CHAPTER III. 

 DRAINAGE SYSTEMS. 



SECTION I. OHIO RIVER SYSTEM. 



This great river system, with an area of over 200,000 square miles, 

 drains all of the region under discussion except a narrow strip on the north, 

 which is tributar3^ to the Grreat Lakes. Its drainage area also extends 

 eastward to, and in places slightly beyond, the crest of the Allegheny 

 Mountains and southward to the border of the Grulf States. Only the 

 part which has been glaciated or somewhat directly affected by glaciation 

 will fall within the limits of the present discussion, and of this part space 

 will permit the treatment of only the more salient features. The valley of 

 the Ohio is first discussed, and then the northern tributaries are taken in 

 succession, beginning with the Allegheny and passing westward to the 

 Wabash. 



OHIO RIVER. 



RATE OF FALL. 



The Ohio River, foi'med by the junction of the Allegheny and Monon- 

 gahela at Pittsburg, Pa., and connecting with the Mississippi at Cairo, 111., 

 has a length of 967 miles.^ It falls from 701 feet above tide at Pittsburg 

 to 275 feet at Cairo, or 426 feet, which is but little more than 5 inches per 

 mile. The fall, however, is somewhat irregular. In the first 15 miles it is 

 about 19 inches per mile, and in the first 26 miles, to Beaver, 16 inches. 

 From Beaver to Wheeling, 64 miles, it is reduced to about 10 inches per 

 mile, and from Wheeling to the head of the Louisville Rapids, 507 miles, 

 to 5 inches per mile. At the rapids a descent of 23.09 feet is inade in 



^A table exhibiting the profile of the Ohio River appears in the report of the U. S. Army Engi- 

 neers on the survey of the Ohio River for 1870-71 (House Doc. No. 72, Forty-first Congress, third 

 session, January, 1871, pp. 139-15.3). Corrections for elevations at important points on the Ohio are 

 represented on a map of the State of Ohio and adjacent territory, which accompanies a report by Capt. 

 H. M. Chittenden on the survey of the canal routes in Ohio (House Doc. No. 278, Fifty-fourth 

 Congress, first session, March, 1896). A profile from Pittsburg to Wheeling, correcting that part of 

 the earlier surveys, accompanies Appendix DD of Ann. Rept. U. S. xVrmy Engineers for 1889, p. 1872. 

 A diagram and table showing the profile of the Ohio River are in Water-Supply and Irrigation Papers of 

 the U. S. Geol. Survey No. 44, Rivers in the United States, by Henry Gannett, pp. 41-43, PI. V. 

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