SPECIAL FARM TOPICS 273 



perpendicular banks, owing to the fibrous roots in the material, so to 

 increase the storage capacity they should have wide bottoms, with 

 bank slopes one-half horizontal to 1 perpendicular, unless places 

 should be found where the material requires a greater slope. It is 

 not practicable to give specific directions for laying out a system of 

 internal drainage, as each marsh must be viewed and treated ac- 

 cording to its shape and peculiar location. 



One of the first problems to be disposed of in considering a pro- 

 ject for the improvement of overflowed lands is the disposal of the 

 storm water which comes from the higher lands back of the district. 

 Where there are wide bottoms along streams having good falls it is 

 often practicable to carry both the hill and the storm water of the 

 district in a channel extending for a long distance near the foot of 

 the bluff and parallel to the main river, finally discharging it at the 

 lower end of the levee into the main stream. 



Outlet ditches are those which are large enough to remove flood 

 water from an area and deep enough to afford underdrainage either 

 directly or by affording outlets to covered underdrains. Since they 

 carry water practically all the time, they may be called wet ditches. 

 Surface ditches are intended only to conduct surface water to outlet 

 ditches or to natural outlets. Since they are of use only during flood 

 flow, they are dry most of the time, and may be called dry ditches. 



The capacity of a drain is the greatest discharge that is pos- 

 sible, and the requirement is the greatest discharge that is necessary. 

 In designing a drain so that the capacity shall equal or exceed the 

 requirement, the depth, size, and gradient are perhaps the greatest 

 factors to be considered. Conditions in these respects that are per- 

 missible or necessary in one type of drain may not be so in the 

 others. (Kept. 9 Irr. and Drain.; Wis. Ex. Sta. B. 199.) 



Levees, The care of levees subsequent to their completion is 

 an important matter too often neglected. The slopes should be 

 smoothed and as soon as practicable a good growth of grass should 

 be secured. For this purpose bluegrass, Bermuda grass, redtop, 

 timothy, and clover are all used. A good growth of sod will hold 

 the soil in place and prevent erosion. A mowing machine can be 

 used on a 3 to 1 slope, but scarcely on a steeper slope. On a steeper 

 slope, too, beating rams are likely slowly to wash out the soil and 

 thus gradually reduce the height of the cross section. All weeds and 

 brush on a levee should be cut at least twice during the growing 

 season, as they are particularly harmful, loosening and disintegrat- 

 ing the soil by their roots. Sometimes the top of a levee is used as a 

 road, but this practice is not to be commended, for the wagon wheels 

 cut off the corner of the top and the ruts likely to be formed 

 grow rapidly to such dimensions as seriously to affect the height and 

 efficiency of the levee. The proper place for a road along a levee 

 is on the level ground just inside the inner toe. Burrowing animals 

 of numerous sorts are a constant menace to the integrity of a levee, 

 and they should be assiduously hunted and driven away. Frequently 

 levees are pastured. This has the advantage of keeping down the 

 vegetation, keeping the soil compacted, and driving away burrow- 



