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66th CONGRESS, | HOUSE OF REPRESENTATIVES. 1st Session.

ATCHAFALAYA RIVER, LA., AND RELATED BASINS.

LETTER

FROM

THE SECRETARY OF WAR,

TRANSMITTING,

WITH A LETTER FROM THE CHIEF OF ENGINEERS, REPORT ON

SURVEY AND FLOOD CONTROL OF THE ATCHAFALAYA RIVER, LA., AND RELATED BASINS.

NOVEMBER 3, 1919.-Referred to the Committee on Flood Control and ordered

to be printed, with illustration,

WAR DEPARTMENT,

Washington, October 31, 1919. The SPEAKER OF THE HOUSE OF REPRESENTATIVES.

SIR: I have the honor to transmit herewith a letter from the Chief of Engineers, United States Army, of yesterday's date, together with a report by the Mississippi River Commission, dated July 17, 1919, with map, on a survey and flood control of Atchafalaya River and related basins, authorized by the river and harbor act approved July 27, 1916, and the flood-control act approved March 1, 1917; also a report of the Board of Engineers for Rivers and Harbors, dated August 12, 1919, concurring in the views of the Mississippi River Commission. Very respectfully,

NEWTON D. BAKER,

Secretary of War.

WAR DEPARTMENT,
OFFICE OF THE CHIEF OF ENGINEERS,

Washington, October 30, 1919.
From: The Chief of Engineers, United States Army.
To: The Secretary of War.
Subject: Survey and flood control Atchafalaya River and related

basins.

1. There is submitted herewith for transmission to Congress report dated July 17, 1919, with map, by the Mississippi River Commission, authorized by the following items of law:

The river and harbor act approved July 27, 1916: That a survey with a report shall be made by the Mississippi River Commission of the Atchafalaya River in accordance with the general plan of said commission for the improvement of the Mississippi River, and in making such survey and report, if in their opinion the improvement of the Atchafalaya is desirable, consideration shall be given and recommendation made as to any plans for cooperation on the part of local interests. Flood-control act approved March 1, 1917:

a survey of the Atchafalaya Outlet so far as may be necessary to determine the cost of protecting its basin from the flood waters of the Mississippi River either by its divorcement from the Mississippi River or by other means

2. The Atchafalaya River Basin, the basin between Bayou des Glaises and Red River, and the basin north of the Red River, amounting in the aggregate to 942,400 acres, and now partially protected from Mississippi River flood waters, can be further protected by an extension of the levee system without disturbing the present connections between the Red and the Mississippi at an estimated cost of $5,131,750.

3. The fullest measure of protection to the Atcha falaya Basin from both the Mississippi and the Red would be secured by closing the Atchafalaya at its head and allowing the Red to flow into the Mississippi. The estimate for this work, including a dam in the Atchafalaya and levee along the Red, is $1,544,500. If this plan were adopted the basin north of the Red River would still require protection, estimated to cost $1,809,000, making the total cost $3,353,500. This plan is not deemed advisable, as it would add to the Mississippi River floods the full discharge of the Red and the present flow from the Mississippi to the Atchafalaya.

4. The plan proposed for the separation of the Red and Atchafalaya Rivers from the Mississippi contemplated the extension of the Tensas levee to a connection with the Atcha falaya levee, a dam across Old River, a canal and lock to provide a navigable connection between the Mississippi and the Red, and the enlargement of the Mississippi River levees to resist additional flood heights, at a total estimated cost of $13,022,500.

5. The commission is of opinion that the interests of navigation are not injuriously affected by the protection of the Atcha falaya Outlet and its basin from the flood waters of the Mississippi and that the separation of the Red and Atchafalaya Rivers is not necessary thereto, and that such protection can be carried out under the provisions of the flood-control act in accordance with the plans and estimates given in its report.

6. This report has been referred, as required by law, to the Board of Engineers for Rivers and Harbors, and attention is invited to its report herewith, dated August 12, 1919, concurring in the views of the Mississippi River Commission.

