18 BULLETIN 124, IT. s. DEPARTMENT OF AGEICULTUKE. 



Character of soil, mixture of light clay and tine 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), 1^ per cent. 



Length, 600 feet, no erosion. 

 Example No. 6. — Washington-Baltimore road: 



Age of road, 5 years. 



Oi'iginal, 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 (gi'ade), 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. 



AJverage width drained- by side ditch, 18 feet. 



Character of soil, clay loam. 



Slope of ditch (grade), 2i per cent. 



Length from summit to where erosion liegins, 1,000 feet. 



Water turned oft 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 7^ 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 jjrade 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 wonld l)e 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 oi water to be 



