UNIVERSITY OF VIRGINIA PUBLICATIONS 



BULLETIN OF THE PHILOSOPHICAL SOCIETY 



SCIENTIFIC SECTION 



Vol. I, No. 17, pp. 349-363 July, 1913 



DRAINAGE CHANGES IN THE SHENANDOAH VALLEY 

 REGION OF VIRGINIA. 



THOMAS L. WATSON and JUSTUS H. CLINE.* 

 PRELIMINARY STATEMENT. 



The Shenandoah A'alley in Virginia forms that part of the Great Val- 

 le.y, extending from New York to Alabama, drained by the Shenandoah 

 River and its tributaries. It is not a structural valley, but owes its exis- 

 tence to the more rapid erosion of the limestones of which it is chiefly 

 composed than of the resistant rocks that form the mountains flanking 

 it on the two sides. 



It occupies a narrow belt between the Blue Ridge and the Alleghany 

 Ridges in northwestern Virginia and the extreme eastern part of West 

 Virginia which lies east of the Alleghany Ridges (see map, fig. 1). Its 

 trend is northeast-southwest, parallel with the bounding mountains, and 

 it varies in width from 15 miles in the southwestern part along the divide 

 between the James and Shenandoah rivers to 25 miles in the latitude of 

 Harpers Ferry. 



The general surface of the Valley is that of a broad undulating plain 

 Ijdng 1000 to 2000 feet below the crests of the bordering mountains, 

 broken in places by low rounded monadnocks which rise 200 to 300 feet 

 above it, or by low longitudinal ridges of greatly subdued character. In 

 the extreme southwestern portion of the divide region between the Shenan- 

 doah and James drainage systems, the elevation approaches 2000 feet. 

 From this point the Valley slopes northeastward to an altitude of 400 

 feet at Harpers Ferry. 



* Read before the Scientific Section in May, 1913. 



349 



