63 



The Wabash River Flood of 1913, at Lafayette, Ind. 



R. L. Sackett. 



The principal factors affecting the flood discharge of rivers in cubic feet 

 per second per square mile are: 



The duration and intensity of rainfall. 



The topography of the watershed. 



The geology of the watershed. 



Temperature and condition of the soil and surface. 



Presence of lakes. 



Slope and general character of the channel. 



Data has not yet been collected so carefully and for long enough periods 

 to permit predicting flood stages with any accuracy. 



Tiefenbacher gives the following estimate of the flood discharge of Euro- 

 pean streams in cubic feet per second (See Ency. Brit., Eleventh Ed., Vol. 

 XIV, p. 77): 



In flat country 8.7 to 12.5 cubic feet second per square mile. 



In hilly country 17.5 to 22.5 cubic feet second per square mile. 



In moderately mountainous districts 36.2 to 45.0 cubic feet second 



per scjuare mile. 

 In very moiuitainous districts 50 to 75 cubic feet second per scjuare 

 mile. 



Various formulas have been proposed to express the maximum ffood flow 

 such as 



O'Connell proposed, Q ecjuals Kl M where K varies "from 0.43 for small 

 rivers draining meadow land" to 67.5 for the Danube. 

 Q is the discharge in cubic feet per second. 

 M is the area in square miles. 



Fanning proposed, Q equals 200 M for New England Rivers. 



M 



Dredge gives, Q ecjual 1300 — where L is the length of the catch- 



T ? 

 ment area in miles. ^ 



