DRAINAGE METHODS FOR COUNTY ROADS. 17 
gutter would be made of different material from the road crust, and constructed 
at a different time or by a different force of laborers. 
11. The maintenance of side ditches consists in keeping them free from ob- 
structions, and in reshaping them whenever this is desirable in order to prevent 
erosion. While a limited amount of vegetation may be advantageous to ditches 
on steep grades, it should not be such as to interfere seriously with the flow 
of water in the ditch. Where drops are employed they should receive frequent 
attention to see that they are not being undermined and that the water is not 
cutting around them. The design of drops sometimes calls for the use of brush, 
logs, saplings, cut stakes, etc., as these often are the only inexpensive local 
materials available in rural sections. While such designs, if carefully con- 
sidered, may produce drops effective for a considerable period, their use is not 
recommended because of the great danger that the drop will break up tinder 
stress of unusual conditions and the floating parts seriously obstruct the 
ditch. 
12. The following examples have been selected from notes regarding some of 
the existing side ditches which have been observed: 
Example No. 1. — Side ditch on Rock Point road, Charles County, Md. : 
Age of road, li years. 
Original shape of ditch, flat V. 
Width of roadway, 24 feet. 
Width of gravel surface, 15 feet. 
Average width drained by side ditch, including slope, 25 feet. 
Character of soil, very light clay. 
Slope of ditch (grade), 2 per cent. 
Length from summit to where erosion begins, 400 feet. 
Ditch empties into cross drain at 500 feet. 
Example No. 2. — Same road and same conditions as example No. 1, except 
slope of ditch is 3 per cent : 
Length from summit to where erosion begins, 200 feet, 
Ditch maintained with considerable difficulty below the 200-foot point by 
means of wooden breakers. 
Example No. 3. — Side ditch on Owings-Prince Frederick road, Calvert County, 
Md. : 
Age of road, 4 years. 
Original shape of ditch, flat V. 
Width of roadway, 23 feet. 
Sandy-clay surface. 
Average width drained by side ditch including slope, 22-§ feet. 
Character of soil, very light clay with small percentage of fine sand. 
Slope of ditch (grade), 6 per cent. 
Length from summit to where erosion begins, 100 feet. 
At 300 feet the ditch has eroded 1 foot below the original section, and below 
550 feet it is maintained with great difficulty by. means of wooden 
breakers. Below 650 feet, in fact, the entire road has been washed out 
at least twice, notwithstanding the breakers. 
Example No. 4. — Same road as No. 3. 
Original shape of ditch, flat V. 
Width of roadway, 24 feet. 
Sand-clay surface. 
Average width drained by side ditch, including slope, 25 feet, 
66998°— 18— Bull, 724 2 
