18 
BULLETIN 190, U. S. DEPARTMENT OF AGRICULTURE. 
BULKHEADS. 
A bulkhead should be constructed at the outlet of the underdrainage 
system to avoid injury from frost and caving of the banks at that 
point. This may be made of concrete, brick, or timber. Care should 
be taken that it has a good foundation, in order that it may not be 
undermined. , Figure 
11 shows a concrete 
bulkhead which may 
be easily and cheaply 
installed and which 
will give satisfactory 
service. A network of 
wires or small rods of 
copper or iron should 
be placed across the 
outlet to keep out 
small animals. 
Section A -B 
iff. 
SOME TYPICAL PROB- 
LEMS AND THEIR 
TREATMENT. 
INTERCEPTION OF LATERAL 
SEEPAGE. 
Figure 12 is a 
map 
and cross section of a 
typical case of water- 
logging due to seepage 
from higher lands, to 
which the interception 
method of drainage 
should be applied. 
The damaging water 
is conducted through 
a pervious stratum 
that lies at a moderate 
depth, and owing to a 
Fig. 11.— Concrete bulkhead for protection of outlet of tile-drainage change in slopefrom a 
system ' steep to a lighter grade 
this water is forced to the surface. 1 The drain should be located at 
the change in slope, as shown, and should be run diagonally across 
1 The slopes of the land are indicated by lines drawn across the map, any one of which lines passes through 
points of the same elevation, this elevation being that shown on the line. These are called contour lines. 
The lines shown on the map are at 1-foot vertical intervals, and may be compared with the successive shore 
lines of a pond of water which is rising or falling 1 foot at a time. It is plain that the degree of slope of 
the land is indicated by the frequency of the contour lines, the latter being close together on steep land 
and spread apart on land of slight slope. 
