4>EPA
            United States
            Environmental Protection
            Agency
             Environmental Monitoring
             and Support Laboratory
             PO Box 15027
             Las Vegas NV 89114
EPA-600/4-79-073
November 1979
            Research and Development
Operation of the
Old River Control
Project, Atchafalaya
Basin:

An Evaluation from
Multiuse Management
Standpoint

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                   RESEARCH  REPORTING  SERIES

Research  reports of the  Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series These nine broad categories
were established to facilitate  further development and application of environmental
technology.   Elimination  of traditional grouping was consciously planned to foster
technology transfer and a maximum interface in related fields.  The nine series are:


      1.   Environmental Health Effects Research
      2.   Environmental Protection Technology
      3.   Ecological Research
      4.   Environmental Monitoring
      5.   Socioeconomic Environmental Studies
      6.   Scientific and Technical Assessment Reports (STAR)
      7.   Interagency Energy-Environment Research and Development
      8.   "Special" Reports
      9.   Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL MONITORING series.This series
describes research conducted to develop new or improved methods and instrumentation
for  the  identification and  quantification  of environmental  pollutants at the lowest
conceivably significant concentrations. It also includes studies to determine the ambient
concentrations of pollutants in the environment and/or the variance of pollutants as a
function of time or  meteorological factors.
This document is available to the public through the National Technical Information
Service, Springfield, Virginia  22161

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                                                EPA-600/4-79-J73
                                                November  1979
OPERATION OF THE OLD RIVER CONTROL PROECT, ATCHAFALAYA BASIN:
     An Evaluation from a Multiuse Management Standpoint
                             by

                    Johannes L. van Beek
                        Ava L. Harmon
                       Charles L. Wax
                       Karen M. Wicker

                 Coastal  Environments, Inc.
                      1260 Main Street
               Baton Rouge, Louisiana    70802
                  Contract No.  68-03-2665
                       Project Officer

                      Victor W. Lambou
                Monitoring Operations Division
       Environmental  Monitoring and Support Laboratory
                 Las  Vegas, Nevada    89114
       ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
             OFFICE  OF RESEARCH AND DEVELOPMENT
            U.S.  ENVIRONMENTAL  PROTECTION  AGENCY
                 LAS VEGAS,  -NEVADA    89114

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                                 DISCLAIMER
    This report has been reviewed by the Environmental  Monitoring  and Support
Laboratory-Las Vegas*, U.S.  Environmental  Protection Agency,  and approved for
publication.  Approval does  not signify that the contents  necessarily reflect
the views and policies of the U.S. Environmental  Protection Agency,  nor does
mention of trade names or commercial  products constitute endorsement or
recommendation for use.
* After June 4, 1979, the Environmental  Monitoring Systems Laboratory,
                                      11

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                                  FOREWORD
    Protection of the environment requires effective regulatory actions that
are based on sound technical and scientific information.  This information
must include the quantitative description and linking of pollutant sources,
transport mechanisms, interactions, and resulting effects on man and his
environment.  Because of the complexities involved, assessment of specific
pollutants in the environment requires a total  systans approach that
transcends the media of air, water, and land.  The Environmental Monitoring
and Support Laboratory-Las Vegas contributes to the formation and enhancement
of a sound, integrated monitoring data base for exposure assessment through
programs designed to:

    •    develop and optimize systems and strategies for monitoring
         pollutants and their impact on the environment

    t    demonstrate new monitoring systems and technologies by applying them
         to fulfill special monitoring needs of the Agency's operating
         programs

    This report evaluates the operation of the Old River Control Project in
the Atchafalaya Basin from a multiuse management standpoint.  The U.S.
Environmental Protection Agency, the U.S. Army Corps of Engineers, the U.S.
Department of the Interior, the State of Louisiana, special  interest groups,
and other interested individuals will use this information to assess the
potential impact of proposed hydrological modifications and to develop
alternative land and management plans, which will  accommodate floodflows and
maintain an acceptable level of environmental quality.  For further
information contact the Water and Land Quality Branch, Monitoring Operations
Division.
                                            George B.  Morgan
                                                Director
                               Environmental  Monitoring and Support  Laboratory
                                                Las Vegas
                                     m

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                                   SUMMARY
    The Atchafalaya Basin in south-central  Louisiana is a large alluvial  basin
whose wetlands are of national  significance.  To meet the need for flood
control, the U.S. Army Corps of Engineers is considering hydrological
modifications for the Basin.  The Basin's present hydrological  cycle and
complex water circulation patterns support  one of the world's most highly
natural productive areas.

    In response to a request by the Governor of Louisiana and a joint  U.S.
Congressional resolution, the U.S. Environmental  Protection Agency (EPA), U.S.
Army Corps of Engineers (USCE)  and the U.S. Department of Interior are
conducting a water and land quality study in the Atchafalaya River Basin.
This study is assessing the potential  impact of proposed hydrological
modifications and developing alternative land and water management plans  to
accommodate flood-flows and maintain an acceptable level of environmental
quality for the Atchafalaya Basin.

    Objectives of the EPA in the Atchafalaya Basin include:  1) land use
requirements to control agriculturally related nonpoint sources of pollution
(Federal  Water Pollution Control Act Amendment (FWPCAA), 1972,  Sec.  208); 2)
the 1983 goal of water quality, which provides for the protection  and
propagation of fish, shellfish, and wildlife and provides for recreation  in
and on the water, and the restoration and maintenance of the chemical,
physical, and biological integrity of the Nation's water (FWPCAA,  1972, Sec.
101); 3)  avoidance of degradation in any way of waters that in their existing
condition could be used for sport fishing with degradation reducing  their
value for that use; 4) reduction of the adverse impact of spoil disposal  on
fishery,  wildlife, or recreational areas (FWPCAA, 1972, Sec. 404); 5)
monitoring of the discharge of  dredged material  in wetlands; 6) the  avoidance
of long-  and short-term adverse impacts associated with destruction  and
modification of wetlands (Exec. Order 11990); 8)  the avoidance of  direct  or
indirect  support of new construction in wetlands (Exec. Order 11990);  9)  the
avoidance, to the extent possible, of long- and short-term adverse impacts
associated with the occupancy and modification of flood plains (Exec.  Order
11988); 10) the avoidance of direct or indirect support of flood-plain
development whenever there is a practicable alternative (Exec.  Order 11988);
and 11) the avoidance of discharge of material that would have an  unacceptable
adverse effect on municipal water supplies, shellfish beds, and fishery,
wildlife, or recreational areas (Public Law 92-500, Sec. 404, C).
                                      IV

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    The Atchafalaya Basin extends inland from the Gulf of Mexico for a
distance of 125 miles to the confluence of Red River and distributary flows
from the Mississippi River.  The Old River Project was placed into operation
in 1963 to regulate, by control structures, the diversion of Mississippi River
flow into the Atchafalaya River.  Previous to this it was noted that
unregulated flows from the Mississippi River were steadily increasing and that
in the absence of man's intervention the Mississippi River would change its
course to that of the Atchafalaya River.  The Old River Project is now being
operated so that the proportions of flow between the Mississippi and
Atchafalaya Rivers are the same as occurred in 1950, i.e., 30 percent of the
latitude flow is carried by the Atchafalaya River and 70 percent by the
Mississippi River.  The volume of water that is allowed through the control
structure determines the character of the aquatic ecosystems in the
Atchafalaya Basin and the Red River backwater area.

    Various alternatives for the future operation of the Old River Control
Project are being considered.  These are:  1) maintain present diversion from
the Mississippi River; 2) limit diversion so that storages in the Red River
backwater area are reduced during the spring planting season and the area
currently inundated is reduced; and 3) manage diversion in order to meet the
requirements of the aquatic ecosystems in the Atchafalaya Basin,   This report
evaluates the operation of the Old River Control Project from a multiuse
management standpoint.

    It was found that limiting diversions to the extent presently being
considered by the Old River Control  Project would effectively remove those
wetlands that are presently flooded for a period of 0 to 4 months from the
aquatic ecosystem.  This type habitat represents as much as 36 percent of the
wetlands of the overflow areas in the Atchafalaya Basin.  Without stronger
land use controls, a reduction in the annual  extent of flooding could
encourage new residential and agricultural  development in the present
wetlands.  This in turn would increase agricultural runoff into adjacent
wetlands, which are already affected by such runoff and in which water
circulation is impeded by a backwater regime as a result of past flood control
increases.

    In order to minimize the present loss of wetlands in the Atchafalaya Basin
as a result of river profile adjustments, the present diversion water must  be
at least maintained.  However, the complete maintenance of present wetlands
requires an increase of diverted discharges to offset the trend toward
reduction in the extent, duration, and depth of flooding.

    As a participant in the planning process for the development of a multiuse
management plan for the Atchafalaya Basin,  the U.S. Environmental  Protection
Agency is using the results of this study to make recommendations, enforceable
through its responsibilities, to insure that Federal  environmental
requirements and objectives are sufficiently considered in the selection of a
final  plan.

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                                  CONTENTS
Foreword	iii
Summary	    iv
Figures	viii
Tables	     x

    Introduction  	     I
    Conclusions 	     2
    Recommendation  	     3
    Background  	     4
    Old River Control  Project 	    11
    The Overflow Regime	    14
    Flood Control	    23
    Present and Future Conditions in the Main Channel	    26
    Agricultural Use and Settlement 	    41
         Red River backwater area	    41
         West Atchafalaya Floodway  	    42
         Morganza Floodway  	    43
         Atchafalaya Basin Floodway 	    44
         Effects of agricultural  development	    45
    Alternatives for Operation of the Old River Control  Project ....    48
         Maintain present diversion 	    48
         Limit diversion	    50
         Manage diversion for aquatic ecosystem 	    58

    Discussion	    59

References	    60

Appendix	    61
                                     vn

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                                   FIGURES


Number                                                                   Page
  1   Physiographic setting of the Atchafalaya Basin,
        Louisiana	    5

  2   Levees of floodway system within the Atchafalaya
        Basin	    6

  3   Natural environments and management-unit boundaries
        of the Atchafalaya Basin 	    7

  4   Old River Control  Project	12

  5   Division of the Atchafalaya Basin into management
        units on the basis of natural  environment  and
        human use	15

  6   Schematic representation of topography, overflow
        regime, and associated habitats in management
        units of the upper floodway	17

  7   Schematic representation of topography, overflow
        regime, and associated habitats in management
        units of the middle floodway	18

  8   Schematic representation of topography, overflow
        regime, and associated habitats in management
        units of the lower floodway above Teche Ridge	19

  9   Atchafalaya Basin  Floodway system	24

 10   Relationships among hydraulic elements in the
        Atchafalaya Basin Floodway system	27

 11   Diversion from the Atchafalaya Basin main channel
        during average annual flood	29

 12   River miles along  Atchafalaya Basin main channel  	   30

 13   Annual flooding of backwater area and associated
        topographic and  water-level changes	32
                                     vm

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Number                                                                   Page

 14   Changes in flow line along the Atchafalaya Basin  main
        channel  for the 450,000 ft3/sec and project  flood
        discharges	34

 15   Schematic  representation of channel  and flow line changes
        along the Atchafalaya Basin main channel	35

 16   Atchafalaya River flow as a percentage of latitude flow	49

 17   Annual  regime of the Atchafalaya River as illustrated  by
        average  daily discharge (1949-74)  and daily  discharges
        during an average water year (1964/1965)  at  Simmesport,
        Louisiana	51

 18   Annual  regime of the Atchafalaya River as illustrated  by
        average  daily stages (1949-74)  and daily stages during
        an average water year (1964/1965)  at Simmesport,
        Louisiana	52

 19   Average daily discharges at Simmesport, Louisiana, at
        present  and for 35 feet, 40 feet,  and 45 feet MSL	53

 20   Comparison of Atchafalaya River discharges at  Simmesport,
        Louisiana, for an average water year (1964/1965) with
        those allowable for the 35-ft,  40-ft, and 45-ft plan	56

 21   Comparison of Atchafalaya River stages at Simmesport,
        Louisiana, for an average water year (1964/1965) with
        those allowable under the 35-ft, 40-ft, and  45-ft  plan 	   57
                                      IX

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                                   TABLES
Number                                                                  Page

  1   Area!  and Percentage Distribution  of  Flooding Duration
        in Management Units of the Atchafalaya Basin  Floodway	22

  2   Rates of Channel  Development along the  Atchafalaya Basin
        Main Channel	37

  3   Possible Net Change in Channel  Cross  Section from Combined
        Changes in the Bed and Flow Line	39

  4   Estimated Time  Requirements  for Natural Channel
        Enlargement to Alternative Dimensions of 100,000 ft2
        and 80,000 ft2	40

  5   Settlement in the West Atchafalaya Floodway	43

  6   Settlement of the Morganza Floodway	43

  7   Ownership and Servitudes in  the Atchafalaya Basin
        Floodway	44

  8   Settlement in the Atchafalaya Basin Floodway 	  45

  9   Comparison of Atchafalaya River Discharges and  Stages at
        Simmesport for Present Conditions and the Limited
        Diversion Alternative	54

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                                INTRODUCTION
    The Atchafalaya Basin in south-central  Louisiana is a large alluvial  basin
that has national  significance as a multiple resource.   It derives this
significance principally from possessing high-quality habitats  for fish and
wildlife, being a semi-wilderness area of high recreational  value, and
functioning as a floodway for the lower Mississippi  River.  To  meet the need
for flood control, the U.S. Army Corps of Engineers  (USCE) is considering
hydrological modifications for the Basin.  The Basin's  present  hydrological
cycle and complex water circulation patterns support one of the world's most
highly natural productive areas.

