Great Rivers, supporting migrating waterfowl, endangered mussel species and the most ancient
lineage offish in North America. Whether this system continues to survive and flourish ~ or
collapses like the Illinois ~ depends on whether dynamic river forces can be sufficiently restored
to make the river system self-sustaining. Preserving and restoring the Upper Mississippi and
Illinois rivers requires three types of actions:
1. Recreate dynamic river forces to achieve self-sustaining habitat restoration.
Resource managers must design restoration projects to recreate dynamic river forces while
simultaneously supporting sustainable levels of navigation and protecting floodplain agriculture
Immediate opportunities exist to restore and utilize the force of river tributaries as they cross the
floodplains, to add floodplain habitat offered by willing sellers, and to provide for occasional low
water levels during late spring and summer to improve sediment consolidation and trigger plant
reproduction. More research needs to be done to determine how main channel river forces can be
marshalled to recarve backwater habitat and to recreate deeper pools near the main channel.
2. Minimize the operational impacts of the navigation system.
The navigation industry, Coast Guard and Corps of Engineers must take steps to minimize the
operational impacts of navigation on the Upper Mississippi River. Barge tows resuspend
sediments ~ some of which are contaminated with toxic materials - and generate wakes that
contribute to backwater loss The placement of dredge spoil impacts the health of floodplain
resources. The introduction of foreign species threatens the long-term health of the river's native
inhabitants. Few steps have been taken to reduce the risk of catastrophic spills. All of these issues
can be addressed with little impact on the navigation industry.
3. Achieve no net increase in sediment by 2010.
Sediment will continue to enter the Upper Mississippi River at unsustainable levels for many
years Nevertheless, resource managers must begin today to set long-term goals for sediment
reduction and watershed restoration so that the Upper Mississippi River will reach an acceptable
state of equilibrium tomorrow Resource managers need to identify and address tributaries that
are contributing the most sediment to the river, and to identify measures that will reduce erosion,
non-point source pollution and restore hydrologic integrity. Our goals should be to reduce inputs
of sediment in each pool so that they equal the quantity of sediments exiting that pool.
L Recreate Dynamic River Forces
A. Manage Water Levels
For large floodplain rivers like the Mississippi, seasonal floods and periods of low water shaped
the diversity and productivity of river species. During periods of highwater, fish and wildlife
migrate out of the channel and onto the floodplain to use newly available habitat and resources
As floodwaters recede, they transport nutrients and food from the floodplain into the river
By occupying large areas of bottomlands, the original Mississippi River ensured that some portion
of the floodplain would meet the habitat requirements for a wide variety of species The critical
zone is the shallow water boundary where fish and waterfowl can concentrate their feeding.
Because that boundary moves across the floodplain during high water, the entire area flooded in
any year can be exploited by fish and migrating waterfowl.
Low water periods are equally critical During low water stages, sediments dry out, compact and
release nutrients. Many marsh plants depend upon the exposure of sediments for successful
germination. Even in areas that remain inundated, the reduced turbidity associated with low water
permits more light to penetrate to the bottom, allowing plants to germinate Because of the
critical role healthy aquatic plants play in stabilizing sediment, high or low levels of suspended
sediment launch either a vicious or benign cycle High levels of turbidity block light from reaching
aquatic plants, preventing their regermination and leading to fewer plants, less stabilization of
sediment and even higher levels of turbidity Low levels of turbidity lead to healthier aquatic
plants and, conversely, even lower levels of turbidity.
