OPEN DRAINS. 



163 



The following examples of ditches of different sec- 

 tions and rates of fall, with computations for velocity, 

 discharge, and number of acres which they will drain 

 (Fig. 31), will serve to show the method of using 



^mmm. 



(1) Fall 2 ft. per Mi. 



(2)Falll.5fl. perMiT 



24 (3) Fall 2 ft. per Mi. 



(4)Fanift.perMi. 



Fig. 3i.-~Data required for Computing Discharge and Acreage Drained 



by Ditches. 



formula (10). This method of determining the nun^- 

 ber of acres for which a ditch will give an outlet is 

 given because it is based on correct principles, is 

 simple of application, and has been found applicable 

 to level tracts of land. Its adaptability to lands of 

 different slopes with a variety of contour lies in the 



