EPA904-B-96-002
January, 1996
BEYOND THE ESTUARY:
The Importance of Upstream Wetlands
in Estuarine Processes
U. S. Environmental Protection Agency
Region 4
345 Courtland Street N. E.
Atlanta, Georgia 30365-2401
U. S. A.
WETLANDS HOTLINE: 800 832-7828
WETLANDS HOTLINE e-mail: Wetlands-Hotline@epamail.epa.gov
WEB site: http://www.epa.gov/docs/Region4Wet/wetlands html
(404) 347-3555 ext. 6515 voice
(404) 347-3830 TTY/TDD
(404) 347-3064 fax
U.S. Environmental Protection Agency
Region 5, Library (PL. 12J)
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BEYOND THE ESTUARY:
THE IMPORTANCE OF UPSTREAM WETLANDS
IN ESTUARINE PROCESSES
WHICH WETLANDS ARE IMPORTANT
TO THE ESTUARY?
Coastal, brackish, and freshwater wetlands
all perform important functions affecting
estuarine processes. In addition to their
aesthetic appeal, coastal wetlands have well-
known functions including habitat for
wildlife, spawning and feeding grounds for
fish and shellfish, flood protection, pollution
removal, shoreline erosion control, and
recreation.
The relative importance of the networks of
wetlands located above estuaries has not
been as widely recognized. These wetlands
include bottomland hardwoods, riparian
forests, bogs, vernal pools, and emergent
marshes. These networks are of ten extensive
and can have a significant impact on the
quality and functions of the downstream
estuary.
The cumulative effects of all of these areas
should be considered in discussions of
estuarineprocesses and impacts. Thebenefits
these inland wetlands provide should be
factored into estuary managementdecisions.
In addition, restoration of previously altered
wetlands along the network of streams and
tributaries may provide a solution to many
of the problems in the estuary itself.
WHAT FUNCTIONS DO THESE AREAS
PERFORM?
Upstream wetlands perform various
functions within a given watershed:
• greatly influence the water quality
of adjacent river or stream by re-
moving pollutants such as
sediments, nutrients, and
organics / inorganics
• increase detention time of
floodwaters thereby reducing flow
velocity, erosion, and flood peaks
in downstream areas
• provide habitat for wildlife
including waterfowl, mammals,
and unique vegetation
• serve as spawning and nursery
grounds for many estuarine and
marine species of fish
• contribute to the aquatic food
chain by providing detritus
(decaying organic matter) to the
biota of the adjoining waters
• prevent excessive water
temperatures during summer
months which could be lethal to
invertebrates or fish
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HOW DO THESE FUNCTIONS
TRANSLATE TO ESTUARINE
PROCESSES?
Water Quality
The estuarine system is complex and highly
dependent on the balance of its many
components. The organically rich water and
sediments within the estuary, in their proper
proportions, support a myriad of aquatic
plant and animal life. During periods of
minimal rainfall in the estuarine zone, the
quality and quantity of inflowing fresh water
from upstream tributaries becomes even
more crucial. Without the pollution removal
function of upstream wetlands, the estuary
could be adversely affected in several ways:
• High levels of nitrogen and
phosphorus (plant nutrients) could
be transported from upstream
areas to the estuary. This often
results in high algal standing crops
(algal blooms) which greatly
reduce the level of available oxygen
which can cause massive fish kills
• Transported pollutants such as
pathogens and toxics could impact
the estuary unless upstream areas
trap and absorb these substances
• Beneficial levels of nutrients and
sediments would not be available
for estuarine systems if stream
flow is decreased or stopped
altogether, or if stream flow is
channelized sending nutrients to
deeper, offshore waters.
Riparian forests,in particular, act as nitrogen
sinks and reduce the load of nutrients from
agricultural lands (Peterjohn and Correll,
1986). Conversion of forested areas to
agriculture has resulted in decreased surf ace
water salinity, increased turbidity, and
increased phosphorus, nitrogen, and
ammonia concentrations in the adjacent
tributary (Kirby-Smith and Barber, 1979).
Within the normally saturated soils of
riparian forests, the process of denitrification
permanently removes excess nitrogen in
surface runoff and shallow groundwater.
