12 Types of Dams With Practical Examples

What Is Dam?

A dam is a hydraulic structure of fairly impervious material built across a river to create a reservoir on its upstream side for impounding water for various purposes which may include, Flood Control, Hydro-power, Water-supply, Irrigation, Navigation, Fishing, and Recreation.

There are various types of dams, each with unique characteristics and construction methods that are suited for specific purposes and environments.

The most common types of dams include concrete dams, earth and rockfill dams, arch dams, gravity dams, and embankment dams.

Each of these types of dams has its own advantages and disadvantages in terms of cost, stability, durability, and environmental impact.

In this article, we will discuss the different types of dams and their characteristics to help understand their suitability for different applications.

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Parts of A Dam

Crest: The top of the dam structure. The crest is sometimes used as a walkway or roadway over a dam.

Parapet walls: Low masonry or concrete walls construction on both sides of the crest to be used as protecting the wall.

Heel: it is part of a dam that is in contact with the ground or riverbed on the upstream side.

Toe: Portion of structure in contact with ground or riverbed at the downstream side.

Spillway: Spillway is the opening or space left on the top dam for the passage of surplus/ excessive water from the reservoir.

Abutments: These are the protecting structure constructed on both sides of the dam ends. Abutments provided protection against the slide of soil.

Gallery: These are the inspection tunnel constructed transverse or longitudinal within the dam with a drain on the floor for seepage water.

Sluice way: It is an opening provided at the base of the dam to empty the dam completely so that no silt remains on the upstream side of the dam.

Freeboard: It distance between the highest level of water in the dam and the top of the dam structure used to store water.

Dead Storage level: Level of water below which no water can withdraw from the dam.

Diversion Tunnel: It is a structure constructed to bypass the flow of water from the dam.

21 Different Types of Dams

1. Storage Dams

Storage dams are mainly constructed to collect water during the monsoon season when there is a large amount of water flowing in the river, channels, and streams.

These dams are also used to water supply or improve habitats for fish and wildlife.

Storage dam water can be used for hydroelectric power generation, irrigation, or flood control projects. These dams are the most common type of dam whose major application is to store water during the rainy season.

2. Diversion Dams

The main function of the diversion dam is to divert river water into the off-taking canal. These dams provide sufficient guidance for pushing water into ditches, canals, or other conveyance systems.

Such a small dam is used in irrigation work, and for diversion from a stream to a distant storage reservoir. These are generally constructed with a small height and storage reservoir on the upstream side.

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3. Detention Dams

These dams were constructed to serve as flood control structures. A detention dam stores the flood water on the river downstream to control the sudden water flows.

Thus it minimizes the sudden effect of flood and gives sufficient time to the government to take precautionary steps.

The water that is stored during floor control is afterward gradually released at a controlled rate according to the carrying capacity of the channel downstream of the detention dam.

4. Debris Dams

This dam is mainly constructed to collect debris, silt, and gravel from the river. So that they may not enter the main dam storage reservoir.

5. Cofferdams

A cofferdam is an enclosed structure built around the dam side so that river water may not enter it and provide dry space for work. So, it can be defined as a temporary dam constructed to facilitate dam construction work.

The cofferdam is generally constructed upstream of the main dam to divert water into a diversion tunnel (or channel) during the construction of the dam.

Cofferdam constructed when the flow in the river is too high, the site is usually enclosed by the cofferdam and pumped dry.

6. Gravity Dams:

A gravity dam is a huge-sized dam mainly constructed from concrete or stone. They are capable of holding a large amount of water behind them.

For this dam construction, if the concrete is used the weight of the dam is actually able to resist the horizontal thrust of water pushing against it.

This is why it is named a gravity dam. Gravity forces mainly hold the dam to the ground and are present from any seepage action.

Gravity dams are well suited for multipurpose projects as they can hold river water in wide valleys or narrow gorges ways.

Since a gravity dam mainly holds backwater by its self-weight, it is necessary that it is built on a solid foundation of bedrock.

Examples of Gravity dams: Grand Coulee Dam (USA), Itaipu Dam, and Nagarjuna Sagar (India) (It lays Between Brazil and Paraguay and is the largest in the world).

7. Earth Dams

These dams are fully constructed from natural earth material by compacting the successive layer of earth on each other, using the most impervious materials to form a core, and placing more permeable substances on the upstream and downstream sides.

The upstream and downstream face of an earth dam is covered with crushed stone to prevent erosion by wind or rain, and an ample spillway, usually of concrete, protects against catastrophic washout should the water overtop the dam.

Earth dam is capable of resisting forces acting upon it mainly due to the shear strength of the soil. The earth dam’s weight also helps in resisting the forces; the structural behavior of an earth dam is entirely different from that of a gravity dam.

The earth dams are generally constructed in wide valleys having flat slopes at flanks (abutments).

For constructing an earth dam foundation requirement is not essential as in the case of a gravity dam, and hence they can be built at sites where the foundations are less strong. 

