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INDIANA UNIVERSITY STUDIES 



It may lay in the form of alluvial material for centuries before it 

 is removed to its final resting place in the ocean. A summary 

 of the denudational processes in the United States is given in 

 'Water Supply Paper No. 234/ by Dole and Stabler. The last 

 paragraph is as follows: 



The estimates reveal that the surface of the United States is being re- 

 moved at the rate of thirteen ten-thousandths of an inch per year, or one inch 

 in 760 years. Though this amount seems trivial, when spread over the surface 

 of the country, it becomes stupendous when considered as a whole, for over 

 270,000,000 tons of dissolved matter and 513,000,000 tons of suspended matter 

 are transported to tide water every year by the rivers of the United States. 

 This total of 783,000,000 tons represents more than 350,000,000 cubic yards 

 of rock substance, or 610,000,000 cubic yards of surface soil. If this erosive 

 action had been concentrated upon the Isthmus of Panama at the time of 

 American occupation, it would have excavated the prism for an eighty-five 

 foot sea level canal in about seventy-three days. 



It has been shown by Humphreys and Abbott that the Missis- 

 sippi River alone transports enough sediment to tide-water in 

 one year to build up a tract of swamp land 268 square miles in 

 area one foot in depth. There has been no consistent effort to- 

 ward using this enormous quantity of sediment that the rivers of 

 the United States carry to the ocean, and as a result all of this good 

 soil is lost. In the case of the Mississippi River, the sediment 

 might be used to build up some of the vast areas of swamp land 

 along its lower course, so that something besides malaria might be 

 produced where the swamps now are. 



The manner in which material is acquired by running water, 

 the way in which it is carried, the effect it has on the bottom and 

 sides of a stream, and how it modifies the flood plain in times of 

 flood can be ascertained by the careful study of a single stream. 

 We think, ordinarily, that the function of a stream is to carry away 

 the stupendous amount of flood water and the general run-off, 

 while in reality its purpose is that of leveling. Salisbury says 

 the purpose of a stream is to carry the lithosphere into the hy- 

 drosphere. The term 'leveling' may seem contradictory to the 

 previous statement that streams make hills and valleys; but leveling 

 is their function in that they reduce, very slowly to be sure, the land 

 to sea level, or approaching it. They etch their way into the plains 

 and cut them into hills and valleys and these hills are in turn worn 

 to a base level. No one person can live long enough to see the life 

 history of any one stream completed, but the physiographer sees 

 many examples of streams representing all stages between youth 

 and old age. He may see stages in which the stream has all of its 