Although storage of nitrogen and
phosphorus by riparian vegetation is mostly
temporary, these nutrients are transformed
inawaythatmakesthemlesslikelyto support
nuisance algae in downstream estuaries
(Elder, 1985).
How can water quality be altered?
In discussions of water quality, it is important
to remember that some factors have the
potential to be both favorable and detrimental
There are levels of certain nutrients,
sediments, or biota that are tolerable or
essential to the overall productivity of the
estuary or other waterbody, yet, when these
levels are surpassed, these same materials
may prove toxic or detrimental. Generally,
water quality can be affected in several ways:
• Addition of artificial materials
• Alteration (increase or decrease) of the
"normal" levels of naturally occuring
materials
• Addition of natural materials which prove
toxic or detrimental when combined with
naturally occurring materials
The first 19 - 20 meters of the wetland,
immediately below the source of
contaminated nonpoint runoff, may be the
most effective filter, both in riparian systems
(Peterjohn and Correll, 1984; Correll and
Weller, in press) and in salt marshes (Hook
and Brinson, 1989). Similarly, studies of
bottomland hardwood wetlands have
indicated that when a significant proportion
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of the watershed is converted to agriculture,
stream concentrations of phosphorus tend to
increase (Gosselink and Lee, 1987).
Water Regime
The ability of wetlands to temporarily store
floodwater plays an integral role in the flow
of freshwater to the estuary. These natural
functions are commonly hindered by
structures, such as dams and levees, which
are designed to do just theopposite—manage
flow and define direction. Constructed levees
result in the increased height of the inflow
downstream because flood waters are not
able to overflow the natural banks of the
river or stream. Such alterations may cause
essential constituents to be deposited into
deeper offshore waters where they will not
be available for estuary processes. Along the
Mississippi River, early modifications to
upstream areas to control flooding increased
flow velocity making it necessary to construct
similar structures downstream closer to the
estuary.
The Charles River Basin, on the other hand,
still remains a prime example of controlling
flooding using the natural process of
watershed wetlands. This flood control
project was developed by the U.S. Army
Corps of Engineers and involved setting aside
upstream wetlands for floodwater detention
along the Charles River in eastern
Massachusetts. These wetlands allowed the
river to overflow in upstream areas, thus,
decreasing the velocity and height of the
floodwaters in the more highly populated
areas downstream. This method was found
to be not only the most effective means of
flood control, but also the most economical.
Habitat
The importance of freshwater wetlands in
providing habitat for numerous species of
waterfowl, fish, and invertebrates, including
many rare and endangered species, is well
known and well documented (Niering, 1988).
Many species are dependent upon both
estuarine and freshwater wetlands during
differentstages of their lifecycles. Waterfowl,
for example, adapt to seasonal food supplies
duringtheirmigraaonpatternsby exploiting
avarietyofhabitats^singfreshwater inland
marshesduringbreedingandcoastalmarshes
during wintering (Bellrose and Trudeau
1988). Prevettet al. (1985) found thatCanada
geese (Branta canadensis) in James Bay made
dailytrips between thecoastal marshes where
they fed and the adjacentmuskeg areas where
they nested. Further, Fredrickson and
Drobney (1977) found a definite tendency
for waterfowl to shift from unstable
freshwater areas utilized during breeding to
morestable,permanentwetlandsandmarine
areas in the winter. In their review of tidal
freshwater marshes, Odum et al. (1988)
reported that in many cases a large number
of freshwater, estuarine, marine, and
anadromous fish and invertebrates utilized
these areas as nursery sites before moving
downstream to the estuary.
In recent years, movement among habitats
has become increasingly difficult due to
various habitat modifications including
reservoirs, hydroelectric dams, and stream
alterations, as well as loss of wetland habitat
to development and agriculture. Habitat
enhancementmeasures, such as fish ladders,
are a component that increasingly needs to
be addressed when viewing estuarine
processes on a watershed level.
Sediment Load
The role of wetlands as sediment sinks has
been well documented (Gosselink and Lee,
1987; Tiner, 1984). Due to their low slope'
and position downslope from uplands,
wetlands such as bottomland hardwood
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forests can remove moderate amounts of
sediment from turbid runoff without
ecological damage. As upstream areas are
altered, sediments are often left exposed.
