448 IOWA DEPARTMENT OF AGRICULTURE. 



There are a few general points in connection with open ditches 

 which may be very briefly discussed before going into the details of the 

 engineering side of this questi'on. One of these is the alignment of the 

 ditch. The ideal alignment is a mathematical straight line, and while 

 this is usually not possible to attain, yet in the case of both the tile 

 drain and open ditches too little effort is usually made to secure favor- 

 able alignment. The drain is made to follow the tortuous course of some 

 natural water channel, when at a little additional cost for deeper dig 

 ging and small lateral tiles to the old channel, cut-offs could be made 

 which would greatly increase the grade and capacity of the ditch an I 

 diminish the permanent disadvantages in cultivation. Wherever pos- 

 sible, as in the case of practically level land, the ditches hsould be lo- 

 cated on the property lines or parallel thereto. 



As to the shape of the ditches, it may be said that since tile draiii- 

 age of the adjacent land will usually be profitable in the end. Mr. C. G. 

 Elliott recommends that the ditches should be given a minimum depth 

 of five to seven feet if possible. Moreover, deep ditches keep themselves 

 cleaner better than shallow ditches. The sides should usually be given 

 a slope of one to one. and the ditch will not be so liable to become choketi 

 if the bottom is made at least three feet wide. 



A point in connection with drainage ditches which is often over- 

 looked is that proper provision should be made from the first for main 

 taining them. A ditch choked by weeds or willows or by caving side^ 

 may prove of little value when it is needed most. 



In regard to the details of the drainage engineer's work for drain- 

 age districts, the writer would urge that the surveys, and maps be made 

 complete and comprehensive. All the natural topography, the property 

 lines and the location of buildings should be shown. In addition, the 

 elevations of important points, and of numerous points on all land re- 

 quiring drainage, should be given. For assessment purposes the lan^' 

 should be divided into, first, rolling land (not requiring tiling), second, 

 low land (which can be cultivated without tiling but would be benefited 

 by it), third, wet land (which can not be cultivated but can be pas- 

 tured without tiling), and fourth, swamp land (which can not even be 

 pastured without drainage). The boundaries of all these classes of land 

 should be located in the field by correct measurements, and accurately 

 shown on the map, so that the number of acres of each class of land on 

 each man's farm can be determined by the commissioners. The exac 

 divide bounding the water shed, and often, branch divides between dif- 

 ferent parts of the water shed, should be carefully located on' the ground, 

 using the level wherever necessary, and accurately indicated on the map. 

 The exact locations and dimensions of the drainage ditch should be 

 given, and profiles to a large scale constructed. All maps should be made 

 on tracing cloth, and all profiles on transparent profile paper, blue prints 

 being furnished for use in the field and the originals being preserved 

 in a safe place. 



A reform which the writer advocates for drainage maps and pro- 

 files is that they should all be made on a standard size of sheet, say 

 eighteen inches by twenty-four inches, and those relating to each drain- 



