LAISTD DRAINAGE BY MEANS OF PUMPS. 13 



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 its 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 burrowing animals. 

 The slight damage to a levee which may result from using it as a 

 pasture is easily observed and repaired and is probably counter- 

 balanced by the good results of the practice. Where the levee is 

 exposed to strong wave action and current erosion, special means 

 must be taken to prevent serious damage during high-water stages. 

 The growth of brush and trees on the edge of the berm next the bor- 

 row pits and on the strip of land between the borrow pit and the 

 river should be encouraged. If there is no such natural protection, 

 willows should be planted. In the period before the willows reach 

 sufficient size to be effective some form of artificial protection should 

 be used. Tight board fences are often used for protection against 

 wave wash; a layer of rock, or rock with willow mattress, is often 

 used where the river is cutting the bank and threatening the founda- 

 tion of the levee. In any case the danger is too serious to be met 

 with halfway measures. 



Constant attention and expense, the latter not large, are required 

 for the proper maintenance of a levee. In the long run it will be 

 found infinitely more profitable to incur this small regular expense 

 than to invite disaster during some period of unusually high water 

 by permitting the levee to deteriorate to the danger point. Proper 

 maintenance will be found the best economy in the end. 



For a more complete discussion of levee construction, methods 

 of protecting inadequate work in emergencies, and the repair of 

 levees after they have been overtopped and broken, the reader 

 should consult a previous publication. 1 



INTERIOR DRAINAGE DITCHES. 



An excessive and injurious amount of drainage water may accumu- 

 late within the district from three sources: (1) Rainfall, (2) run-off 

 from higher lands draining naturally into the district, and (3) seep- 

 age under the levees when the river level is higher than the surface 

 of the land inside the levee. This water must be collected in ditches 

 and led to some suitable point near the levee where the pumps may 

 lift it over the levee and discharge it into the river. The amount 

 of rainfall to be removed by pumping depends upon the amount and 

 distribution of the seasonal precipitation. 



' U. s. Ucpi. .Ut., ohm liiil. i.'ih, separate 9, Report of Drainage Investigations for 1904. 