This makes them highly susceptible to the
effects of erosion which result in increased
loads of sediment to adjacent streams or
rivers and, ultimately, to the estuary.
Upstream vegetated wetlands also stabilize
soils along the banks of rivers and streams
which helps control the volumes of sediment
transported downstream (Mahoney and
Erman, 1981).
The turbidity caused by suspended
sediments affects estuarine waters in several
ways. High turbidity can interfere with the
recreational aspects of the watershed making
water contact sports or fishing undesirable.
The amount of light available for aquatic
plants is significantly reduced which is
detrimental to many species. As excess
sediments settle, bottom dwelling organisms
may be adversely affected. Finally, high
turbidity can adversely affect fish spawning.
In larger quantities, loads of sediment can
change the pattern of stream flow, fill a
channel, or raise the level of the channel bed
which increases the chance of flooding.
Furthermore, upstream wetlands reduce
the amount of toxic laden sediment particles
that might otherwise be transported to the
estuary as well as produce organic substances
which reduce the toxicity of heavy metals to
estuarine life (Sugai and Burrell, 1984). Even
though sediment transport is an important
factor in building and maintaining some
coastal wetland areas, as with nutrients,
there exists a delicate balance which is ideally
regulated by the upstream wetlands.
HOW ARE UPSTREAM WETLANDS
THREATENED?
There are many threats to these wetland
resources due to physical, chemical, and
biological impacts. As more and more
people occupy the watersheds of the nation,
these areas become more susceptible to
alterations.
• The practices of clearing, draining,
and filling wetlands for agriculture
continue. When an agricultural area
is cultivated right to the edge of a
river or stream, runoff of
agricultural chemicals or pesticides
increases. As these chemicals are
deposited into the tributaries, the
chances of transport to the estuary
are greatly increased. In addition,
some timber harvesting practices,
such as clear cutting, may
significantly degrade wetlands.
• Development and other activities in
urban areas continue to pose threats
to wetlands. The most obvious
impacts are filling or draining
wetlands for development.
Urbanization of these areas has
introduced high levels of nutrients,
toxics, and sediments into upland
runoff. Toxic input has also been
traced to industrial plants, domestic
sewage, hazardous waste sites,
illegal dumping, pesticides, oils, and
heavy metals from urban runoff,
petroleum hydrocarbons from oil
exploration and production, and
spraying of herbicides for aquatic
weed and insect control. Even
though wetlands have been
identified as a potential filter for
pollutants, the long term effects of
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the indiscriminate introduction of
substances to these ecosystems have
not been determined.
• Levees for flood control and water
supply may completely eliminate some
wetlands and may substantially change
water flow patterns. In some instances,
the presence of these structures has
completelyeliminated freshwater inflow
thus upsetting the delicate balance of the
brackish environment which is
characteristicoftheestuarineecosystem.
• Other channel alterations such as dams,
channel diversion structures, and linear
canals all contribute to the limitations
placed on wetlands in the natural
functions they perform.
/HAT CAN WE DO?
The wave of awareness is growing.
Increasingly, estuarine and wetland
environments are receiving recognition as
delicate ecosystems deserving our protection
and restoration. By promoting this
awareness we can coordinate our efforts in
thecomprehensive management, protection,
and enhancement of the upstream wetlands
and the estuaries.
Estuary resource advocates have already
begun developing a network to address the
problems and concerns relating to these areas.
OnerecentlyestablishedmechanismisEPA's
National Estuary Program (NEP) which
goes through a process of identifying
problems, setting goals, selecting options,
and developing action plans. Through the
expansion of this network, awareness of the
role of upstream wetlands to estuarine
systems can be increased. Since many of
these areas are privately owned, we must
also increase citizen involvement and seek
support on a watershed basis, not just at the
site specific level.
Limitations in our current understanding
obviously exist. However, we must join
together to improve our understanding of
the complexities of the systems—both
ecologicaUyandpolitically—toeffectchange.
Here are some steps to improve protection of
these vital resources:
Resource Assessment
• Locate the wetlands along rivers
and streams which eventually feed
into the estuary of concern
• Identify the wetland types
• Map out the wetlands to allow a
landscape understanding of how
they work within the watershed
• Use historical data (if available) to
determine the extent and location
of wetland losses and associated
problems
• Assess the value of remaining
wetlands
Planning
1.