    In response to a request by the Governor of Louisiana and a joint U.S.
Congressional resolution, the U.S. Environmental  Protection Agency (EPA),
U.S. Army Corps of Engineers, and U.S. Department of the Interior (USDI)  are
conducting a water and land quality study in the Atchafalaya Basin.  The study
is assessing the potential impact of proposed hydrological modifications and
developing alternative land and water management plans  to accommodate flood
flows and maintain an acceptable level of environmental quality for the
Atchafalaya Basin.  The purpose of the report is to  consider from a multi-use
management standpoint the operation of the Old River Control Project in the
Atchafalaya Basin.

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                                 CONCLUSIONS
    The following were concluded from this study:

1.  Reducing the presently authorized discharges by the Old River Control
Project will result in destruction, loss, and degradation of the wetlands in
the Atchafalaya Basin and Red River backwater area and is in direct conflict
with what is necessary for their preservation and enhancement.

2.  Reducing maximum discharges at Simmesport to 260,000 ft3/sec* would
effectively remove those wetlands that are presently flooded for a period of
0 to 4 months from the aquatic ecosystem as a type habitat.  This habitat
represents as much as 36 percent of the wetland system of the Atchafalaya
Basin Floodway below U.S. Highway 190.

3.  Without stronger land use controls, a reduction in the annual extent of
flooding would encourage new residential and agricultural development in
present wetlands.  This, in turn, would increase agricultural  runoff into
adjacent wetlands, which are already affected by such runoff and in which
water circulation is impeded by a backwater regime as a result  of past flood
control measures.
*Because many of the available data used in preparing this report were in
 English units, metric units are not used throughout this report.  Conversion
 factors are given in the Appendix.

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                               RECOMMENDATION
    It is recommended that the present diversion ratio by the Old River
Control Project be at least maintained in order to minimize the present loss
of wetlands as a result of river profile adjustments.   However, the complete
maintenance of present wetlands requires an increase of diverted discharge to
offset the trend toward a reduction in the extent, duration, and depth of
flooding.

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                                 BACKGROUND


    The Atchafalaya River Basin, Louisiana, coincides  with  the  natural  basin
formed by alluvial ridges that relate to present and former Mississippi  River
courses (Figure 1).  The Basin extends inland from the Gulf of  Mexico  for  a
distance of 125 miles to the former confluence of the  Mississippi  River and
Red River.  Continuity of the Basin is only interrupted by  an alluvial  ridge,
the Teche Ridge, that crosses the Basin at the latitude of  Morgan  City,
Louisiana.  Central to the Basin is the Atchafalaya River,  which connects  the
Mississippi River and the Red River to the Gulf of Mexico and flows  through
the Teche Ridge at Morgan City where it becomes the Lower Atchafalaya  River.

    Until 1928, the entire Basin functioned as the Atchafalaya  River flood
plain and afforded a natural outlet for Mississippi  and Red River  floodwaters
to the Gulf of Mexico.  Since then major changes have  evolved.   In 1928  and
1956, respectively, Congress authorized the construction of a floodway through
the Basin and the construction of control  structures at Old River  to regulate
the diversion of Mississippi River flow into the Atchafalaya River (Figure 2).
To provide a defined floodway, guide levees were constructed east  of,  west of,
and parallel to the Atchafalaya River and at an average distance of  15 miles
apart.  Floodflows, as well  as the annual  overflow of  the Atchafalaya  River,
thus became confined to the central part of the natural  Basin as far south as
the Teche Ridge.  Through the ridge, flows are temporarily  further confined to
only the channels of the Lower Atchafalaya River and the constructed Wax Lake
outlet until the guide levees terminate and water escapes the channels into
adjacent wetlands and the Gulf of Mexico.

    Despite the many adverse changes that have taken place  as a result of
indiscriminate use of the Atchafalaya Basin's water- and land-related
resources, the Basin still constitutes a resource complex of exceptional
recreational, ecological, and commercial  significance.   The floodway system
above the Teche Ridge is one of the largest remaining  alluvial  flood-plain
hardwood swamps in the United States.  It contains more than 700,000 acres of
hardwoods, nearly one-third of which are cypress-tupelo swamps, and  53,000
acres of water bodies (Figure 3).  To this must be added the hardwood  swamps
of the Basin outside the floodway.  Below the Teche Ridge,  the  Basin
environment becomes one of freshwater and brackish water marshes and bays,
where the present development of the Atchafalaya River delta is one  of the
most important processes from an environmental  quality standpoint.  This delta
offers the potential development of a 300 mi'2 area of  new wetlands by  the
year 2020 in a State where the loss of wetlands amounts to  a staggering  16
mi^ per year.

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        Bordering
         Natural
          Levees
         OWLF OF MEXICO
Figure 1.   Physiographic setting of the Atchafalaya Basin,  Louisiana.

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                fled River
                                   OLD RIVER CONTROL STRUCTURE
         vermilion

           Bay   Cote Blanche
                      Bay
                             East
Figure  2.   Levees  of floodway  system within the  Atchafalaya  Basin.

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              >/(V^
         ..^&$$&*^- .*
Figure 3.  Natural environments and management-unit boundaries of the
          Atchafalaya Basin.

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    Use of the Atchafalaya Basin for flood control  has significantly affected
the integrity of the Basin's waters physically, biologically,  and chemically.
Most drastic has been the segmentation of the natural  basin and associated
modification of the overflow regime.  Floodway guide levees have divided the
Basin into a central floodway and two subbasins on  either side, the Verret
Subbasin on the east side and Fausse Point Subbasin on the west side (Figure
2).  The resultant restriction of the active flood  plain has intensified
riverine processes within the floodway area while it has eliminated annual
overflow in the marginal areas.  Within the floodway,  the overflow regime was
further modified as a result of partial channelization of the  Atchafalaya
River and associated spoil disposal along its lower course from Interstate
Highway 10 to Morgan City.  In combination with other  actions  related to
navigation and oil and gas extraction, the modification of the hydrologic
regime has had a major adverse impact.

    Adverse impacts on the Basin's wetland system and  related  biological  and
recreational value could be further increased as a  result of future actions
for the purpose of improved flood control.  Achieving  the authorized and
needed floodway capacity of 1,500,000 ft3/sec requires further development
of the Atchafalaya River channel from 1-10 to the Teche Ridge  and the
restriction of sedimentation in the overbank area.   Depending  on the
alternative selected to meet the requirements for flood control use, the
hydrologic regime may be modified to the point that the viability of the
present wetland system is severely threatened.  Adverse effects of improper
management on the duration and extent of flooding and  on circulation and water
quality could destroy the viability of the system.   Indirect support provided
for expansion of agricultural development adjacent  to  and in present wetlands
could destroy the wetlands directly and indirectly.

    After flood control, maintenance dredging, mainly  for navigation, is the
most detrimental to the Basin's ecology.  Annual maintenance above the Teche
Ridge requires dredging of approximately 2,000,000  yd3 (U.S. Army Corps of
Engineers 1975).  One-half of this dredging is done in waterways in the
backwater areas and waterways connecting the former to the Atchafalaya River.
These include the east and west access channels, which account for 600,000
yd3, the freshwater distribution channels, and the  alternate route of the
Gulf Intracoastal Waterway.  As indicated to some extent by the volume of
maintenance dredging required, these channels are also the main route for the
diversion of excessively large volumes of sediment  into the backwater area of
the floodway below 1-10.  Not only does this result in a decrease in floodway
capacity, it also results in the degradation of environmental  integrity of the
floodway's wetlands.  Introduction of sediments through these  channels into
the flood-plain swamps greatly contributes to the present reduction of the
total water area and the degradation of the quality of forested wetlands.

    Equally detrimental  has been the disposal of spoil on streambanks.  This
has been a major cause of reduced circulation and resultant water quality
problems, in particular the depression of dissolved oxygen values.  While
annual reduction of dissolved oxygen values is in part a natural  phenomenon
resulting from large organic litter input and the organic nature of swamp
sediments, at present the oxygen values in large swamp areas as well as

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streams are depressed for periods in excess of one month to levels where the
water can no longer support fishes and other aquatic life.

    In the Lower Atchafalaya River connecting Morgan City and the surrounding
industrial development to the Gulf of Mexico, provisions for navigation are
creating a serious degradation of the environment.  Because this navigation
route traverses the area of the most rapid growth of the Atchafalaya Delta,
maintenance of the authorized navigation channel  requires annual dredging.
This action channelizes water and sediment through the active delta to deeper
water and thus reduces the potential for valuable development of new wetlands.

    The direct and indirect support for agricultural development in the Basin,
inside and outside the floodway, is creating destructive pressure on the
systems in the Basin.  Expansion of agricultural  development is facilitated by
a number of processes and actions.  Within the floodway, enlargement of the
Atchafalaya River channel has resulted in a lowering of annual  flood stages
above 1-10 thus reducing backwater flooding in the upper floodway.  Since that
area is already protected from direct river overflow by levees  within the
floodway along the Atchafalaya River, the reduced backwater flooding has
allowed the expansion of agricultural development through the clearing of
flood-plain forests.  Application has been received by the United States Soil
Conservation Service (USSCS) for planning of a small watershed  project
involving 165,000 acres.  Similarly, agricultural expansion takes place along
and into the swamp forests of the Basin outside the floodway with support of a
number of USSCS watershed projects.

    The potential for further expansion of agricultural  development and
habitation of the floodway is increased by the consideration of reducing
diversion of waters from the Mississippi River into the Atchafalaya River
during annual  flood stages.  This plan is considered for the purpose of
enhancing agricultural  development in the flood plain of the Red River
immediately north of the floodway.  Such reduction in flows would equally
affect the backwater stages in the northern part  of the floodway, thus
providing for increased flood-plain development,  and would reduce annual
overflow in the lower floodway, affecting the hydrologic regime of the
wetlands there.

    Concern for the protection of the environment has been growing, as has
concern that the flood control value of the floodway is becoming increasingly
less than it should be.  On June 11, 1968, and March 23, 1972,  the United
States Senate Committee on Public Works, and on June 14, 1972,  the United
States House of Representatives Committee on Public Works, adopted resolutions
concerning management and use of the water and related land resources of the
Atchafalaya River Basin.  These resolutions directed the USCE to determine
whether, in light of changed conditions, modifications to the operation of  the
Old River Control Project are warranted and to review, in cooperation with
other agencies including the EPA, the report on the Mississippi  and
Tributaries Project, House Document 308, 88th Congress,  and other pertinent
reports, with a view to developing a comprehensive plan  for the management  and
preservation of the water and related land resources of  the Atchafalaya River

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Basin, Louisiana.  As directed, this would include provisions  for reduction  of
siltation, improvement of water quality, and possible improvement of the area
for commercial and sport fishing.

