64 



II. Influence of Forests upon Water Flow. 



1. Kainfall. 



(a) Deposition on foliage, trunks, underbrush, litter and forest 



floor. 



(b) Reduction of progress of erosion, washing of soil. 



(c) Prevention of formation of shifting sand and sand dunes. 



2. Drainage. 



(a) Surface drainage changed to subsoil drainage. 



(b) Porous soil absorbs rainfall. 



(c) Time element in "run off" prolonged. 



(d) Force and rapidity of surface waters reduced. 



3. Snow. 



(a) Distribution of snow masses more even. 



(b) Melting of snow under forest cover prolonged. 



(c) Spring floods reduced. 



4. Floods. 



(a) Large floods dependent upon cosmic causes and uncontrol- 



lable terrestrial causes. 



(b) Large floods modified by 



(1) Topography of land. 



(2) Character of the soil. 



(3) River systems. 



(4) Forest cover. 



5. Modifying Influence of Forests. 



(a) Prolongs time of "run off." 



(b) Reduces water stages. 



(c) Reduces extremes of drought and flood. 



(d) Reduces extremes in low and high temperature. 



6. Condition of Forest Floor. 



(a) More important in influence upon soil conditions and water 



flow than trees. 



(b) Forest fires destroy litter. 



7. Regulafion of Water Supply. 



(a) Relation of water supply to agriculture. 



(b) Relation of forests to conservation of water. 



8. Sanitary Influences. 



(a) Reduction in extremes of temperature. 



(b) Reduction of severity of winds. 



(c) Comparative freedom from microbes. 



(d) Injurious lack of rapid evaporation on poorly drained soil. 



Southern swamps. 

 0. Relation of Agriculture to Forestry. 