The transformation of the river into a series of pools has changed water levels most dramatically
by eliminating, or even inverting, low water periods in two-thirds of the pools The upper portion
of most pools retain a relatively natural flood pulse But the operation of the navigation dams has
converted the former floodplain/channel complex in the middle portions of the pools into largely
permanent shallow water areas Managed propedy, areas can flmction as extensive marshes or
areas of submerged aquatic plants Absent low water levels, they can become shallow deserts of
turbid sediment The lost marshes of Weaver Bottoms in Pool 5 below Wabasha, Minnesota, and
the declining wild celery beds in Lake Onalaska above LaCrosse, Wisconsin, illustrate the
consequences of permanently high water levels in the midpools
The lower pools have a similar problem Some remain permanently high Others with mid-pool
control points may be drawn down precisely when the river has high water flows to prevent the
upper portions of the pools from flooding. The probable effects of these unnatural drawdowns
during high flow periods is to disrupt species that are adjusted to using the floodplain in these
periods of high flow
The solution is to release water from the dams and lower water levels in the pools at least some
years when river flows naturally drop In 1994, water level drops were conducted in Pools 24, 25
and 26 and resulted in expected positive impacts on plants. A similar benefit occuned on Lake
Chautauqa along the Illinois River where a levee permits controlled water management
Although the ecological necessity of low water periods is clear, much remains unknown about
the biological response to low water levels at different depths, seasons, durations and
frequencies. Different forms of low water levels will also have differing impacts on vegetation.
Figure 1 Frequency of occurreiioe for i
1975 vA 1991. Nivipdoo Pool No. 8, upper Mississippi River.
I isd an areu oombioed, '
The impacts of water level management on river users must be carefiilly considered. While some
low water levels may prevent navigation for short periods, others may only reduce the navigation
depths slightly for short periods, and still others may have no impact on navigation at all. The
potential also exists to coordinate low water level periods with dredging. In each pool, certain
spots in the mid or upper pools tend to develop the shallowest water and determine the capacity
to maintain a nine foot channel. By dredging these spots to a greater depth shortly before
lowering of water levels, impacts on navigation caii in some cases be avoided or minimized.
1) Lower water levels on Pool 5.
Recent studies indicate that water levels in Weaver Bottoms could be lowered by three feet or
more for 30 consecutive days, on average, once every three years between May and August, and
by two feet or more 30 consecutive days for roughly two thirds of all years (C J Woltemade
1995 Water Level Management Opportunities for Ecological Benefit Pool 5 Upper Mississippi
River) Three foot lowerings would expose sediments over one third of the total Weaver Bottoms
area (or approximately 1,274 acres) and should decrease water levels in enough of the remainder
of Weaver Bottoms to provide a vegetative response. Two foot lowerings would expose roughly
one sixth or 574 acres. Within the pool, problem dredge sites occur adjacent to the Bottoms, and
when dredged, are dredged to approximately twelve feet. If dredging is coordinated with water
level reductions in Pool 5, a nine foot navigation channel could be permanently maintained.
Although a three foot reduction would leave a nine foot channel, this reduction might impede
optimal barge weight. The exact timing of any lowering also cannot be predicted with certainty
because it would depend on low water flows, which in turn depend on rainfall and the amount of
waters in soils. A combination of occasional major water lowerings that affect navigation and
minor lowerings that do not affect navigation could sufficiently restore natural river processes
Lowering of water levels must also be coordinated for other potential impacts on marinas,
houseboats, and other river users, and should always be preceded by substantial public education
2) Conduct a system-wide study of water level management by 1998.
