178 



ENGINEERING FOR LAND DRAINAGE. 



which requires large flood capacity for a short time 

 only. 



D is the form of shallow scraper ditch suitable for 

 surface drainage and overflow ditches. They may be 





D 



-' — Z^mune 



Tr'7?r'^7"'7 ' ' ' W, 



mj 



*FiG. 33 — Sections of Open Ditches. 



mere depressions which can be easily crossed with teams 

 or may be moderately deep ditches with flat sloping 

 sides which can be cleared of grass and weeds by the 

 use of the mowing-machine. 



Such a form of ditch should be selected as will be 

 suited to the purpose, taking locality and work to be 

 accomplished into account 



