508 



FORESTRY AND IRRIGATION 



November 



An examination of the watersheds 

 and a general investigation of the 

 streams in this mountain region were 

 made by the United States Geological 

 Survey during the summer of 1900. 



During the hydrographic investiga- 

 tion of this region, extending through 

 1900 and 1901, measurements of flow 

 were made on the larger streams and 

 more than one thousand of their upper 

 tributaries, and 54 gauging stations 

 were established. At each station a 

 gauge was permanently placed, upon 

 which the height of the water surface 

 was read and recorded daily by a local 

 observer, and to which were referred 

 the current - meter measurements, 

 which were made about every sixty 

 days, or oftener, as circumstances de- 

 manded or permitted. From these 

 data a curve was platted, according 

 to the method usually followed by 

 the Survey. From this curve, the 

 mean of the daily gauge readings be- 

 ing known, the approximate daily 

 discharge has been calculated. The 

 great difficulty encountered at these 

 stations was to obtain measurements 

 at the time of high water, for after 

 a rain the rivers rise rapidly and fall 

 as quickly. Hence, unless the observer 

 is on hand at the time, the high water 

 passes before he can reach the point of 

 measurement. 



VALUE OP THESE MOUNTAIN STREAMS 

 FOR WATER-POWER PURPOSES. 



The greater part of mis region is 

 occupied by gneissic rocks, having for 

 the most part a characteristic north- 

 east-to-southwest strike, the irregular 

 rock layers dipping beneath the sur- 

 face at varying but generally steep an- 

 gles. The southern half of the region 

 has along its western border an ir- 

 regular belt of bedded slates, lime- 

 stones, quartzites, and conglomerates. 

 These rocks, which make up the great 

 bulk of the surface, have a general 

 northeasterly strike, and a steep but 

 varying dip ; while near the eastern 

 border there is another, but narrow 

 and more irregular, belt of rock of 

 somewhat similar character, which fol- 



lows approximately the general posi- 

 tion of the Blue Ridge, and dips steeply 

 southeastward. 



As stated above, the important 

 streams rising in Virginia, the Caro- 

 linas, and Georgia have their origin 

 on the slopes of the Blue Ridge. Those 

 rising on the eastern slope, such as the 

 James, Roanoke, Yadkin, Catawba, 

 Broad, Savannah, and Chattahoochee, 

 flow generally toward the southeast, 

 their head streams plunging down the 

 mountain slopes many hundreds of 

 feet in short distances and soon reach- 

 ing the gentle slope of the Piedmont 

 Plain. The streams rising on the 

 western slopes of the Blue Ridge the 

 Watauga, Nolichucky, French Broad, 

 Pigeon, Little Tennessee, Tuckasegee, 

 and Hiwassee Rivers flow in the gen- 

 eral characteristic northwesterly direc- 

 tion across the upturned ridges of the 

 gneiss and more recent bedded rocks, 

 with frequent falls, into the great val- 

 ley of East Tennessee. The Holston 

 River, which flows along this valley 

 from its upper end to its junction with 

 the Tennessee system, forms an excep- 

 tion to the general direction of flow in 

 this region, for its course lies toward 

 the southwest; and the Coosa River, 

 of Alabama, which has its headwaters 

 on the southeastern slopes of the Blue 

 Ridge, takes a similar direction. The 

 New River, also, which rises in the 

 cross ranges connecting the Unakas 

 and the Blue Ridge, flows toward the 

 northwest into the Ohio. The eleva- 

 tion of the country is so great and the 

 decent of the stream is so rapid that 

 the general course of the principal riv- 

 ers has been but little modified by the 

 geologic structure of the region, though 

 they lie directly across the strike of the 

 rocks. The resulting conditions pro- 

 duce occasional falls and cascades in 

 the streams ; but the larger part of the 

 courses of these streams consists of a 

 succession of rapids, furnishing ample 

 opportunities for water power devel- 

 opment by the building of dams at in- 

 tervals across the deep narrow gorges. 

 A number of the small tributary 

 streams in North Carolina and in Vir- 





I 



b 







