The Dawn of a New Constructive Era 



81 



it is found advisable to construct a new channel which should be 

 located usually down the middle of the valley. Rock is fre- 

 quently found in these valleys and hence it is essential that ^^^^ Methods 

 sufficient borings be made to locate any rock that might be to Follow 

 encountered in constructing the ditches. Experience has shown 

 that by carefully determining the location and area of rock ledges 

 the ditch can be so located as to avoid them. 



The amount of water removed by these streams is so large 

 that it has not been found economically practicable to prevent 

 entirely the overflow of the bottom lands. The amount of runoff 

 that must be provided for on these streams is considerably more 

 than that on the low-lying level areas. Satisfactory results have 

 been secured in reclaiming bottom lands draining from 35 to 50 

 square miles when the ditches provided for one inch in depth in 

 twenty-four hours over the entire watershed. On other streams 

 a somewhat lower rate of runoff has been used with quite satis- 

 factory results. The most important factor seems to be to have 

 the ditch as deep as possible so that during periods of low water 

 in the ditch the bottom can be thoroughly drained. The over- 

 flows that occur after the ditch has been constructed are usually 

 of short duration and many landowners believe they are ben- 

 efited more by the deposit of silt on their lands than they are 

 injured. 



The period of usefulness of ditches constructed in these 

 valleys will depend largely on how successfully erosion on the 

 hillsides is controlled. Control the erosion on the hillsides and 

 you perform a double function ; namely, the conservation of the 

 fertility of the hill lands and the extension of usefulness of the 

 ditches in the lowlands. It has been amply demonstrated in this 

 country and abroad that erosion can be controlled by improved 

 methods of agriculture and the use of terraces. Successful ex- 

 amples of terracing can be found in every Southern state. Con- 

 struction of ditches in the lowlands without proper attention to 

 the hillsides means excessive and frequent maintenance costs if 

 the ditches are to be kept in good working condition. 



A word on the subject of costs. Drainage improvements for 

 low-lying level areas range from $2 to $10 per acre. In the nar- 

 row valleys the cost ranges from $15 to $50 an acre. These costs 

 are for outlet drainage only and do not include the cost of drain- 

 ing the individual tracts or of terracing the hill lands. Neither 

 do these prices include clearing of the lands. 



Costs of 

 Drainage 



