DRAINAGE 



227 



to keep the ditches open and in good condition (Figs. 98, OS), 100). 

 In a few years the fall may become very uneven, due to more rapid 

 erosion, at one place than at another. Obstructions may get into 



FIG. 98 



FIG. 99 



FIG. 98. The obstructions interfere with the current and cause deflections. (H. C. Wheeler.) 

 Flo. 99. Ditch gradually being filled by soil due to current being retarded by grass. 



(C. C. Comstock.) 



Fio. 100. A neglected ditch often soon in heavily wooded ureas. (.11. C Wheeler.) 



the ditch which will cause deflection? of the current and result in 

 wearing away of the hank. There is always a considerable waste 

 of land in connection witli open drains even at the verv best, and 



