490 



CONSERVATION' 



afterward, thus acting as true reservoirs 

 in equalizing the run-off. 



"(2) By retarding the snow-melting 

 in the spring and prolonging the run- 

 off from that source. 



"(3) ^y increasing precipitation. 



"(4) By preventing erosion of the 

 soil on steep slopes and thereby pro- 

 tecting water-courses, canals, reservoirs 

 and similar works from accumulations 

 of silt." . 



This will probably be admitted to be 

 a fair statement of what the believers 

 in the benefits of forests consider to be 

 true, except that some do not consider 

 that there is yet sufficient demonstration 

 that they increasie the rainfall, and also 

 except that the water is not stored sim- 

 ply in the bed of humus, but also in 

 the ground beneath. 



With reference to the first of these 

 points, the author states that it is 

 "strictly true of average conditions." 

 He says: "It is true, therefore, as 

 popularly understood, that, in periods 

 of ordinary rainfall, with sufficient in- 

 tervals for the forest bed to dry out 

 somewhat, forests do exert a regulative 

 effect upon run-off. They modify 

 freshets and torrents and prolong the 

 run-off after storms have passed, and 

 therefore realize in more or less per- 

 fection the commonly accepted theory." 

 He believes, however, that this benefi- 

 cial effect is not exerted under extreme 

 conditions,, i. c, great floods and ex- 

 cessive low waters, and he states that 

 these extreme conditions "determine the 

 character and cost of river control." 



Even if it be admitted that the pres- 

 ence of forests does not affect "extreme 

 conditions," this is no argument against 

 the value of forests, for it is certainly 

 not true that only extreme conditions 

 affect the navigability of streams or 

 "determine the character and cost of 

 river control." Extreme conditions de- 

 termine certain elements, such, for in- 

 .'.tance, as the height of levees. Colonel 

 Chittenden certainly cannot mean to 

 state that ordinary, every-day floods do 

 not carve away banks and cause shoal- 

 ing of channels, rendering dredging 

 necessary for navigation. A few high 

 but not extreme floods mav do much 



more damage than one extreme flood, 

 and may necessitate more expenditure 

 for dredging and other purposes. Ex- 

 treme conditions are in the nature of 

 freaks. They occur only at intervals of 

 many years. It would seem to be more 

 nearly correct to state that the interests 

 of navigation are governed more by 

 the usual conditions, and that it is pos- 

 sible for extreme conditions at rare 

 intervals to interrupt traffic for a short 

 time without causing much loss. It may 

 as well be argued that it is not wise to 

 attempt improvements on railroads be- 

 cause an earthquake or a tornado or 

 an extreme flood in a river may destroy 

 a portion of the track and interrupt 

 traffic for a while. It matters little in 

 the navigability of a stream if at inter- 

 vals of twenty, thirty, or fifty years an 

 extreme drought occurs for a few days 

 or weeks, making the depth of the 

 channel insufficient for the largest 

 vessels. 



If it be true, therefore, that extreme 

 conditions do not govern the question. 

 Colonel Chittenden has admitted all 

 that the advocates of forests desire. 

 Let us consider, however, the argu- 

 ments with reference to such extreme 

 conditions : 



The argument with reference to ex- 

 treme floods appears to be that floods 

 are always the result of combinations 

 from various tributaries, the highest 

 flood from one stream coming at the 

 same time as the highest flood from 

 other streams, occurring after periods 

 of long-continued and widespread pre- 

 cipitation. In such cases the forest bed 

 becomes completely saturated, the stor- 

 age capacity exhausted, and when this 

 point is reached "the forest has no more 

 power to restrain floods than the open 

 country itself." 



It is, of course, evident that the rain- 

 fall may be so great and long continued 

 that the forest bed becomes saturated 

 and that the water flows over the sur- 

 face, but it does not seem correct to 

 say that in this case the forest has no 

 more power to restrain floods than the 

 open country tiself. The discharge will 

 be hindered in the forest by the physical 

 conditions, and because the soil will not 



