PREVENTIOlSr OF EROSION BY TEEEACING. 



19 



against subsequent settling. Examinations of a great number of 

 poorly terraced fields showed that breaks occur usually at such cross- 

 ings, because of the failure to build the terrace to a sufficient height 

 or to the required breadth at the base. 



The advantage of crossing a depression at a low elevation lies in 

 the convenience and facility of cultivation. It eliminates the neces- 

 sity of following around abrupt bends in farming operations. Some 

 objections to it are the initial cost of constructing the large embank- 

 ment, the impracticability of cultivating such an embankment, the 



Plan 



103 _ 



102 ■ — .-_c 



101 '^ 



Cross Section atE-p 



Fig. 8. — Showing two methods of crossing gully. Note height of embankment at D. 



extreme susceptibility of this portion of the terrace to failure, and 

 the standing of impounded water above the terrace sufficiently long 

 to injure crops.' The disadvantage of the impounded water can be 

 offset by a tile drain laid down the middle of the depression to 

 a natural drainage outlet, and the adoption of this expedient can 

 not be recommended too strongly. 



Figure 9 shows a cross section taken down the center line of a de- 

 pression, or gully, and the method of removing impounded water and 

 retaining sediment by means of a tile drain and drop inlets. If 

 more rapid drainage is desired on a field of level terraces a complete 

 system of tile drains can be installed. The lateral tile drains should 



