SOUTHEEN APPALACHIAN KEGION. 



117 



From season to season the rivers vary in flow. Their in rivers, 

 least volume is in the early fall, when they have been 

 reduced by the droughts and heat of summer. Only the 

 smallest branches are ever entirely dried, however, and 

 the severest droughts fail to stop any considerable stream. 

 The greatest volumes are attained in the spring, when the 

 snows melt rapidly and the winter's accumulation of water 

 is leaving the soil. The freshets are not limited altogether 

 to the spring, however; a cloud-burst, for example, may 

 swell a lesser stream tenfold, or a hard rain of four or 

 five days may flood even the largest river. In the upper 

 coarses of the streams, where the grades are highest, 

 floods produce exceedingly swift currents, which are able ^^^^^ °* 

 to destroy obstructions and barriers which at ordinary 

 stages would seem insurmountable. The rapid delivery 

 of the waters from the stream heads make a sudden con- 

 centration where the branches have united and the grades 

 are less, causing deep water and overflow. Thus, four 

 days of hard rain recently raised Catawba River 30 feet 

 and overflowed miles of bottom lands. The power of the 

 upper and steeper streams at such times is almost incred- 

 ible; bowlders tons in weight become mere playthings. 

 On the lower reaches in deeper waters and slackened cur- 

 rents no fragments larger than cobblestones are moved, 

 but wholesale changes in the shapes of the bottom lands 

 are often accomplished. The same steep grades which 

 cause the rapid floods are equally effective when the rains 

 have ceased, so that the waters subside about as quickly as 

 they rise. Aside from these temporary changes in vol- 

 ume the flow of the rivers is very steady, dependent as it 

 is upon the discharge of countless springs and the seepage 

 of waters from the soils. 



CLIMATIC FEATURES IN THE MOUNTAINS. 



The region covered by this mountain mass possesses a Temperature, 

 climate which differs greatly from that of the surrounding 

 regions. This is manifest first in lower temperatures and 

 is due directly to the greater altitudes. The peaks, of 

 course, are colder than the intermountain valleys, and 

 both are colder than the adjoining Gieat Valley or the 

 Piedmont Plateau. The differences in temperature are 

 greater in summer than in winter, so that the climate of 

 the higher portions is more equable than that of the 

 valleys. 



