The Mississippi River
||The Mississippi River |
and Tributaries Project
Without question America's greatest river, the Mississippi, has made major
contributions to the physical and economic growth of the nation. It is a
navigation artery of great importance to the nation's transportation system,
carrying an ever-growing commerce. Coursing through the heart of America, it
supplies water for the cities and industries that have located along its banks.
More and more the Mississippi's importance is emphasized as America continues to
grow. This great river is, truly, one of the Nation's outstanding assets.
Uncontrolled, it would be just as great a liability.
The Mississippi River always has been a threat to the security of the valley
through which it flows. Garciliaso de la Vega, in his history of the expedition
begun by DeSoto, described the first recorded flood of the Mississippi as severe
and of prolonged duration, beginning about March 10, 1543, and cresting about 40
days later. By the end of May the river had returned to its banks, having been
in flood for about 80 days.
Since that time, explorers, traders, farmers, men of commerce, and engineers
have known -- sometimes too well -- the Mississippi in flood.
The Mississippi Drainage Basin
The Mississippi River has the third largest drainage basin in the world,
exceeded in size only by the watersheds of the Amazon and Congo Rivers. It
drains 41 percent of the 48 contiguous states of the United States. The basin
covers more than 1,245,000 square miles, includes all or parts of 31 states and
two Canadian provinces, and roughly resembles a funnel which has its spout at
the Gulf of Mexico. Waters from as far east as New York and as far west as
Montana contribute to flows in the lower river.
By the year 1879, the need for improvement of the Mississippi River had
become widely recognized. The necessity for coordination of engineering
operations through a centralized organization had finally been accepted.
Accordingly, in that year, the Congress established the Mississippi River
Commission and assigned it the duties. . . " to take into consideration and
mature such a plan or plans and estimates as will correct, permanently locate,
and deepen the channel and protect the banks of the Mississippi River, improve
and give safety and ease to navigation thereof, prevent destructive floods,
promote and facilitate commerce, trade, and the postal service."
The Commission was to consist of three officers of the Corps of Engineers,
one of whom would be President; one member from the U.S. Coast and Geodetic
Survey; and three civilians, two of whom would be civil engineers. All
appointments would be nominated by the President of the United States, subject
to confirmation by the Senate.
In 1882, three years after establishment of the Commission, one of the most
disastrous floods ever known devastated the entire delta area. The losses were
appalling. During that flood there were hundreds of crevasses, and the outlook
for a permanent solution to flooding in the Mississippi Valley was
Major floods again occurred in 1912, 1913, and 1927. The flood of 1927 was
the most disastrous in the history of the Lower Mississippi Valley. An area of
about 26,000 square miles was inundated. Levees were breached, and cities,
towns, and farms were laid waste. Crops were destroyed, and industries and
Property damage amounted to about $1.5 billion at today's prices. Over 200
lives were lost and over 600,000 people displaced. Out of it grew the Flood
Control Act of 1928, which committed the federal government to a definite
program of flood control. This legislation authorized the Mississippi River and
Tributaries (MR&T) Project, the nation's first comprehensive flood control
and navigation act.
The Mississippi River Drainage
with MR&T Project area (in pink).
The lower alluvial valley of the Mississippi River is a relatively
flat plain of about 35,000 square miles bordering on the river which would
be overflowed during time of high water if it were not for man-made
protective works.This valley begins just below Cape Girardeau, Missouri,
is roughly 600 miles in length, varies in width from 25 to 125 miles, and
includes parts of seven states -- Missouri, Illinois, Tennessee, Kentucky,
Arkansas, Mississippi, and Louisiana.
Floods of 1849 and 1850, which caused widespread damage in the
Mississippi River Valley, revealed the national interest in controlling
the mighty river. |
The Project Flood
The flood control plan is designed to control the "project flood." It is a
flood larger than the record flood of 1927. At Cairo, the project flood is
estimated at 2,360,000 cubic feet per second (cfs). The project flood is 11
percent greater than the flood of 1927 at the mouth of the Arkansas River and 29
percent greater at the latitude of Red River Landing, amounting to 3,030,000 cfs
at that location, about 60 miles below Natchez.
Description of Plan
The four major elements of the Mississippi River and Tributaries Project
are: levees for containing flood flows; floodways
for the passage of excess flows past critical reaches of the Mississippi;
channel improvement and stabilization for
stabilizing the channel in order to provide an efficient navigation alignment,
increase the flood-carrying capacity of the river, and for protection of the
levees system; and tributary basin improvements for major drainage
and for flood control, such as dams and reservoirs, pumping plants, auxillary
channels, and the like.
Main Stem Levees
The Mississippi River levees are designed to protect the alluvial valley
against the project flood by confining flow to the leveed channel, except where
it enters the natural blackwater areas or is diverted purposely into the
The main stem levee system, comprised of levees, floodwalls, and various
control structures, is 2,203 miles long. Some 1,607 miles lie along the
Mississippi River itself and 596 miles lie along the south banks of the Arkansas
and Red rivers and in the Atchafalaya Basin.
