• The spillways may be uncontrolled or controlled types.
  • Uncontrolled spillways do not require any gate.
  • Controlled spillways are provided with gates.
  • Controlled spillways are considered superior to uncontrolled ones, as better control on the reservoir level can be exercised with gates.
  • During low flows,

fig 14.18


  • additional storage can be done in the reservoir with the help of gates.
  • However, during high floods gates are fully lifted or opened so that the full discharging capacity of the spillway may be used to dispose of flood water.
  • In case of earth dams, spillways are not provided with gates.
  • Slakness on the part of lifting the gates, may cause over-topping of the earth dam and may lead to its failure.

Following are the various types of gates, which are commonly used:

1. Flash Boards

2. Stop log or needle gates

3. Tainter gates or radial gates 4. U.S.B.R. Drum gates

5. Bear tap gates

6. Vertical lift gates

7. Rolling gates

8. Trash rack

9. Flap gates

10. Fish Belly Flap gates Brief description and sketches of all the gates are given here one by one.