Stabilization of banks will reduce the sand in motion, will fix the locations of crossings and will reduce the amount of dredging required to maintain the 9-foot channel of the existing project. It is estimated that the existing authorization for maintenance dredging will therefore be ample to secure a minimum low-water depth of 12 feet after stabilization is accomplished. Certain improvement dredging will be required in some reaches to produce the best possible alinement for stabilization before that work is undertaken. Low pile dikes also may be required in some wide reaches to fix the low-water channel. 5 A program of such magnitude of necessity will extend over a period of about 15 years. We are now in a period of high prices for construction work. It is impossible to foresee what costs will be after the Judging by past experience they should be substantially lower. All things considered, an estimate made on the basis of current costs should be adequate. On the basis of such costs the 230 miles of bank stabilization work might require $165,000,000. Allowing $35,000,000 for improvement dredging and low dikes, the total estimate in round numbers is $200,000,000. VI. CONCLUSIONS Document No. 90, Seventieth Congress, which was enacted into law by the act of May 15, 1928, visualized the progressive revetment of caving banks to protect the foundations of the levees and to stabilize the river both for flood control and navigation. The following is quoted from that report: 131. Channel stabilization. Since the levees within the limits of this project are to be greatly enlarged, they will be much more expensive than heretofore, so something must be done to avoid the frequent moving of them from the proximity of caving banks. In addition, the river cannot be regulated for low-water navigation until the banks are made stable, this both to keep the channel in one place and to stop the enormous dumping of earth into the river by bank caving. A general bank protection scheme must be carried out * * * That statement is fully as sound today as when it was written. For the reasons stated in this report, the Commission believes that the time has now arrived in the development of the alluvial valley of the Mississippi for undertaking to hold the river's meander within narrow limits as rapidly as funds can be made available. The Commission is of the opinion that stabilization of the river is necessary in order to retain reduction in flood heights obtained by channel rectification, and is advisable for the purpose of safeguarding the main Mississippi River levees and protecting the investment which they represent. The Commission is of the further opinion that such stabilization may materially increase the flood-carrying capacity of the river channel and together with the maintenance dredging already authorized, will provide a minimum depth of 12 feet at low water for navigation. The great investments made by the Government and the local people in the levee system, the constantly increasing population and property values protected by the levees, and the benefits accruing to the country as a whole from the navigation of the river both in war and in peace justify the further expenditures required. VII. RECOMMENDATIONS The Mississippi River Commission recommends that the exist project for flood control, Mississippi River and tributaries, be modif to authorize a navigation channel 12 feet deep and 300 feet wide at water between Cairo, Ill., and Baton Rouge, La., and the executies in the interest of navigation and flood control, of a channel impro, ment and stabilization program at an estimated cost over that no authorized, of $200,000,000. T LEO O. COLBERT, Member Member. HARRY N. PHARR, Member APPENDIX I EXISTING PROJECT operation the point a section stage com will opera In reco breaks in St. Franc levees nes latter leve the main along the In the and Missis to be prote case of dan resume its such use w free rights free from storage pur required by levee syster plan for con Between charge exces Outline of project. The project for flood control, Mississippi River and tributaries, their junction adopted by the Flood Control Act of May 15, 1928, and amended The Bonnet 18, 1941, provides for the control of floods on the main river bele grades rangin the acts of June 15, 1936, August 28, 1937, June 28, 1938, and Augus outlet into Cape Girardeau, Mo., by means of levees designed to keep overban freeboards re stages off the lands and improvements and out of the cities, towns, an on the lower villages of the alluvial valley; channel improvements to provide th Basin floodwa The projec in the floodwa tion channel not less than 300 feet wide and 9 feet deep from Cai River without by revetments and dikes at selected locations. of the draina the river channel and floodways substantially in their present cor the Wax Lake to the assumed peak discharges of the project or "design" flood wi bridges over th Levee grades for main river levees have been fixed to