LAND 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. 
1 U. S. Dept. Agr., Office Expt. Stas. Bui. 158, Separate 9, Report of Drainage Investigations for 1904. 