    In response to the Senate and House resolutions,  the Atchafalaya Basin
Land and Water Resources Interagency Study was initiated in  1972.
Participants are the USCE, EPA, USDI, and State of Louisiana.   As a
participant in the planning process, the EPA is in a  position  to  make
recommendations, enforceable through its responsibilities, to  insure that
Federal environmental requirements and objectives  are sufficiently considered
in the selection of a resource management plan.  Objectives  of the EPA in the
Atchafalaya Basin include:  1) land use requirements  to  control agriculturally
related nonpoint sources of pollution (Federal Water  Pollution Control  Act
Amendment (FWPCAA), 1972, Sec. 208); 2) the 1983 goal  of water quality, which
provides for the protection and propagation of fish,  shellfish, and  wildlife
and provides for recreation in and on the water, and  the restoration and
maintenance of the chemical, physical, and biological  integrity of the
Nation's water (FWPCAA, 1972, Sec. 101); 3) avoidance of degradation in any
way of waters that in their existing condition could  be  used for  sport fishing
with degradation reducing their value for that use; 4) reduction  of  the
adverse impact of spoil disposal  on fishery, wildlife, or recreational  areas
(FWPCAA, 1972, Sec. 404); 5) monitoring of the discharge of  dredged  material
in wetlands; 6) the avoidance of long- and short-term adverse  impacts
associated with destruction and modification of wetlands (Exec. Order 11990);
7) the avoidance of direct or indirect support of  new construction in wetlands
(Exec. Order 11990, Federal Register, 1977); 8) the avoidance, to the extent
possible, of long- and short-term adverse impacts  associated with the
occupancy and modification of flood plains (Exec.  Order  11988, Federal
Register, 1977); 9) the avoidance of direct or indirect  support of flood-
plain development whenever there is a practicable  alternative  (Exec. Order
11988); and  10) the avoidance of discharge of material  that would have an
unacceptable adverse effect on municipal water supplies, shellfish beds, and
fishery, wildlife, or recreational areas (Public Law  92-500, Sec. 404,  C) .
                                      10

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                          OLD RIVER CONTROL PROJECT
    On July 13, 1963, the Old River Control  Project was placed in  operation
(Figure 4).  The Old River Control  Complex is a part of the Flood  Control,
Mississippi River and Tributaries (FC,MR&T)  Project, a comprehensive flood
control project dating from the Flood Control Act of 1928 and extending  from
Cape Girardeau, Missouri, to the Head of Passes below New Orleans, Louisiana.
One of the essential features of the FC,MR&T Project is the continued use of
the Atchafalaya Basin as a floodway.  Previous to the Old River Control
Project, Mississippi River waters entered the Atchafalaya Basin via a short
channel known as Old River, which connected  the Mississippi  and Atchafalaya
Rivers.  A steady increase was noted in the  volume of water flowing from the
Mississippi River into the Atchafalaya River, and by the early 1950's it
became apparent that, in the absence of any  intervention by man, the
Mississippi River would use the Old River connection to change its course to
that of the Atchafalaya River.  To  prevent such an occurrence, Congress, by
the Flood Control Act of 1954 (P.L. 780, 83rd Congress), modified  the FC.MR&T
Project by authorizing the Old River Control  Project to regulate the flow of
water from the Mississippi River into the Atchafalaya River.

    The Old River Control Project is located on the right descending bank of
the Mississippi River about 50 miles northwest of Baton Rouge, Louisiana.
Principal features of the Old River Control  Project (see Figure 4) are:  two
mechanically operated control structures, designated the low sill  structure
and the overbank structure; an inflow channel from the Mississippi River to
the low sill control structure; an  outflow channel  connecting the  low sill
control structure with Red River; a lock for navigation connecting the
Mississippi and Old Rivers; forebay and tail bay channels for the lock; an
earthen dam closing Old River; enlargement and extension of main line
Mississippi River levees; and bank  stabilization as required in the Red  and
Atchafalaya Rivers between the outflow channel and the vicinity of Simmesport.

    The authorizing legislation for the Old  River Control  Project  made it
obligatory that flow and sediments  between the Mississippi  and Atchafalaya
Rivers be in the proportions that occurred in 1950.  In 1950 the Atchafalaya
River carried 30 percent of the latitude flow and the lower Mississippi  River
carried 70 percent.  Latitude flow  is the total  flow of the Mississippi  and
Red Rivers at the latitude of, but  just above, the Old River Control  Project.
At Mississippi River stages (at Old River Control  Project)  of 52.0 feet  and
below, the overbank structure cannot be operated and all  diversion is
regulated through the low sill structure. At stages above  52.0 feet, both
structures are normally operated.
                                      11

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    The volume of water that is allowed through the control  structures
determines the character of the entire Atchafalaya Basin Floodway complex.
Because the channel leading from the control  structures to the head of  the
Atchafalaya River also receives the waters from the Red River, the volume of
water diverted through the structures not only controls the annual stage
variation and flooding in the Atchafalaya Basin Floodway complex but, through
backwater flow, also greatly influences the stages in the Red River backwater
area.  The Old River Control Project therefore plays a vital  role in
controlling the use of water and related land resources in both the
Atchafalaya Basin Floodway complex and the Red River backwater area.

    The resource uses that are affected most  by the amount of discharge
diverted are commercial and sport fisheries and recreation (affected because
the amount of discharge is critical to aquatic ecosystems),  agriculture
(because the amount of discharge controls flooding during the spring planting
season), silviculture (because the amount of  discharge controls flooding
during the growing season), and flood control (because the amount of discharge
has an effect on the size of the Atchafalaya  Basin main channel).  It can be
seen that the percentage of the Mississippi River's water that is diverted  by
the Old River Control Project is a factor that affects every  use and value  in
the Basin.
                                      13

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                              THE OVERFLOW REGIME
    The process most important to the ecology of the Atchafalaya  Basin is  the
annual flooding and dewatering of the Atchafalaya River flood  plain within the
floodway guide levees.   This annual  inundation by flood waters constitutes an
energy subsidy that increases the swamp's productivity (Odum 1969)  and makes
the overflow swamp environment one of the most diverse and  productive of our
native environments (Wharton 1970).   The entire system is  adapted to and based
upon seasonal fluctuations of water  level.  Therefore, the  relationship
between the hydrologic  regime and the environment must be  understood.  Without
this understanding, it  is impossible to evaluate the impacts of activities or
changes in the Basin, and it is impossible to formulate a multiuse management
plan.

    A number of studies have been undertaken on this subject since 1972 by the
EPA and U.S. Fish and Wildlife Service (FWS).  From these  studies has evolved
a basic understanding of the role the flooding regime plays  in determining
diversity, type, and quality of the  Basin's environments and of the
requirements for maintaining and restoring environmental integrity.

    The diversity of habitats and habitat distributions as  they exist at
present are controlled  primarily by  the extent, duration, depth,  and time  of
flooding.  (The second  major controlling factor is the rate  of deposition  of
inorganic sediments.)  While the average time of flooding  has  been relatively
stable because it is controlled by the April discharge peak  of the Atchafalaya
River, the duration, depth, and extent of flooding are variable in time and
space.  They are variable in time because sedimentation within the floodway
continues to elevate the flood plain relative to the Atchafalaya  River stages.
They are variable in space because of topographic variation  within the
floodway and variation  in stage fluctuations along the Atchafalaya River.

    The spatial variation in the floodway regime means a variation in
habitats, hydrologic requirements, and suitability for certain uses.  To deal
with this variation, the floodway has been divided in a former study (van  Beek
et al. 1977) into a number of subbasins that are amenable to surface-water
management.  These subbasins can be  considered as management units, and their
locations and names can be seen on Figure 5.  The temporal  variation means
that surface-water management must not only meet present requirements for
maintenance and restoration of environmental quality within  management units
but also counter or redirect present trends that are undesirable.

    Duration, depths, and extent of  flooding, and therefore  the distribution
of habitats in the Atchafalaya Basin Floodway complex, show  two trends. The
first is a north-to-south trend from mixed hardwoods to cypress-tupelo swamps
                                      14

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        Unit BctndwlM


        Arai of Study Emphaill


        Study Araa Boundary
Figure  5.   Division of the Atchafalaya  Basin into management  units
            on the  basis of natural environment and  human use.
                                    15

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and open water bodies.  The second trend occurs  within  individual  subbasins  or
management units and is directed away from the higher levee  ridges  that
surround, fringe, or traverse each unit.  From the  higher ridges  to the  lower
part of each unit, one finds again the sequence  of  mixed  hardwoods  with
increasing flood tolerance to cypress-tupelo to  permanent water bodies.

    The habitat trends can be illustrated by means  of three  diagrams (Figures
6-8).  Each diagram represents a subbasin or management unit within the
Atchafalaya Basin Floodway complex and shows:  1) the average annual  stage
hydrograph; 2) topography in terms of an elevation  frequency curve  (percent  of
the area below a given elevation that is equivalent to  the percent  of the area
submerged for given river stage); 3)  distribution and extent of habitats
(permanent water (PW), cypress-tupelo (CT), mixed hardwoods  (MH); 4)  duration
of flooding; and 5) time of flooding  for given duration (period of  flooding).
The depth of flooding can be obtained from the stage hydrograph and the
elevation frequency curve.  The diagrams represent  management units in the
upper (Figure 6), middle (Figure 7),  and lower (Figure  8)  part of the
Atchafalaya Basin Floodway complex.   Accordingly, maximum river stages,
amplitude of stage variation, and land elevation decrease from Figure 6  to
Figure 7.  Also, topographic characteristics change as  indicated  by the
changing shape of the elevation frequency curves.   Related to progressively
southward flood-plain sedimentation,  topography  in  the  upper floodway is
marked by broad levee ridges and gradual changes in elevation, while in  the
lower floodway, subbasins are still marked by extensive low-lying and
relatively flat areas over which the  duration and depth of flooding are  fairly
uniform.  The middle floodway represents a transitional condition.   The  bottom
line in Figures 6 and 7 illustrates also how the trend  of topography-
hydrograph combinations results in a  trend in habitats.   With regard to
habitats, four average conditions are most important.  These are:   1) flooded
continuously; 2) flooded for a period in excess  of  seven  months;  3) flooded
from one to seven months; and 4) not  flooded beyond April  15. The  areas
flooded continuously represent the permanent water  bodies that serve as  the
only remaining fish habitat following dewatering of the swamps in  late spring,
as habitat for fish requiring measurable flow, and  as a habitat for the  many
aquatic-oriented species of wildlife  including birds, reptiles, and mammals.

    The areas flooded for a period of at least 7 months and  up to as much as
12 months are the areas dominated by  cypress-tupelo forests.  Since the  7-
month flooding period extends from December 15 through  July  15, far into the
growing season, these conditions are  not favorable  to the mixed hardwood
forest species.  Related to the hydrograph-topography combination,  these
extended flood durations are seen to  occur much  more extensively  in the  lower
part of the floodway (Figure 8) than  in the upper floodway (Figure  6).

    The cypress-tupelo forest habitat is extremely  important in the
Atchafalaya Basin.  Besides having a  unique and  highly  scenic quality, the
habitat plays a major role in the Basin ecology. During  periods  of limited
water depth, as in the flooding in late winter and  early  spring,  the
cypress-tupelo forest serves as the main habitat for juvenile crawfish,  which
are the direct link in the aquatic food chain between detritus material  and
predatory fishes and aquatic-oriented wildlife.  Following an increase in
                                      16

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                                   Months
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40


36


32


28


24



20


16


12


 8
   N  ID
                             I  M
                                           I M I
       I    \   TTTI   I    f     Ml  I
109   8   7   6543   2   1     1234
               Period of Flooding in Months
                   Elevation Frequency
                               Curve (?
1*
                                                     5  6789 10
                        Average
                        Annual Stage
                        Hydrograph
                                      I
             10    20     30    40    50    60
       PW    '                 Percent Area
                                              70
       I * mi
       L_t^^^
       H2H   7
                        Mixed Hardwoods (MH)
                                             80
              65    43210

               Habitats & Duration of Flooding in Months
    90    100
               (PW = permanent  water; CT = cypress-tupelo)

    *Seven months is the minimum duration of flooding for areas to be
     dominated  by cypress-tupelo forests

    Figure 6.   Schematic representation of topography, overflow regime,
               and associated habitats in management units of the upper
               floodway.
                                  17

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                                    Months
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16


14


12


10


 8


 6


 4
      O    N I  D  j
                               F .'  M  I  A '.M.'.J
               I   I    I    I  I  I  I    I    I     I  I  I  I
           109   8   7   6543   2   1     1234   5678910
                           Period of Flooding in  Months
Average
Annual Stage
Hydrograph
                             5^7 Months* ^
         / \
                               Elevation Frequency Curve
                                   U	I
             10    20    30     40    50 |    60
                                  Percent Area
                                                70
80
90
                                  100
                                                 Mixed Hardwoods
                    Habitats of Duration of Flooding in Months
              (PW = permanent water; CT = cypress-tupelo)

   *Seven months is the minimum duration of flooding for areas to be
    dominated by cypress-tupelo forests

   Figure 7.   Schematic representation of topography, overflow regime,
              and associated habitats in management units of the middle
              floodway.
                                   18

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03
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                                     Months
     8
     3


     2
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               N  ID  I  J  I   F  I  M  I  A  I  M  I  J
       II   Till   II
109   8   7   6543   2   1
                                              Tl
                                              1234   5  6789 10
                            Period of Flooding in Months
                         Average
                         Annual Stage
                         Hydrograph
                    I
                    Elevation Frequency Curve


                      I      I       I      I
             10    20    30     40    50     60    70    80   |  90    100
                                   Percent Area
                           ||Cypress-TupeloT|
                           VOm\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\WA\W\WO
                                                       MH

                    10
                  11
                      8

                Habitats of Duration of Flooding
                        in Months
              (PW = permanent water;  MH = mixed hardwoods)

   *Seven months  is the minimum duration of flooding  for areas  to be
    dominated  by  cypress-tupelo forests

   Figure 8.   Schematic representation  of topography, overflow  regime,
              and associated  habitats in management  units of the lower
              floodway above  Teche Ridge.
                                   19

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water depth during March and April, the cypress-tupelo swamp becomes a major
feeding area for adult and juvenile fishes.   At that  time the increased water
depths also allow access for extensive commercial  crawfishing,  commercial
fishing, and recreational  fishing uses.  Such access  is not  allowed  equally  in
mixed hardwood forest habitat, which becomes flooded  at that time because  of
much denser understory shrub vegetation.   In addition, duration of flooding  is
shorter and does not provide for as long  a growing season for the crawfish.

