UNIVERSITY OF VIRGINIA PUBLICATIONS 



BULLETIN OF THE PHILOSOPHICAL SOCIETY 



SCIENTIFIC SECTION 



Vol. I, No. 20, pp. 437-442 July, 1914 



EXAMPLES OF INTERCISION TYPE OF STREAM PIRACY IN 

 WESTERN VIRGINIA 



THOMAS L. WATSON, JUSTUS H. CLINE, 

 AND THOMAS K. HARNSBERGER. 



During the progress of systematic field work by the Virginia Geological 

 Survey in western Virginia, a type of stream capture due to the removal 

 of divides by lateral planation was studied by the writers. Three cases 

 have been selected which illustrate different stages of the process and 

 while they involve no new physiographic principle, they illustrate an 

 interesting type of drainage change. 



The removal of divides by lateral planation is the last work accom- 

 plished by streams in the base leveling process; consequently captures 

 due to lateral shifting of the position of streams under conditions of old 

 age must be common. In the lower Mississippi Valley, for instance, 

 many such captures have occurred or are about to occur. In such regions 

 where streams have passed the stage of maturitj^ the accompanying physio- 

 graphic results are apt to be sHght. In regions of more youthful or mature 

 drainage, stream captures affected by lateral planation are of less frequency, 

 but are likely to be attended by more or less prominent physiographic 

 consequences. In case III described below a water gap has been devel- 

 oped in this way, and in case II a natural bridge may result. 



When captures due to lateral planation occur under conditions other 

 than those of old age the disposition to such captures will usually have 

 been inherited from a previous cj^cle of erosion. In each case described 

 below the stream occupies an entrenched meandering valley characteristic 

 of a rejuvenated region. These meanders existed at the beginning of the 

 present cycle, and therefore a tendency toward lateral planation was 

 probably manifested at a relatively early stage. In a rejuvenated region 



437 