Incorporate wetland protection
into the NEP estuary planning
conference or through other
federal, state, regional, and
local planning processes such
as:
• Special Area Management
Plans (authorized under the
Coastal Zone Management
Program)
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2.
• Multi-Objective River Corridor
Management Plans (supported
by the National Park Service)
• Advance Identification
(conducted by EPA and the
Corps of Engineers)
• Critical Habitat Plans
(authorized by the Endangered
Species Act)
• Statewide Comprehensive
Outdoor Recreation Plans
(state acquisition plans prepared
for Fish and Wildlife Service)
• Regional or local zoning and
land use plans
Use such planning approaches to
coordinate wetlands protection
tools on the local, state, and
federal levels within the
watershed
Regulation
Enhance the wetland protection
afforded by the Section 404
Clean Water Act federal
regulatory program
Develop state regulatory
programs designed explicitly to
protect wetland areas as they
relate to the entire watershed
Improve the wetlands protection
potential of states' existing
authority under Section 401 of
the Clean Water Act to certify
that a federal permit or license
will comply with state water
quality standards
• Incorporate wetland protection
measures into local and regional
zoning provisions
Restoration and Acquisition
• Develop restoration and
acquisition strategies, including
funding mechanisms, and
incorporate these components
into local comprehensive plans
• Identify opportunities for
restoration of wetland sites or
upstream embankments as one
solution to problems in the
estuary downstream
• Encourage farmers in the
watershed to enroll their cropped
wetlands into the Conservation
Reserve Program. Also
encourage farmers to participate
in exchanges of debt, or grant
conservation easements, where
allowable, to permanently
protect wetland resources
Public Education / Awareness
• Promote values of wetlands
through the community including
local schools
• Start an "Adopt A Wetland"
program for citizen monitoring
of key wetland areas
Additional information on these wetland
and estuary protection measures can be
obtained from the EPA regional offices or
from other agencies and organizations listed
in the back of this brochure.
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Sources cited in this document:
Bellrose,F.C.andN.M.Trudeau. 1988. Wetlands and
their relationship to migrating and winter populations
of waterfowl. Pp. 183-194 in D.D. Hook and others
(eds.) The Ecology and Management of Wetlands.
Vol. I: Ecology of Wetlands. Timber Press, Portland,
Oregon.
Bryant, M.D.1984b. The role of beaver dams as coho
salmon habitat in southeast Alaska streams. In JJtf
Walton and D.B. Houston (eds). Proc. Olympic Wild
Fish Conf., Port Angeles, WA. pp. 183-192.
Burger, C.V. and D.B. Wangaard, R.L. Wilmot, AJST.
Palmisano. 1983. Salmon investigations in the Kenai
River, Alaska. U.S. Fish & Wildl. Serv., Anchorage.
Correll, D.L. and Weller, D.E. In press. Factors
limiting processes in freshwater wetlands: an
agricultural primary stream riparian forest.
Elder, J.F. 1985. Nitrogen and phosphorus speciation
and flux in a large Florida river wetland system
Water Resour. Res. 21:724:732.
Fredrickson, L.H. and R.D. Drobney. 1977. Habitat
utilization by postbreeding waterfowl. Pp. 119-131 ,'„
T.A. Bookhout (ed.) Waterfowl and Wetlands - An
Integrated Review. Proc. of symposium at 39th
Midwest Fish and Wildlife Conference. Madison
Wisconsin. '
Gosselink,J.G.andLee,L.C. 1987. Cumulative impact
assessment in bottomland hardwood forests. Center
for Wetland Resources, Louisiana State University
Baton Rouge. LSU-CEI-86-09. 113pp.
Hook, P.B. and M.M. Brinson. 1989. Influence of
landscape position, hydrologic forcing, and marsh
size on ecological differentiation within an irregularly
flooded brackish marsh. Paper presented at the 4th
Annual Landscape Ecology Symposium, Fort Collins,
Colorado, March 15-18,1989.
Jordan, T.E., D.L. Correll, W.T. Peterjohn and D.E.
