STBUCTUBES TJSED 1ST DBAINING AGBICULTTJBAL LAND 
17 
Where occasional floods pass from high lands down the main 
drains, water must be prevented from backing up in laterals across 
flat bottom land. The type of structure used is similar to an ordi- 
nary sluice gate hinged at the top, except that the gate is placed 
at the inner instead of the outer end and a manhole is over the 
gate to permit of easy inspection and for making repairs. 
Plate 2, F shows a sluiceway with hand-operated gates. At the 
location of these gates there is no tidal action, but they protect part 
of the interior area from river floods. The structure is under a 
