CONSERVATION AND ITS MEANING 



591 



It has been estimated that the transporting power of water varies 

 as the sixth power of its velocity. This means the carrying power of 

 water is increased sixty-four times if its rate of flow is doubled. From 

 such figures it is easy to account for the enormous destruction by 

 streams at a time of flood, as was witnessed in March, 1936, in the 

 eastern part of the United States. The annual damage by "spring 

 freshets" in cut-over areas in the East, the recent floods in the Ohio 

 and Mississippi valleys, where the forest cover has given place to farms 

 and cities, and the damage done by cloudbursts in denuded areas in 

 the Southwest, all testify to the power of uncontrolled water and show 

 the need of forest cover to hold back flood waters. 



Erosion areas in the United States. 

 1, Area of most serious erosion : 2, harmful erosion widespread ; 3. fiat areas, 

 slight erosion ; 4, erosion generally not serious ; 5, much serious wind erosion ; 

 6. much erosion from over-grazing. 



But erosion does damage in a more insidious way than through 

 spectacular floods. A plowed area on a hillside allows more rain to 

 run off than a similarly located area covered with grass. A plowed 

 field allows more soil to be carried off by wind than does a similar 

 field covered with grass. A plowed field will be left covered with 

 mud after a heavy rain and the pores of soil will be found to be 

 clogged with soft mud, making plant growth practically impossible. 

 A glance at the map shows the very large area in this country in 

 which more or less serious erosion takes place. A check-up with the 

 map showing forest areas on page 605 makes clear that the areas of 



