DRAINAGE 



277 



which has been assessed, the outlets which are necessary 

 for the economical drainage of that tract, without having 

 to cross the land of other owners. Outlet systems should 



4' 8' 



Fig. 226. Diagrams of 1 to 1 and 2 to 1 slope 



be so planned that the necessary outlets are furnished, and 

 at the same time due attention should be given to the lower 

 part of the outlet or the natural stream into which it flows, 

 to prevent the flooding of lands lying lower down. The 

 drainage of one area at the cost of another is not good engi- 

 neering, good agriculture, or good economy. The planning 



fYiCH-»>*T£/? LtAZ 



&OTTOM 



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— i ' — t -:■.—_- 



After University of Minnesota 



Fig. 227. Typical cross section of a drainage channel constructed by a 

 steam dredge. Indicated by technical names. 



of outlets should be done with due consideration for all 

 interests, to serve the land benefited in such a way that 

 outlet privileges from land assessed cannot be withheld by 

 obstinate owners of intervening farms. 



A drainage system, open or tile, works by gravity, and to 

 remove the water there must be a fall. It has been common 

 practice to run a drainage ditch into a slough at practi- 

 cally the same depth as the bottom of the slough. Such 



