1352 



AMERICAN FORESTRY 



evident. It is possible on some types of soil, most notably 

 the heavier clays, to cultivate on rather steep hillsides 

 without serious damage from erosion. But even here 

 continual vigilance is necessary to avoid the ultimate ruin 

 of the land. On soils of a lighter character, or loamy 

 condition, erosion is very destructive if once the land be- 

 comes gullied. On the other hand, soil of an open, porous 

 nature is easily dealt with if the proper precautions are 

 maintained to stop any indication of surface washing. 

 The fact that stream flow is greatly influenced by the 

 presence of forests is so well known that it is almost 

 trite to refer to it. However, when we consider the 

 enormous damages each year from floods, as well as the 

 cost of continual dredging of streams to maintain open 

 channels for navigation, it becomes imperative that the 

 forests' influence be emphasized. As already pointed out, 

 many of the Appalachian streams rising in the mountain 



show that floods are increasing in frequency and height. 

 The evidence collected in this region shows that the 

 Kiskimmitas and Youghiogheny rivers are the most im- 

 portant rivers in producing floods at Pittsburgh. The 

 two streams drain extensively deforested areas of about 

 the same size, with heavy precipitation and a high rate of 

 run-off. In consequence of this deforestation both rivers 

 collect and move their floodwaters to Pittsburgh in about 

 the same time. This is but one of the worst instances 

 where removal of the forest covering results in disaster 

 to the low lying country. 



Much of the erosion in forest is started by careless 

 handling of logs. Under conditions where excessive 

 erosion would not take place if care were exercised in 

 handling cut timbers, the "snaking" and dragging of logs 

 result in the formation of smooth depressions into which 

 water gathers and drains from the steep hills. The 



THE DEVASTATING RESULT OF EROSION 



A one-time fertile valley in Tennessee ruined by a covering of sand brought down from the nearby hills, deprived of thin forests and subjected 



to erosion. 



forests are clear and free from sediment ; but many, and 

 they are fed invariably from watersheds, in part, at 

 least, cleared of their forests, carry a heavy burden of 

 sediment. 



The Flood Commission of Pittsburgh appointed to 

 investigate the cause of floods at Pittsburgh and to recom- 

 mend means of removing the danger, reported that ex- 

 tensive deforestation of the drainage areas of the Alle- 

 gheny and Monongahela Rivers by giving a higher rate 

 of run-off, has been the cause, in part, of the increase in 

 frequency and height of floods along these and the Ohio 

 rivers. It is furthermore well known that the carrying 

 capacity of the river channels at Pittsburgh has been 

 considerably reduced in the last fifty years. The records 



rapid cutting of these depressions quickly results in the 

 formation of gullies which advance into sections other- 

 wise not susceptible to erosion. 



The peculiar climatic and soil conditions of the South- 

 ern Appalachian region, especially, are conducive to the 

 development of gullies. In some localities erosion start- 

 ed in the manner described continues to work its way 

 back into the hills, constantly increasing in depth and 

 width the eroded section with numerous gullies starting 

 from the sides, until immense areas are devastated and 

 the gullies formed almost defy the ingenuity of man to 

 check their progress. 



The removal of vegetable covering from the hills has 

 resulted in a largely increased burden of solid material 