correspon capacity of th dition. i the White-Arkansas are generally 1 foot above the estimated flow lin Cocodrie in Lo Net levee grades at Cairo, Ill., and below Cairo approximately erees; and fo In addition headwater floo of the project flood with the Birds Point-New Madrid floodway plates levee puted crest with net gra line to Vicks Below Old river, from I and from Ol and West A operation. The floodway extends on the west or right bank between the points named in its designation. The project contemplates that a section of the front line levee of the floodway will be degraded to a stage corresponding to 55 feet on the Cairo gage and that the floodway will operate in floods exceeding that stage at Cairo. In recognition of the fact that it is more important to prevent breaks in main levees along the upper parts of the highly developed St. Francis, White, and Yazoo River Basins than in the backwaterlevees near the mouths of the St. Francis and White Rivers, these latter levees are to be maintained at grades 2 feet lower than those of the main levees opposite them. The grade of the levees and walls along the Cairo front is 2 feet above project flow line. In the White River backwater region, the area between the White and Mississippi Rivers from Oldtown Lake south to Laconia Circle is to be protected from all but great floods by a system of levees, which in case of danger to main line levees, can be opened to permit the area to resume its important function of storing floodwaters. The right of such use was guaranteed by local interests and the duty of providing free rights-of-way, caring for drainage, and holding the United States free from damages incident to the use of the area for backwater storage purposes was assumed by them as conditions of construction required by section 5 of the act approved June 15, 1936. Opening this levee system near the crest of a great flood is an integral part of the plan for controlling the river downstream. Between the Arkansas River and Old River the project contemplates levees on the west bank with net grades 1 foot above the computed crest flow line of the project flood and, on the east bank, levees with net grades 3 feet above that flow line (Coahoma-Bolivar County line to Vicksburg). Below Old River it provides for levees on both sides of the main river, from Baton Rouge to below Pointe a la Hache on the east bank and from Old River to Venice on the west bank, with the Morganza and West Atchafalaya floodways on the west bank designed to discharge excess flood flows into the Atchafalaya floodway, formed by their junction at the lower end of the Atchafalaya River levee system. The Bonnet Carre spillway on the east bank affords a controlled relief outlet into Lake Pontchartrain. The main river levees have net grades ranging from 1 to 5 feet above project flood flow line, the higher freeboards representing levees constructed under previous projects. on the lower river anterior to the introduction of the Atchafalaya Basin floodways. The project provides for levees on both sides of the Atchafalaya River without increase in 1927 grades for about 45 miles downstream from its head; for the east and west guide levees of the Atchafalaya floodways, with net grades 2 feet above estimated maximum flow line in the floodways; for the Wax Lake outlet to supplement the discharge capacity of the lower Atchafalaya River; for railroad and highway bridges over the Morganza floodway, the West Atchafalaya floodway, the Wax Lake outlet, and the Charenton Canal, which latter disposes. of the drainage cut-off by the West Atchafalaya floodway guide levees; and for the improvement of Bayous Rapides, Boeuf, and Cocodrie in Louisiana. In addition to the foregoing, provision is made for the control of headwater floods in the St. Francis Basin by means of a reservoir on the St. Francis River at Wappapello, Mo., and levees and chann Wit The project also provides for the control of headwater floods of the require The Yazoo backwater area is to be protected by an extension of the be Ark., ha From White River on the west bank 271 miles of levee required raising to attain the approved 1941 grade. Work has been completed or is under contract on 112 miles of this levee. bank 80 the 194 South pleted. in the 19 Under similar conditions the protection of a part of the Red Rive backwater area against less than a project flood is authorized. guide lev the levee The project also authorizes emergency repairs to any levees tributaries of the Mississippi River damaged or threatened by floods and Federal participation to the extent of two-thirds of the con except fo struction cost, in levee construction along the main river betwee: solidation Rock Island, Ill., and Cape Girardeau, Mo., and on tributaries and ficiencies, outlets of the Mississippi within the limits of the influence of Mis lock in t sissippi River backwaters. The cons The law provides that levces shall be built at Federal expense with the durat the exception just noted. Local