THE DRAINAGE OF FARM SOILS 203 



must have sloping banks. If the soil is a tenacious 

 clay a slope of 15 to 20 may be sufficient to hold 

 the banks. More often a slope of 45 is barely 

 enough to prevent caving in, which means much 

 extra work. The greater the fall of the ditch, the 

 flatter should be the banks. 



In many cases, especially for wet meadows, the 

 best kind of ditch is merely a broad hollow, about 

 one or two feet deep and six or eight feet wide. 

 These places may be grassed over, if in a meadow ; 

 if the land is used for tilled crops and the ditch 

 serves as a water carrier only in winter and early 

 spring, it may be planted. All kinds of farm 

 machines can pass over such a ditch; it is the 

 most serviceable kind whenever it will drain the 

 land sufficiently. On nearly all comparatively 

 flat land, and especially on western prairie lana, 

 there are many shallow natural water-courses, 

 variously called "runs," "draws" and "sloughs." 

 The heavy spring rains turn these into drainage 

 channels. If necessary shallow ditches, ten or 

 twelve feet wide and two feet deep, may be scooped 

 out in these draws with plow and scraper and the 

 bottom and sides seeded to grass. 



The Grade. The grade of an open ditch must 

 be low. A fall of five or six inches in a hundred 

 feet is usually about all that an ordinary soil will 

 stand without washing, especially if the banks have 

 not enough slope. If it is necessary to make 

 curves in a ditch, they should be very gradual, 

 particularly if the fall is greater than it ought to be, 

 for when me ditch runs full the water will tend to 

 eat into the outer bank, as it does in streams. 

 When an average ditch is running full after a 

 freshet a fall of two inches in a hundred feet makes 

 a current of about four miles an hour. This 



