EarthEarth ScienceEnvironment

What is a Dam? Components and Different Types of Dams

All Different Types of Dams and Components Explained:

Dams are water reservoirs or just a wall-like structure built across a river to retain the water and increase the flow when needed, used for electricity generation, and various other functions.



Most of the people have several questions about the basics of a dam and various purposes of it. Also, it may be an excellent question for students in exams too.

So here in this article, we will discuss all things about a dam so that you can easily understand and retain it for a long time. Hence, let’s dive right in.

What Is the Dam?

So, before knowing different sorts of dams, the first question is, what a dam is?

Thus, in simple words, dams are structures built for water storage for different purposes in the future. In other terms, we can say dams are human-created large impervious material structures to reserve water and to control its flow. The upstream side of a dam is called a reservoir, where the water mass has been stored for various requirements.

A dam can be built for a single purpose or multiple purposes. For example, sometimes dams are created only for irrigation or electric power production or simply navigation purposes.

Purposes of Building a Dam

The artificially created barriers called Dams are used for various purposes. Some of the major requirements are written below.


Water reserved in dams is mostly used for irrigation. By constructing a dam in a specific water source, the water is directly transported to a crop field.

Flood Control

Other than irrigation, the mass of water in dams is also used to control the flood to save many lives near the river area. The dams built and utilised for flood control hold floodwaters and then release that water into the lower region of the river or simply store and use that for other purposes.

Water supply

Another function of a dam is storing, purifying, and distributing water evenly in various locations through channels and pipelines.

Hydropower Generation

In addition to the above purposes, the most critical functions of creating a dam are to generate electricity. Nowadays, power has become an essential factor in living. Most of the electricity comes from freshwater reservoirs by making a dam where we convert the mechanical energy of water into electrical energy.

Water storage

For agriculture, municipal and industrial usage, water is stored by constructing a dam, which acts as a reservoir.


By creating a dam, we can provide lots of recreational activities such as skiing, boating, picnic facilities, camping, etc.

Navigation of flow

We can also navigate water flow in a particular area by just constructing a dam or lock.

Control of Debris

Yes, the dam is also used to control pollution. Dams can help safeguard the environment by storing harmful items (hazardous materials) and preventing or controlling sedimentation.

Components (Structure) of Dam

There are different kinds of dams, but various dam components remain the same in each case. Dam generally has an upstream slope and a downstream slope, and both have different sections. Thus, several parts of a dam are given below:




The crest is the top part of a Dam, used for providing a walkway above.


The heel is the part that touches the ground on the upstream side of a dam.


Like the heel, the toe is a structure that remains in contact with the river-bed on a downstream slope.

Parapet walls: 

Parapet walls are the less protecting walls on each side of the roadway or walkway of the crest.


The gallery is a small room like space that is transverse or longitudinal in shape inside the dam. The gallery is required as a drilling grout holes and drainage hole and for monitoring the dam’s operation.


For the surplus water movement from the pool, a sort of passage was made known as a spillway. The spillway is of two types; one is controlled where gates control the water flow, and another one is uncontrolled, where the only control is the elevation of spillway crest. Further, four types of spillways are present according to the structure: auxiliary, fuse plug, bell mouth, and siphon.


On either side of the dam wall, which serves as an abutment for the left and right ends of the dam, the valley slopes.

Sluice way: 

Aperture in the structure near the bottom part arranged for cleaning the silt gathering in the reservoir.


The freeboard is the gap between the uppermost level of water in the reservoir and the structure’s cap.

Dead Storage level: 

It’s the permanent storage level below which water won’t be taken out.

Diversion Tunnel:

A diversion tunnel is a channel made to divert the way of water flow to bypass it to the construction site. Therefore, the river flows through it during the construction of hydraulic structures.

Different Types of Dams

Dams are classified into various types based on multiple factors like hydraulic design, functions, the material of construction, structure, or even materials. So, let us know the different kinds of dams according to various aspects.


Types Based on Hydraulic Design

Based on the hydraulic design, there are two types of dams;

Overflow dam

Overflow dams are made for the passage of excess water which cannot store in the reservoir. Such dams permit the overflow of water over the entire length of the dam crest. Furthermore, overflow dams are the concrete type of dams.

Non-overflow dam

In some cases, there is no spillway made for the passage of surplus or overflow water. So, these are known to be non-overflow dams.

