MISSISSIPPI RIVER IMPROVEMENT. 



of machine-shops and shin-yards, this could 

 only be slowly obtained. The revetments for 

 bank protection and the permeable dikes have 

 therefore not been completed. Nor can their 

 adequacy be estimated until one high-water 

 stage has tested their resisting power, and one 

 low-water stage has shown their actual effect 

 upon the shoals. The detail is experimental, 

 but of the practicability of the general plan for 

 deepening the channel of the river below Cairo 

 to the full extent of the demands of com- 

 merce, the commission do not entertain a doubt. 

 They thus briefly sum up their views : 



The improvement is to be secured by narrowing the 

 low-river channel-way to an approximately unitorm 

 width of three thousand feet in localities where the 

 widths are excessive and the navigation bad, to bo 

 accomplished and rendered permanent through tho 

 agency of such works as will also create comparative 

 uniformity in the width of the high-water channel. 

 For the attainment of this result, two distinct classes 

 of works, differing widely in character and purpose, 

 will be required, viz., revetments for the protection of 

 caving banks, and dikes or other structures for the 

 contraction ot the channel-way. The bank revetments 

 are intended not only to stop the constant and, in some 

 localities, very rapid enlargement produced by erosion 

 and caving of concave bends, but in addition thereto 

 to check the growth of bars and shoals below by ac- 

 cretions rappuad directly therefrom. The process of 

 laying this revetment will vary greatly in different 

 localities, but will commonly, or at least in many cases, 

 consist in first freeing the banks of snags, stumps, ana 

 brush, and then placing a mattress, composed of wire 

 netting overlaid or interlaced with brush, upon that 

 portion of the slope extending from deep water to a 

 lew feet above the water-level, and weighting it with 

 sufficient rip-rap stone to hold it in place. The revet- 

 ment is afterward completed by grading the bank 

 above the water-level to a proper slope with streams 

 of water under high pressure, after the manner com- 

 monly followed in hydraulic mining, and laying there- 

 on a supplementary mattress, overlapping the one 

 previously laid, and < 

 bank. 



. extending up to the crest of the 



More expensive additions of stone and gravel 

 can be safely omitted for some years until the 

 brush decays. A growth of grass and willows 

 can be encouraged, forming the natural and 

 best protection of such banks. Works of this 

 general character have already been employed 

 at points on the Missouri and Mississippi, and 

 they have proved their permanence and utility. 

 The other class of works for narrowing the 

 river have also been executed on these two 

 great rivers. Failures and disappointments are 

 to be expected in dealing with their powerful 

 floods and using novel expedients. These light, 

 permeable dikes, composed of piles, poles, brush, 

 and wire, placed either longitudinally or trans- 

 versely to the channel, do arrest the velocity 

 of the water, cause a deposit of silt, and thus 

 build up new banks, correcting the channel and 

 causing it to deepen itself. Solid structures do 

 not stand in the bed of the Mississippi unless 

 built down to so great a depth that their cost 

 alone would preclude their use. However ex- 

 perimental these slighter methods may appear, 

 impediments to the free flow of the river, suf- 

 ficient to check its velocity, do cause a deposit 

 which builds up a new bank and regulates the 



channel. The absence of precedents, the new 

 modes of construction, the possible existence 

 of gravel-beds requiring to be dredged out, and . 

 the fact that new bars may form where navi- 

 gation is now easy, render it difficult to form 

 a close estimate of the expense. The initial 

 works on the 184 miles of bad navigation be- 

 tween Cairo and Vicksburg were computed to 

 require $4,113,000. Tho additional works to 

 complete and render permanent these improve- 

 ments can not cost more than that sum, amount- 

 ing in all to $8,226,000, or $45,000 per mile for 

 184 miles. "These estimates cover about one 

 fourth of the length of the river where navi- 

 gation needs improvement, viz., from Cairo to 

 Red River; and, assuming that the remaining 

 three fourths will cost proportionately, the ag- 

 gregate cost of the entire improvement would 

 reach $33,000,000. These are outside figures, 

 based on detailed estimates of the worst por- 

 tion of the river." However much they may 

 differ on minor points concerning methods of 

 river regulation, the commission record their 

 unanimous opinion that they can thus main- 

 tain a continuous low-river channel showing 

 a minimum depth of ten feet on all bars and 

 shoals between Cairo and the head of the 

 passes, while there is a strong probability of 

 deepening it much beyond that mark. They 

 are, therefore, " prepared to recommend the 

 application of the methods and details hereto- 

 fore described, to the lower river, from Com- 

 merce, Missouri, downward, with such con- 

 tinuity as will not only improve the immediate 

 localities where navigation is now bad, but will 

 also establish and retain such control over the 

 high-water discharge as will arrest that tend- 

 ency toward deterioration which has rendered 

 the systematic improvement of the entire river 

 necessary. "While this order of progress is 

 proper for works designed to amend and reg- 

 ulate the existing channel, those undertaken 

 for the purpose of retaining or increasing the 

 volume of discharge within the bed, such as 

 levees and dams for closing outlets, should 

 begin below and be carried continuously up- 

 stream." 



The commission repeat (see " Annual Cyclo- 

 paedia," 1880) their opinion of the utility of lev- 

 ees as a means "to prevent destructive floods," 

 which, by confining the flood-waters of the 

 liver within limits, tend to increase the scour- 

 ing and deepening power of the current. Their 

 researches into the early condition of the banks 

 of the Mississippi bring only meager informa- 

 tion. The discoverers and adventurers did not 

 direct their observations in scientific directions. 

 They report that its immediate banks were 

 densely clothed with forests and cane (Arundo 

 gigantea). Cane will not grow on land subject 

 to inundation, therefore it marks the precise 

 limits of habitual overflow. A canebrake is, per- 

 haps, the best possible device to check water en- 

 croachment, by causing a sedimentary deposit 

 and consequent elevation of the bank. Darby 

 (1817) states, in his " Statistics of Louisiana " : 