    As can be seen in Figures 6, 7, and 8, changes in topography (as a result
of sedimentation that builds the land higher) have increasingly reduced the
area! extent of cypress-tupelo habitat by reducing the duration of flooding
and allowing invasion by mixed hardwoods.  While in the lowest  part  of the
Atchafalaya Basin Floodway complex (Figure 8) topography still  provides for
limited depth of flooding over a wide area during late winter and early
spring, these conditions are found in the upper Atchafalaya  Basin Floodway
complex (Figure 6) only in a narrow zone  surrounding  the permanent water
bodies.  Consequently, in the upper and to some extent the middle Atchafalaya
Basin Floodway complex, the area allowing for prolonged crawfish growth and
commercial harvesting has been greatly reduced.

    A second reduction of cypress-tupelo  habitat has  occurred where
sedimentation has led to ponding of water or where the duration of flooding
has increased as a result of an increase  in average daily river stages such  as
in the lower part of the floodway.  These conditions  adversely  affect
regeneration of cypress-tupelo and when combined with poor water quality,  in
particular low oxygen values, result in mortality of  the cypress-tupelo and  a
succession to open water bodies.

    Areas flooded less than seven months  are occupied by mixed  hardwoods of
varying flood tolerance.  A considerable  gradient exists within these
hardwoods as related to flood duration, which may range from seven months  of
submergence to no flooding.  Equally important is the time of flooding.
Because highest average daily stages occur in the middle of  April, flooding
periods are approximately centered around April 15.  Accordingly, half of  each
increase in flood duration will extend into the growing season.  As  a result,
the most rapid tree growth and the more desirable species of mixed hardwood
from a silviculture point of view, such as oaks and sweet gums, will  occur
primarily in areas that are not flooded but where soils become  saturated prior
to April 15.  These are, however, also the areas suitable for and increasingly
used for agriculture, in particular soybean farming.

    The area of mixed hardwoods is alternately part of the terrestrial  and
aquatic ecosystem as a transitional zone  between the  cypress-tupelo  forests
and the oak-sweet gum forest type.  Accordingly, this transitional zone serves
both the aquatic and terrestrial species.  In spring  and early  summer, these
mixed hardwood swamps serve as feeding areas for crawfish, nursery and feeding
areas for young-of-year and adult fishes, respectively, and  habitat  for
aquatic wildlife.  The area is of additional major importance in that the
dewatering process traps many fishes and  other aquatic species, thus providing
important food and feeding areas for wading birds and mammals;  the floodway's
                                      20

-------
swamps contain a number of wading-bird rookeries.  During late spring,  summer,
and fall  the swamp mixed hardwoods serve as feeding area  and shelter for
terrestrial wildlife such as deer, rabbit, etc.

    A number of complex ecological relationships exist between the three types
of habitats with regard to their importance to Basin productivity and use.
These relationships in turn dictate certain requirements  necessary to maintain
overall  integrity of the floodway environment.  One major relationship  is that
between permanent water bodies and the periodically flooded areas.  The latter
provide for a large periodic increase in feeding and nursery area for many
aquatic species.  However, it must be realized that many  of these species will
be confined to what water bodies are left upon dewatering of the  swamps in  the
summer and early fall.  Consequently, full utilization of the periodically
flooded swamp forest within the aquatic ecosystem requires a certain area of
permanent water bodies with physical and chemical characteristics that  meet
habitat requirements.

    Similarly, the periodically dewatered swamp can be fully utilized by
terrestrial wildlife only if a sufficient flood-free area remains during the
spring high-water period and if this flood-free area meets habitat
requi rements.

    Present areal and percentage distribution of the three major  flooding
conditions are given in Table 1 for the management units  within the
Atchafalaya Basin Floodway (based on data in van Beek et  al. 1977).

    While it is not presently known what proportions between permanently
flooded,  periodically flooded, and flood-free areas represent the most
desirable conditions from an aquatic point of view, the table points out
certain aspects of the present environment that are important. First,  it
shows that 84 percent of the Atchafalaya Basin Floodway is subject to annual
overflow, while part of the remaining 16 percent has periodically saturated
soils.   It is safe to say, therefore, that at least 90 percent of the
Atchafalaya Basin Floodway can be thus classified as a wetland environment.
Within given management units, the area flooded annually  varies from 98
percent  in the Upper Belle River unit to 61 percent in the Warmer Lake  unit.
From these observations, it must be concluded that most of the periodically
flooded  lands in the Atchafalaya Basin Floodway serve aquatic and aquatic-
oriented  species rather than the terrestrial  biota.  Consequently,
availability of permanent water bodies of sufficient size and quality to serve
as aquatic habitat during low-water months is of major importance.

    A second observation that can be made from Table 1 is that in the
Atchafalaya Basin Floodway below U.S. Highway 190 only a  limited  area,
16 percent, is suitable for growth of high-quality timber hardwood.  In most
areas, periodic flooding together with the occurrence of  maximum  water  levels
at the beginning of the growing season result in lesser quality hardwoods from
a timber  point of view and in slow growth rates.  It is furthermore evident
that those mixed hardwood forests not subject to periodic overflow are  of
extreme  importance as terrestrial wildlife habitats during high-water season,
since they occupy a small  area relative to the habitat that  is only
periodically available.


                                      21

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                                 FLOOD CONTROL


    The Atchafalaya Basin is a vital component in the flood control  plan for
the Lower Mississippi River and tributaries.  Its planned function in
accommodating part of the project design flood is illustrated in Figure 9.
This flood is estimated to have a magnitude of 3,030,000 ft3/sec at the
latitude of the Old River Control Project, of which 310,000 ft3/sec is
accommodated by storage in channel and overbank areas.  Thus a discharge of
2,720,000 ft3/sec must be conveyed to the Gulf of Mexico.

    The project plan provides for passage of 1,500,000 ft3/sec by the
Mississippi River and Bonnet Carre Spillway past the urban-industrial area
including the cities of Baton Rouge and New Orleans.  Thus 1,220,000 ft3/sec
must be accommodated by the Red River backwater area and the Atchafalaya Basin
Floodway complex.  These must, however, also accommodate a projected inflow of
350,000 ft3/sec from the Red River and tributaries.  Therefore the total
accommodation by the Red River backwater area and the Atchafalaya Basin
Floodway complex must be 1,570,000 ft3/sec.

    The project plan calls for diversion from the Mississippi River of
620,000 ft3/sec into the Red River backwater area through the overbank and
low sill control structure of Old River and of 600,000 ft3/sec directly into
the Atchafalaya Floodway complex through the Morganza control structure.  Of
the combined Mississippi River and Red River inflows into the Red River
backwater area, 40,000 ft3/sec is accommodated by storage, leaving 930,000
ft3/sec to be routed into the Atchafalaya Basin Floodway.  Of this amount, a
discharge of 680,000 ft3/sec is to enter through the main channel  of the
Atchafalaya River and 250,000 ft3/sec is to pass through the West
Atchafalaya Floodway by natural or artificial  crevassing of the so-called fuse
plug levee.  With a projected storage capacity of 30,000 ft3/sec, the
Atchafalaya Basin Floodway complex must convey a flow of 1,500,000 ft3/sec.
Of this flow, 300,000 ft3/sec is to leave the floodway through the Wax Lake
outlet and 1,200,000 ft3/sec through the Lower Atchafalaya River past Morgan
City.

    The Atchafalaya Basin Floodway complex presently meets neither the
required conveyance capacity of 1,500,000 ft3/sec nor the required storage
capacity of 30,000 ft3/sec.   Deficiencies occur primarily in the Atchafalaya
Basin Floodway from the leveed portion of the Atchafalaya River main channel
down to the Gulf of Mexico.   The extent of these deficiencies was brought out
during the 1973 Mississippi  River flood when the Atchafalaya Basin Floodway
was used to its greatest capacity.  The largest introduction of water occurred
on May 16, 1973, when 763,000 ft3/sec was discharged from the Red River
backwater area through the Atchafalaya Basin main channel  and 106,000
ft3/sec from the Mississippi  River through the Morganza structure (U.S.  Army


                                      23

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Corps of Engineers 1975).  Maximum total introduction thus was 869,000
ft-Vsec.  At that date, outflows through Wax Lake outlet and the Lower
Atchafalaya River attained magnitudes of 257,000 and 640,000 ft3/sec,
respectively, or a total of 897,000 ft3/sec.  These flows produced a near
overtopping of the guide levees of the lower floodway and of the floodwall  at
Morgan City and, thus, made obvious a deficiency at that time of at least
600,000 ft3/sec, or 40 percent.  Lack of conveyance capacity in the lower
floodway prevented the use of the West Atchafalaya Floodway and the use to
full capacity of the Morganza Floodway.  The leveed portion of the Atchafalaya
River main channel accommodated 15 percent more than the design flow.

    The present deficiency in floodway capacity relates to two major project
parameters.  These are the grade of the protection levees and the elevation of
the project flow line.  Notwithstanding continued improvements, the protection
levees of the Atchafalaya Basin Floodway have remained deficient in both grade
and section.  This is partly because of poor foundation conditions and
resulting subsidence and partly because of a continuous upward movement in  the
project flow line below river mile 55, or approximately Interstate Highway  10.

    The project flow line is the flow line that would be produced during
passage of 1,500,000 ft3/sec through the floodway complex.  The upward
movement of this flow line is being caused by two major processes.  The first
is sedimentation in the backwater areas of the Atchafalaya Basin resulting  in
reduced cross-sectional  area for overbank flow and storage.  The second is
development of a major delta in Atchafalaya Bay, which results in the  seaward
extension of the floodway (by the conversion of Atchafalaya Bay from an open
water body to a complex of channels and overbank areas).
                                      25

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              PRESENT AND FUTURE CONDITIONS IN THE MAIN CHANNEL
    In a natural  system, a river channel  is not a  static  shape  but  is
constantly changing size, cross-sectional  shape, and alignment.   In the
alluvium of a coastal  zone, these processes are more obvious.   A river
enlarges its bed by scouring when the water velocity is high  and fills in  its
bed with sediment deposition when water velocity is  low.   It  builds natural
levees when overbank flooding takes place.   This process  leaves  sediment on
the banks of the river channel  and permits  the flood plain  to receive  water
that does not bring with it enormous amounts of sediment.   These natural
levees, in turn, affect the channel, tending to increasingly  confine the river
between the banks of the natural levee before overbank flooding  takes  place.
This changes every part of the river through time  in a seaward  direction.  The
river and its channel  also change through  time as  the entrained  sediment
continuously builds a  delta.  This changes  the gradient of  the  channel  and the
slope of the water surface.  There are daily changes. The  discharge will  be
higher during some parts of the year than  others,  and a larger  part of the
flood plain must be used to carry the water.

    Furthermore, the plant and animal  communities  in the  water  ana  in  the
flood plain are delicately tuned to all  of  this fluctuation.  Any change in
course, any change in  seasonal  variation or overbank flooding,  or any  change
in sediment deposition must cause an equal  adjustment in  the  ecological
balance of the entire  flood plain.

    No matter how complicated a system has  developed, however,  flood control
is an essential use of the Atchafalaya Basin.  Channel conditions in the Basin
must meet flood control needs and provide  for long-term use of  the  flood plain
for that purpose.  Unfortunately, this is  not a simple requirement, even if
ecological considerations are ignored.  The hydraulics of maintaining  a
channel of sufficient  size, and of obtaining a channel that will  remain at a
sufficient size, must  include a calculation of all the factors  that make the
river and its channel  a constantly fluctuating system.

