604 



MISSISSIPPI RIVER IMPROVEMENT. 



name, have, in low water, proved almost im- 

 .!)lo, having a depth of only from fifteen 

 to twenty-four inches. This company, in 1870, 

 placed a jetty of willow mattresses in Snaggy 

 Bar, and in forty-eight hours the depth had 

 increased from twenty inches to five and a half 

 feet. In 1877, after the high water, the jetty 

 \\a> found intact, and, during the extremely 

 low water of that year, there was a steep chan- 

 nel and not a moment's detention to navigation. 

 Tho company, in the autumn of 1877, placed 

 jetties on Alexandria Bar, where their boats, 

 after transshipment of cargo, could not pull 

 across. From sixteen inches, a four and a half 

 to live feet channel was gained, although the 

 river continued to fall during several weeks 

 afterward. Freight charges, in consequence, 

 were lowered one third. 



Between the Red River and the Gulf of 

 Mexico, the prairies west of the Teche and the 

 Mississippi, exists a net-work of rivers and 

 hayous. Sloping hoth south and east, it has a 

 double system of drainage. The more west- 

 erly of these water-courses are in a state of 

 decadence, the more easterly are increasing. 

 The deposits of the Red River are clearly 

 traceable in their 4 banks, showing that at differ- 

 ent times that stream has poured through 

 each of them. It seems probable that the 

 Robert, Boauf, and Teche Bayous once consti- 

 tuted the main continuation of the Red, while 

 the Atchafalaya was the lower trunk of the 

 Black and Ouachita, and a clear stream. These 

 various changes have occurred during high 

 water, from their tendency, through the slope 

 of the valley, to seek an easterly debouchure. 

 Choked by the raft, which moves steadily up 

 stream, from accretion at the head and decay 

 at the foot, the Red River seeks lateral outlets. 

 At one time the Atchafalaya, thirty miles from 

 the Mississippi, was covered with rafts which 

 became solid floating bridges. The State of 

 Louisiana undertook the removal of this ob- 

 struction, and the rapid enlargement of the 

 stream followed. The old residents testify that 

 whereas it was shot-gun distance across, it is 

 now fully rifle-distance. Its navigation is now 

 good, but the fine plantations that once bor- 

 dered it are wholly abandoned, and lands once 

 above overflow are at present constantly sub- 

 merged. Yet the increase of the Atchafalaya 

 as an outlet of the Mississippi has caused no re- 

 duction of the flood elevation of that river. 



Tho distance to the Gulf by the Atchafalaya 

 is 160 miles and the average fall per mile is 3f 

 inches, while the distance by the Mississippi is 

 327 miles, and the fall less than If inch per 

 mile. The flood and low-water grades of the 

 Red and Atchafalaya Rivers are below those of 

 the Mississippi in the same latitude. 



The commission apprehend the enlargement 

 of the Atchafalaya, even to the point of becom- 

 ing the main river. The diversion of the dis- 

 charge of the Mississippi would impair the nav- 

 igation below and through the jetties, jeopard- 

 izing the commerce of the valley and the in- 



terests of its port, while the establishment of 

 favorable navigation through the Atchafalaya 

 could only belong to some distant and doubtful 

 day. The commission, therefore, recommend 

 the building of a continuous brush-sill across 

 Old River, between Turnbull's Island and the 

 Mississippi, with the object of checking the en- 

 largement of that outlet. 



Floods of an abnormal nature occurred in 

 the Missouri during the spring of 1881. The 

 preceding winter was umisually severe, and the 

 river was entirely closed in November. A 

 February thaw caused an overflow and 

 piled up ice. When the spring rises began, 

 these gorges broke above Sioux City, and the 

 snow-water came sweeping down, submerging 

 the valley for 600 miles. One flood came down 

 on the 7th of April and another on the 22d. 

 The river was out of its bed. It was trans- 

 ferred from its ordinary section to one of slight 

 depth and great width. The slope was nearly 

 doubled, but owing to frictional resistance the 

 rear water piled upon that in front and pro- 

 duced the unusual rise of from five to eight 

 feet. 



Hence, if the flood had been restrained by levees 

 where necessary, and, still better, if the high-water 

 section had been reduced to any approximately uni- 

 form and suitable width, the water-surface would no- 

 where have surpassed, and would generally have fallen 

 much below, the level of the present banks. . . . Any 

 fill which took place in the bed proper during the 

 overflow, was pretty much scoured put on the falling 

 stage, after the river got within its banks again. 

 From all points it was reported that during this period 

 the force and velocity of the current were extraordina- 

 ry. Bars which had been permanent fixtures for years 

 were removed and a general deepening was noticed on 

 all sounded sections. But on islands and bars which 

 were sheltered from this great scour, the depth of the 

 deposit gives sufficient evidence of the extent to which 

 fill took place during the overflow. 



Extensive changes in the channel resulted, 

 which exercised a serious influence on the pro- 

 jected system of improvement. 



Up to a recent date it has been supposed that 

 the bed of the Mississippi consists of layers of 

 tenacious blue clay belonging to the tertiary 

 formation, so little susceptible of erosion that 

 it is practically permanent. To determine this 

 point, under the direction of the Engineer De- 

 partment of the United States Army, and lat- 

 terly of the commission, borings in eighty- 

 three places have been made. Though these 

 borings were not less than one hundred, and 

 oftentimes more than two hundred feet in 

 depth, only twenty-two pierced the alluvial 

 deposits and reached the underlying tertiary 

 beds. It appears, then, that the great trough 

 in which the river runs was hollowed for a 

 still mightier stream. 



The depth of these alluvial beds averaging 

 one hundred and thirty-one feet below high 

 water of 1880, it follows that it can only be in 

 exceptional cases that the river scours down to 

 the clay, and there is space for deepening, 

 should it ever become desirable. Nor would 

 this underlying stratum offer insuperable diffi- 



