205 



In the first period (1890-1898) of nine years there were forty-seven 

 floods lasting 116 days. There were 5G6 days of low water. 



In the second period (1899-1007) of nine years there were fifty-eight 

 floods lasting 170 days. There were 292 days of low water. The rainfall 

 decreased .17 of an inch per year. 



The Ohio River was measured at Wheeling, W. Va. It drains a basin 

 of 23,S20 square miles. 



In the first period (1882-1894) of thirteen years there were forty-six 

 floods lasting 143 rlays. There were 1,333 days of low water. 



In the second period (1S95-1907) of thirteen years there were fifty- 

 nine floods lasting 188 days. There were 1,609 days of low water. The 

 rainfall decreased .14 of an inch annually. 



The data here cited for the above mentioned rivers is also true for 

 many other streams, but these will serve as good examples of what has 

 been and is taking place wherever deforestation has occurred. In such 

 rivers as the Ohio, Cumberland, and Wateree, changes are most conspicuous, 

 and it is in these that most of the forest has been removed, while least 

 change appear in those streams where most of the forests remain.' 



This state of affairs is what we should expect, but the data given for 

 the rivers referred to proves this by direct observation and leaves the 

 matter no longer a question of guesses or opinion. 



From what has just been said it is certain that as deforestation prog- 

 resses floods will, with equal amoxints of precipitation, become more fre- 

 quent and increase in severity. To be sure, there are other factors that 

 enter somewhat into any consideration of the cause of floods. Among 

 these may be mentioned rainfall, season of the year and temperature, 

 character of the soil, presence of lakes which might impound a good part 

 of the "run-off" temporarily and afterwards gradually supply it to the 

 streams, nnd thus while at first preventing flood afterwards lessen the 

 lengthy periods of low water. Also the question of whether the land is 

 nearly level or very hilly and steep is important. A heavy precipitation 

 iniglit do no damage wluitsoe\er in the foi-mer case, whereas in the latter 

 am mg steep and deforested land the destrtiction might be appalling. 



But after we have considered all these points and many others that 

 might be mentioned, the fact remains that the chief cause of the frequent 



Hall, Wm. nnd Maxwell, Hu. Forest Service Circuhiv 170, p. 