7. After due consideration of the above-mentioned reports, I concur in the views of the Mississippi River Commission and the Board of Engineers for Rivers and Harbors, and therefore report that such work as is necessary for the protection of the Atchafalaya Basin from the flood waters of the Mississippi River can be accomplished under the provisions of the flood-control act in accordance with plans and estimates submitted by the Mississippi River Commission, and that the divorcement of the Atchafalaya from the Mississippi is not necessary thereto.

W. M. BLACK, Major General.

REPORT OF THE BOARD OF ENGINEERS FOR RIVERS AND HARBORS.

(Second indorsement. )

BOARD OF ENGINEERS FOR RIVERS AND HARBORS,

August 12, 1919. To the CHIEF OF ENGINEERS, UNITED STATES ARMY:

1. The following is in review of report submitted by the Mississippi River Commission under the following authorities: The river and harbor act approved July 27, 1916:

That a survey with a report shall be made by the Mississippi River Commission of the Atchafalaya River, in accordance with the general plan of said commission for the improvement of the Mississippi River, and in making such survey and report, if in their opinion the improvement of the Atchafalaya is desirable, consideration shall be given and recommendation made as to any plans for cooperation on the part of local interests. Flood-control act, approved March 1, 1917:

a survey of the Atchafalaya Outlet so far as may be necessary to determine the cost of protecting its basin from the flood waters of the Mississippi River, either by its divorcement from the Mississippi River, or by other means

2. Levees now extend down both sides of the Atchafalaya River for a distance of 47.5 miles and protect about 842,240 acres. These levees may be extended and thereby protect an additional area in the Atcha falaya Basin of about 237,400 acres at an estimated cost of $1,830,000. In the basin between Bayou des Glaises and Red River, 138,000 acres can be protected from Mississippi flood waters by extending levees down the right bank of the Red, and down the Atchafalaya River to connect with the existing system at Bayou des Glaises, at an estimated cost of $1,050,000. North of Red River is an area of about 567,000 acres subject to overflow. Of this about 272,000 acres west of the Black River and 295,000 acres east of the Black River can be protected by levees at an estimated cost of $2,251,750, making a total cost of $5,131,750, to protect about 942,400 acres.

3. The fullest measure of protection to the Atcha falaya basin from the flood waters of the Mississippi, and also the Red River, would be secured by closing the Atchafalaya and allowing the Red to flow into the Mississippi. The estimated cost of the work involved, including dam in the Atchafalaya and necessary levee along the Red, is $1,544,500. If this plan were adopted the basin north of the Red River would still require protection, estimated to cost $1,809,000, making the total cost $3,353,500. This plan would add to the flood volume of the Mississippi the full discharge of the Red and the present outflow through the Atcha falaya, and is not recommended.

4. Three principal reasons have been advanced in favor of the separation of the Red and Atchafalaya Rivers from the Mississippi:

(a) The flow from the Mississippi through the Atchafalaya is increasing in volume, and enlarging the cross section of the latter to an extent that threatens to change the course of the Mississippi to the much shorter Atchafalaya route.

A study of available data apparently indicates that the average increase in cross sectional area has been only 13.2 per cent, and the commission states that this should allay the apprehension of a divergence of the waters of the Mississippi River down the Atchafalaya, and that should such a tendency develop it can be controlled by an extension of the system of submerged sills, which have already been constructed in the upper reach of the river.

(6). The flow through the outlet into the Atchafalaya has caused deposits whereby the cross section and flood capacity of the Mississippi at and below the outlet have been diminished to the extent of obstructing low-water navigation and closing the outlet would restore the normal cross section.

With reference to the diminished cross section of the Mississippi and the formation of a bar, due to the escape of Mississippi water down the Atchafalaya, it appears from a comparison of surveys covering the period, 1895–1910, that the average width of the river in the vicinity of the bar increased 7 to 10 per cent, the average area decreased 18 per cent at low water, and 19 per cent at medium stage, and increased nearly 1 per cent at bank-full stage. The average mean depth decreased 3.2 per cent to 4.7 per cent at different stages. Practically all sections show a decrease in depth. At the bank-full stage, however, which controls the flood capacity of the river, there has been but slight change.

