8 



BULLETIN 512, U. S. DEPARTMENT OE AGRICULTIJEE. 



depends upon the amount of soil moved down the slope each year and 

 upon the vertical distance between the terraces. It is necessary to 

 maintain a shoulder of earth at the lower side of the bench for slop- 

 ing-bench terraces, and it is advisable that this be done for hori- 

 zontal-bench terraces, for the purpose of retaining that portion of 

 the rain water which does not sink into the soil. This shoulder and 

 the lower side of the embankment should be seeded to grass. (See 

 PI. ly, fig. 1.) The sod permits the use of a steep slope on the lower 



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Fig. 2. — Actual profiles of terraced fields, taken across terraces. 



side of the embankment and protects both the shoulder and the em- 

 bankment from erosion due to surface water overtopping the shoul- 

 der. The leveling-down process mentioned above sometimes is con- 

 tinued ointil the slope of the bench is reversed. Thus, the water falling 

 on the bench will flow to the foot of the embankment above. In this 

 case no shoulder will be required to prevent the water from washing 

 over and eroding the embankment. 