Weller. 1986. Nutrient flux in a landscape: the Rhode
River Watershed and receiving waters. Pp. 57-76 in
D.L. Correll (ed.), Watershed Research Perspectives.
Smithsonian Institution Press, Washington, D.C.
Kirby-Smith, W.W. and Barber, R.T. 1979. The water
quality ramifications in estuaries of converting forest
to intensive agriculture. Water Resources Research
Institute of North Carolina Report No. 148.
Mahoney, D.L. and Erman, D.C 1984. The role of
streamside buffer strips in the ecology of aquatic
biota. In R.E. Warner and K.M. Hendrix (eds.),
California riparian systems: ecology, conservation,
andproductivemanagement. UniversityofCalifornia
Press. Berkley, CA.
Merrell, T.R. Jr. and K.V. Koski. 1979. Habitat values
of coastal wetlands for Pacific Coast Salmonids. Pp.
256-266m P.E.Greesonetal. (eds.) Wetland Functions
andValues:TheStateofOurUnderstanding. AWRA,
Minneapolis, MN.
Niering,WA. 1988. Endangered, threatened and
rare wetland plants and animals of the continental
United States. Pp. 227-238 in D.D. Hook and others
(eds.) The Ecology and Management of Wetlands.
Vol. 1: Ecology of Wetlands. Timber Press, Portland,
Oregon.
Odum, W.E., L.P. Rozas and C.C. Mclvor. 1988. A
comparison of fish and invertebrate community
compositionin tidal freshwater andoligohalinemarsh
systems. Pp. 561-569 in D.D. Hook and others (eds.)
The Ecology and Management of Wetlands. Vol. 1:
Ecology of Wetlands. Timber Press, Portland,
Oregon.
Peterjohn, W.T. and Correll, D.L. 1984. Nutrient
dynamics in an agricultural watershed: observations
on the role of riparian forest. Ecology 65:1466-1475.
Peterjohn, W.T. and Correll, D.L. 1986. The effect of
riparian forest on the volume and chemical
composition of baseflo win an agricultural watershed.
In D.L. Correll (ed.), Watershed research properties.
Smithsonian Institution Press, Washington, D.C.
Peterson, N.P. 1982, Immigration of juvenile coho
salmon into riverine ponds. Can. J. Fish. Aquat Sci
39:1308-1310.
Powell, G.VJST. 1987. Habitat use by wading birds in
a subtropical estuary: implications of hydrology The
Auk 104:740-749.
Prevett, J.P., I.F. Marshall, and V.G. Thomas. 1985.
Spring foodsof snow and Canada geese at James Bay.
J. Wildl. Manage. 49(3): 558-563.
Sugai, S.F. and D.C. Burrell. 1984. Transport of
dissolved organic nutrients and trace metals from the
Wilsonand Blossom Rivers to Smeaton Bay, Southeast
Alaska, USA. Can. J. Fish. Aquat Sci. 41:180-190.
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U.S. Environmental Protection Agency Regions
For more information, ask for the Wetlands
Coordinator or the Estuarine in any of these
EPA regions:
EPA Region 1
JFK Federal Building
Boston, MA 02203
(617)565-4430
EPA Region 2
26 Federal Plaza
New York, NY 10278
(212)264-5170
EPA Region 3
841 Chestnut Street
Philadelphia, PA 19107
(215)597-9301
EPA Region 4
345 Courtland Street, N.E.
Atlanta, GA 30365
(404)347-3004
EPA Region 5
230 South Dearborn Street
Chicago, IL 60604
(312)353-2079
EPA Region 6
1445 Ross Avenue
Dallas, TX 75202
(214,655-2260
EPA Region 7
726 Minnesota Avenue
Kansas City, KS 66101
(913)236-2823
EPA Region 8
One Denver Place
99918th Street. Suite 1300
Denver, CO 80202
(303)293-1575
EPA Region 9
215 Fremont Street
San Francisco, CA 94105
(415)974-2318
EPA Region 10
1200 Sixth Avenue
Seattle, WA 98101
(206)442-1412
ion Agency
For EPA Headquarters:
EPA Headquarters
401 M Street, SW
Washington, DC 20460
Office of Wetlands Protection
^-— (202) 4f
Office of Marine and Estuarine
Protection
(202) 382-7166
"\~ J7 /]
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