PREVENTION OF EROSION BY TERRACING. 



9 



Figure 3 shows a cross section of two adjacent sloping-bench ter- 

 races, with the various dimensions designated by letters for reference. 



Surveys were made of a number of fields in the Piedmont sections 

 of Georgia and South Carolina which have sloping-bench terraces. 

 The average dimensions of the terraces in each field were determined. 

 The minimum and maximum of these averages are shown in the fol- 

 lowing table : 



Actual dimensions ^ of sloping-bench terraces. 



Dimension. 



Height of shoulder, h.... feet . . 



Width of upper side of shoulder, b do 



Vertical distance between terraces, v do 



Ratio of c to (Z : per cent . . 



Slope of land do — 



1 See fig. 3. 



A comparative study was made of the conditions existing in the 

 fields and the data obtained from the surveys with a view to ascer- 



FiG. 3.— Cross section of two adjacent sloping-bench terraces. 



taining proper values to use in constructing a terrace of this style. 

 The best terraces were found where the greatest height and width 

 of shoulder were used with the smallest vertical distance between the 

 terraces. It is believed that the height of shoulder (A) should be not 

 less than 0.5 foot for horizontal-bench terraces or less than 1 foot 

 for newly constructed sloping-bench terraces, and that the width (h) 

 should be not less than 2 feet for the former or less than 3 feet for 

 the latter. The vertical spacing between the terraces should be gov- 

 erned by the type of soil, the slope of the land, and the ease of start- 

 ing and maintaining a heavy sod on a steep and high embankment. 

 The best practice indicates that this spacing never should be less than 

 3 feet or more than 6 feet. The smaller spacing should be used on 

 gently sloping land while the greater spacing applies to steep land. 

 The question of proper spacing depends to a great extent upon the 

 care and maintenance of the terraces. Unless considerable attention 

 is to be given to the maintenance of the terrace banks the smaller 

 71775°— Bull. 512—17 2 



