FLOOD CONTROL SURVEY REPORT-YAZOO RIVER WATERSHED, MISSISSIPPI Presenting a Program of Watershed Treatments, Including Measures To Retard Run-off and Prevent Soil Erosion for the Control of Floods on Valley Lands SUMMARY The Yazoo River Basin of some 5,696,000 acres, drains the northwestern one-quarter of the State of Mississippi. The eastern part of the watershed comprises undulating to hilly uplands with numerous broad valleys. The western half of the basin, the Yazoo delta, is a level alluvial plain which was shared originally with the Mississippi River. Four major tributaries, the Coldwater, Tallahatchie, Yocona, and Yalobusha Rivers drain the uplands and two sluggish streams, the Sunflower River and Steele Bayou, drain the delta. The Yazoo Basin has suffered flood damage since its history has been recorded. Prior to construction of the main Mississippi River levee, major Mississippi River floods inundated a large part of the delta. Even at present about a million acres in the lower delta are subject to Mississippi backwater overflow. Headwater floods originating in the Coldwater, Tallahatchie, Yocona, and Yalobusha Rivers are more frequent and damaging than Mississippi backwater. Future flood and sedimentation damage, in the absence of remedial measures, is estimated at approximately $3,187,000 annually.1 Of the $2,550,000 direct flood damage, $1,800,000 is caused by floodwater and $750,000 is caused by flood-borne sediment. About $637,000 damage is caused indirectly by flooding and sedimentation. Most of the damage is suffered by farmers and most of the farm loss is due to reduction in crop yields. Almost 20 percent of the entire upland area is subject to flood and sediment damage. Lands in the tributary valleys are not infrequently overflowed 10 to 15 times in a single year and 24 floods have been experienced in a year on 1 tributary. The bottom lands along the main upland streams are overflowed at least once each year and in some years several floods are experienced. Floods occurred in the past, even before settlement, but the frequency and severity of flooding have increased during the past century. Two readily apparent circumstances are responsible for more severe flooding, greater storm run-off and choked stream channels. These are sedimentation and increased surface run-off. The fertile upland soils are subject to excessive erosion when exposed. The original forest cover prevented all but incipient erosion, 1 Not included is $1,200,000 annual damage in the Little Tallahatchie River Basin. This situation is discussed in H. Doc. 892, 77th Cong., 2d sess., 1942. but after clearing and the establishment of cotton as the predominant crop, the soil has been left uncovered for much of the year. In consequence, some stream channels are completely filled with the eroded material and the capacity of the upland soils to absorb the rains has been reduced. Conditions are now so severe that a rain of less than an inch may cause damaging flooding. The flood-control program herein proposed by the Department of Agriculture will yield flood and sedimentation-control benefits having an annual value of $1,675,600. Furthermore measures employed in reducing floodwater at its source are all beneficial to crops, both field and forest, and private annual income will be enhanced by $5,487,200. To be added to this would be $968,600 benefits to public agencies, largely in the form of increased income from lands to be acquired. Total annual benefits thus are over $8,131,400. The proposed program, which could be completely installed in 20 years or less, involves the treatment of 2,353,000 acres or 80 percent of all rural lands in the upland portion of the watershed. One of the most essential features of the program is public purchase of some 730,000 acres of submarginal farm land. This land, much of it now abandoned, is so badly deteriorated and its productive and sustaining power is so low that under private ownership it could not possibly carry the cost of the required remedial measures. Revegetation of about 170,000 acres of submarginal land, including 47,000 of badly gullied land also requiring special erosion control measures, is essential. Forest management practices required to regain an adequate cover for optimum water retention and erosion prevention, will be inaugurated on 1,176,000 acres, including 532,000 acres to remain in private ownership. Fire control will be established or strengthened as required on more than 11⁄2 million acres of private and public forest lands. Soil- and water-conservation measures, including terracing, crop rotations, and winter cover crops, will be applied to 269,000 acres of cropland. About 382 miles of diversion terraces will be constructed to protect croplands against damaging run-off from adjacent land. Protective perennial vegetation will be established on 54,000 acres of more seriously eroded cropland. The water-holding and soil-protecting capacity of 407,000 acres of pasture land will be improved by contour furrowing, fertilizing, seeding and planting, and related measures. Road-bank erosion and run-off will be controlled on 4,950 miles of public roads by establishment of protective and permanent vegetation. The cost of installation of the watershed program to the Federal Government will be $21,725,000, to the State and local governments $1,200,000, and to private individuals $2,350,000, or a total over-all cost of $25,275,000. Installation and maintenance costs will total approximately $50,500,000 for the 20-year installation period. The cost to the Federal Government will total approximately $26,300,000, to State and local governments about $1,250,000, and to private individuals approximately $23,000,000. After the installation period, the annus! cost to the Federal Government for maintenance and supervision wil |