Spillway:
- Spillway is the passage provided for disposal of surplus flood water on the downstream side without affecting stability of water.
- This is necessary as water will go on rising even above high flood level.
- Also it will start flowing from top of the dam which as a result may affect the stability of dam.
- Therefore,it is essential to provide spillway to dispose surplus water.
Requirements:
The various essential requirement of spillways are:
- Firstly, it must have adequate discharge capacity.
- Secondly, One should provide some devices with it for energy dissipation.
- Thirdly, its discharge should be such that it should not cause flooding on downstream side.
- Fourthly, it must be safe.
- Fifthly, it’s surface must be erosion resistant.
- Lastly, it should be located such that it should not erode downstream toe of dam.
Factors Affecting its capacity:
The various factors which affect its capacity are as follows:
- Inflow
- Capacity of outlet.
- Possible Damage
- Available shortage Capacity.
- Gates of Spillway.
- Site condition.
- Type of dam and its purpose.
- Height of the crest of spillway.
- Geological condition.
Component Parts of Spillway:
The component parts are as follows:
- Body,Weir or Spillway
- Approach Channel
- Energy Dissipators
- Tail Channel
- Guide wall
- Discharge Channel
1.Body,Weir or Spillway:
- It may be Ogee shaped, U shaped, semicircular or circular.
- These are sometimes provided with gates to control flow of water.
2.Approach channel:
- It removes excess water from reservoir and further direct it to downstream side.
- Moreover, it helps in controlling discharge.
3.Energy dissipators:
- These are provided at downstream end of the discharge channel.
- It avoids damage to the dam as a result the high velocity of water may scour the downstream side.
- Generally, Ski jump bucket, roller bucket are provided to dissipate the energy.
4.Tail Channel:
- It conveys spillway discharge to the downstream side.
5.Guide wall:
- It guides the water to flow directly into the reservoir downstream.
6.Discharge Channel:
- The main function is to convey the water safely from reservoir downward to the river.
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