554 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1916. 



traffic by the river channels are now far in advance of the use made 

 of them. 



In the section between the Missouri River and the Ohio, a length 

 of 200 miles, the character of the river changes ver}'^ noticeably, and 

 we encounter a new class of problems presented hj caving banks 

 and shifting shoals (pi. 2). These shoals are largely made of sand 

 and gravel brought down by the Missouri in flood, and largely by 

 the caving banks carried into the channel by scour. In this section 

 the present project contemplates the maintenance of an 8-foot chan- 

 nel 200 feet wide throughout its entire length. This depth has been 

 kept for many years, but only with constant work. In 1872 the first 

 eifort v\^as made to deepen the shoals, which had then only 3| to 4 

 feet of water on them, using solid dams and dikes of stone and brush 

 to concentrate the low water flow into a single channel. These were 

 only partially successful, and in 1881 the uniform depth of 8 feet 

 was adopted for the entire section, and the use of permeable dikes 

 and hurdles was actively begun. These were found successful in 

 holding and consolidating the moving sediment of the river, and thus 

 providing new banks where needed. In 1907 the project was radi- 

 cally changed as to methods, and since then dredging has been largely 

 relied on for maintenance of the channel. Four hydraulic dredges 

 of large capacity are now used in this work. Bank protection, 

 permeable dikes, and hurdles are still extensively used, however, 

 to produce permanent results. The last estimate of cost, made in 

 1903, was $21,000,000, in addition to the expenditures of about two 

 and a half millions spent up to that time. In all about fourteen and 

 one-half millions of dollars have now been spent, leaving over seven- 

 teen millions to complete the plan, which is now about one-third 

 done. The use of the river for commerce has fallen off to a fraction 

 of its former figures, notwithstanding these large expenditures. This 

 will be shown by the following table of traffic at five-year intervals : 



Freight traffiie by five-year intervals, 1890-1912 {Repts. of Chief of Engineers) . 



Tons. 



1890 1, 299, 670 



1895 838, 900 



1900 810, 230 



Tons. 



1905 470, 093 



1910 191, 915 



1912 205, 720 



In the lower portion of the river, from the Ohio to New Orleans 

 Harbor near the Head of the Passes into the Gulf of Mexico, a length 

 of nearly a thousand miles has been under the charge of the Missis- 

 sippi River Commission since 1879. During all this time many ex- 

 periments have been tried, and much has been learned with regard 

 to this great river. Among the most noteworthy of these lessons is 

 the importance of protecting the banks from caving and the greater 

 reliance that can be placed on the operation of the hydraulic dredge. 



