Attack by Drainage 143 



Where sharp bends or curves occur in lined 

 ditches, and especially on heavy grades, provision 

 must be made to prevent storm water climbing 

 out of the ditch, and undermining a considerable 

 section of the lining. This is easily arranged by 

 introducing one or more key walls on the outer 

 side of the curve, widening the ditch near the 

 point of curvature, or by raising the outer wall in 



Goncrete Lining 



EelnforcingTViro 



Reinforced Goncxete Tlnlng, J 



Junction of branch ditch with a lined ditch. 



the vicinity of the point of curvature. In small 

 ditches the same result is obtained by decreasing 

 the slope of the outer wall, or making it vertical 

 near the point of curvature. 



It is not advisable to have a branch ditch meet a 

 larger ditch and be at right angles to it. It is 

 better to curve the small ditch near the junction 

 of the two so that they meet in a Y joint. If this 

 is not done, much vegetable debris, mud, and stone 

 may be deposited in the smaller ditch. It is well 

 to make the main ditch somewhat wider at junc- 

 tion points, sharp bends, and points of curvature. 