    Relationships among hydraulic elements  in the  Atchafalaya Basin Floodway
system are summarized  in Figure 10.  The most important elements are the
annual discharge regime as governed by the  Old River Control  Project,  the
distance between the Old River Control Project and the Gulf of  Mexico, which
is identified as the river length, and the  division  of flow between Wax Lake
outlet and the Lower Atchafalaya River.   With the  ability of  the river to
modify its channel through scour and deposition, discharge  regime and  river
length will ultimately determine the river slope and channel  form of the
future stable channel  in which width, depth, and slope are  related  to
discharge in such a manner that velocity is just sufficient to  transport the
sediment load.


                                      26

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                                 OLD RIVER CONTROL
                                     STRUCTURE
     DELTA BUILDING
      RIVER LENGTH
     DIVERSION  WATER
    AND SEDIMENT  INTO
     WAX LAKE OUTLET
                                DISCHARGE REGIME  &
                                   SEDIMENT  LOAD
                                  DREDGING AND
                                 SPOIL  DISPOSAL
CHANNEL FORM, SIZE,
 VELOCITY, SURFACE
    WATER SLOPE
     DIVERSION
     WATER  AND
   SEDIMENT INTO
      OVERBANK
        DREDGING
   NAVIGATION  CHANNEL
    ATCHAFALAYA BAY
                                                 	1
                                                         CAPACITY
                                                         OVERBANK
                                                           AREA
                   BANK
                 ELEVATION
                                MODE OF
                                DIVERSION
   ENVIRONMENTAL
      INTEGRITY
FLOODWAY
CAPACITY
Figure 10.   Relationships among hydraulic  elements  in the  Atchafalaya
              Basin Floodway  system.
                                      27

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    Along the stream course, a number of other variables  affect  development
and ultimate size, form, and surface-water slope of the channel.   The most
important among these is the diversion of water from the  stream  into  the
backwater area.  The magnitude of discharge diversion along  the  Atchafalaya
Basin main channel is illustrated in  Figure 11.  Below river mile 55
(Figure 12), diversion reduces main channel  discharges from  10 percent to 25
percent at flows of approximately 425,000 ft3/Sec depending  on return flows.
The largest reduction follows with diversion of 30 percent of the  initial
discharge into Wax Lake outlet so that only 60 percent remains after  about
mile 100 flowing toward Morgan City and the Lower Atchafalaya River.

    Since river channels are continuously adjusting to seasonal  and annual
variation in discharge, the future stable channel  must be viewed as an average
future condition.  At present, a reasonable working hypothesis for the
Atchafalaya River is to consider this average condition to be associated with
discharges within the range of 400,000 to 450,000 ft3/sec as measured at
Simmesport and to have a frequency of occurrence between  1.5 and 2.5  years
(van Beek et al. 1977).  This discharge will  be referred  to  hereafter as the
"channel determinant discharge."

    It is evident that any changes in operation of the Old River Control
Project will affect the discharge regime and therefore the size, form,
velocity, and surface-water profile characteristics of the future  stable
channel.  More specifically, the reduction that is being  considered (reducing
the annual flood stage in the Red River backwater area by reducing annual peak
flows) would diminish the discharges for given frequencies;  this would affect
the channel determinant discharge and size of the channel that would  be stable
and self-maintaining.

    River length must also be considered a variable parameter because of
division of flows between the Lower Atchafalaya River and Wax Lake outlet and
because of delta building in Atchafalaya Bay.  Since the  progradation of the
delta in the 1950's, river length has increased from 135  to  145  miles. By the
year 2020, length can be expected to have increased to 160 miles,  or  an
increase of almost 20 percent.  As a result, the surface-water profile must be
expected to continue to move upward in the lower part of  the Atchafalaya
River.

    Diversion is mostly controlled by flood-plain topography and by the
natural or manmade changes (Figure 10) affecting bank elevation, storage
capacity of the overbank area, and the mode of diversion  --  that is,  whether
diversion occurs through overflowing of the streambanks or through diversion
channels.

    Where diversion of water in the flood plain is prevented by  artificial
levees such as along the upper part of the Atchafalaya River, discharges of a
given frequency are larger, and consequently the future stable channel will be
larger, than along the lower reaches.

    When diversion of water and sediment occurs from the  channel into the
flood plain mainly by overflow of the channel banks, most sediment is
deposited on the streambank as natural levee ridges (Figure  13A).   The


                                      28

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                        100%
           100%
Discharge at Simmesport
Atchafalaya Basin Main Channel
         E.IW.IF.D.C.   East (West)  Freshwater
                    Diversion Channel
         E.IW.IA.C.   East (West)  Access Channel
       »»•«»«•«>•»» Levees
                                                 30%
                                                             70%
Figure 11.  Diversion from the Atchafalaya Basin main channel  during
            average annual flood.
                                 29

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                           fltchofaloyo  Basin. La.
Figure 12.   River  miles  along  Atchafalaya Basin main
            channel.
                         30

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resultant increase in bank elevation confines larger discharges for a given
frequency thus allowing the river to maintain a larger channel.  The process
of enlargement will continue until the grade of the natural levee ridges
follows the surface-water profile for the discharge of the channel  determinant
frequency.  This type of adjustment reduces adverse deposition of sediments in
the backwater area to only flood occurrences greater than the determinant
discharge.

    When most of the diversion of water into the flood plain takes  place
through diversion channels, however, a quite different condition develops
(Figure 13B), in particular where banks have been elevated by spoil  until
overflow no longer occurs on a regular basis.  Under those circumstances,
diversion of water takes place at high velocity into the flood plain, enabling
the water to carry large quantities of sediment.  Most of the sediment is
deposited in the backwater area, gradually reducing overbank capacity.  Any
resultant increase in channel discharges as a result of loss in overbank
capacity will perpetuate the process of backwater sedimentation as  long as the
greater channel discharges or overall adjustment of the river gradient elevate
the surface-water profile and thereby maintain the gradient into the backwater
area.  Channel enlargement will take place at much less than the potential
rate since the increase in elevation of the surface-water profile minimizes
the losses of overbank storage relative to the river so that channel
discharges increase only slowly.  Loss of overbank storage relative to a fixed
datum plain, however, is considerable and represents a major loss of floodway
capacity.

    Enlargement of the Atchafalaya Basin main channel  through dredging must be
viewed also in terms of the above-discussed hydraulic  relationships.   Dredging
will change the form, size, velocity, and surface-water slope characteristics
of the main channel, as shown in Figure 10.  This in turn will  affect the
diversion of water and sediments into the overbank area and therewith the
discharge regime of the main channel.  Whether the acquired channel  will  be
stable depends on whether the new channel  characteristics are in equilibrium
with the then-occurring discharge regime,  including the sediment load.  Any
major deviation from the required velocity and gradient for the channel
determinant discharge and sediment loads will  otherwise result in deposition
within the channel.  This would negate the channel  enlargement accomplished by
dredging, while any adverse impacts resulting from spoil  disposal and from the
decrease in annual  duration and extent of  flooding of  the wetlands  would
remain.

    The second effect of channel  dredging  stems from the associated  spoil
disposal  if no measures are taken to control  inflow through diversion
channels.  The spoil  deposition would add  to  the relative change in  bank
elevation resulting from a lowering of the surface-water profile.   This  is
true, in  particular,  since dredging would  take place along the lower  course of
the main  channel  where overbank flow at present is still  significant.  The
elimination of the overbank flow process during average annual  floods would
change the mode of water diversion into the overbank area to channel  flow at
higher velocities.   This would adversely affect the desired reduction of
sediment  diversion into the overbank area  obtained through lowering  of the
flow line.


                                      31

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32

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    Along the lower course of the Atchafalaya River, the most important factor
becomes the division of main channel flows beween Wax Lake outlet and the
Lower Atchafalaya River and the processes influenced by this division as shown
in Figure 11.  First, the division controls the channel determinant discharge
for the remainder of the main channel and the Lower Atchafalaya River.
Because of gradient advantage (the Wax Lake outlet route is some 15 miles
shorter), discharges through the Wax Lake outlet and, consequently channel
size, have increased since construction.  Conversely, the channel determinant
discharge along the Lower Atchafalaya River route continues to decrease.

    Present processes of deltaic growth reinforce this trend.  With 70 percent
of total discharge still passing through the Lower Atchafalaya River, delta
progradation is much more rapid on the east side of the Atchafalaya Bay
causing a more rapid increase in length of the Lower Atchafalaya River than of
Wax Lake outlet.  That process is further augmented by maintenance of a
navigation channel through the Atchafalaya River Delta.

    With the above-described process-relationships in mind, we may now focus
on present conditions and trends of the Atchafalaya Basin main channel.  At
present, neither the flow line nor the cross-sectional area of the Atchafalaya
Basin main channel is stable.  Figure 14 illustrates the trend flow-line
change for a discharge of 450,000 ft3/sec at Simrnesport.  Since 1969 the
flow line has decreased in elevation upstream from the Whiskey Bay Pilot
Channel (WBPC) while below the Whiskey Bay Pilot Channel the flow line has
increased in elevation.

    Also shown in Figure 14 are the project flow lines as determined in 1963
and in 1973 during the floodflows.  The difference comprises a 4 ft upward
revision as a result of sedimentation in the overbank areas and delta
development.  Since 1973, as a result of the flood and associated
sedimentation, the flow line is being revised upward again, but the new flow
line has not been made available yet.

    The change in flow line for the 450,000 ft3/sec discharge has been
associated with a change in cross-sectional  area of the channel.  This trend
is best illustrated by the bank-full datum plane (Figure 14), which at one
time followed natural  streambank elevation.   The present flow line for 450,000
ft-Vsec is seen to lie well  below this datum plane above mile 70 and far
above this plane below mile 70.  The change has been associated with strong
scouring of the channel above mile 70 and with channel, levee, and flood-plain
development below mile 70.  These two processes are schematically shown in
Figure 15A and Figure 15B, respectively.

    Figure 15A shows the scouring of the channel  and the associated lowering
of the water level for a given discharge.  Since water levels in the channel
become lower relative to the overbank area,  less water will  be diverted and
stages in the overbank area will  decrease, resulting in a loss of aquatic
habitat and reduction of the area periodically flooded.  Below mile 55 such
loss is further augmented because sediment introduction into the overbank area
occurs increasingly through diversion channels rather than through overbank
flow, and therefore most sediment is deposited in the aquatic habitats rather
than on the channel  bank.  The process illustrated in Figure 15A will  continue


                                      33

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                         35

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until the flow line has stabilized; future loss of aquatic habitat and
wetlands to mixed forest hardwoods must thus be expected.   Likewise, a shift
to drier hardwoods must be expected, along with increasing encouragement for
agricultural development following forest clearing.

    Also illustrated by Figure 15A is the increase in channel  area below a
fixed reference level  such as the project floodflow line.   Consequently, the
frequency at which use of the overbank area for flood control  is necessitated
diminishes and increases the likelihood of agricultural  development and
settlement.  At present, the channel area below the 1963 and 1973 project
floodflow lines exceeds 100,000 ft2 as far downstream as mile  55; the
100,000 ft^ dimension  is the requirement for flood control  stated by the
USCE.

    Figures 15B-^ and B£ illustrate the two major processes occurring below
mile 70.  The two are  successive in time, with the processes illustrated in
Figure 15B^ preceding  those in Figure 15Bo.  From mile 70 to mile 95
(approximately Myette  Point) channel development has long since progressed
beyond the filling stage to the stage depicted in Figure ISB^.   Although
channel enlargement takes place, processes differ from those illustrated in
Figure 15A.  While overbank deposition and past spoiling tend  to confine
increasingly greater discharges to the channel, thus resulting  in channel
enlargement, the flow  line moves upward at the same time.   This tends to
partially offset the loss in overbank storage as well  as to negate the need
for the river to enlarge its channel through scour so as to maintain a
cross-sectional area in equilibrium with the discharge regime.   Consequently,
the rate of channel enlargement is low.

    Continuation of upward movement of the flow line is expected as a result
of delta building, which lengthens the channel  as a  result of  continuing
sedimentation that decreases storage in the overbank area, and  as a result of
overall adjustment of  the stream gradient.  Associated with this will be
natural building of the channel banks in the form of natural  levees where
banks have not yet been elevated to greater heights  as a result of previous
spoil deposition.

    It is evident that elevating the streambanks beyond the natural levee
height by spoil deposition makes flow into backwater areas increasingly
dependent on diversion channels, thus enhancing sediment introduction into
these areas with resultant loss of aquatic habitat,  loss of periodically
flooded area, and loss of floodway capacity.  Preservation of  wetlands is much
better served by natural building of streambanks so  that overbank flow is
maintained and sedimentation is concentrated along the channel.  Furthermore,
it is apparent that the limitation of flow diversion into backwater areas to
only the volume necessary to maintain water quality and high productivity
increases the rate of  channel development.

