304 



A NATIONAL PLAN FOE AMERICAN FORESTRY 



TABLE 4. Partial summary of disastrous local floods since 1900 and reported 



damage 



EROSION 



A process common to nearly all parts of the United States is the 

 washing by rains from unwisely cleared and unskillfully cultivated 

 lands, from overgrazed pastures and ranges, and occasionally from 

 devastated and badly burned forest lands of the fertile topsoil that 

 has required centuries and sometimes vastly longer periods to accumu- 

 late. In some places the effects of this washing have reached tragic 

 proportions. Erosion not only robs the uplands of fertility but loads 

 the streams which drain them with silt and heavier material that clogs 

 irrigating ditches, navigable channels, and harbors; fills reservoirs; 

 increases the height of floods ; and permanently ruins much overflowed 

 land. Erosion is unquestionably most serious from land cleared for 

 agriculture. So much of this land as fully justifies the careful manage- 

 ment necessary to prevent erosion will remain in agriculture and is 

 beyond the scope of this report. But on the piedmont plateau of the 

 Southern States, on the rich bluff lands of the Mississippi as far north 

 as Wisconsin, in the high valleys of the Appalachian Mountains, in 

 the States bordering the Ohio Kiver, in Missouri, Oklahoma, and 

 eastern Texas, and in other agricultural sections of the United States 

 erosion has been the chief cause for abandoning millions of acres of 

 cleared land. All of this will continue to erode unless reclothed in 

 permanent vegetation, such as forest or brush. Over the wide expanse 

 of the public domain unregulated grazing has started erosion that has 

 already seriously reduced the value of the forage and shortened the 

 life of irrigating reservoirs. 



DOES FOREST COVER AID IN SOLVING THE PROBLEMS 

 OF STREAM FLOW AND EROSION? 



No one can question the seriousness of the stream flow and erosion 

 problems that confront practically every section of the United 

 States. Does the condition of the forest cover on the watersheds of 

 streams appreciably influence stream flow and erosion, and how far 

 may forest management be expected to aid in solving these problems? 



