A spillway is the outlet portion of the dam, over which surplus discharge flow from the reservoir to the downstream. Hence, a spillway is known as surplusing work.
Purpose of Spillway
- It resists water pressure at the mid reservoir level.
- It can be able to control excessive flood water.
- It can be able to save free-board and crest of the dam.
- It’s shape and size so constructed that it should be able to resist excessive water pressure.
- It should be able to protect the downstream side portion of the dam water-fall into the downstream.
Types of Spillway
- Waste weir type
- Ogee type
- Chute Spillway
- Straight drop type
- Siphon type
- Conduit type
- Shaft type
- Crest type
At the top of the spillway control gate is constructed that is called spillway gate.
It may be different type
- Dropping shutters or permanent flash-boards.
- Stop logs and needles.
- Verticle lift-gate or rectangular gate.
- Redial or triangular gate.
- Drum gate