THE TOPOGRAPHY AND HYDROGRAPHY OF ILLINOIS Ivii 



Hydrographic conditions in the Wisconsin glaciation have been 

 greatly changed within comparatively recent years by large drainage 

 operations, carried on at public expense under the operation of state 

 law. Swamps, marshes, and lakes have virtually disappeared, and 

 their places have been taken by rich and highly cultivated farms. 

 Much less change has been made in the lower Wabash valley as a 

 consequence of human occupancy, but the original rather general 

 covering of both lowland and upland forest has been mainly re- 

 moved, with the effect to expose the surface to more rapid erosion 

 than heretofore, and to increase the extremes of flood and low water. 



WABASH RIVER 



Wabash River was given, by the earliest explorers, the name 

 of Ouabouskigou, said to mean 'Svhite water" in one of the Indian 

 tongues, and it bears this Indian name on the maps of both Joliet 

 and Marquette. This was later contracted by the French to Oua- 

 bache, the spelling of which has since been simply anglicized. The 

 earlier explorers regarded the lower Ohio and the Wabash as form- 

 ing one stream, to which they gave the latter name, while the upper 

 Ohio bore either its present name or that of "la Belle Riviere." 



The Wabash forms, for 198 miles, the boundary between Indiana 

 and Illinois, lying in this part of its course in a preglacial valley, the 

 former bed of a very much larger stream. This valley, five or six 

 miles across in its upper part, is filled with drift which buries the old 

 stream bed to a depth of 60 or 70 feet, and is bounded by bluffs 

 rising from 100 to 200 feet above the river. The Illinois section of 

 the Wabash has a comparatively sluggish current, its fall being less 

 than eight inches to the mile. 



Two, and in some places three, different levels are distinguish- 

 able in the AVabash valley to-day. The bottom-lands of the river 

 subject to overflow at ordinary high w^ater are from twelve to fifteen 

 feet above the stream, and at about the same height above these are 

 the second bottoms, covered with water only by exceptional floods ; 

 and in some places a terrace level may be traced half-way up the 

 bordering bluff. The river flows for the most part along the western 

 side of its valley, occasionally, indeed, quite close to the bluffs, 

 leaving the bottoms largely on the Indiana side of the stream. The 

 bed of the river is often rocky and the current locally swift, and 

 rapids greatly interfered in early days with the use of the stream for 

 transportation purposes. The waters of the Wabash are, like those 

 of the Illinois and the Kaskaskia, commonly brown and opaque with 



