210 LAND DRAINAGE 



falls apparently have always occurred and may be ex- 

 pected to continue to occur. 



280. The relation of forests to floods. " The most 

 important effect of forests on climate is the economic 

 conservation of precipitation, diminishing the intensity of 

 floods by the restriction of flow-off [run-off], and by shad- 

 ing the snow deposited during the winter from the in- 

 creasing sun of spring and early summer. . . . Investigation 

 in Germany and India seems to indicate that there is an 

 appreciable increase in rainfall as a result of reforesta- 

 tion." 1 Moore, however, does not give figures and uses 

 the term " seem to indicate." 



Unwise deforestation is, in numerous cases, a serious 

 factor in augmenting the destructiveness of floods. 



281. The relation of drainage to floods. It is some- 

 times charged that drainage, both open and tile, increases 

 the destructiveness of floods. It is possible that this 

 assertion might be proved in a few cases. In general, 

 drainage should materially lessen the destructiveness of 

 floods. Drainage increases the cut-off. With good 

 methods of tillage, the cut-off is further increased. With 

 ordinary rains, the complete and long continued satura- 

 tion ofc the above-tile soil is prevented ; so that the net 

 cut-off is increased and the net run-off is considerably 

 controlled by the tile, and even by the open drain. (See 

 paragraphs 77-83.) 



282. Observations concerning rainfall. " There are 

 few places in the Western Division [of England] where 

 the rainfall is less than 35 inches ... in the low ground 

 about the mouth of the Thames estuary, and around the 

 wash, the mean annual rainfall is less than 25 inches." 2 



1 Willis L. Moore, Cyclopedia Americana, Vol. 5. 



2 Encyclopaedia Britannica, Climate of England. 



