18 BULLETIN 724, U. S. DEPARTMENT OF AGRICULTURE. 
Character of soil, mixture of light clay and fine sand. 
Slope of ditch (grade), 6 per cent. 
Length from summit to where erosion begins, 150 feet. 
Below 200 feet it has been necessary to employ breakers, and below 400 
feet the breakers have been washed out on several occasions and the 
ditch has become dangerous to traffic. 
Example No. 5. — Same road and same conditions as No. 4, except width 
drained by side ditch, 13 feet: 
Slope of ditch (grade), 11 per cent. 
Length, 600 feet, no erosion. 
Example No. 6. — Washington-Baltimore road: 
Age of road, 5 years. 
Original shape of ditch, wide flat V. 
Width of roadway, 27 feet. 
16-foot bituminous macadam surface. 
Average width drained by side ditch, 16 feet. 
Character of soil, sandy clay with considerable gravel. 
Slope of ditch (grade), 4 per cent. 
Total length of ditch, 900 feet. 
Below 800-foot point the ditch has eroded slightly, but maintenance is very 
light. 
Example No. 7. — Washington- Atlanta highway in North Carolina : 
Age of road, over 5 years. 
Original shape of ditch, irregular but approximates the cross section shown 
in figure 1, with average bottom width of about 1 foot. 
Width of roadway, 24 feet. 
Earth road. 
Awerage width drained- by side ditch, 18 feet. 
Character of soil, clay loam. 
Slope of ditch (grade), 21 per cent. 
Length from summit to where erosion begins, 1,000 feet. 
Water turned off at 1,100 feet. 
Example No. 8. — Same road and same conditions as No. 7, except slope of 
ditch, 4 per cent: 
Length from summit to where erosion begins, 500 feet. 
Ditch becomes dangerous to traffic below 600 feet. 
Example No. 9. — Same road and same conditions as No. S, except soil is a 
very stiff clay and slope of ditch is 1\ per cent : 
Length from summit to where erosion begins, 500 feet. 
Difficult to maintain ditch below 600 feet; water turned off at about 700 
feet. 
GUTTERS. 
Where the grade of a road is so steep that the ordinary earth side 
ditches can not be maintained satisfactorily at a reasonable cost, or 
where earth side ditches would be unsanitary or appear unsightly, 
it is customary to provide paved gutters for removing the surface 
water. The point at which it is economical to change from earth 
side ditches to paved gutters on account of the steepness of the grade 
depends on the character of the soil and the amount of water to be 
