A spillway is a passage that allows surplus water to pass over or around a dam when the reservoir is full. Spillways are crucial safety features for many types of dams. They may lead over the dam, around it via a channel, or through a conduit. Spillways should discharge surplus water automatically, handle the largest floods without raising the reservoir level excessively, and avoid increasing downstream flood problems. The energy of discharged floodwater must be controlled to prevent damage to the dam and riverbed.

Why are spillways important in dams and reservoirs?

Spillways are crucial for dam safety, providing a passage for surplus water when a reservoir is full. They prevent overtopping, which can have serious consequences, especially for earthfill dams. An inadequate spillway may lead to erosion and catastrophic failure of the dam. Spillways allow the automatic, uncontrolled discharge of extra water past the dam. A wide spillway intake ensures that large floods pass without raising the reservoir level excessively. The discharged floodwater's energy is controlled and dissipated to prevent damage to the dam structure and riverbed.

How does a spillway control the flow of water?

Spillways are crucial for dam safety, providing a passage for surplus water when a reservoir is full. They operate automatically, discharging excess water without human intervention. Spillway intakes are designed to be wide enough to handle large floods, preventing significant increases in the reservoir's water level. By controlling the flow, spillways prevent overtopping, which can cause erosion and catastrophic failure, especially in earthfill dams. Some designs also incorporate features to dissipate the water's energy, preventing damage to the dam's structure and the riverbed.

What are some different types of spillways used in engineering?

Spillways are crucial for dam safety, providing a passage for surplus water when a reservoir is full. They prevent overtopping, which can cause catastrophic failures, especially in earthfill dams. Different types of spillways include: * Open Spillways With concrete gravity dams, the sloping downstream face of the structure can serve as the spillway. * Ski-jump Spillways Higher dams use these to deflect the jet of spilling water from above the dam's base. * Shaft and Tunnel Spillways These carry water away to a point downstream, using self-priming siphons or bell-mouthed drop shafts, also known as morning-glory spillways. * Gated Spillways Arch dams use gated openings in the shell structure to discharge water downstream.

How do engineers design spillways to handle different amounts of water?

Engineers design spillways to automatically discharge surplus water around a dam when the reservoir is full, with the spillway intake wide enough to handle the largest floods without raising the reservoir water level excessively. The rate of floodwater discharge should not increase much above that experienced before the dam was constructed to avoid causing flood problems downstream. Spillway design depends on the dam type. Embankment dams typically have a separate spillway structure to the side, while concrete gravity dams often use the sloping downstream face as a spillway. Other designs include shaft and tunnel spillways, gated openings, and ski-jump spillways.

What problems can occur if a spillway fails or is not designed properly?

If a spillway fails or is not designed properly, serious consequences can occur, especially for earthfill dams. Overtopping, resulting from inadequate spillway capacity, can erode the dam and its foundations, potentially leading to catastrophic failure. Even spillage over a concrete gravity dam can erode the foundation at the downstream toe. A properly designed spillway should automatically discharge surplus water, accommodate large floods without raising the reservoir level excessively, and control floodwater discharge to prevent downstream flooding. It should also manage the energy of discharged water to prevent damage to the dam structure and riverbed.

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What is a spillway?
A spillway is a passage that allows surplus water to pass over or around a dam when the reservoir is full. Spillways are crucial safety features for many types of dams. They may lead over the dam, around it via a channel, or through a conduit.

