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1. Dam illustration

2. SPILLWAY
• A spillway is a structure used to provide
for the controlled release of flows from
a dam or levee into a downstream area,
typically being the river that was
dammed.
• to prevent overtopping and possible
failure of the dam.
2
Four Mile Dam, Australia –
Ogee Spillway

3. Spillway

4. Essential requirements of spillway

6. Spillway

7. Types of spillways
• Main spillway
• Subsidiary or emergency spillway

8. Components of spillway
• Straight head spillway
• Ogee spillway
• Side channel spillway
• Chute spillway
• Tunnel spillway
• Siphon spillway

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Free overfall or straight drop spillway
•In this type, water drops freely from the crest.
•Occasionally the crest is extended in the form of overhanging lip
to direct small discharges away from the face of overfall section.

10. Straight head spillway
1. It should be consists of lower height.
2. Narrow crested weir at the downstream side.
3. The overflow of water pass though free
nappe or crest weir
4. It should be consists of lower dams and rock
fill and earthen dams
5. It is not suitable for weak type of foundations

11. Straight head spillway

15. Ogee or overflow spillway
•The Ogee spillway is generally provided in rigid dams and forms a part of the
main dam itself if sufficient length is available.
•The overflow type spillway has a crest shaped in the form of an ogee or S-
shape.
•The upper curve at the crest may be made either larger or sharper than the
nappe.

16. Ogee spillway

18. Ogee spillway

19. Ogee spillway design

20. Ogee spillway

25. Steeped spillway

26. Side channel spillway

27. Side channel spillway

30. Chute spillway
•chute spillways are used in flow ways where water is to be lowered from
one level to another and where it is desirable to avoid a stilling basin.
•These are mostly used with earth dams and have the following merit.
It can be provided on any type of foundations.
Simplicity of design.
However this type of spillway should not be provided where too
many bends are to be given as per topography.
Baffle apron or chute spillway

31. Chute spillway

32. Chute spillway

33. Chute spillway

36. Tunnel spillway

37. Tunnel spillway

42. Siphon spillways
• Instead of allowing water to spill over the
crest of a dam the surplus water may be
discharged d/s through siphon spillways
consisting of one or more units.
Types of siphon spillways
saddle siphon spillway
volute siphon spillway

43. Saddle spillways
•A siphon spillway is a closed conduit system formed in the shape of an
inverted U.
•This type of siphon is also called a Saddle siphon spillway.
•Siphonic action takes place after the air in the bend over the crest has been
exhausted.
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44. 44
Spillways
Overflow
Side
Channel
Chutes
Tunnel
Siphon