ILLINOIS RIVER DRAINAGE BASIN. 505 



floods from that stream (Cooley). These flood plains have been built up 

 by overflow to about the average high-water level. 



At Joliet an eastern tributary — Hickory Creek — having a watershed < »f 

 130 square miles, enters the valley and forms a limited area of flood plain 

 in its delta. Its source is in the midst of the Valparaiso moraine. Another 

 eastern tributary — Jackson Creek — having a watershed of about 86 square 

 miles, enters nearly opposite the mouth of the Dupage and helps to swell 

 the lower Des Plaines. This stream heads in the main belt of the Valpa- 

 raiso system and passes through the outer ridge of that system just north of 

 Elwood. 



The Dupage River, which enters only 4 miles above the junction of 

 the Des Plaines with the Kankakee, has a watershed of about 366 square 

 miles. It drains the plain lying between the Minooka till ridge and the 

 Valparaiso morainic system. Its east branch for a few mile's flows south- 

 ward between the outer ridge and the main moraine of the Valparaiso 

 system, but passes westward through a gap in this ridge before uniting with 

 the west branch. 



The old lake outlet down the Des Plaines, the channels connecting 

 the Des Plaines with the lower Dupage, aiid the gravel terraces on each 

 stream, have received attention on preceding pages. 



KANKAKEE RIVER. 



The Kankakee River, which unites with the Des Plaines to form the 

 Illinois, drains an estimated area of 5,146 square miles, of which 3,040 

 square miles lie in Indiana and the remainder in Illinois. The general 

 trend of its watershed is east to west, and the extreme length is about 200 

 miles. The greatest width from north to south is about 70 miles. 



The watershed has its northern limits in the Valparaiso morainic system, 

 and all the important northern tributaries find their sources in this morainic 

 system. Its southern limits in the portion below the mouth of the Iroquois 

 are found in the Marseilles moraine. The Iroquois is a somewhat distinct 

 watershed, draining basins south of the Iroquois and Marseilles moraines 

 and passing through a g*ap in the Marseilles moraine to enter the Kankakee. 

 There is no well-defined ridge separating its watershed from the Wabash 

 watershed. The eastern limits of the Kankakee watershed are mainly in 

 the Maxinkuckee moraine of the Saginaw lobe, but Yellow River drains a 



