The existing engineering plan for flood control in the alluvial valley of the Mississippi River is modified so as to provide for the construction of plan 4 as set forth in the report of the Mississippi River Commission, dated March 7, 1941, to the Chief of Engineers, except that the levees in the Yazoo Basin on the east bank of the Mississippi River south of the Coahoma-Bolivar County line in said plan shall have a three foot freeboard over the project flood, and all levees shall be constructed with adequate section and foundation to conform to increased levee heights. The Boeuf Floodway in the project adopted by sections 702a, 702b to 702d, 702e to 702g, 702h, 702i, 702j, 702k, 702l, 702m, and 704 of this title, and the Eudora Floodway as well as the Northward Extension and the back protection levee extending from the head of the said Eudora Floodway north to the Arkansas River in the project adopted by sections 642a, 702a–1, 702a–2 to 702a–12, 702g–1, 702j–1, 702j–2, 702k–1, and 702k–2 of this title, are abandoned, and the provisions of said sections relating to the prosecution of work on said floodways and extension are repealed; except that the Ouachita River Levees, Louisiana, authorized by section 702a of this title, shall remain as a component of the Mississippi River and Tributaries Project and afforded operation and maintenance responsibilities as provided under section 702c of this title.

The project for flood control of the Yazoo River shall be as authorized by sections 642a, 702a–1, 702a–2 to 702a–12, 702g–1, 702j–1, 702j–2, 702k–1, and 702k–2 of this title, except that the Chief of Engineers may, in his discretion, from time to time, substitute therefor combinations of reservoirs, levees, and channel improvements; and except that the extension of the authorized project and improvements contemplated in plan C of the report of March 7, 1941, of the Mississippi River Commission are authorized, including the extension of the levee on the east bank of the Mississippi River generally along the west bank of the Yazoo River to a connection in the vicinity of Yazoo City with the Yazoo River levee, authorized by the existing project for protection against headwater floods of the Yazoo River system, and the adjustment in the discretion of the Chief of Engineers of the grades of the existing levees in the backwater area on the east bank of Yazoo River below Yazoo City, all at an estimated additional cost of $11,982,000: Provided, That the Chief of Engineers shall fix the grade of the extension levees along the Yazoo River, with higher levees in his discretion, so that their construction will give the maximum practical protection without jeopardizing the safety and integrity of the main Mississippi River levees: And provided further, That prior to the beginning of construction local authorities shall furnish satisfactory assurances that they will (1) maintain the levees in accordance with the provisions of section 702c of this title, and will (2) not raise the levees in the backwater above the limiting elevations established therefor by the Chief of Engineers.

In the development of the authorized project, the construction of a levee and improvements contemplated in the report of March 7, 1941, of the Mississippi River Commission from the main-line levee on the west bank of the Mississippi River in the vicinity of Shaw, Louisiana, westward and northward to the vicinity of Newlight, Louisiana, for the protection of that part of the Red River backwater known as the Tensas-Cocodrie area at an estimated cost of $6,976,000 is authorized: Provided, That the Chief of Engineers shall fix the grade of said levee, with a higher levee in his discretion, so that its construction will give the maximum practical protection without jeopardizing the safety and integrity of the main Mississippi River levees: And provided further, That prior to the beginning of construction local authorities shall furnish satisfactory assurances that they will (1) maintain the levee in accordance with the provisions of section 702c of this title, and will (2) not raise the said levee above the limiting elevations established therefor by the Chief of Engineers: Provided further, That subject to the foregoing conditions of local cooperation the Chief of Engineers may in his discretion substitute other levees and appurtenant works for, or make such modifications of, the levees and improvements herein authorized for the protection of the Tensas-Cocodrie area as may be found after further investigation to afford protection to a larger area in the Red River Backwater at a total cost not to exceed $29,000,000 and without jeopardizing the safety and integrity of the main Mississippi River levees and without preventing or jeopardizing the diversions contemplated in the adopted project through the Atchafalaya River and Atchafalaya Basin.

The Chief of Engineers, with approval of the Secretary of the Army, shall reimburse local authorities for actual expenditures found by the Chief of Engineers to be reasonable, for providing at the request of the United States, in accordance with local legal procedure or custom, rights-of-way and flowage easements required for future setbacks of main-line Mississippi River levees.

The existing engineering plan for flood control of the Saint Francis River is modified so as to permit the substitution for the suspended portions of the original project below Oak Donnick, Arkansas, of the construction of a ditch in Cross County, Arkansas, beginning in the vicinity of the outlet end of the existing Oak Donnick to Saint Francis Bay floodway and terminating in Saint Francis Bay about two miles north of Riverfront, including the construction of a highway bridge at State Highway Numbered 42 made necessary by the ditch construction: Provided, That local interests give assurances satisfactory to the Secretary of the Army that they will (1) provide without cost to the United States all lands, easements, and rights-of-way necessary for the construction; (2) hold and save the United States free from damages due to the construction works; and (3) maintain the works after completion in accordance with regulations prescribed by the Secretary of the Army.

In the development of the authorized project, the construction of improvements for Bayou Rapides, Boeuf, and Cocodrie, Louisiana, contemplated in the report dated March 24, 1941, of the Special Board of Officers at an estimated cost of $2,600,000 is authorized.

The total authorizations heretofore made for the flood control project of the alluvial valley of the Mississippi River shall not be increased by reason of any provision in this Act, except for the additional amounts necessary for the Yazoo and Red River backwater improvements, and any appropriations heretofore or hereafter made or authorized for said project as herein or heretofore modified may be expended upon any feature of the said project, notwithstanding any restrictions, limitations, or requirements of existing law: Provided, That funds hereafter expended for maintenance shall not be considered as reducing present remaining balances of authorizations.