EROSION IN THE APPALACHIAN AND PIEDMONT REGIONS 



BY R. O. E. DAVIS 



THROUGHOUT the South Atlantic States the exces- 

 sive erosion of the soil is probably more marked 

 than in any other section of the country. The re- 

 sults of this excessive erosion are worst in the Piedmont 

 section of the coast states. There are many factors in- 

 fluencing the rate of erosion, but the character of the soil 

 causes a marked difference in the rates of erosion under 

 the same conditions. 



The heavy clay soil of the region erode fairly rapidly 

 developing the shoestring type of gully with rounded 

 edges. Where 

 soils somewhat 

 lighter with a 

 higher percent- 

 age of sand 

 particles in 

 them are en- 

 countered, the 

 type of erosion 

 is that of the 

 gully with ver- 

 tical sides, or 

 the caving gul- 

 ly type. Differ- 

 ences in the 

 soil and subsoil 

 influence pro- 

 f o un d ly the 

 c h a r a cter of 

 erosion. Silty 

 soils or clayey 

 soils with sub- 

 soils of a sandy 

 c h a racter ex- 

 hibit the most 

 rapid and most 

 difficult c o n - 

 trolled erosions. 



The regions of the South subject to excessive erosion 

 are in a number of soil provinces, but the greatest amount 

 of eroded soil occurs within the Appalachian and Pied- 

 mont regions. It is in the Piedmont Plateau, near the 

 "Fall line," that the greatest difficulty is experienced in 

 dealing with erosion. The Fall line forms the boundary 

 between the Appalachian and Piedmont provinces and it 

 is here that the rapids occur in the various streams in 

 their course from the mountains to sea. 



The soils of the entire section are mainly residual, i. e., 

 derived from the underlying rock and in general the 

 topography of the region conforms to the structural char- 

 acter of the underlying layers. While erosion has affect- 

 ed the relation between the surface form and rock con- 

 figuration locally, especially in the southern portion of 



1350 



CLE.\R .^ND STRIKl.XG EVIDENCE OF \VH.\T EROSIO.N WILL DO 



A gully in the lowlands has gradually eaten its way back into the hill of this Georgia pine forest 

 rain adds to the length and breadth of the gulch. 



the region, the main ridges correspond with the position 

 and the prevailing northeast and southwest direction of 

 the more resistant rocks. 



In localities where the surface is smooth the soils lie 

 directly over the rock from which they are derived, but 

 on slopes a considerable movement to lower levels has 

 taken place mainly through the action of water. Outcrop 

 of rock is frequent, but by far the larger part of the area 

 is covered with a soil mantle of sufficient depth for the 

 support of forests. IMuch of it is so steep that it is not 



suitable for 

 cultivation, and 

 is best adapted 

 to forests, graz- 

 ing or small 

 fruit pro duc- 

 tion. The prin- 

 cipal soils are 

 the loams, clay 

 loams, silt 

 loams, sandy 

 loams, clays, 

 fine sandy 

 loams and stony 

 loams. 



In the south- 

 ern Appalach- 

 ian region the 

 forests on the 

 hill and moun- 

 tain sides have 

 maintained an 

 open and por- 

 ous soil ; kept in 

 this c o ndition 

 by the cover- 

 ing of leaves 

 and debris of 

 the forest. The rains falling on the forest floor never 

 reach the soil with unbroken force, so that the finer soil 

 particles are not pounded and stirred and carried off in 

 the water which flows over the surface. The velocity 

 of the moving water is so reduced that where the forest 

 covering is intact erosion is almost a negligible quantity. 

 Where this rate of erosion is slow there has been estab- 

 lished gradually a state of equilibrium between the slopes 

 and rainfall. This slope remains practically constant for 

 very long periods if the conditions are not changed. 

 There is a slow movement of material, but this is not 

 sufficient to disturb the general contour or to injure the 

 vegetal covering. Only occasional cloud-bursts or ex- 

 ceedingly heavy rains produce a visible effect on the 

 soil surface conditions. 



Each 



