FOREST LANDS FOR THE PROTECTION OF WATERSHEDS. 123 



River amounting to $400,000 for the construction of dams for the 

 purpose of preventing the silting up of the lower channel of the river 

 as a result of hydraulic mining in the mountains. 



In France, the first efforts to repair the disastrous torrents were 

 made by engineers along the lower water courses. Dredging and 

 dams, however, proved at best but temporarily effective. Only when 

 they began to push this work up to the headwaters of the streams did 

 they find themselves on the right road. 



RELATION OF THE FORESTS TO FLOODS. 



Flood damage in the United States has increased from $45,000,000 

 in 1900 to 1118,000,000 in 1907. All rivers on whose watersheds the 

 forests have been heavily cut show flood increases. They are greatest 

 in such streams as the Ohio, Cumberland, Wateree, and Santee, where 

 the most timber has been removed, and least in those streams on whose 

 watersheds forest conditions have been least changed. Except in the 

 change of forest conditions there have been no factors that could have 

 intensified flood conditions. In the Ohio River in seventy years the 

 number of floods at Wheeling has increased 62 per cent and their 

 aggregate duration 116 per cent. 



In the Cumberland River at Burnside, Ky., the number of floods 

 increased 330 per cent in the fifteen years between 1891 and 1905 and 

 the duration in the same proportion. During the same period in the 

 Wateree River at Camden, S. C., the number of floods increased 65 

 per cent and the duration 82 per cent. In the Congaree River the in- 

 crease during the same time has been 94 per cent in number and 113 

 per cent in duration. In the Savannah River at Augusta, Ga., be- 

 tween the years 1876 and 1905 the increase in the number of floods 

 has been 94 per cent and in duration '266 per cent. Between 1891 and 

 1905 the Alabama River at Salem, Ala., had an increase in number of 

 floods of 83 per cent and in duration of 31 per cent. 



The Geological Survey has made a careful study of floods in the 

 Tennessee River during the past thirty-four years, and has found that 

 on the basis of equal rainfall floods in the last half of the period have 

 increased 18f per cent. 



At the Tenth International Congress on Navigation, held in Milan in 

 1905, engineers from the various countries of Europe were unanimously 

 of the opinion that mountain forests were beneficial in .preventing 

 floods, in regulating the low water in streams, and in retaining the 

 soil upon the mountains. 



RELATION OF FORESTS TO SOIL WASH. 



The annual soil wash in the United States is estimated by the Inland 

 Waterways Commission atabout 1,000,000,000 tons, of which the greater 

 part is the most valuable portion of the soil. It is carried into the 

 rivers, where it pollutes the waters, necessitates frequent and costly 

 dredging, and reduces the efficiency of work designed to facilitate 

 navigation and prevent floods. Soil when once lost is replaced with 

 great difficulty, if at all. Consequently the protection of the forests 

 on the slopes which are too steep otherwise to be utilized means 

 actually immense gain in soil conservation. 



