LTkS /'roccrdiiif/K of Indidiui Aaidoini of Science. 



Vig. 4. ()ltli(|uc \u'w across the "Cut-off Col" from the soiithwest. The 

 deeply intrenched reversed draiuasje of the Invadin.i: portion of Upper 

 Cut-off Creek is shown in the hack-f^round. 



took phice. Thus, tliis planation piracy started uormal successive head- 

 ward erosion i>iracy." Tliis type of piracy is uot yet complete in tlie area. 

 Otlier small ravines to the west of the col will eventually he taken into 

 the upper stream system. This successive piracy proceediufj down the 

 cour.si' of the old parent stream will continue until the gradients of the new 

 reveised stream and Lower Cut-off Creek are in a balanced condition. Thus 

 Cut-off Col may be expected to migrate west of its present position prob- 

 ably as much as a half-mile before the balanced condition is attained. 



The whole basin of former Cut-off Creek had an area of some 1,040 

 acres. Inanediately following the planation piracy this area was divided 

 into an upper basin of api>roximately 2<tO acres in area and a lower basin 

 of about ISO acres. On account of the headward erosion piracy following 

 the ]ilanation piracy. T'pper Cut-oft" Creek stream system now consists of a 

 drainage basin of approximately 400 acres in area, while the lower 

 stream ba.sin has dwindled to approximately 040 acres in area. AVhen the 

 gradients of the present invading portion of the upper stream and the lower 

 stream have reached a balanced condition, it is probable that the basins 

 of the two stream systems will be approximately ecpial. as it appears that 

 some T_'() acres in area will be taken from the lower system by the invad- 

 ing part of the upper system. 



A^ummari/ and Conclusion. 



The subject matter of this paper is introduced by a definition of stream 

 piracy and a classification of the tyi)es. The classification simply defines 



^The writer has described a ease of suecessive headward erosion stream piracy 

 in detail in a paper entitled "Some Special Physiographic Features of the Knob- 

 stone Cuesta Region of Southern Indiana", Proceedings of the Indiana Academy of 

 Science, 1919. The expression "successive lieadward erosion piracy" is rather 

 bunglesome, but should be easily understandable. 