interests are required to furnish the with their rights-of-way for the main Mississippi River levees below Cape railway a Girardeau, except where setbacks of existing levees are required, and way one for the levees required for the protection of the St. Francis and Yazootion. Th Basins from headwater floods. Between Rock Island and Cap the Morga Girardeau and for other levees in which the Government participates Over the only to the extent of two-thirds of the construction cost, local interests war. are required to provide rights-of-way and to pay one-third the con struction cost. Ordinary maintenance of levees is a responsibility local interests. No Bayous R of The g the Atel Of the w water floo Levees on tection of of the St. The project contemplates the improvement of the main river channel below Cairo for flood-carrying capacity and for navigation by securing a better alinement and by a limited amount of stabilization by means of revetment of the banks and construction of dikes at selected locations. The prescribed minimum dimensions of the navigation channel are: depth, 9 feet; width, 300 feet. Necessary Wappapell the require Channel Status of completion. the 1941 grade. A set-back levee on the Ohio River side is under an operatio The levee at Cairo on the Mississippi River side has been raised to completed. construction to 1941 grade. Raising of the river wall on the Ohio Sardis Rese River front and construction of the Cache River diversion have been designed, b the suspended for the duration of the war. On the east bank between Hickman, Ky., and Slough Landing Neck are 22%1⁄2 miles of levee, all of which require raising to the 1941 grade. degrading of the fuse plug section. From Commerce, Mo., to the of the back The Birds Point-New Madrid floodway is completed except for the Black Oal war. Work is Cassidy Ba No work With the completion of contracts in force the White River backvater levee will be finished, except for about 4 miles of very low levee required along the high ground along Oldtown Lake, and some adjustnent at the fuse-plug sections. Between Yancopin on the Arkansas River and Old River, the 1941 grade necessitated work on 263 miles of levee on the west bank. Eighty-two miles have been completed or are under contract. All the old Eudora fuse-plug levee between Yancopin, Ark., and Vaucluse, Ark., has been completed or is under contract. From the head of the Yazoo Basin to the Yazoo River on the east bank 80 miles of levee out of a total of 236 miles requiring raising to he 1941 grade have been completed or are under contract. South of Old River the levees on the main river are practically completed. The Bonnet Carre spillway has been completed and was used n the 1937 flood. The guide levees of the Morganza floodway, the cast guide levee of the Atchafalaya floodway from Morgan City northward, the west guide levee from the vicinity of Head of Berwick Bay northward, and the levees along the upper Atchafalaya River are generally completed except for the correction of minor deficiencies in grade due to consolidation of embankments, flow-line adjustments, foundation deficiencies, and the closure of openings left for bighways, railways, a lock in the east guide levee and floodgates in the west guide levee. The construction of the lock and floodgates has been postponed for the duration. The Wax Lake outlet and Charenton drainage canal with their highway and railroad bridges are completed. Of the three railway and two highway bridges provided for the Morganza floodway one railroad bridge and one highway bridge are nearing completion. The two other railroad bridges and one highway bridge over the Morganza floodway and the one railroad and one highway bridge oyer the West Atchafalaya floodway cannot be built until after the war. No work has been done on the improvements authorized for Bayous Rapides, Boeuf, and Cocodrie. Of the works for he protection of the St. Francis Basin from headwater floods, the Wappapello Dam is completed and in operation. Levees on Little River are comple sed except those required for protection of the Elk Chute drainage district. Levees on the right bank of the St. Francis River below Tulot, Ark., and on the left bank below Black Oak are completed. All channel work is under contract. Necessary levees on the St. Francis River between Tulot and the Wappapello Dam cannot be constructed until local interests furnish the required levee rights-of-way. Channel work on the Yazoo headwater project is about 48 percent completed. Two of the four reservoirs have been completed and are in operation, namely, Arkabutla Reservoir on Coldwater River and Sardis Reservoir on the Little Tallahatchie. The other two are being designed, but their construction will not be undersaken until after the war. Work is in progress on the levees north of Darling, Miss., and on Cassidy Bayou. No work has been done on the authorized levees for the protection of the backwater areas at the mouths of Yazoo River and Red River. |