The levees are constructed by the federal government and are maintained by
local interests, except for government assistance as necessary during major
floods. Periodic inspections of maintenance are made by personnel from the U.S.
Army Corps of Engineers and from local levee and drainage districts as it is
essential that the levees be maintained in good condition for their proper
functioning in the flood control plan.
From Cairo to New Madrid, Mo., the east bank bluffs and the levee as
originally built on the west bank left only a narrow channel through which the
river could flow at flood stage. To protect communities along the Mississippi
and Ohio rivers and to reduce the flood heights to which the controlling levees
on the Missouri side would otherwise be subjected, the project provides for a
setback levee about 5 miles west of the riverfront levee through this reach. The
strip between this setback levee and the levee adjacent to the river forms what
is known as the Birds Point-New Madrid Floodway, operated only at extremely high
stages. Water enters the floodway through lower levee sections or "fuse plugs"
in the old front levee below Cairo and reenters the main river just above New
Madrid. The floodway was operated in 1937 and was of material aid in reducing
flood heights at and above Cairo.
At the latitude of Red River Landing, the project flood is estimated at
3,000,000 cfs. The project provides for dividing this great quantity of water,
with 1,500,000 cfs of the flow continuing down the main river channel, the
remaining 1,500,000 cfs being diverted to the Atchafalaya River via the Morganza
and West Atchafalaya floodways, and the Old River Control structures.
Of the 1,500,000 cfs flowing down the main channel below Morganza Floodway,
250,000 cfs are to be diverted to Lake Pontchartrain and the Gulf through the
Bonnet Carre' Spillway, located about 25 miles above New Orleans. The remaining
1,250,000 cfs will continue down the river to the Gulf.
That portion of the flow diverted from the main channel near Old River is
carried by the Atchafalaya River, the Morganza Floodway, and the West
Atchafalaya Floodway. The Morganza and the West Atchafalaya floodways follow
down on opposite sides of the Atchafalaya River until the end of the levee
system along the Atchafalaya River is reached; there they merge into a single
broad floodway that passes the flow to the Gulf through two outlets, Wax Lake
and Berwick Bay. In major floods, the Morganza would be the first of these two
floodways to be used, with water entering it through a control structure just
Channel Improvement and
Stabilization and protection of the riverbanks are important to the flood
control and navigation plan, serving to protect flood control features and to
insure the desired alignment of the river's navigation channel. This is
||Shortening the river and reduce flood
||Controlling the river's meandering.
||Directing the flow. |
|Realigning the channel.
|The Corps Dredge Jadwin at work.
||Mississippi River revetment
Principal Tributary Basin
The Flood Control Act of 1928 authorized work that would give the various
basins protection against Mississippi River floods only, although the tributary
streams within the basins caused frequent flood damage that could not be
prevented by the main stem Mississippi River protective works. Later amendments
to this act have authorized work that provides alleviation of the tributary
There are four major drainage basins in the lower Mississippi River Valley
Project: St. Francis in east Arkansas; Yazoo in northwest Mississippi; Tensas in
northeast Louisiana; and Atchafalaya in south Louisiana. There are five flood
control reservoirs in the tributary basin improvement plan: Wappapello Lake in
the St. Francis Basin, and four lakes -- Arkabutla, Sardis, Enid, and Grenada --
in the Yazoo Basin.
Old River Control
One of the most important modifications to the project was made in 1954 when
Congress authorized the feature for the control of flow at Old River to prevent
the capture of the Mississippi by the Atchafalaya River.
The first two features completed were the low-sill and overbank structures,
the former to pass low and medium flows from the Mississippi to the Atchafalaya
River in a controlled manner, and the latter to pass flood flows to the
Atchafalaya in conformance with the flood control plan. Inflow and outflow
channels were constructed connecting the low-sill structure with the Mississippi
and Red-Atchafalaya rivers. A third facility -- called the Auxillary Structure
-- was placed in service late in 1986.
As the closure of Old River would cut off an important shallow-draft
navigation artery, a navigation lock was constructed just south of the junction
of the Old and Mississippi rivers. This navigation lock is one of the most
modern in the nation's inland waterway system. Channels were dredged connecting
the lock to the Mississippi and Old rivers, and this feature was opened to
navigation in 1963.
No river has played a greater part in the development and expansion of
America than the Mississippi. In 1705 the first cargo was floated down the
river from the Indian country around Wabash, now the states of Indiana and
Ohio. This was a load of 15,000 bear and deer hides brought downstream for
shipment to France.
Invention of the steamboat in the early nineteenth century brought
about a revolution in river commerce. The first steamboat to travel the
Mississippi was the "New Orleans."
The Mississippi River is the main stem of a network of inland
navigable waterways which form a system of about 12,350 miles in length,
not including the Gulf Intracoastal Waterway of 1,173 miles.
Waterborne commerce on the Mississippi rose from 30 million tons in
1940 to almost 400 million in 1984. This heavy commercial traffic includes
grains, coal and coke, petroleum products, sand and gravel, salt, sulphur
and chemicals, and building materials among others. In addition, many
pleasure craft from all parts of the country now use the Mississippi for
vacation and travel.
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