Ch. 18] MISSOURI RIVER 331 



longer operational. Only the Big Sandy and Cumberland projects are 

 considered worthy of modernization. 



The Tennessee River, largest tributary of the Ohio, is canalized by 

 high dams built by the Tennessee Valley Authority principally for 

 electric power production. This might be considered an extreme form 

 of channel control, in which the river is converted into a continuous 

 series of reservoirs. 



The entire Ohio River system of 137 locks and dams provides nearly 

 3,000 miles of canalized channels. 



Missouri River 



The Missouri River was an important traffic route during the period 

 of western settlement, but shallow-draft steamboat navigation practi- 

 cally ceased by 1880. The Missouri River Commission, established in 

 1884, inaugurated a policy of regulation by training dikes, bank re- 

 vetment, and dredging, which was carried on by the Commission in a 

 small way until 1902, and subsequently by the Corps of Engineers, 

 but effective results were not obtained until after 1928, when the scale 

 of work was increased. The regulation works for a channel 6 feet deep 

 were sufficiently complete so that regular barge transport was in- 

 augurated up to Kansas City in 1935, and extended in 1939 to Omaha, 

 632 miles above the mouth. In 1945 the project was modified to pro- 

 vide a navigation channel 9 feet deep and 300 feet wide to Sioux City, 

 760 miles above the mouth. This project is about 85 percent complete. 

 The Fort Peck multiple-purpose reservoir on the headwaters provides 

 supplemental water at times of deficient natural discharge. 



In its natural state the Missouri River below Sioux City had many 

 sand bars and islands within a channel varying from 1,500 feet to 1 

 mile in width, meandering irregularly within a flood plain 1% to more 

 than 10 miles wide, underlain by about 100 feet of alluvial deposits 

 which are mostly sand, with a surficial silt and clay cover generally 

 less than 10 feet thick. Bank erosion was very active, and shifting 

 channels were a serious hazard both to navigation and to use of the 

 alluvial plain for agriculture. 



Now most of the river below Sioux City has been converted into a 

 narrower, regularly curving channel with comparatively stable banks, 

 as illustrated in Figs. 1 and 2. The low-water channel widths are 

 generally 700 to 1,100 feet, increasing progressively downstream, with 

 bends 2 to 5 miles long having a minimum radius of 4,000 feet and 

 maximum radius of about 20,000 feet, the optimum radius being 7,000 

 to 10,000 feet, increasing downstream. Where possible, the radius of 

 curvature is made to decrease from head to foot through a bend. 



