6 BULLETIN r)12, U. S. DEPAKTMENT OP AGRICULTURE. 



Terracing affords the best means of conserving the hillside soils 

 against the washing due to heavy rains. 



A field trip was made by the writer through the States of North 

 Carolina, South Carolina, Georgia, Alabama, and Mississippi for 

 the purpose of studying the nature, causes, and effects of erosion, and 

 more particularly the method of preventing erosion by means of 

 terraces. Surveys of terraced fields which afford typical examples 

 of every form of terrace in use were made with a view to deducing 

 from a close study of the field data comprehensive and definite in- 

 structions for the design and construction of adequate and efficient 

 systems of terraces. It w^as found that a great diversity of opinion 

 exists among the landowners as to the best form of terrace and in 

 the rules employed in planning a system of terraces. However, this 

 difference of opinion, in most cases, could be attributed directly to 

 varying conditions of soil and topography or to differences in 

 farming methods. 



The subject of the proper methods of terracing was discussed at 

 length with experienced farmers — ^men who are pioneers in the prac- 

 tice of terracing and who are interested vitally in the preservation 

 of their lands for themselves and their posterity. The deductions 

 and conclusions reached are the result of an endeavor to treat from 

 an engineering standpoint the information obtained from actual 

 observation of field conditions in connection with the data derived 

 from field surveys and the advice and opinions of the best informed 

 and m.ost experienced farmers. 



DEFINITION AND CLASSIFICATION OF TERRACES. 



As applied to the protection of ^arm lands, a terrace is any ar- 

 rangement or disposition of the soil the object of which is to retard 

 the rapid movement of surface water and thereby arrest the process 

 of erosion. According to the earliest practice, terracing consists of 

 building land up in a series of level areas resembling stair steps, the 

 interval between the risers being horizontal and the riser itself being 

 vertical or nearly so. This type of terrace has long been used ex- 

 tensively in Europe and China and is used to a great extent on the 

 steeper lands in the United States. It is known generally as the 

 level bench terrace, but to avoid confusion in the use of the term 

 " level " it will be referred to in this paper as the horizontal bench 

 terrace. Strictly speaking, this is the only true terrace, but the word 

 " terrace " in this country is applied also to ridges of soil thrown up 

 and located in such manner as to prevent the rapid flow of water 

 down a slope. This type of terrace will be referred to in this paper 

 as the ridge terrace to distinguish it from terraces of the bench type. 

 The following classification (fig. 1) of terraces shows the various 

 forms of bench and ridge types. 



