The Act of 28 June 1879, by which the com mission was created, defines its duty in part as follows : To direct and complete such surveys of said river. between the Head of the Passes neat its mouth to its headwaters as may now be in progressand to make such additional surveys, examinations, and investigations, topographical, hydro graphical, and hydrometrical, of said river and its tributaries as may be deemed necessary by said commission to carry out the objects of this act. . . . To take into con sideration and mature such 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 the navigation thereof ; prevent destructive floods; promote and facilitate commerce, trade, and the postal service; . . .
Under the authority of this and subsequent acts mating appropriations and relating to the subject, surveys and observations have been carried on and works of improvement under the authority and direction of laws making appropriation for that purpose have been un dertaken and executed. The original contained in the report of the Mississippi River. Commission dated 17 Feb. 1880 contemplated the permanent fixing and improvement of the channel to a depth of at least 10 feet at ex treme low water by the construction of the low-water width to about 3,000 feet, the protection of the banks against caving and the control of the flood water by means of levees. This report was the one upon which Congress made its first appropriation for the improvement of the Mississippi River under commission plans, thereby officially adopting such plans for the inauguration of this work.
When the Mississippi River Commission be gan the work of improvement there were few, if any, precedents of practical value to serve as guides in a project of such magnitude. But very meagre data as to the regimen of the river were available, and a thorough knowledge of, its many varying phases was essential before satisfactory comprehensive plans of improve ment could be developed. Exhaustive surveys and observations of the physics of the river from the headwaters to the mouth were there fore inaugurated and carried on until the data needed were secured and experiments with vari ous kinds of plant and material were also made in order to develop the equipment and type 9f construction needed for efficient work. This work occupied several . years. During these years the appropriations were compara tively small, and sometimes failed altogether, with disastrous results to the channel works, so progress was necessarily slow. As a result
of the knowledge of the regimen of the river acquired and the lesson taught by the experi mental work, definite projects are now entered upon with confidence of success, but efforts looking to improved methods to secure greater efficiency and economy will be continued.
The earlier works were designed primarily for the rectification and improvement of the channel, and were confined to the Plum Point Reach, 147 to 186 miles, and Lake Providence Reach, 517 to 552 miles below Cairo. These reaches were selected because here the shifting sand bars and deficient depths were most pro nounced and the low-water navigation most diffi cult. Highly beneficial results were obtained in the improvement of the channel depths in those reaches, and the work done in them confirmed the soundness of the theory upon which it was based, but also demonstrated that more sub stantial types of construction were needed and that the permanent improvement of the channel by contraction and revetment works would con sume a long period of time, while the press ing needs of commerce called for immediate relief. The development in hydraulic dredging machinery had reached such a stage at this time as to hold out the hope that an immediate and economical solution of the problem of temporarily deepening the channel for naviga tion purposes might he found in the opening and maintenance of channels across the ob structing bars at each low-water season by means of dredging. After extended studies and experiments, hydraulic dredges of large capacity adapted to the peculiar service re quired were developed by the commission and this method of temporary improvement of the low-water channel was adopted with • a view, of maintaining a navigable channel not less than 250 feet in width and 9 feet in depth, and has been applied with success.
Since the adoption of dredging, the perma nent work of channel improvement has been confined to the revetment of banks, and a of revetment has been developed which suc cessfully withstands the scouring action of the river. Concrete has been largely substituted for the upper bank revetment, and its use for sinking the present type of willow mat, as well as a possible substitute for the mat itself, is being tried out with a view to further economy and increased efficiency.