302 A. G. LEONARD DRAINAGE CHANGES IN NORTH DAKOTA 



old valley floor, so that now the tributaries of Kedwing Creek meander 

 over the flats in shallow trenches cut in the valley plain. 



That portion of Squaw Creek above the sharp bend was formerly a 

 tributary of the Little Missouri when it occupied the old valley. But in 

 postglacial time the young and vigorous Squaw Creek, which is now tribu- 

 tary to the Little Missouri of today, with a fall of about 22 feet per mile, 

 worked its way back until it captured the northward flowing tributary of 

 the preglacial river and diverted the waters to the south, thus forming 

 the sharp bend in the present course of Squaw Creek. 



The abnormal features of the Cherry Creek drainage are even more 

 striking than those of Kedwing Creek. The upper valley from Elsworth 

 to the bend several miles north of Schafer is broad, the valley floor being 

 in many places from one to one and one-half miles wide; the side slopes 

 are for the most part gentle, and the rather numerous tributaries enter 

 by broad, flat-bottomed valleys. In contrast to this the lower valley is 

 comparatively narrow, from one-quarter to one-half mile wide, and the 

 side walls are quite steep. In its upper course the creek has an average 

 fall of 7.4 feet per mile, while below the bend the average fall is almost 

 10 feet per mile. The normal stream has its broad flats along its lower 

 course, where the fall is also less than in the upper portions of its valley. 

 The explanation for the abnormal features of Cherry Creek is clearly to 

 be found in the fact that above the bend near Schafer it follows the old 

 preglacial valley of the Little Missouri Eiver, while below the bend it 

 flows in a much younger postglacial valley. After the Little Missouri 

 had been forced by the ice-sheet from its former valley and had cut its 

 present trench, a tributary developed and extended itself by headward 

 erosion, forming the present lower valley of Cherry Creek. This vigorous 

 young stream worked back until it reached the preglacial valley of the 

 Little Missouri and captured the upper portion of the creek flowing 

 through it, diverting it to its present southeasterly course below the bend 

 where the piracy took place. With such a development the Cherry Creek 

 drainage would possess the abnormal features mentioned above. 



Evidence of postglacial Age of Lower Little Missouri Valley 



When the Little Missouri River was forced by the ice-sheet to seek a 

 new channel, it probably flowed for a time through the Pleistocene valley 

 of the Missouri and Yellowstone rivers, previously described. But later 

 it took an easterly course and formed its present postglacial valley, which 

 extends from the mouth of Bowling Creek to the Missouri River, a dis- 

 tance of 100 miles. There is abundant evidence that this lower valley of 



