wide strips are required for forest-dwelling birds. Bird populations may continue to decline in strips before regeneration of adjacent clear-cuts provides suitable habitat for forest-dwelling species.
Article
A 5-year effort to characterize highway runoff in Washington State resulted in the accumulation of data from more than 500 storms at nine locations and the development of a guide for assessing aquatic impacts of operating highways. The data were used to construct a simple model that expresses cumulative pollutant loadings as functions of highway segment length, average runoff coefficient, and vehicles traveling during storm periods. To assess pollutant loadings and concentrations in runoff from an individual storm, cumulative distributions were analyzed to determine the probability of specific loading and concentration values being exceeded in a given case. Bioassay studies of highway runoff indicated toxicity to aquatic life when heavy deposition of metals from high traffic volumes or high concentrations of metals in rainfall caused concentrations in runoff to exceed lethal levels. Draining highway runoff through grass channels 200 to 300 ft long greatly reduced concentrations of solids and metals and the consequent toxic effects. The impact assessment guide incorporates these results in a stepwise procedure for use by highway designers and environmental impact analysts in the Pacific Northwest.
Article
Bird abundance increased 21% and 23% on 2 clearcuts during the 2nd growing season after cutting. Bird species richness and bird diversity were highest on an uncut control area of mature forest and a best management practices harvest unit with a riparian buffer strip. Bird diversity and species equitability were lowest on a logger's choice unit without a buffer strip. -from Authors
Article
A watershed study conducted on the Leading Ridge Experimental Watersheds in central Pennsylvania suggested that the best management practices (BMPs) were effective in controlling nonpoint-source pollution from a 44.5-hectare commercial clearcut. Slight increases in stream temperature, turbidity, and nitrate and potassium concentrations were observed, but these increases did not exceed drinking water standards. -from Authors
Article
Riparian is a kind of landscape representation of aquatic-terrestrial ecotone, the vegetation area in the terrene that has interactions with waters, and the transition region between waters and upland vegetations. At present, people pay attentions to the riparian conservation and management increasingly, and riparian management has been the indispensable aspect for management of natural resources. In this paper, the overseas research and practice of riparian management summarized and the objectives, effects, approaches, current problem, and developing direction of riparian management discussed. The riparian forest buffers system in the USDA-FS report introduced in detail, and it is necessary to develop the studies and practices of riparian management in China.
Article
For landscapes with riparian buffers, we develop and analyze models predicting landscape discharge based on material release by an uphill source area, the spatial distribution of riparian buffer along a stream, and retention within the buffer. We model the buffer as a grid of cells, and each cell transmits a fixed fraction of the materials it receives. We consider the effects of variation in buffer width and buffer continuity, quantify the relative contributions of source elimination and buffer retention to total discharge reduction, and develop statistical relationships to simplify and generalize the models. Width variability reduces total buffer retention, increases the width needed to meet a management goal, and changes the importance of buffer retention relative to source elimination. Variable-width buffers are less efficient than uniform-width buffers because transport through areas of below-average buffer width (particularly gaps) dominates landscape discharge, especially for narrow buffers of highly retentive cells. Uniform-width models overestimate retention, so width variability should be considered when testing for buffer effects or designing buffers for water quality management. Adding riparian buffer to a landscape can decrease material discharge by increasing buffer retention and by eliminating source areas. Source elimination is more important in unretentive or wide buffers, while buffer retention dominates in narrow, retentive buffers. We summarize model results with simpler statistical relationships. For unretentive buffers, average width is the best predictor of landscape discharge, while the frequency of gaps was best for narrow, retentive buffers. Together, both predictors explain >90% of the variance in average landscape transmission for any value of buffer retentiveness. We relate our results to ecological theory, landscape-scale buffer effects, buffer management, and water quality models. We recommend more empirical studies of buffer width variability and its effects on material discharge. Landscape models should represent width variability and the nonlinear interactions between buffers and source areas.
Article
Two approaches were used: 1) deposition estimates based on changes in depth to the argillic horizon along transects from fields to streams and 2) calculations of mass of deposition derived from estimated 100yr upland erosion based on the universal soil loss equation and a sediment delivery ratio. The average annual rate of sediment deposition on this watershed during the 1880-1979 period was 35 to 52Mg ha-1yr-1. These data suggest that riparian ecosystems are important sinks for sediments. -from Authors
Article
Discharge of hormones contained in poultry litter into the environment may disrupt the health and reproduction of fish and other animals. A runoff study was conducted to evaluate grass filter effectiveness in reducing transport of the estrogen hormone 17β-estradiol in runoff from pasture-applied poultry litter. The study objectives were to determine the effects of source (litter-treated) length and grass filter length on runoff concentrations and loss of 17β-estradiol from poultry litter applied to tall fescue (Festuca arundinacea Schreber) plots. Litter was applied at 5 Mg/ha (2.2 ton/ac) to the upslope 6.1, 12.2, and 18.3 m (20, 40, and 60 ft) of 24.4-m (80-ft) long grass strips. The corresponding grass filter lengths were 18.3, 12.2, and 6.1 m (60, 40, and 20 ft), respectively, with the downslope edge of source areas evaluated as a 0-m long filter. Simulated rain was applied at 50 mm/h (2 in/h) to produce runoff samples for 17β-estradiol analysis. Runoff concentrations and mass losses were not significantly affected by source length and averaged 3.5 μg/L (ppb) and 1413 mg/ha (0.02 oz/ac), respectively. Runoff concentrations were reduced by 58, 81, and 94% and mass losses by 79, 90, and 98% by filter lengths of 6.1, 12.2, and 18.3 m (20, 40, and 60 ft), respectively. The data from this research indicates that grass filter strips can effectively reduce runoff transport of 17β-estradiol from tall fescue-applied poultry litter.
Article
The goals of current management practices in riparian areas in the Pacific Northwest include protecting and maintaining habitat for terrestrial wildlife. However, little is known about the use of riparian buffers by terrestrial wildlife, particularly how buffer width may affect abundance and species composition of wildlife communities. In this study, I compared bird assemblages in logged and unlogged riparian areas along headwater streams and assessed the relations between bird abundance and riparian buffer width. The abundances of 4 species of forest-associated birds that were more abundant in unlogged than in logged headwater riparian stands (Pacific-slope flycatcher [Empidonax difficilis], brown creeper [Certhia americana], chestnut-backed chickadee [Poecile rufescens], winter wren [Troglodytes troglodytes]) increased with increasing width of riparian buffers. However, 4 other species that also were more abundant in unlogged than logged riparian stands (Hammond's flycatcher [Empidonax hammondii], golden-crowned kinglet [Regulus satrapa], varied thrush [Ixoreus naevius], hermit warbler [Dendroica occidentalis]) were rarely observed in even the widest buffers sampled (40-70 m on 1 side of the stream). Although riparian buffers along headwater streams are not expected to support all bird species found in unlogged riparian areas, they are likely to provide the most benefit for forest-associated bird species if they are >40 m wide, and density of large trees within buffers is not reduced by harvesting.