168 PUBLIC PARKS OF IOWA 



DRAINAGE OF CERRO GORDO COUNTY. 

 By Samuel Calvin. 



With respect to drainage, as in the case of topography, Cerro Gordo 

 county is divisible into two areas. The portion of the county occupied 

 by lowan drift has relatively perfect drainage, and the stream channels 

 are fairly well defined. With the exception of that part of the channel 

 of Lime creek which passes through the northwest corner of Grant town- 

 ship, it can scarcely be said that there is a well defined water course 

 in the area of the Altamont moraine. 



Lime Creek. Lime creek drains the larger part of Cerro Goro county. 

 It enters the county from the southwest, and in the first part of its 

 course it traverses the morainic belt already described. Entering Grant 

 township in section 19, the stream flows northeast and passes into Worth 

 county. Soon after entering Worth its direction is changed toward the 

 east, and after flowing eastward for a few miles it escapes from the 

 moraine and enters upon the area of lowan drift. Here its course be- 

 comes normal for streams in this part of Iowa. It flows southeast, and 

 soon re-enters Cerro Gordo county, crossing the north line of section 5 

 of Lincoln township. From this point its course is in the main southeast 

 until it leaves the county at the east line of section 36 of Portland town- 

 ship. 



Within the morainic belt, in Grant township, the course of Lime creek 

 is very tortuous, since, of necessity it winds back and forth to avoid the 

 lawlessly disposed knobs and hills of drift. In this region the channel 

 is new, dating only from the retreat of the Wisconsin ice. It is now a 

 mere shallow trough in loose glacial detritus, showing only an incon- 

 siderable amount of erosion since the stream began work upon it. There 

 is here properly no river valley, nor are there any tributary streams with 

 definitely marked channels. The drainage waters from .adjacent lands 

 find their way into Lime creek, sometimes by very roundabout courses, 

 along broad, flat-bottomed swales, or through reedy, ill-drained marshes. 

 In the lowan drift area, however, Lime creek follows a preglacial valley 

 that was originally in places two or three miles in width. In depth the 

 valley varies from twenty to seventy feet. Its history is well recorded 

 in the western part of Lime Creek township. Here the present stream 

 flows in a small, shallow and narrow channel near the southern margin of 

 the valley. The south bank of the stream rises abruptly to a height 

 of thirty or forty feet. On the north side a plain with gentle slope be- 

 gins near the level of the water and extends back to a terrace that is 

 eight or ten feet in height. At the summit of the terrace there begins 

 another plain that may be two miles or more in width, and is terminated 

 on the north by an irregular line of low hills. The history seems to 

 have been as follows: The preglacial valley had a width reaching 

 from the south bank of the present stream to the line of hills which form 

 the northern border of the second plain noted above. The sub-Aftonian 

 drift, if it was ever deposited in this region, cannot be differentiated 

 from the Kansan, but it is certain that at the close of the Kansan stage 

 the old valley was only partially filled with detritys, and an important 