    Channel development from mile 70 to mile 95, the reach represented by
Figure 156-^, has progressed to the extent that the present channel size is
approximately 70,000 ft^ as measured below the 1963 project flow line and
approximately 58,000 ft^ as measured below the channel bank.
                                      36

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    Between the time dredging was stopped,  in 1968,  and  early  1973,  the
channel increased in size from mile 70 to mile 83 and  remained  stable  from
mile 83 to mile 95.  However, the 1973 flood produced  a  reduction  as a result
of sedimentation throughout the 25-mile reach.  Table  2  summarizes the
changes.
               TABLE 2.   RATES OF CHANNEL DEVELOPMENT ALONG
                         THE ATCHAFALAYA BASIN MAIN CHANNEL

Period
1969-1973
1973
1969-1973
1973
1969-1973
1973
1971-1973
1971-1973
1972-1973
1973
1973
Years
4
1
4
1
4
1
2
2
1
1
1
Main
Channel
Segment
(mi)
55 -
55 -
70 -
70 -
83 -
83 -
95 -
103 -
112 -
95 -
112 -
70
70
83
83
95
95
103
112
120
112
120
Total
Average
Change
(ft2)
+5,746
+10,702
+2,840
-4,603
+48
-3,343
+2,097
+348
-17
-967
+19,191
Average
Annual
Rate of
Change
(ft2)
+1,436
+10,702
+710
-4,603
+12
-3,343
+1,048
+174
-17
-967
+19,191
                                      37

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    Below Myette Point (mile 95)  where the main channel  follows  Six Mile Lake,
the flow conditions are rapidly changing as a result  of  the  processes  shown  in
Figure 1582-  Through deposition  in the lake on either side  of the main
current thread, the channel  increasingly gains definition  and the  flows  become
more confined.  This contributes  further to the rise  in  flow line.  With
additional confinement of flows and an increase in  velocities, the river will
increase its depth by scour  insofar as sufficient depth  is not provided  by the
rise in flow line.

    The situation just described  is complicated, however,  by the partial
diversion of discharge to the Wax Lake outlet at approximately mile 103
and by the fact that the diversion ratio has been increasing because of
gradient advantage.  Related to this,  the channel size from  rnile 95 to mile
103 averages 50,000 ft^ below the 1963 flow line but  decreases to  about
30,000 ft^ in the confined reach  of the Lower Atchafalaya  River.  The  rate
of channel development follows the same trend, being  much  greater  above  the
diversion point than below that point  as shown in Table  2  (miles 95-103  and
103-112).  Deposition and decrease in  channel  size  associated with the 1973
flood were about equal in both reaches.

    At this point it must be emphasized again that  a  distinction has to  be
made between active channel  cross section and channel  cross  section as
expressed by the USCE.  The  active channel  cross section is  the  cross-
sectional area of the channel  occupied by the river during flood discharges
that are representative for  the river's regime.  The  cross-sectional area as
expressed by the USCE is the area below a fixed datum plane  in which
channel-flow conditions occur when water level in the river  equals the level
of the datum plane.  This can be  extremely misleading  to  those  not familiar
with the USCE meaning of channel  cross section when changes  in cross-sectional
area of the channel are considered. True changes can only be observed by
considering both the change  in surface-water profile  and cross-sectional  area
below a fixed datum plane.  This  is illustrated by  Table 3.

    Simultaneous consideration of riverine processes  and the trends of the
surface-water profile and channel cross section below a  fixed datum plane
indicate the following.  Through  a complex system of  interacting processes
(Figure 10) involving the river channel, overbank area,  and  delta, the
Atchafalaya River attempts to achieve  stability for the  present  discharge
regime.  This stability requires  a change in surface-water slope,  active
channel cross section, and velocity.   Above approximately  mile 70  the  change
involves a downward adjustment of the  surface-water profile  associated with
channel enlargement through  scour (Condition 7, Table 3).  Because the rate of
scour greatly exceeds the rate of profile adjustment, the  active channel  is
enlarging through scour.

    Below mile 70 the gradient adjustment results in  an  upward movement  of the
surface-water profile that is associated with a decreasing rate  of scour from
mile 70 to mile 95 (Condition 1,  Table 3) and with  essentially no  change from
mile 95 to Morgan City (Condition 2, Table 3)  except  between mile  95 and 103.
Scouring between mile 95 and 103  is, however, a superimposed condition related
to rapid scouring in the branch channel leading to  Wax Lake  outlet, which
scoured at an average annual rate of 2,000 ft2.  Active  channel  cross


                                      38

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sections are thus enlarging along both of the above reaches  at  greater rates
than indicated by physical channel  changes because of surface-water profile
adjustments.  From mile 70 to 95 active channel  enlargement  amounts to
approximately 1,200 ft2 per year, which includes 700 ft2  as  a result of
scour and 500 ft2 as a result of increased water levels for  the
representative discharge.  Below mile 95 the active channel  enlargement
represents primarily an increase in water levels and an associated increase in
elevation of the banks through deposition and amounts to  about  250 ft2 per
year.  The absence of scour suggests that, presently, changes in  the
discharge-channel relationships are still  accommodated by changes in slope and
depths without necessitating scouring to satisfy hydraulic requirements.   In
other words, the channel  appears stable for the  given conditions  of slope,
water depth, and velocity.  This is further indicated by  a decrease in
cross-sectional  area as the result of deposition following the  termination of
channel enlargement by dredging in 1963.

    As can be seen from this discussion, the potential rate  of  channel
enlargement through scour for average discharge  conditions is on  the order of
at least 1,500 ft2 per year when adjustment of surface slope insufficiently
increases or diminishes water depth and forces a greater  water  depth through
scour.  This means that channel dimensions below the 1963 datum plane that are
considered for flood control could be attained according  to  the time frame
given in Table 4 if the projected channels would be in accord with the stable
conditions the river attempts to establish under present  regime conditions.
   TABLE 4.  ESTIMATED TIME REQUIREMENTS FOR NATURAL CHANNEL ENLARGEMENT
             TO ALTERNATIVE DIMENSIONS OF 100,000 ft? AND 80,000  ft2

Channel Area
below 1963
Datum Plan
ft2
100,000
80,000
100,000
80,000
100,000
80,000
80,000
Main Estimate of
Channel Years Required
Segment this Report
River Miles (base year 1973)
0
0
55
55
95
95
95
- 55
- 55
- 95
- 95
- 105
- 105
- 112
0
0
20
7
33
20
35
Estimate of
Years Required
USCE*
(base year 1973)
0
0
32
3
60+
21
42

  *New Orleans District, U.S. Army Corps of Engineers, letter of March 29,
   1978, to Victor W. Lambou, Project Officer for this study, from Early J,
  Rush III, District Engineer.

                                      40

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                       AGRICULTURAL USE AND SETTLEMENT
    The combined Red River backwater area and  Atchafalaya  Basin  Floodway
complex were meant to provide protection from  floodwater for urban,
industrial, and agricultural  development along the  Lower Mississippi  River.
However, their structural  and nonstructural  provisions  have also encouraged
expanded agricultural development and settlement  within the Atchafalaya Basin
areas designated to receive floodwaters and  in the  areas adjacent to  the
floodway that must serve as storage for local  storm runoff during operation  of
the floodway system.  That development has invariably expanded  into bottom-
land hardwoods and forested wetlands and generated  demands for  small  watershed
drainage projects to be undertaken by the USDA Soil  Conservation Service  as
well as demands for reduced diversion of Mississippi  River water through  the
Old River Control Project.

    In this section, the settlement and agricultural  uses  that  have developed
will be treated separately for the Red River backwater  area, the West
Atchafalaya Floodway, the Morganza Floodway, and  the Atchafalaya Basin
Floodway.  Then, an analysis will follow of  the general  effects  of
agricultural development (and, specifically, its  inescapable byproduct,
agricultural runoff) on floodway capacity and  on  aquatic habitats.


RED RIVER BACKWATER AREA

    The Red River backwater area comprises approximately 1,360,000 acres,
nearly all  of which is privately owned.  Despite  its designated  role  as a
floodwater storage area and the frequent overflow of much  of the area, the Red
River backwater area is undergoing increased residential  and agricultural
development.  This development expands from  the low alluvial  ridges into  the
even lower flood-plain areas following the clearing of  bottom-land hardwoods
and in some cases construction of local flood-protection levees.  In  1959,
about one-third of the area (or 450,000 acres) had  been cleared  (U.S. Army
Corps of Engineers 1968).   In 1976, approximately 655,500  acres  were  in use  as
croplands or pastures (FWS, unpublished data).

    This entire area drains, through the Red River, into the upper Atchafalaya
River above Simmesport.  The stages in the Red River will  be higher,  because
of backwater flooding, if  the stages in the  upper Atchafalaya River are high.
Since the stages of the Atchafalaya River are  a result  of  the volume  of water
diverted from the Mississippi River by the Old River Control  Project, the
stages of the Red River backwater area are directly dependent upon operation
of the Old River Control Project.
                                      41

-------
    Even though, geographically, the Red River backwater area is  not in the
Atchafalaya Basin, it must be considered here because of its dependence on the
diversion by the Old River Control  Project.   Increasing development into the
flood-plain areas of the Red River backwater area will  generate mounting
political pressure to decrease the volume of diversion  by the Old River
Control Project.  The ecological system of the Atchafalaya Basin  as well  as
its value as a floodway is integrally related to the volume of diversion by
the Old River Control Project.

    The extent to which agricultural  development has moved into marginally
suited areas is illustrated by the 1974 conditions within the 365,000 acres of
the Red River backwater area that fall  within the New Orleans district of the
USCE (U.S. Army Corps of Engineers 1975).  The 1974 flood conditions, which
occur with a frequency of one in five years, resulted in the flooding  of
55,000 acres of agricultural land and 500 acres of rural  residentially
developed land.  Floodwaters reached depths  of 6 to 8 ft over some
agricultural lands.  As a result, damage amounted to more than $2,000,000 in
lost crops alone.

    Under present conditions, no control  can be exerted over further
development and the associated clearing of bottom-land  hardwoods.  Except for
11,000 acres within the ring levee system of Bayou des  Glaises Loop
immediately north of the West Atchafalaya Floodway, even simple fTowage
easements have not been obtained.
WEST ATCHAFALAYA FLOODWAY

    This floodway contains approximately 760,000 acres,  which  are practically
all in private ownership.  The area is seperated from the Red  River backwater
area by the fuse plug levee, and a main levee prevents annual  overflow from
the Atchafalaya River main channel.  Annual  water-level  fluctuations are
therefore controlled by local  runoff and by  backwater flooding from the Old
Atchafalaya River into which part of the Atchafalaya River flow is directed
from the main channel at river mile 55.  This condition  has afforded
considerable protection from Atchafalaya River flood stages.   Protection  from
flooding combined with restriction to land use of only simple  flowage
easements has resulted in expanding agricultural  development in the West
Atchafalaya Floodway and the clearing of bottom-land hardwoods (U.S. Army
Corps of Engineers 1975).  Recent mapping (1977)  of land resources by the USCE
and FWS show that more then one-third of the area, or about 58,500 acres, is
presently used for croplands and pastures.  The USDA Soil  Conservation Service
has received an application for planning of  a small  watershed  project
involving 165,000 acres (U.S.  Department of  Agriculture  1976).  The
expansionary trend of development and settlement is further illustrated by the
biannual USCE census data.  This trend is shown in Table 5. Despite the  1973
flood and the continued above-normal stages  during 1974, the rate of
population increase from 1974  to 1976 was nearly double  that of 1970 to 1974.
                                      42

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            TABLE 5.  SETTLEMENT IN THE WEST ATCHAFALAYA FLOODWAY*

Year
1970
1974
1976
Structures
1,147
1,217
1,322
Persons
3,426
3,509
3,581
Growth Rate

20.75/yr
36.00/yr
Livestock
11,501
10,000
10,832

*USCE, unpublished data.


    Under present conditions, agricultural use of the West Atchafalaya
Floodway is further stimulated.  The present capacity deficiency of the
Atchafalaya Basin Floodway prevents the use of the West Atchafalaya Floodway
for diversion of floodwaters from the Red River backwater area across the fuse
plug levee.  Furthermore, the Atchafalaya River main channel  within the levee
reach exceeds considerably the design capacity of 600,000 ft3/sec.

