32 
BULLETIN 675, U. S. DEPARTMENT OF AGRICULTURE. 
systems can usually be effectively broken up by the construction of 
terraces laid out approximately at right angles to the gullies but so 
placed as to allow water to be carried through their channels. If 
reinforced by small rock fills built into the washes at sufficiently 
frequent intervals to check the run-off before the cumulative effect 
of the water's force becomes uncontrollable, the terraces appear to 
be effective. 
Terrace 
Roe* butt 
Dry rill 
Continues 
< Plays out 
Fig. 7. — Tree and shrub planting to check erosion. 
The place of successful attack of an evil like the one in question 
is at the origin of its source. In order thoroughly to test the value 
of terraces located near the heads of the gullies and planted to soil- 
binding species, a badly gullied area was selected on a southwest 
slope at an elevation of approximately 10.000 feet. This study is 
still in an experimental stage. As shown in figure 7. the distances 
between the terraces which were established vary considerably, being 
determined by the number of gullies and other topographic features. 
In establishing a terrace, strips are plowed about 4 feet wide, or 
even wider on the steeper slopes, following which the loosened soil 
