water from the Mississippi River, and hence are included in the Mississippi River and tributaries project. The basins of some of the smaller tributaries are wholly, or almost wholly, in the alluvial valley and consequently, are included entirely in the project. These include the west Tennessee tributaries, the St. Francis, and the Yazoo. In the lower portion of the valley, the Atchafalaya River, a distributary of the Mississippi, extends in a generally north-south direction from its confluence with the Red River to the Gulf of Mexico. It lies entirely within the alluvial valley and serves to discharge part of the combined flows of the Mississippi and Red Rivers into the gulf.

HISTORY

Early flood control works constructed by tocal interests.-The necessity for flood control was recognized immediately by the early settlers in the valley and a levee in the vicinity of New Orleans was completed in 1727. As the settlers prospered and lands were cleared, the local people continued levee construction to protect their lives and properties against the ravages of floods until by 1844 the levee system was practically continuous on the west bank from below New Orleans to the mouth of the Arkansas River, and on the east bank from well below New Orleans to Baton Rouge. Also many levees were constructed by local people in the lower part of the Yazoo Basin. This work was accomplished by local interests using their own resources in spite of several damaging floods. However, the great flood of 1844 overtopped or breached practically every levee system in existence and severely set back their efforts to protect themselves.

Early Federal interest in the valley. During this early period of development of flood protection by local interests, Federal interest had been directed to improving the river for navigation. In 1824, the Army Corps of Engineers undertook the removal of snags in the Mississippi River below the mouth of the Missouri River and this work continued on an intermittent basis until 1846 when Congress passed a bill for the general improvement of the Mississippi. Although navigation was the primary objective of this act, flood control was considered and thus began to gain some official recognition as a Federal responsibility. Control of floods of the Mississippi River was further recognized as a Federal responsibility in the act of March 1, 1917, which provided for Federal participation in construction of works for control of floods of the Mississippi River, subject to the requirements that local interests contribute one-half the construction and repair cost of levees, furnish necessary rights-of-way for levees, and maintain the completed levees. Destructive floods frequently overtopped or broke the levee systems and inundated large portions of the alluvial valley. This history of frequent flooding culminated in the great flood of 1927.

The great flood of 1927.-The flood of 1927 was the most disastrous in the history of the lower Mississippi Valley. In spite of the flood control work accomplished by local interests in the alluvial valley at a cost of $292 million, a figure equivalent to more than $1 billion today, and the flood control work accomplished by the Federal Government, the main river levees were breached at 13 locations. About 26,000 square miles of the 35,000 square miles in the valley were inundated. Cities, towns, and farms were flooded, crops were destroyed and industry paralyzed. Property damage amounted to about $236 million which is equivalent to $930 million today. Two hundred fourteen lives were lost and 637,000 persons were displaced.

This disaster awakened the national conscience to the dire need for flood control in the lower valley. Out of it grew the Flood Control Act of 1928, which is the basic authority under which the project is being constructed.

The Flood Control Act of 1928.-The act of 1928 authorized a Federal project to provide flood control in the alluvial valley, and navigation from Cairo to New Orleans. Local interests were charged with furnishing rights-of-way for the levees and the maintenance of the levees.

The basic project has been modified and expanded by several congressional acts since 1928 to include: (a) reservoirs, floodways, and levees for the control of floods; (b) major drainage in tributary basins; (c) levees to protect backwater areas from all except very large floods; (d) improvement of the channel of the Mississippi by means of cutoffs, dikes, dredging, and bank stabilization; (e) an ultimate 12-foot minimum depth for navigation; (f) control measures at Old River to prevent eventual capture of the entire flow of the Mississippi River by the shorter Atchafalaya River route; and (g) harbor developments at Memphis, Greenville, Vicksburg, and Baton Rouge.

Effectiveness of project.-Up to the present time, appropriations totaling about $1.4 billion have been made for the project. As a result of the work accomplished with these funds, there has been, with one exception, no failure of flood control works and no general overflow of the valley since 1928, despite high waters that

have reached record stages at some points within the valley. This long period of freedom from major flood damage has created a feeling of security in the valley which did not exist previously. The result has been a tremendous advance in the social and economic development of this part of the Nation.

The effectiveness of the completed flood control works and the soundness of the plan have been amply demonstrated during high water periods; for example, although the flood of 1927 is generally considered to be the greatest flood to occur in the lower Mississippi Valley in modern times, the flood of 1937 was greater in the area between Cairo and Memphis. In the lower reaches of the river, the control works were given a severe test by the flood of 1945. The most recent high water experienced in the lower Mississippi River Valley was that of 1950 when, although flood damage estimated at about $6.6 million occurred in unprotected backwater and tributary areas, the main stem Mississippi River levees and completed tributary works prevented damage estimated at $119 million. Since 1928, the project is estimated to have prevented flood damage of about $74 billion, based on the state of development and price index at the time when the individual floods occurred. This represents a return of more than $5 for every dollar expended to date.

In addition to flood control, 9-foot minimum depths are being maintained in the river for navigation, providing a vital link in the Nation's transportation system. The river is the main stem of a vast network of inland waterways important to domestic and international trade, and over which such important commodities as petroleum, grain, chemicals, and iron and steel products are transported. Between 1954 and 1963, commerce on the river between Cairo and the gulf increased from about 70 million tons to 135 million tons annually. It is significant that the tonnages have doubled at about 10-year intervals since 1930. Development in the valley.-The security against floods and availability of water transportation have led to a phenomenal development in the valley. In fact, the rate of growth in the valley has far exceeded the national average. Between 1940 and 1960, the value of the gross national product increased about fivefold from $100 billion to $503 billion. Value added by manufacture in the alluvial valley increased sevenfold from $155 million to $1.1 billion during the period. Personal incomes increased 12 times from $310 million to $3.8 billion.

In addition to flood control and navigation, the availability of an almost unlimited source of fresh water from the Mississippi River has contributed toward industrial expansion throughout the valley. The multibillion dollar petrochemical complex between Baton Rouge and New Orleans, which has largely come into being since World War II, requires in excess of 5 billion gallons of water per day for industrial purposes. This growing use of the river will assume increasing national importance in the future.

COMPREHENSIVE PLAN OF IMPROVEMENT

General. The comprehensive plan of improvement for the authorized Mississippi River and tributaries project includes—

(a) Levees for containing floodflows;

(b) Floodways for passage of excess flows past critical reaches;

(c) Channel improvement and bank stabilization for increasing the floodcarrying capacity of the main river, for navigation, and for protection of levees; and

(d) Tributary basin improvements for flood control and major drainage. The report contains an evaluation of the authorized improvements under conditions existing in 1956 with price levels adjusted to those existing in 1959. These authorized improvements have been reevaluated to reflect the additional work necessary to make them effective under conditions and price levels existing in 1965.

The report also contains recommendations for additions and modifications to the authorized project that require the approval by Congress. These recommended additions and modifications have also been reevaluated to reflect today's conditions and price levels.

During the reevaluation, the need for additional monetary authorization also became more apparent. The current authorization will be nearly exhausted by the end of fiscal year 1966 as only about $26 million-a sum equivalent to about one-half year's work-will remain unappropriated by that date.

Plates 2, 3, and 4 of the report show the comprehensive plan of improvement. Table 1, page 300, contains a summary of costs for the individual features of the plan. This table adjusts the estimated costs in the report to reflect the cost of each feature after it has been reevaluated under 1965 conditions and price levels. Both the improvements now authorized and the new work requiring authorization are tabulated.