    In 1973, the channel accommodated 781,000 ft3/sec, and the stage-
discharge rating curve for Simmesport indicates that present  channel  capacity
below the project flow line is at least 950,000 ft3/sec -- that is, 270,000
ft3/sec in excess of the magnitude required for passage of the project
flood.  This reduces greatly the frequency of events necessitating use of the
West Atchafalaya Floodway and thus encourages development of  and settlement in
the floodway.
MORGANZA FLOODWAY

    In the Morganza Floodway nearly all lands are also privately owned.
However, a greater degree of control can be and has been exerted over land use
through acquisition of comprehensive flowage easements.  In addition to  the
right of overflow, the easements provide for control  over settlement, grazing,
and land clearing insofar as these are related to maintenance and operation of
the area as a floodway.  As a result, no building of permanent structures has
been allowed.  However, the biannual census showed a total  of 97 structures
and 21 persons residing in the floodway in 1976 (Table 6).   This settlement
has been possible by allowing settlement in house trailers.


                TABLE 6.  SETTLEMENT OF THE MORGANZA FLOODWAY*

Year
1970
1976
Structures
33
97
Population
0
21
Livestock
3,242
3,110

*USCE, unpublished data.


                                      43

-------
    The easements have not been administered to prohibit land clearing,  since
removal of timber was not considered to have a direct,  adverse effect on the
floodway operation.  As a result, approximately 18,000  of the 64,000  acres
contained in the Morganza Floodway are presently in  use as croplands  and
pastures.
ATCHAFALAYA BASIN FLOODWAY

    At present very little control  can be exerted  over land use in  the
Atchafalaya Basin Floodway.  This is illustrated in  Table  7.   The table shows
that, of the 600,000 acres contained in the Atchafalaya Basin  Floodway, only
132,000 acres, most of it water bodies, are subject  to direct  control  under
State ownership.  Included is the Atakapas Outdoor Recreation  Area, which  is
presently administered by the Louisiana Department of Culture,  Recreation,  and
Tourism but is expected to be transferred in 1978  to the Louisiana  Wild Life
and Fisheries Commission as a Wildlife Management  Area.

    Nearly 470,000 acres, or 80 percent, are privately owned with few  or no
restrictions on use.  Present authorization allows the USCE to  acquire simple
flowage easements on a claim basis  for those areas not subject  to frequent
overflow as of 1928.  Although this applies to 68,000 acres, claims have been
filed and simple flowage easements  obtained on only  9,100  acres or  less than 2
percent of the floodway area to date.   In addition,  the USCE has required
servitudes for channel realignment  and spoil disposal on 50,000 acres, which
precluded permanent structures except  hunting or fishing camps.
    TABLE 7.  OWNERSHIP AND SERVITUDES IN THE ATCHAFALAYA BASIN  FLOODWAY*
Ownership
Acres
of Total
Servitudes
Comments
Private
Private
Private
350,000
9,000
58,000
58
2
10
none
simple flowage
none


Simple


flowage
Private
50,000
             Spoil  disposal
              and channel
              servitude
                 easement can be
                 claimed by owner
                No structures
State

State
25,000

107,000
4

18
Atakapas Recre-
ation area
Water bottoms

*USCE, unpublished data.
                                      44

-------
    The above data can be integrated with habitat information as developed
under the USCE and FWS Habitat Evaluation Program.  Spoil  servitudes and State
ownership apply mostly to open-water and willow-cottonwood-sycamore habitats.
Present flowage easements are largely coincident with already cleared lands
that are in cropland or pasture use.  This leaves approximately 250,000 acres
of bottom-land hardwoods and 135,000 acres of swamp forest that are privately
owned and on which no direct control concerning use can be exerted.

    Higher elevation and partial protection from annual overflow by
Atchafalaya River levees have allowed for agricultural  development mostly in
the upper part of the Atchafalaya Floodway between U.S. Highway 190 and
Interstate Highway 10.  In this area, land cleared for agriculture has
increased from approximately 5,800 acres in 1969 to 8,500 acres in 1974, and
to 9,300 acres in 1977.

    Table 8 shows a significant decrease in population following the 1973 and
1974 floods.  Population only slightly increased after those years.  The
majority of permanent settlement is in the northwestern part of the
Atchafalaya Basin Floodway along U.S. Highway 90.

    Most permanent structures are hunting and fishing camps, but vacation
house development is proceeding as a real estate venture near the community of
Butte la Rose near 1-10.
EFFECTS OF AGRICULTURAL DEVELOPMENT

    It is difficult to evaluate the effects of agricultural  development and
specifically of the associated agricultural runoff on the aquatic habitats of
the Atchafalaya Basin inside and outside the floodway.  It is also hard to
evaluate the effect of agricultural runoff on floodway capacity.  A better
evaluation of the effect on aquatic habitat may be possible following
completion of the Atchafalaya Basin Water Quality Study by the EPA.  However,
the fact cannot be ignored that runoff from agricultural fields contains large
quantities of eroded topsoil, fertilizer chemicals, and animal manure.
Roughly 50 percent of fertilizers applied to crops ultimately reach natural
waters (Gillian and Terry 1973).  In view of this, a number of observations
should be made.
            TABLE 8.  SETTLEMENT IN THE ATCHAFALAYA BASIN FLOODWAY*

Year	Population	Structures	Livestock

1970                673                     490                     1154

1974                690                     294                      970

1976                888                     308                      735


*USCE, unpublished data.

                                      45

-------
    Agricultural runoff from the fields in the Morganza Floodway, West
Atchafalaya Floodway, and Atchafalaya Basin Floodway is discharged directly
into the wetlands to the south, without the benefit of dilution by being first
incorporated in the Atchafalaya River discharge.  The same is true for
agricultural runoff diverted through the Courtableau drainage structure into
the Bayou Fordoche management unit from the Basin area to the west of the
floodway.  In all cases agricultural runoff is received by aquatic habitats
that are subject to backwater flooding with inherent reduced circulation.

    The above conditions must also be viewed against present water quality
parameters other than low dissolved oxygen values.  The flux of nutrients
into the Atchafalaya Basin is high.  Craig et al. (1977)  estimated the mean
annual flow of nutrients through the basin to be 30,000 metric tons/yr
phosphorus and 264,000 metric tons/yr nitrogen.  The mean nutrient concen-
trations in the Atchafalaya River at Simmesport are 1.53 mg/1  of total
nitrogen and 0.18 mg/1 of total phosphorus (U.S. Geological  Survey 1976).
These values are even higher within the swamp basins.  Mean  concentrations in
water of the Buffalo Cove and Upper Belle River management units were found to
be 1.86 mg/1 for total nitrogen and 0.21 mg/1 for total  phosphorus.  Craig et
al. (1977) state that these levels are high compared to areas in the Louisiana
coastal zone that are considered eutrophic.

    Agricultural runoff as a result of expanding development in the swamp
basins adjacent to the floodway may even be more detrimental  since these
systems are entirely dependent on local rainfall for water supply.  No data
concerning nutrient influx into these basins are presently available.  Neither
is the projection of water quality conditions related to expansion of
agricultural development as a result of USSCS watershed projects.  A large
number of such projects are in the planning stage or have been approved for
implementation.  Along the east side, in the Verret Subbasin, these include
the Johnson Bayou, Bayou Grosse Tete, Choctaw Bayou, Bayou Plaquemine, and
Lake Verret watersheds with a total of 729,793 acres.  All plans except those
for Bayou Plaquemine have been approved for operation.

    Along the west side of the floodway, USSCS watershed projects affecting
the Basin are the Upper Bayou Teche, Wauksha-Courtableau, Avoyelles-St.
Landry, Chatlin Lake Channels, and Bayou Boeuff projects with a total of
894,490 acres.  These projects affect quality of the waters  and associated
wetlands of the Fausse Point Subbasin as well as those of the floodway swamps.
The swamps are affected because drainage for the four northernmost projects is
to be provided by diversion of runoff into the floodway at the latitude of
U.S. Highway 190.

    Information on sediment content in runoff from farmlands peripheral to the
Atchafalaya Basin is almost nonexistent.  State and Federal  agencies that were
contacted (Louisiana State Planning Office, Soil Conservation Service, U.S.
Geological Survey, Agriculture Research Service, and U.S. Army Corps of
Engineers) all agreed that such information would be invaluable in any
management pursuit.  However, they all stated that acquiring this type of
information for the Atchafalaya Basin and surrounding area would be very
expensive and would require lengthy field investigation because of the
                                      46

-------
complexity of runoff and circulation in the area.  The Lake Verret watershed
project is the only attempt that has been made to quantify the sediment-runoff
relationship for this area, and the data collected in that study were never
verified.

    Consequently, quantification of how much sediment enters the Atchafalaya
Basin from either the surrounding or the internal agricultural  lands  still
needs to be made through acquisition of realistic data.  Some indication  of
the potential importance of the problem can be obtained from studies  in other
areas of similar topographical  and climatological setting such as was
performed in the delta area of Mississippi by the U.S. Department of
Agriculture.
                                     47

-------
                    ALTERNATIVES FOR OPERATION OF THE OLD
                            RIVER CONTROL PROJECT
    Three alternatives for the future operation of the Old River Control
Project will be evaluated.  The first alternative is  to maintain diversion  as
presently authorized.  The second alternative is to limit diversion  so that
the stages in the Red River backwater area at Acme, Louisiana,  are reduced
during the spring planting season and the area currently inundated is  reduced.
Three different stage levels are analyzed under this  "limit diversion"
alternative — the so-called 35-ft,  the 40-ft, and the 45-ft plans,  the
numbers referring to the stage levels at Acme during  spring planting.   A third
alternative is to manage diversion in order to meet the requirements of the
aquatic ecosystems in the Atchafalaya Basin Floodway  complex.


MAINTAIN PRESENT DIVERSION

    The percentage of the latitude flow to be diverted at the Old River
control structure to the Atchafalaya River was mandated by the  83rd  Congress
to be 30 percent.  Allowing for a 7.5 percent operational  margin either way,
the operation of the Old River Control  Project has been in general  compliance
with the mandated diversion of flows.  This is illustrated in Figure 16,  which
gives the Atchafalaya River flows at Simmesport as a  percentage of the
latitude flow for the months of January, March, June, September, and December
for the period of operation.

    However, four significant deviations from mandated flow control  can be
noted.  These include deficits in 1963, 1964, 1966, and 1976 and flow  excesses
in 1974 and 1975.  The 1963 deficit  is  associated with the first months of
structure operation following its opening on July 15.  In 1964  as well  as
1966, barge accidents in front of the structure necessitated partial closure
of the gates for salvage operations  and to prevent further damage.

    Both deficits and excesses from  1974 through 1976 relate to the  1973  flood
when the Old River control structures were severely undermined  as a  result  of
scour.  To prevent further scour, stage differentials across the structures
are no longer allowed to exceed 18 ft.   This necessitates increased  diversion
during annual flood conditions.  In  1976 partial closure of the structures  was
needed to make possible some necessary repairs in the stilling  basin.

    Diversion of Mississippi River flow results presently in an average annual
peak flow of 430,000 ft3/Sec into the Atchafalaya River at Simmesport,
Louisiana.  The associated stage at  this location is  40.7 MSL based  on the
1976 discharge rating curve.  The annual regime of the Atchafalaya River at
                                      48

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                                 49

-------
Simmesport is presented in Figure 17 in terms of average daily discharges  and
in Figure 18 as average daily stages.  In addition,  the graphs show the
average annual peak discharge and stage for the period 1949  to 1974 and the
daily discharges and stages during the 1964 and 1965 water year.   The latter
stages are adjusted for 1976 hydrologic conditions on the basis of the
discharge rate occurring for that year.  Average daily discharges  and stages
for the period 1949 to 1974 are based on diversion of 30 percent  of latitude
flow.

    It should be noted that the difference between the average annual  peak and
the peak resulting from averaging daily volumes is 100,000 ft^/sec in
discharge and 7.1 ft in stage, because of the temporal  variation  in peak flow
occurrence.  This difference should be taken into account when annual  flooding
requirements of the aquatic ecosystem are considered.  A typical  difference is
illustrated (Figures 17 and 18) by the Atchafalaya River, Simmesport,
hydrographs for the 1964-65 water year.  Peak flow for that  year  equaled the
average annual peak while total discharge for that year approximated the
average annual total discharge.


LIMIT DIVERSION

    Limiting the percentage diverted by the Old River Control  Project makes it
possible to limit maximum stages in the Red River backwater  areas  and reduce
the area currently subject to annual flooding during the spring planting
season.  It must be remembered, however, that to limit this  diversion for  the
sole benefit of agricultural development in the Red  River backwater area is to
influence similarly the flood plain and aquatic ecosystems in  the  Atchafalaya
Basin Floodway complex.

