FOREST LANDS FOR THE PROTECTION OF WATERSHEDS. 17 



rains, for an investigation which does not take into account the num- 

 ber of flood-producing rains is very imperfect. I can not, of course, 

 in the five minutes time present these results in detail. I will sum 

 it up in a sentence and leave the question to be proved by Mr. Leigh- 

 ton in case you desire it, but the result of his investigation shows that 

 as a consequence of the change of conditions due to deforestation 

 during the past twelve years the floods are 18.75 per cent more fre- 

 quent than they were during the previous twelve years, taking into 

 account the precipitation, the number of flood-producing rains, as 

 well as all the other factors. This is the first investigation which has 

 been made, and this investigation concerns directly this southern 

 Appalachian forest reserve. 



. Now, the second point is this : The Government spends millions of 

 dollars in dredging out harbors, and yet no effort is made by the Gov- 

 ernment to prevent the silt from going down into harbors and filling 

 them up, and so that process goes on year after year and year after 

 year and must continue to go on, because it will never be possible to 

 altogether prevent the silt from going down into the harbors. 



The CHAIRMAN. Has it not always gone down? 



Doctor VAN HISE. It has always gone down. 



The CHAIRMAN. Does not the location of the great bar at the mouth 

 of the Columbia, which has existed ever since navigation discovered 

 that access, indicate that there has been very severe, erosion through 

 that watershed from time immemorial, and extending through a time 

 when the watershed was just as perfectly protected as it ever could be 

 by forests? 



Doctor VAN HISE. That is entirely true. There never will be a 

 time in which the silt will not be carried down into the harbors and 

 rolled over and over and carried along by the waves meeting the cur- 

 rent. There never will be a time when that is not the fact, and there 

 never will be a time in which the harbors will not fill up. But the 

 amount of silt that is carried down from the mountains has been 

 vastly increased as a result of this deforestation. 



The CHAIRMAN. Is that merely a deductive opinion, or is it a 

 demonstrated fact? 



Doctor VAN HISE. It is a demonstrated fact, as it seems to me, from 

 the results of these very investigations that have been made with 

 reference to the Tennessee. There is no question on the part of any- 

 body that the erosion in the South and in the headwaters of these 

 streams, as the result of the removal of the forests, has gone on at a 

 speed which never occurred before. That is to say, before the forests 

 were removed the forces of nature were making the soil faster than it 

 was being washed away, so that the soil was ever getting thicker and 

 thicker and thicker. Wherever the forests have been removed, and 

 especially on the steeper slopes, erosion has gone on faster than the 

 making of the soil, so that the bare rocks are protruding, conclusive 

 proof that there has been carried down with the streams, and ulti- 

 mately to the mouths of the streams, much more material than was 

 carried down under conditions of forest cover. 



The CHAIRMAN. Has any investigation been made to determine 

 what proportion of the soil, eroded from the slopes at the headwaters 

 of a stream like the Tennessee, reaches the navigable portions of that 

 stream ? 



72538 AGR--09 2 



