006 



MISSISSIPPI KIVER IMPROVEMENT. 



of it which would otherwise be lost from the dejfrada- 

 tion of the banks. 



It may be said of outlets (which term we restrict 

 t<> well-defined depressions connecting the river with 

 the s\\ amps and their drains on either .side, while it is 

 .still within its banks) that, whenever they are directly 

 connected with the improvement and maintenance 

 of navigation, they should be efficiently and perma- 

 nently closed. 



the volume and elevation of the river 

 constant from season to season, as it flows 

 through yielding soil, it would adjust itself to 

 its bed and find a permanent pathway. But 

 in flood and at its low stage there are such dif- 

 tori-nces of elevation, velocity, and new direc- 

 tion alternately flowing along the same general 

 i -nurse, each modifying the mold of the other, 

 and each obstructed by the other's work, that 

 in effect they are two different streams. All 

 these intricate questions of action and reaction, 

 each exercising a controlling influence as the 

 river rises, falls, or rests at the intermediate 

 stage, have a practical bearing on the revet- 

 ments and contraction works. 



On April 27, 1876, the river broke through a 

 long peninsula jutting out from the Louisiana 

 shore in front of Vicksburg. This cut-off 

 changed the channel, and its damaging effects 

 may be traced for two hundred miles. The 

 harbor of Vicksbnrg, once the finest on the 

 river, began to silt up, and the changes were so 

 rapid and so alarming that a board of engineer 

 officers was convened, who recommended re- 

 vetments and dikes, followed by dredging out 

 of the harbor, and, if these prove insufficient, 

 that the Yazoo River be diverted, to assist in 

 keeping open the lake that is forming. Con- 

 gress has already expended $229,000 on these 

 works; but, before they had progressed suffi- 

 ciently to arrest the filling process, the lower 

 part of the harbor received so much deposit that 

 it goes dry at twenty feet above low water. 

 Though the upper end is still open, the channel 

 is so circuitous that at low stage the wharf- 

 boats are moved down below the bar two 

 miles from the old landing. The dredging and 

 revetment now needed will cost $436,000. 

 Only after their completion need the question 

 of diverting the Yazoo be considered. 



Above St. Louis the Mississippi is a clear 

 river. The Missouri brings a vast amount of 

 sediment. At St. Charles, in 1879, the sedi- 

 ment, by weight amounted to 5-| 7 part of the to- 

 tal river-discharge, and on July 4th it was ^7- of 

 the discharge. If no sediment is derived from 

 the upper river, the average sediment ratio of 

 the Mississippi below the junction is y^. The 

 effect of this sediment is felt far down. At 

 Carrollton it averages T5 V?r an( l at Columbus 

 nVy The low-water discharge at St. Louis is 

 about 47,000 cubic feet per second ; the high- 

 water discharge is twenty times as great. At 

 St. Louis the range in stage is thirty-seven and 

 at Cairo fifty-one feet. 



Between St. Louis and the mouth of the 

 Ohio the Mississippi flows within rock bluffs, 

 or else wanders between alluvial valleys with 



caving banks. There are points of shifting 

 shoals and bad navigation wherever the river 

 is more than 2,500 feet wide. At Kaskaskia, 

 sixty-three miles from St. Louis, and sixteen 

 miles below that city, at Widow Beard's Isl- 

 and, during low water, the channel gave four 

 feet. A uniform minimum depth of ten feet 

 is attainable by the same means applied to the 

 lower river, except at Grand Chain, where re- 

 moval of bowlders and points of rock is advis- 

 able. 



The committee desire additional legislation 

 to define their powers and appoint the manner 

 in which owners are to be compensated for 

 material used. An ascertained authority over 

 the river and over the newly-formed banks, 

 where willows and other trees must be planted, 

 is necessary to prosecute the work successfully. 

 The report of the commission is a statement of 

 facts, not theories. None the less it is a con- 

 clusive argument against outlets, and for closed 

 gaps, continuous levees, narrow banks, and the 

 jetty system. The Atchafalaya is an "out- 

 let," and apparently one of most formidable 

 proportions. Between 1851 and 1870, at its 

 head, the cross-section increased from 24,400 

 to 52,100 feet. Between 1878 and 1879 the 

 discharge swelled from 120,000 to 180,000 

 cubic feet per second. Within fifty years the 

 discharge of that river has trebled. Already 

 one sixth of the volume of the Mississippi 

 passes through the Atchafalaya. '' The eleva- 

 tion of the water-surface of the junction of Old 

 River and the Mississippi," says the report, 

 "is almost constantly above that at the head 

 of the Atchafalaya, the difference on the 13th 

 of last October being 7 T 3 T feet in a distance of 

 about five miles." A fall like this of over a 

 foot a mile is sufficient to drain the Mississippi, 

 which is now, with the Red River, tributary 

 to the Atchafalaya. Those whose zeal with- 

 out knowledge propose outlets as a remedy 

 for all perils by shoal and flood, should learn 

 by the "inexorable logic of events" that the 

 bed of the Atchafalaya has been deepened and 

 its flood-surface lowered by the additional vol- 

 ume of water sweeping through it; while the 

 Mississippi, under the injurious effects of its 

 outlet, shows a higher elevation of the flood 

 level, menacing the country above Red River 

 with overflow ; and the lower river, shorn of 

 its due proportions, can no longer sweep out 

 its own pathway, bearing onward silt and de- 

 bris through stable banks and jetties to drop 

 them into the deep waters of the Gulf of Mex- 

 ico. 



The report embodies the results of a careful 

 study of data in regard to slope, velocity, sedi- 

 ment, and the mutual relations of river sec- 

 tions under different conditions of discharge 

 and curvature and reservoir action. " It needs 

 no argument to prove that drainage and recla- 

 mation of swamps and wet lands generally 

 must be destructive of the natural reservoir 

 action, and hence that the variations of vol- 

 ume of any given stream wih 1 be more extreme 