The Corps of Engineers should lead a team of public and private partners, in coordination with
navigation and other river interests, to conduct a two-year, systemwide study of the Upper
Mississippi River to determine how to restore more natural water patterns in each of the river's
pools. This effort should include field tests of vegetative responses to different water level
B. Tributary Restoration
Natural rivers build deltas and recarve channels. Recarving primarily occurs during occasional
large floods which multiply the energy of the water. Unlike the main channel - which has been
physically altered to maintain a nine-foot channel ~ few of the Upper Mississippi's tributaries
support navigation Those tributaries once moved dynamically across the floodplain carrying out
in miniature what the Mississippi carried out on a grand scale - carving new channels, creating
new marsh deltas Connected to the river, these tributaries created backwater habitats of great
value to river fish Most of these tributaries have now been channelized as they enter the
floodplain Unchannelizing tnbutaries provides one of the greatest opportunities for recreating
dynamic river forces and dynamic fish habitats because doing so would not interfere with
navigation In fact, tributary restoration would trap sediment in the floodplain and reduce
Restoring tributaries in the floodplain also provides a mechanism for redressing declines in
floodplain forests and connected uplands and wet meadows Oak forests, persimmon, hickories
and pecans ~ critical habitat for wildlife, including songbirds - are declining throughout the
river's floodplains. Restoring tributaries also provides the potential to permit fish to pass around
locks and dams that now block passage. Many native fish and mussels migrated in the original
river ~ the skipjack herring and the American eel migrated from the Gulf of Mexico. The ebony
mussel, which attaches to the herring, has lost its capacity to move and is declining rapidly.
Paddlefish, and other river species, migrate long distances in search of suitable habitat. These
migrations have been greatly curtailed by dams, which block migration completely when gates are
in the water, and which allow migration only when high flood flows impede efforts to move
upstream. Many tributaries originally had channels, or side-channel connections from the
Mississippi, which, if restored, would recreate extensive opportunities for fish to move upstream
and around dams through tributary side channels.
Action: Begin a tributary restoration project in each state by 1998.
Each state, in cooperation with public and private partners, should lead a team to begin to
implement by 1998 one major tributary restoration project. Existing easement and acquisition
programs should be targeted to tributary restoration, and high priority should be placed on
retiring agricultural lands offered by willing sellers that contribute to such projects. River
communities should be involved in planning any restoration project.
Restoring the Vermillion River below Hastings, Minnesota, for example, might assist fish passage
around Lock and Dam 3. Restoring the Spoon River where it passes through the Illinois River
floodplain would substantially reduce the amount of sediment entering the system and reduce
C. Floodplain Restoration
Linkages between the river and its floodplain are critical to maintaining the long-term biological
health of the Upper Mississippi River. Most of the plants and animals inhabiting the Upper
Mississippi River floodplain have adapted to the river's flood pulse: the annual advance and retreat
of floodwaters onto the floodplain During periods of highwater, fish and wildlife migrate out of
the channel and onto the floodplain to use newly available habitat and resources As floodwaters
recede, nutrients and organic matter from the floodplain are transported into the river. By
occupying large areas of bottomlands, the original Mississippi River ensured that some portion of
the floodplain would meet the habitat requirements for a wide variety of species during high flow
In addition to providing fish and wildlife access to seasonally-inundated spawning and nursery
habitat, these river-floodplain interactions also trigger the biological and chemical transformations
that make food available higher up the food chain. Like all river systems, energy flows from
primary producers (plants) through an invertebrate consumer community to species consumed and
enjoyed by humans (fish and waterfowl). When floodwaters inundate floodplain
habitats, energy stored in floodplain plants is released to the aquatic environment The boundary
that separates land and water, known as the river-floodplain aquatic terrestrial zone or moving
littoral zone, is where most of these important energy transfers occur
Large remnants of the Upper Mississippi's original floodplain remain above the Quad Cities and
support large, diverse fish and wildlife populations But, elevated water tables associated with
impoundment have had a devastating impact on floodplain forests By increasing the elevation of
floodplain groundwater levels, the navigation dams have increased the elevation and duration of
saturated soil conditions throughout much of the remaining emergent floodplain and reduced the
available rooting depth for trees and other vegetation Increased wind fetch in the impounded
areas of the navigation pools, coupled with the shallow rooting depth, has made floodplain trees
vulnerable to wind throw Targetted floodplain land needs be acquired in this reach in order to
reestablish these disappearing floodplain forests
Between the Quad Cities and St. Louis, the river retains far less access to its floodplain. And,
below St. Louis, most river-floodplain interactions have been eliminated In these areas, the
conversion of floodplain habitat to agriculture has had a far more dramatic effect on fish and
wildlife populations, causing severe population declines Waterfowl populations, in particular,
have been reduced by the loss of critical habitat and feeding opportunities along the Mississippi
River migration corridor The concentration of waterfowl into few remaining habitats has made
waterfowl more susceptible to disease.