It is suited to any type of foundation. However, earth dam height is limited and it depends upon the strength of the foundation material.

Examples of earth-fill dams are the Rongunsky dam (Russia) and the New Cornelia Dam (USA).

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8. Rockfill Dams

Rockfill dams are constructed using rock or large-size boulders. On the upstream side of the dam, an impervious membrane layer is placed on the rockfill to reduce the seepage through the dam.

The impervious membrane may be made of cement concrete or asphaltic concrete.

In the early, dams like rockfill dams timber, and steel membranes were also used, but now they are obsolete.

For the distribution of water load and for providing support to the membrane a dry rubble cushion is placed between the rockfill and the membrane.

In some cases, an impervious earth core is placed in the middle to check the seepage instead of an impervious upstream membrane.

It is essential to provide a filter between the rockfill on the upstream and downstream sides of the core so that the soil particles are not carried by water and piping does not occur.

The slope on both sides of the rockfill dam is usually kept equal to the angle of repose of rock, which is usually taken as 1.4:1 (or 1.3:1). 

Rockfill dams require a foundation compared to that requires for the earthen dam.  

Examples of rockfill dams: The Chicoasen Dam (Mexico), Mica Dam (Canada)

9. Arch Dams

It is one of the curve-shaped dams in the plan with its convexity towards the upstream side. The arch dam resists water pressure and other force by abutment by arch action.

This dam is most suitable when there is a good canyon available with strong flanks that are capable of resisting the thrust produced by the arch action.

Its section is almost triangular in shape similar to the gravity dam but the section is comparatively thinner. 

The arch may construct in single curvature or double curvature in the vertical plane. Practically, a double curvature arch dam is proven economical for construction.

Examples of Arch dam: Idukki Dam (India) and Hoover Dam (USA)

10. Buttress Dams In India

Buttress dams in India are of three types: (i) Deck type, (ii) Multiple-arch type, and (iii) Massive-head type. A deck type of buttress dam has a sloping deck supported by buttresses.

The buttresses’ walls are the ones that are triangular in shape. They transmit the water pressure from the deck slab to the foundation. Buttresses are compression members.

Buttresses are typically spaced across the dam site every 6 to 30 meters, depending upon the size and design of the dam. A Buttresses dam is sometimes also known as a hollow dam because the buttresses do not form a solid wall stretching across a river valley.

The deck is generally constructed as a reinforced concrete slab supported between the buttresses, which are usually equally spaced.

In a multiple-arch type buttress dam, the deck slab is replaced by horizontal arches supported by buttresses.

The arches of the dam are generally small and made up of concrete. In a massive-head-type buttress dam, there is no provision of the deck.

An example of a buttress dam in India

• The foundation requirements of a buttress are usually less stringent than those in a gravity dam.

Examples of Buttress types: The Daniel-Johnson Dam (Canada) and Bartlett dam (USA)

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11. Steel Dams

Steel dams are constructed as a steel framework, with a steel skin plate on its upstream face.

Steel dam is classified as (i) Direct-strutted, and (ii) Cantilever type. In direct strutted steel dams, the water pressure is transmitted directly to the foundation through inclined struts.

In a cantilever-type steel dam, there is a bent supporting the upper part of the deck, which is formed into a cantilever truss.

This arrangement introduces a tensile force in the deck girder which can be taken care of by anchoring it into the foundation at the upstream toe.

In the steel dam, the heavier steel section is recommended because tension at the upstream toe may be reduced by flattening the slopes of the lower struts in the bent. However, it would require heavier sections for struts.

Another option to reduce tension is to build a frame together and the entire bent rigidly so that the moment is due to the weight of the water on the lower part of the deck.

This deck is used to offset the moment induced in the cantilever. This system, however, demands bracing and this will increase the cost. These are subjected to corrosion and are costly too.

These dams are almost obsolete. Steel dams are majorly utilized as cofferdam for construction of the permanent ones.

The volume inside the steel cofferdam is then emptied by dewatering and another method so that free space is available for work.

Examples of Steel types: Ashfork-Bainbridge Steel Dam (USA) and Redridge Steel Dam (USA)

12. Timber Dams

In timber, the dam is a small-sized dam in which the main load-taking portion is made of timber, primarily coniferous varieties such as pine and fir.

Timber dams are made for small heads (2-4 m or, rarely, 4-8 m) and usually have sluices; according to the design of the apron, they are divided into a pile, crib, pile-crib, and buttress dams.

The dismantling of the timber dam is restrained by an abutment on sides where the sluice is provided longer it is divided into several openings by intermediate supports: piers, buttresses, and posts.

This open space is covered with wooden shields, usually several in rows one above the other. Simple hoist permanent or mobile winches are used to raise and lower the shields.

Uses of Dam

Major dam uses are discussed below.

Water Supply

• Irrigation
• Electrical Generation.
• Flood Control
• Water Storage.
• Mine Tailings.
• Debris Control.
• Navigation.

FAQs: Dams

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