154 GEOLOGICAL SURVEY OF NEW JERSEY. 



CATCHMENTS OVER 2,OOO SQUARE MILES. 



Merrimac, Mass., .... 4,599 20.9 0.31 



Connecticut, Conn., . . . 10,234 53 20.3 0.31 



Delaware. N. J., ..... 6,790 53 37.5 0.17 



Ohio, Pa., 19,900 . . . . o.i i 



Potomac, Va., 4,640 52 22.2 0.08 



Kanawha, Va., 8,900 . . 13.5 0.12 



James, Va 6,800 . . 0.19 



Since the flood-flow is always at a less rate per square mile on 

 large catchments than on small ones, we have grouped the 

 streams according to the size of the catchment. It will be seen 

 that there is no relation between the forest area and either the 

 greatest or least flow. 



In February, 1896, during the progress of these forest surveys, 

 floods of great severity occurred on all of the streams of Northern 

 New Jersey, and a good opportunity was afforded to study the 

 relative rate of discharge on forested and deforested catchments. 

 These floods were caused by a warm rain, amounting to about 

 3.7 inches, falling upon an accumulation of from 6 to 7 inches of 

 snow, the ground being frozen ; and of the total amount of water 

 resulting, equivalent to about 4^ inches of rain, 2.7 to 3.7 inches 

 was discharged with great suddenness into the streams. Care- 

 ful studies were immediately made of the rate of discharge and 

 the results are shown in the following table : 