The anticipated growth of navigation traffic increases the need for floodplain restoration
Floodplain development continues in many urban areas, including St Paul, for example, where a
long-term commitment to floodplain parks and open space may be reversed by a proposed metal
shedding operation. As navigation traffic increases, additional terminals and other facilities will
continue to be constructed on the floodplain, exacerbating the fragmentation of existing habitat
Urban sprawl also threatens the river's Bluf!lands, as new developments spread from the Twin
Cities, Cedar Rapids and the Quad Cities In addition to destroying large, continuous tracts of
woodlands, navigation-induced development reduces the scenic values of the river.
1) Begin one major floodplain restoration project in each state by 1998.
Restoring a small fraction of lost floodplain habitat will substantially aid the long-term
productivity of the Upper Mississippi River system Each state should lead a team of public and
private partners to begin a floodplain restoration project in each state by 1998 State and federal
acquisition and easement agencies should seize opportunities to acquire easements and fee title on
floodplain lands that could be reconnected to the mainstem river Lands that can be reconnected
to the river should be given the highest priority
For example, state and federal agencies should restore the confluence of the Mississippi and
Missouri rivers In addition to providing urban spaces for recreation and wildlife, this region has
been identified by experts on neotropical migrants as critical bird habitat. The creation of
Emiquon National Wildlife refuge would also restore floodplain functions This proposed 1 1,000-
acre national wildlife refuge will restore the once vast marshes, bottomland forests and backwater
lakes that converted the floodplain at the confluence of the Illinois and Spoon Rivers near
Havana, Illinois Most of the land has been drained, leveed, cleared and converted to intensive
row-crop agriculture Like the confluence project, this project will illustrate the benefits of river-
floodplain connections, restore lost fish and wildlife habitat and protect backwater lakes from
sedimentation. In addition, restored wetlands will store floodwaters, convey flood flows away
from the upstream town of Liverpool, and capture sediment from the Spoon River that would
otherwise contribute to backwater accretion.
2) Promote alternative agricultural uses of the floodplain.
Each state department of agriculture should lead a team of public and private partners to
encourage alternative uses of floodplain lands. Floodplain restoration need not always mean the
complete dedication of floodplain land to conservation purposes Occasionally flooded farmland
can provide fish spawning and migratory bird habitat and many of the hydrologic functions of land
that is held in public ownership for conservation purposes Preserving land in farm uses may also
be less expensive in some cases than complete acquisition and more acceptable to land owners. A
variety of alternative agricultural practices have the potential to produce substantial economic
returns and could be developed further: production of switchgrass or fast-growing trees for
biomass, intensive rotational grazing, and dry season row cropping
D. Create Diversity of Water Depths
Whether river forces, now used only to maintain a channel for navigation, can be used to
simultaneously meet the needs of navigation and to create and maintain backwater channels and
deepwater pools is among the most difficult questions facing resource managers
The wing dikes, revetments and closing dams that help make navigation possible have disrupted
many of the processes by which the Mississippi created a wide diversity of habitats Prior to the
construction of the navigation system, fluvial processes produced frequent changes in the
geometry of the Mississippi's channels and floodplains. Wing dams, closing dams, revetments,
levees and navigation dams have concentrated river flow in the main channel, prevented channel
meandering, and reduced bathymetric diversity. The placement of these structures has been
described by natural resource managers as the single largest "geological event" since the end of
the last glacial period While existing habitat is being lost due to sedimentation and river
regulation, these structures prevent the river from creating new aquatic habitat.