    The USCE is considering three plans under the "limit diversion"
alternative.  Limitations of the diversion percentage would  result in maximum
stages in the Red River backwater area of 35, 40, or 45 ft MSL as  measured at
the Acme gauge near the confluence of the Red and Black Rivers.  The present
low sill structure may allow only partial realization of these alternatives if
the structure has to be operated under the constraints of a  maximum allowable
head differential across the structure.  Through use of a modified
mathematical model of the Old River Control  Project, the USCE  estimated the
average daily discharge of the Atchafalaya River at  Simmesport that would
result from the operation of the control structure for each  of the above three
plans.  The Simmesport discharge hydrographs for the 35-, 40-, and 45-ft MSL
plans respectively are given in Figure 19 (USCE, unpublished data).

    The data show that the maximum average daily discharge,  occurring after
April 1, would be limited for the 35-, 40-, and 45-ft plans  to approximately
250,000 ft3/sec, 262,500 ft3/sec, and 300,000 ft3/sec, respectively.  A
comparison of these discharges with present average  daily discharges (Figure
19) is made in Table 9 and shows the extent of flow  reduction  that would
result from operation of each of the three plans.
                                      50

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     It should again be kept in mind that the months during which diversion is
to be limited will in most years include the occurrence of annual peak flow.
For  the 45 ft plan, limitations of discharge will occur on the average from
March 15 to June 5, and for the 40-ft and 35-ft plans from February 5 to June
15.  A better evaluation of the effects of limiting the stages in the Red
River backwater area and the Atchafalaya Basin Floodway complex is therefore
obtained by comparing the allowable discharges and stages with the average
annual peak discharge and stage and the representative hydrograph such as the
one  for 1964-65.  These comparisons are made in Figures 20 and 21,
respectively, which show the resultant reductions in flow and stage at
Simmesport.

     The diagrams indicate that, even with the 45-ft plan, the total annual
flow through the floodway during an average water year such as 1964/1965,
would have been reduced by 4,161,000 day/second/ft (dsf) or 6.2 percent.  For
the  35-ft plan this increased to 7,011,000 dsf or 10.6 percent.  The diagrams
also show that for such an average year flooding conditions in the aquatic
ecosystem of the floodway would not have progressed beyond those occurring in
the  middle of February.

     The detrimental effect of such a change with regard to integrity of the
ecosystem can be evaluated by referring back to the discussion concerning the
overflow regime.  Reducing maximum discharge at Simmesport to 260,000
ft3/sec would effectively remove from the aquatic ecosystem those wetlands
that are presently flooded for a period of 0 to 4 months (Figures 6-8 and
Table 1).  This amounts to 17 percent of the floodway system below U.S.
Highway 90 alone, with a range of 36 percent of the Bayou des Glaises
management unit to 5 percent of the Upper Belle River unit.  In area, the 17
percent translates to approximately 100,000 acres.  On the basis of
topographic characteristics and the percentage increase in northward
direction, it must be expected that an even larger percentage would be removed
from the aquatic systems in the upper floodway.  Consequently, large areas of
mixed bottom-land hardwood would become susceptible to clearing and
agricultural  development.

     The removal  of the mixed hardwood habitats presently flooded from 1 to 4
months represents a major perturbation of the aquatic ecosystem.  These swamps
serve as a nursery area for juvenile fishes and as a feeding area for adult
fishes.  Crawfish use these short-hydroperiod swamps as feeding and growing
areas.  An additional  effect is caused by the elimination of the influx of
detritus and related nutrients from these swamps into surrounding aquatic
systems during fluctuations of water levels.   This also would apply to some
extent to the remaining swamps because the discharge fluctuation, during
periods when 30 percent of the latitude flow exceeded the allowable diversion,
would be eliminated.

     In addition, the effect on commercial  fishing of limiting maximum stages
to mid-February conditions should be considered.   No further increases in
stages would greatly reduce access into the cypress-tupelo swamps, which form
the backbone of commercial  crawfishing.   The limitation and discharge to
                                      55

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                                       57

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300,000 ft3/sec under the 35-ft plan would mean a reduction in stage of
approximately 3 ft during the peak crawfishing season in units such as Buffalo
Cove and Upper Belle River, which are most extensively used for that purpose.


MANAGE DIVERSION FOR AQUATIC ECOSYSTEM

    The volume of water diverted by the Old River Control  Project is critical
to the aquatic ecosystems in the Atchafalaya Basin Floodway complex because
the volume of water diverted provides all  of the water available, with the
exception of the much smaller amount available from precipitation.  The
question of what diversion percentage would be the most benefical to the
Basin's ecology is a complex one, however.  Complicating factors include the
sediment carried by the water, the way in  which the water is made available to
the backwater areas of the swamp, and the  development of the main channel
system.  All three of these complicating factors are now susceptible to
management, but determining the volume of  diversion must be done as part of a
plan that deals with all  these variables.
                                      58

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                                 DISCUSSION
    Although there is pressure to do so from the Red River backwater area,
reducing the discharges would be in direct conflict with what is necessary for
preserving and enhancing the natural and beneficial values of the Atchafalaya
Basin's wetlands.  The regime change would adversely affect the productivity
of existing wetlands, their habitat diversity and stability, hydrologic
utility, and associated fish and wildlife resources (and the commercial,
recreational, and other uses thereof) by reducing extent, duration, and depth
of annual flooding.  Direct loss of wetlands would occur particularly in the
Bayou des Glaises, Bayou Fordoche, Pigeon Bay, Cocodrie, Beau Bayou, and
Buffalo Cove management units and would greatly alter existing habitats in all
management units.  The change would effectively remove from the aquatic
ecosystem those wetlands that are presently flooded for a period of 0 to 4
months.  This type habitat represents as much as 36 percent of the wetland
system of the Atchafalaya Basin Floodway below U.S. Highway 190.  Similar
changes would occur in the Red River backwater area.

    Without stronger land-use controls, a reduction in the annual extent of
flooding would encourage new residential and agricultural development in
present wetlands.  This in turn will increase agricultural runoff into
adjacent wetlands, which are already affected by such runoff and in which
circulation is impeded by a backwater regime as a result of past flood control
measures.

    In order to minimize the present loss of wetlands as a result of river
profile adjustments, the present diversion ratio must be at least maintained.
However, the complete maintenance of present wetlands requires an increase of
diverted discharge to offset the trend toward reduced extent, duration, and
depth of flooding as experienced by all but three of the management units.
                                      59

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                                 REFERENCES
Craig, N., J. Day, Jr., P. Kemp, A.  Seaton,  W.  Smith,  and R.  Turner.   1977.
    Cumulative Impact Studies in the Louisiana  Coastal  Zone:   Eutrophication,
    Land Loss.  Report to Louisiana  State Planning  Office.   Center for
    Wetland Resources, Louisiana State University,  Baton Rouge,  Louisiana.

Federal Register.  1977.  Flood Plain Management.   Executive Order 11988.
    Vol. 42, No. 101.  Wednesday, May 25, 1977.

Federal Register.  1977.  Protection of Wetlands.   Executive Order 11990.
    Vol. 42, No. 101.  Wednesday, May 25, 1977.

Gilliam, J. W., and D. L. Terry.  1973.  Potential  for Water Pollution from
    Fertilizer Use in North Carolina.  North Carolina  Agriculture Extension
    Service.  Circular 550.

Odum, E. P.  1969.  Fundamentals of  Ecology.  3rd  Edition.   W. B. Sanders,
    Philadelphia.

Public Law 92-500.  Federal Water Pollution  Control  Act Amendment of  1972.
    92nd Congress.  S. 2770.  October 18, 1972.

U.S. Army Corps of Engineers.  1973.  Preliminary  Draft Environmental
    Statement.  Atchafalaya Basin Floodway.

U.S. Army Corps of Engineers.  1975.  Flood  of  '74  --  Post  Flood Report.
    USCE, New Orleans District.  96  pp.

U.S. Army Corps of Engineers.  1968.  Record of the Public  Hearing for Old
    and Atchafalaya Rivers.  New Orleans District.

U.S. Department of Agriculture.  1976.  Status  of  Watersheds (Map).   U.S.
    Department of Agriculture Soil  Conservation Service.

U.S. Geological Survey.  1976.  Water Resources Data for Louisiana, Water
    Year 1976.  The Agency, Reston,  Virginia.

van Beek, J. L., W. G. Smith, J. W.  Smith, and  P.  Light.  1977.   Plan  and
    Concepts for Multi-Use Management of the Atchafalaya Basin.   Ecological
    Research Series, EPA-600/3-77-62.  EPA,  Las Vegas, Nevada.  204 pp.

Wharton, C. H.  1970.  The Southern  River Swamp --  A Multiple Use
    Environment, Georgia State University, Atlanta, GA.  44 pp.
                                      60

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                                   APPENDIX

                              CONVERSION FACTORS
    In this report, English units are frequently abbreviated using the
notations shown below.  The English units can be converted to metric units by
multiplying the factors given in the following list:
English unit                        Multiply
to convert                             by

acres                               4,047
cubic feet per second (ft3sec)      0.02832
cubic yards (yd3)                   0.7646
day/second/feet (dsf)               0.02832
feet (ft)                           0.3048
miles (mi)                          1.6093
square feet (ft2)                   0.09290
square miles (mi2)                  2.590002
    Metric unit
    to obtain

square meters
cubic meters per
cubic meters
day/second/meters
meters
kilometers
square meters
square kilometers
second
                                      61

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                                   TECHNICAL REPORT DATA
                            (Please read Instructions on the reverse before completing)
1. REPORT NO.
     EPA-600/4-79-073
                             2.
                                                           3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
 OPERATION  OF THE OLD RIVER  CONTROL  PROJECT,
 ATCHAFALAYA BASIN:  An Evaluation from a Multiuse
 Management Standpoint
                                      5. REPORT DATE
                                          ..ovember  1979
                                      6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)

J.  L.  van Beek, A. L. Harmon,  C.  L.  Wax,  K.  M. Wicker
                                                           8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
 Coastal  Environments, Inc.
 1260  Main Street
 Baton Rouge, Louisiana  70802
                                                           10. PROGRAM ELEMENT NO.
                                           1BD613
                                      11. CONTRACT/GRANT NO.

                                          68-03-2665
12. SPONSORING AGENCY NAME AND ADDRESS
U.S.  Environmental  Protection Agency-Las Vegas
Office of Research and Development
Environmental  Monitoring and Support  Laboratory
Las Vegas, Nevada  89114
                                                           13. TYPE OF REPORT AND PERIOD COVERED
                                           Final  Report
                                      14. SPONSORING AGENCY CODE
                                           EPA/600/07
15. SUPPLEMENTARY NOTES
Project officer:  V.
W. Lambou, EMSL-LV
16. ABSTRACT
     This report evaluated from a multiuse management standpoint the  operation of the
 Old  River Control  Project.  It was  found  that limiting diversions to  the  extent
 presently being considered by the Old  River Control Project would effectively remove
 those wetlands that are presently flooded for a period of 0 to 4 months from the
 aquatic ecosystem as a type habitat representing as much as 36 percent  of the wetlands
 of the overflow areas in the Atchafalaya  Basin.  Without stronger land-use controls, a
 reduction in the annual extent of flooding could encourage new residential  and
 agricultural  development in the present wetlands.  This in turn will  increase
 agricultural  runoff into adjacent wetlands that are already affected  by such runoff
 and  in which water circulation is impeded by a backwater regime as a  result of past
 flood control increases.  In order  to  minimize the present loss of wetlands in the
 Atchafalaya Basin as a result of river profile adjustments, the present diversion of
 water must be at least maintained.   However, the complete maintenance of  present
 wetlands requires an increase of diverted discharges to offset the trend  toward
 reduction in the extent, duration,  and depth of flooding.
17.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                         b.IDENTIFIERS/OPEN ENDED TERMS  C. COS AT I Field/Group
 Water resources development
 Flood control
 Sedimentation
 Hydrography
                          Atchafalaya Basin
                          Old River Control  Project
                          Water management
   02 F
   08 A, F, H
   13 B
18. DISTRIBUTION STATEMENT
 RELEASE TO PUBLIC
                         19. SECURITY CLASS (This Report)
                          UNCLASSIFIED
21. NO. OF PAGES
  72
                                              20. SECURITY CLASS (Thispage)

                                               UNCLASSIFIED
                                                                         22. PRICE
EPA Form 2220-1 (Rev. 4-77)
                      PREVIOUS EDITION IS OBSOLETE
                                                          * U.S. GOVERNMENT PRINTING OFFICE: 1979— 683-282/2213

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