(c) The flood waters from the Mississippi menace life and property along the Atchafalaya, increase the cost of protection and drainage, and retard development.

A study of flood conditions here indicates that even if the diversion is accomplished, levee construction and extensive drainage plants will be required in the Atchafalaya Basin. A serious objection to the closure of the Atcha falaya outlet is the increase in flood heights along the Mississippi River which will result therefrom.

5. The plan contemplated for the separation of the Red and Atchafalaya from the Mississippi provides for the gradual extension of the Tensas levee to a connection with the Atcha falava levee near Torras, the building up of the bed of Old River with deposits by means of dikes, the provision of a lock and short canal for navigation between the Mississippi and the Red River system, and finally complete separation by a dam across Old River. The estimate for this work made in 1913 is $13,022,500. This includes $7,200,000 for enlarging the Mississippi River levees to meet probable increased flood height. An estimate in the sum of $3,751.200 is given as representing the cost of protecting the interior basins from the flood waters of the Red if the separation is completed. To sum up, the estimates of the several plans considered are as follows: 1. Protecting the Atchafalaya River basin (including the area north

of the Red River) from the flood waters of the Mississippi River. $5, 131, 750 2. Closing the Atchafalaya River at its head, permitting the Red River to flow into the Mississippi.---

3, 353, 500 3. Separating the Red and Atchafalaya from the Mississippi. 13, 022, 500

6. The commission is of opinion that the interests of navigation are not injuriously affected by the protection of the Atchafalaya Outlet and its basin from the flood waters of the Mississippi River, and that the separation of the Red and Atcha falaya Rivers is not necessary thereto; that such protection can be carried out under the provisions of the flood-control act in accordance with the plans and estimates given in its report.

7. After careful review of all data presented, the board concurs in the opinion of the Mississippi River Commission as expressed in the preceding paragraph. For the board:

PETER C. Hains,
Major General, United States Army, Retired,

Senior Member of the Board.

SURVEY OF THE ATCHAFALAYA RIVER AND RELATED BASINS.

OFFICE MISSISSIPPI RIVER COMMISSION,

St. Louis, Mo., July 17, 1919. , From: The Mississippi River Commission. To: The Chief of Engineers, United States Army. Subject: Report on survey and flood control of Atchafalaya River

and related basins. The river and harbor act approved July 27, 1916, provided

That a survey with a report shall be made by the Mississippi River Commission of the Atchafalaya River in accordance with the general plan of said commission for the improvement of the Mississippi River, and in making such survey and report, if in their opinion the improvement of the Atchafalaya is desirable, consideration shall be given and recommendation made as to any plans for cooperation on the part of local interests.

Subsequently, the flood-control act approved March 1, 1917, under which the commission now acts, provided for

a survey of the Atchafalaya outlet so far as may be necessary to determine the cost of protecting its basin from the flood waters of the Mississippi River either by its divorcement from the Mississippi River or by other

means

The field work of the survey required by Congress was completed in March, 1917, and covered the Atcha falaya River from its head at Red River to Butte la Rose, including the bed and banks of the river, location of levee lines, and cross sections coincident with those of the survey of 1904–5, for the purpose of ascertaining the changes that have occurred in the river. The survey continuing southward from Butte la Rose to near Morgan City embraced shore lines and soundings of the main bayous and lakes between Grand River on the east and Grand Prairie on the west.

The reduction of field notes and the preparation of maps were necessarily suspended owing to the exigencies of war, which depleted the available force.

PRIOR REPORTS. The river and harbor act of June 25, 1910, called on the commission for

an examination and report upon the necessity, urgency, and practicability of permanently separating the waters of the Red and Atchafalaya Rivers from those of the Mississippi River, together with an estimate of the cost of such work.

This report with detailed maps and extensive hearings on the questions involved, was submited by the commission November 21, 1913, and was printed as House Document No. 841, Sixty-third Congress, second session, to which attention is invited.

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