The loss of water depth (bathymetric) diversity occurs in both the lower and upper portions of
each pool In the lower pools, islands have rapidly eroded, and w/ith them, critical lower water
litorral zones on their downstream side and critical upland habitats where many species can escape
predation At the same time, deep areas within those pools have filled in, limiting habitat for many
fish that rely on those areas Of greater concern, upper pools that have maintained the
most productive and diverse fish and wildlife populations are also slowly filling in. Channels
that once provided a range of water depths are smoothing out into once common depth, limiting
their habitat value at different seasons and for different species. Closing structures that limi t flow
into these side channels have blocked the creation of new habitat, as has the limitation of flow at
the dam into defined spillways.
Wingdams necessary to maintain a narrow channel inherendy limit the edacity to restore a more
naturally wandering river, but most of the carving force provided by the river occurs during
floods when it might be possible to divert excess water from the main channel. Where and how
reopening of charmels might be effective has not been smdied.
Because the potential to restore natural river forces in the deep lower pools is even more limited,
those areas justify greater human manipulation to serve ecological and recreational needs. At
least three concepts should be explored: the use of different weir structures to carve deeper
habitats off of the main channel, the manipulation of water levels within leveed areas, and the
inexpensive construction of small islands. In the interim, there are other opportunities to improve
habitat in the main channel. One is the potential to improve habitat along the river banks between
wingdams. Over time, sediment has accumulated between dikes, causing rapid river bed
aggradation and the conversion of riverine habitat into upland habitat, most severely reducing the
habitat value of these structures below St. Louis. Possible alterations include making notches
within the wingdams to allow flow through to create more complex habitat below wingdams.
Other techniques have included placing rip-rap several feet from the eroding bank The Corps may
have alternatives to side-channel closing dams. One alternative is the chevron dike, V-shaped
structures placed in a staggered arrangement that maintain channel maintenance objectives
without closing off secondary channels.
1) Modify wingdams and closing structures to improve habitat
The Corps should lead a team of public and private partners to develop a plan with
implementation schedules for modifying wingdams, channel closing structures and rip-rap to
improve habitat Although channel training structures like wing dikes have eliminated the river's
ability to create new habitat, areas along the banks from dike to dike provide much of the river's
low current velocity and structurally complex habitat between St Louis and Cairo, and attract or
support large numbers offish and invertebrates. Although the environmental costs and benefits of
these structures have not been fully evaluated, studies suggest that organic materials trapped in
dike-created eddies may help support local invertebrate and fish populations.
2) Develop and demonstrate technologies to recreate and maintain backwater and diverse
water depths by 1998.
The Corps should lead a team of public and private partners to investigate techniques for restoring
natural river forces to recreate bathymefric diversity.
n. Minimize N avigation Impacts
A. Dredged Material Placement
Despite the negative environmental impacts of dredged material placement on floodplain forests
and riverine habitat, the Corps of Engineers has no consistent policy regarding dredge disposal
practices Indeed, the Upper Mississippi River is plagued by a hodge-podge of practices -
including open water disposal â€” that have evolved in response to the presence or absence of
political pressure and, consequently, vary widely from district to distria
The St Paul District has developed the most comprehensive and collaborative approach to dredge
spoil disposal While ultimate control remains with the District Engineer, a consultative group
consisting of the Corps, the US Fish and Wildlife Service, the Coast Guard and the Minnesota,
Wisconsin and Iowa departments of natural resources is actively engaged in spoil disposal
planning Pool by pool plans have either been completed or underway, ultimately creating a
channel maintenance plan for the entire district This plan is designed to anticipate dredging and
dredge spoil requirements until the year 2035, and will allow the Corps to acquire
needed disposal sites, arrange for more flexible equipment, remove spoil from the floodplain and
identify beneficial uses.
Neither the Rock Island or St. Louis districts has developed a long-term system for dredge spoil
disposal The planning and consultative process in the Rock Island district is primitive when
compared to Saint Paul ~ there is no long-term channel maintenance plan and, in the last 1 5 years,