Spillways should discharge surplus water automatically, handle the largest floods without raising the reservoir level excessively, and avoid increasing downstream flood problems. The energy of discharged floodwater must be controlled to prevent damage to the dam and riverbed.
2 Britannica Sources
1. dam: Spillways
2. spillway
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Why are spillways important in dams and reservoirs?
Spillways are crucial for dam safety, providing a passage for surplus water when a reservoir is full. They prevent overtopping, which can have serious consequences, especially for earthfill dams. An inadequate spillway may lead to erosion and catastrophic failure of the dam. Spillways allow the automatic, uncontrolled discharge of extra water past the dam. A wide spillway intake ensures that large floods pass without raising the reservoir level excessively. The discharged floodwater's energy is controlled and dissipated to prevent damage to the dam structure and riverbed.
2 Britannica Sources
1. dam: Spillways
2. spillway
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How does a spillway control the flow of water?
Spillways are crucial for dam safety, providing a passage for surplus water when a reservoir is full. They operate automatically, discharging excess water without human intervention. Spillway intakes are designed to be wide enough to handle large floods, preventing significant increases in the reservoir's water level. By controlling the flow, spillways prevent overtopping, which can cause erosion and catastrophic failure, especially in earthfill dams. Some designs also incorporate features to dissipate the water's energy, preventing damage to the dam's structure and the riverbed.
2 Britannica Sources
1. dam: Spillways
2. spillway
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What are some different types of spillways used in engineering?
Spillways are crucial for dam safety, providing a passage for surplus water when a reservoir is full. They prevent overtopping, which can cause catastrophic failures, especially in earthfill dams.

Different types of spillways include:
* Open Spillways With concrete gravity dams, the sloping downstream face of the structure can serve as the spillway.
* Ski-jump Spillways Higher dams use these to deflect the jet of spilling water from above the dam's base.
* Shaft and Tunnel Spillways These carry water away to a point downstream, using self-priming siphons or bell-mouthed drop shafts, also known as morning-glory spillways.
* Gated Spillways Arch dams use gated openings in the shell structure to discharge water downstream.
2 Britannica Sources
1. dam: Spillways
2. spillway
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do engineers design spillways to handle different amounts of water?
Engineers design spillways to automatically discharge surplus water around a dam when the reservoir is full, with the spillway intake wide enough to handle the largest floods without raising the reservoir water level excessively. The rate of floodwater discharge should not increase much above that experienced before the dam was constructed to avoid causing flood problems downstream.

Spillway design depends on the dam type. Embankment dams typically have a separate spillway structure to the side, while concrete gravity dams often use the sloping downstream face as a spillway. Other designs include shaft and tunnel spillways, gated openings, and ski-jump spillways.
2 Britannica Sources
1. dam: Spillways
2. spillway
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What problems can occur if a spillway fails or is not designed properly?
If a spillway fails or is not designed properly, serious consequences can occur, especially for earthfill dams. Overtopping, resulting from inadequate spillway capacity, can erode the dam and its foundations, potentially leading to catastrophic failure. Even spillage over a concrete gravity dam can erode the foundation at the downstream toe. A properly designed spillway should automatically discharge surplus water, accommodate large floods without raising the reservoir level excessively, and control floodwater discharge to prevent downstream flooding. It should also manage the energy of discharged water to prevent damage to the dam structure and riverbed.
2 Britannica Sources
1. dam: Spillways
2. spillway
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

spillway, passage for surplus water over or around a dam when the reservoir itself is full. Spillways are particularly important safety features for several types of dams. They may lead over the dam or a portion of it or along a channel around the dam or a conduit through it, and the erosive energy of the water at the foot of the spillway is dissipated away from the foundation.

Serious consequences can follow if a dam is overtopped. Disaster is likely in the case of an earthfill, or embankment, dam that was not designed to permit uncontrolled flow of water on its downstream slope. In the case of an inadequate or missing spillway, overtopping can dramatically erode such dams and their foundations, possibly leading to a catastrophic failure. Indeed, inadequate spillway capacity has been a problem for many older earthen dams built before modern flood data became available. Spillage over a concrete gravity dam is also serious, because the floodwater erodes the foundation at the downstream toe. Arch dams possess greater resistance to failure after overtopping.

Four general aspects of spillways are worth noting. First, the uncontrolled discharge of surplus water past the dam should be automatic and not dependent upon human control. Second, the spillway intake should be wide enough so that the largest floods can pass without increasing the water level in the reservoir enough to cause a nuisance to upstream property owners. Third, the rate of floodwater discharge should not increase much above that experienced before the construction of the dam. An increase in discharge can cause flood problems downstream, but a dam usually reduces the peak discharge rate because of the lag effect caused by a flood passing through the reservoir. Fourth, floodwater discharged over the height of a dam can be destructive to the dam structure itself and to the riverbed unless its energy is controlled and dissipated in harmless turbulence.

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