6 BULLETIN 180, V. S. DEPAETMENT OF AGRICULTURE. 



EXCESSIVE TRANSLOCATION OF SOIL MATERIAL. 



The methods of translocating soil material either by wind or water 

 have played important parts in the geologic history of the earth. 

 The complex relations between topography, climate and erosion, 

 and transportation and sedimentation can not be discussed in a paper 

 of this character, but these relations are clearly brought out in articles 

 by Joseph Barrell.^ 



It is not with this movement of material in its natural condition 

 that we are especially concerned, but with conditions in which man 

 has for some purpose, either for agriculture, lumbering, mining, or 

 power, interfered with the natural - process, so that an excessive 

 removal of soil material results. Since it is necessary to follow the 

 vocations that disturb the balance established by nature between 

 rainfall, slope, and erosion, methods of minimizing this disturbance 

 as much as possible should be determined and employed. 



CAUSES OF EROSION. 



Erosion of land surface is produced by water flowing over its surface 

 or by wind action. Wind erosion has been studied and described by 

 Free and the general principles underlying soil erosion by water have 

 been described by McGee,^ so that only a short statement is here 

 necessary. In the South it is of course the action of water that plays 

 the more important part in soil translocation. 



Water reaching the surface of the soil either sinks into the soil, 

 evaporates, or runs off the sui-face. That portion which evaporates 

 enters into the formation of clouds and is later returned to the earth; 

 the portion that sinks into the ground increases the underground 

 store of water, a part of it reaching the streams and wells by seepage 

 and a part being returned through capillary action to the surface, 

 where it may be utilized in the growth of plants, or may join the 

 evaporated portion. This downward movement into the soil causes 

 a slight movement of particles, resulting in the alteration of the 

 mechanical composition of the soils and subsoils,^ but this is small 

 in comparison to the movement of soil material by the water wliich 

 runs off the surface. It is this water which lifts and carries along 

 soil material, cutting into the soil surface and leaving it bare and 

 gullied. 



The water running off the surface of the soil has been estimated in 

 a number of cases. The Illinois experiment station * reports that 

 48.9 per cent of the rain falling in the Savannah River basin reaches 

 the sea. Of the rain falling in the Potomac drainage basin it is esti- 



1 Jour. Geol., 16, 1.59, 255 and 363 (190S). 



2 W J McGee, Soil Erosion, Bui. No. 71, Bu. of Soils, U. S. Dept. of Agr. (1911). 



3 Davis and Fletcher; Distribution of Silt and Clay Particles in ^ils. 8th Intemat. Cong, of App. Chem., 

 15, 81 (1912). 



4 ni. Expt. Sta. Circ. No. 119 (1908). 



