141 



The Woek Done by Noemal Beook in Thirteen Yeaes. 



By Chaeles R. Dryer and Melvin K. Dams. 



A small stream ^Ybich enters the Wabash Yalley three miles east of 

 Terre Haute attracted the attention of the senior author of this paper many 

 years ago by its remarl^able meanders. Within a length of 1,000 feet it 

 [)resents most of the phenomena characteristic of the lo\Yer Mississippi, 

 and it has been Yisited so often by geography and geology classes from the 

 Normal school that it has acquired the name of Normal brook. 



The stream rises by two principal forks ^Yhich drain about a square 

 mile of Illinoian glacial clay plain, cuts through the east blulf of the 

 Wabash Yalley and is lost upon the great graYcl terrace belo\Y, by percola- 

 tion and cYaporation. Along the edge of the bluff the clay OYcrlaid by a 

 belt of sand dunes about half a mile \Yide, and the most interesting part 

 of the stream, is that ^Yhere it passes through the dune belt. A hasty 

 surYey of this part of the Yalley was made in 1S97 and a map of it was 

 published In the Inland Educator for June, 1S9S. During the past season 

 (1910) a second and more careful sn.rYey has been made and a comparison 

 of the two maps shoYS the changes which liaYe taken place in thirteen 

 years. (See Figs. 1 and 2.) 



The part of the Yalley shown measures along the median line 1,1.50 

 feet, while the stream, Ity its meanders measures 1,960 feet, an excess of 

 68 per cent. In the u])per 050 feet of the Yalloy the length of the stream 

 is 1,360 feet, an excess of 109 per cent. The valley floor, 100 to 200 feet 

 wide, is flat flood plain liounded by bluffs 2.5 to 40 fett high. The ma- 

 terial exposed on the floor is wholly alluYial, mostly sand with occasional 

 bars of fine gravel and beds of tough, blue clay. In the valley floor the 

 stream has cut a channel 20-70 feet wide and three to six feet deep. The 

 stream is perennial ana in ordinary stages is a thread of clear water four 

 or five feet wide and six incjies to a foot deep, which is much more crooked 

 than the channel. In times of flood it fills the clianucl, but has never, in 

 seventeen years of obser\^ation, overflowed the valley floor. 



Sharp zigzags, oxbow bends, cut-offs, caving banks on the outside and 

 bars on the inside of the bends are numerous. 



