20 BULLETIN 180, U. S. DEPARTMENT OF AGRICULTURE. 
some places sandy, extending to a considerable depth. Where such 
areas are forested erosion is slow, but with the removal of the forest 
growth the erosion is very rapid. Any rut or path breaking through 
the upper layer of heavy soil soon develops into devastating erosion. 
In some places, owing to this condition, any attempt to" cultivate 
the soil should never be made. With plowing and clean cultivation 
it is practically impossible to prevent erosion. In a few counties a 
rough estimate places the eroded and abandoned areas at 25 to 33 
per cent of the total. 
The great danger of losing large areas of valuable land is appre- 
ciated in Tennessee, and under the direction of the State geologist 
the best methods of preventing erosion and reclaiming eroded land 
are being studied. Plate VIII illustrates the seriousness of the situa- 
tion in some parts of the State. The main problem is to arouse the 
farmers to a realization of the importance of treating their soil in 
the manner best suited to its condition. Soils that can not be 
cultivated without danger of erosion should be used for the produc- 
tion of hay, for pasture, or for forestry, either of which may pay 
better under the circumstances than the crops obtained from clean 
cultivation. 
In extreme western Tennessee and Mississippi the deep silty soils 
erode in a slightly different way. The soils of nearly uniform composi- 
tion to a great depth are compact and the pore spaces are compara- 
tively large, so that in their natural condition they absorb much of 
the water falling on the surface. The surface soils and subsoils having 
the same composition, the sides of cuts are vertical, with very little 
tendency toward caving, such as occurs where the subsoil becomes 
saturated and is washed out, leaving the surface layer without 
support. The attrition of the surface, producing a loose layer, 
furnishes the most favorable condition for the ready removal of the 
soil by water, the loose soil being readily carried away with the 
surface run-off. This condition is most noticeable in old roadways 
which have been lowered by erosion sometimes 15 to 20 feet, and the 
vertical walls along the sides show little effect from later rains. 
The control of this type of erosion by terracing is a simple matter. 
Any sort of growth completely covering the ground will prevent 
the excessive removal of soil material. 
DAMAGE TO FLOOD PLAINS. 
In clearing slopes hillside erosion is often so increased that the 
streams carry a much larger burden of material than usual. The 
excess material is deposited in the lower courses of the streams, 
causing a filling or shifting of the channel. One result is that in 
times of heavy run-off the stream channel is not sufficient to carry 
the increased volume of water and overflows result. The flood plain 