Types Based on Various Functions

According to the various functions, five kinds of dams are found;

Storage Dam or Impounding Dam

The storage or impounding dams are the most common types used to retain water, especially in the rainy season, when most of the rainwater surpasses and wastes. That stored water can be used in the summer when water is scarce. We can also use such a reservoir for the fishery or any other similar purpose. Further, we can use that stored water for agriculture, hydropower generation, or water supply to different locations. So, as we can use these dams for various purposes, these come under multi-purpose dams.

Detention Dam

These are otherwise known as flood control dams as their function is to prevent a flood. During floods, detention dams store some flooded water to avoid the downstream area from being damage by a surge. Thus, when the situation improves, it allows the excessive water in a control spillage and thus protects the city.

Diversion Dam

For diversion of water into different canals, ditches, and other conveyance systems, diversion dams are constructed. In other words, a diversion dam can also be called a storage weir, otherwise used as a compact storage dam for irrigation.


Coffer is a temporary dam made for constructing full form in a dry condition that eases building. However, the cofferdam encloses the construction site during the low flow of water.

Debris Dam

A debris dam is made for the retention of debris such as sand, driftwood, and debris in the flowing river water. So, the pure water is released from the other side, supplied and used as drinking water to various regions through canals and pipelines.

Types Based on the Material of Construction

If we classify the dams according to the construction material, we get two types. That is,

Rigid Dam

If the dams are constructed with rigid materials such as stone, timber, steel, masonry, or concrete, they are called rigid dams.

Non-rigid Dam

Unlike the above one, the non-rigid dam is formed of non-rigid materials like tailing, rockfill, etc.

Types Based on Structure

Again, based on the structure, there are the following types of dams;

Arch Dams

For transferring the water pressure and other forces, the upstream of some dams are curved, known as arch dams. Idukki dam is an example of an arch dam in India. There are many benefits of an arch dam as they are powerful, need less constructing material hence cheaper, and are suitable for narrow regions.

Gravity Dams

Gravity dams are triangular-shaped made up of masonry. Generally, four different kinds of gravity dams are found, such as straight, curved, hollow, and solid gravity dams. Moreover, these are of massive size for retaining a large quantity of water. The Grand Coulee Dam (USA) is an example of a gravity dam.

Buttress Dams

It is supported by a series of buttresses (triangular concrete walls) and consists of sloping membranes (protected concrete slabs) and decks for water retention. It is similar to that of gravity dams in structure and can be classified under a gravity dam. Such dams are of three types; multiple-arch type, deck type, and massive head type. However, these are sometimes called hollow dams as they don’t form the stable wall. Examples of Buttress dams are Bartlett dam (USA) and The Daniel-Johnson Dam (Canada).


The particular kind of dam formed with many gates for controlled passage of water is known as barrages. These are also used at the lagoon to extract tidal energy, and such type is known as a tidal barrage.

Embankment Dams

These dams are trapezoidal in structure and form of the earth (clay, sand, and gravel), relatively smaller in size, and broader at the bottom used for support in a region where concrete dams are weakened. Furthermore, this is a non-rigid dam.

Types Based on Material

And finally, based on the varieties of materials, two dam types are found. These are such as;

Steel dams

So, Steel dams are generally named so as the upper stream of such dams is made up of steel plates. This is of two types, such as Direct strutted and cantilever.

Timber dams

Timber dams are made up of some kind of pine and fir. Hence, these are short head dams that can be classified as pile, crib, pile-crib, and buttress type.


We discussed various purposes of dams, which can otherwise be considered as advantages of their construction. So, now let us know some of the limitations of it.

  • Nature has its settings, but these artificially made dams are ruining the natural beauty of water resources.
  • Due to river valley flooding, several wildlife animals are suffering.
  • The local people are said to be displaced for the construction projects.
  • The dams also ruin the seasonal migration of fishes.
  • Expensive to build.
  • Soil erosion happens downstream due to over spillage of water.
  • It’s destroying the aquatic ecosystem.


Dams have become a superior technology discovered from ancient times. At that time, we didn’t require much energy, and we used dams as a reservoir for irrigation purposes. Water is the most crucial aspect of life on earth as air and soil. And with the increased population, the usage of water also increased.

Nowadays, we must need electricity to operate all types of electronic gadgets, which makes our lives easier. For that reason, dams are created in most rivers where hydroelectric power generation is a significant function. Besides, a large population needs a vast quantity of food as well, for that also dams are created and used mostly.

After all, good and bad are mirror images of each other. So, we should never be dependent on anything too much to be the primary reason for our destruction.

Therefore, here, we described the definition of dams, their different types, various components, and the negative side of it to get control over things.

Let us know whether you have any doubts by commenting down below; we’ll instantly clear your doubt.


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