24 POPULAR SCIENCE MONTHLY 



could be added, and the only possible source of increased volume is 

 by giving the Great Lakes an artificial outlet by way of the Illinois 

 Eiver. A certain amount of diversion or rearrangement of tributaries 

 would be possible, though not very practicable, as in getting rid of the 

 load of sediment from the Missouri, or in turning the Tennessee 

 through the Big Hatchie Eiver to reduce the Ohio floods. But in all 

 of these radical schemes the possible benefits to be derived are far out- 

 weighed by the inevitable difficulties and disadvantages. It is unques- 

 tioned that the tributary system must remain as it is now. 



The construction of artificial outlet channels to take off the excess 

 volumes which produce floods has been suggested many times, and it 

 seems likely that if constructed in sufficient numbers they would prove 

 effective. There would, however, always be great difficulty in keeping 

 the outlets sufficiently free from sand so that their usefulness should 

 remain unimpaired. A second and more serious objection to the outlet 

 scheme is that in the lower valley, where the flood control is most 

 difficult and the flood damage most wide-spread, the outlets would have 

 to be provided by turning the water over the low-lying bottom lands. 

 Outlet reservoirs could not be maintained because of the sand and mud 

 with which they would be speedily filled. Under such conditions, there- 

 fore, the outlet plan clearly defeats one of the chief objects of flood 

 control — the protection of rich plantations covering thousands of square 

 miles on the river bottoms. 



The solution by building a series of reservoirs in the head-waters 

 'of the chief tributaries appears to be the cheapest and most certain 

 remedy for all these difficulties. By the construction of reservoirs the 

 excess of water which produces flood stages could be impounded and 

 held up with these important results : excessive and destructive high- 

 water stages could not occur, while, on the other hand, by regulating 

 the discharge from the reservoirs, a more even flow of water could be 

 maintained at all times, eliminating to a large degree the losses from 

 diminished water supply, reduced power and fouling of streams inci- 

 dent to the low stages of late summer and early autumn. As soon as 

 the irresistible rush of flood waters is stopped the sapping and caving 

 of banks will be reduced to a minimum, with the efficiency of revet- 

 ments increased many fold; finally, cutting down the flood volumes 

 means a great diminution of the amount of sediment carried, and a 

 marked alleviation of the sand-bar evil. The reservoirs would, more- 

 over, eliminate floods from the whole system, not merely from the 

 lower course. The prevention of the annual flood damage in the Ohio 

 would in itself be worth the entire cost of the reservoirs, yet until the 

 work of control is carried to the headwaters no relief can be secured 

 for that populous valley. 



The solution by head-water reservoirs, of all proposed plans, has 

 probably provoked the most discussion — on the one side, those who 



