There are various types of dams used for storage of water, here we will learn the major types of dam with diagram.
A dam is a barrier built into a river or natural stream that creates a reservoir for water or facilitates the diversion of river water.
Water accumulates behind this barrier forming a pool of water, the side on which the water collects is called the upstream side and the other side of the barrier is called the downstream side.
The lake of water that collects on the top of the dam is called a reservoir.
The dam is a very large structure, typically, about half a kilometer in length is constructed around the river to store water for many purposes such as irrigation, industrial supplies, hydropower, recreation etc.
Site selection for dams:
The following points should be considered while selecting the site for the various types of dams as follows:
- A good foundation should be available.
- It should be located in a narrow valley.
- It should have enough space for the spillway.
- They have an impermeable bed and sides to minimize erosion.
- It should serve the purpose of irrigation, drinking etc.
- Materials should be easily available on a nearby site.
- It should have less submerged area i.e. not more than 10%.
- The site should be such that the length of the dam should be minimal as it directly affects the cost.
- It should be easily accessible throughout the year.
Types of Dams with Diagram:
Classification of dams based on the purpose:
Following the various types of dams classified based on purpose as follows:
These dams are used to store water during the rainy season and further, it can be used for various purposes like water supply, hydroelectric generation, and irrigation in the other season.
Cofferdam is a temporary structure built in a river or lake, so that the area below is completely water-free to take the construction work to a reasonably dry state.
Cofferdam is temporarily built for projects such as bridge piers and abutments, dams or locks, etc.
This type of dams are being constructed to avoid the flow of sand, gravel, effluent debris along with rain water in the river.
In this way the water becomes relatively clean after the debris passes over the dam.
This type of dam is of relatively low height. It is specially constructed to convert the river water into a closed canal or drain.
These type of dams are being constructed in case of excessive flood and these such dams control the floods.
Classification of dams based on hydraulic action:
Following the various types of dams classified based on hydraulic action as follows:
Overflow dam in which surplus water is allowed to pass through the crest of the spillway.
Non Overflow Dam:
Non-overflow dam, in which no water flow.
This type of dam can be made from any material like concrete, earth, wood, rock filler, masonry etc.
Classification of dams based on Structural action:
Following the various types of dams classified based on the structural action as follows:
The Gravity Dam is a concrete structure made of masonry or concrete and is built on its own weight across the river.
These dams are heavy and massive wall-like structures with full load downstream.
As the entire load is transmitted over a small area of the foundation, dams are built where the rocks are capable and stable.
This kind of dams is constructed from concrete or masonry dams which are curved or convex within the plan.
This shape helps decompose the major a part of the water load.
Arc dam have been constructed across narrow, deep river however in recent times, they are also considered to have only a few valleys.
Buttress means to assist that exerts pressure from one roof or wall to a different supporting structure.
The buttress dam is a gravity dam reinforced by structural support.
Such a construction might be considered even when the foundation rocks are slightly weak.
These are non-rigid structures constructed on extensive valleys with various foundations.
They are trapezoidal in shape manufactured from the identical kind of material (such as earth filler or rockfill) or a combination of a number of materials.
The primary benefit of those dams is that it may be constructed on a weak foundation, the impervious core is positioned in the middle of the embankment body.
The material used for such a dam is rock fill and earth fill.
Earthern Dam, as well as Rockfill Dam, falls below the type of embankment dam.
Most frequently a large part of a dam might be either an embankment or a gravity dam, with an embankment or gravity dam, responsible for producing electrical energy.
Classification of dam based on Material:
Following the various types of dams classified based on materials used for their construction as follows:
Concrete dams are gravity dams that are usually constructed in large blocks divided by joints to make construction more convenient and reduce thermal stress.
The joints are grooved after the dam cools, the transverse joints are perpendicular to the dam’s axis.
The material used for such a dam is concrete.
Concrete dams are principally classified into two types:
Concrete Gravity Dam:
A concrete gravity dam is an inflexible type of dam by which exterior pressure such as water pressure, wave strain, silt pressure, the uplift pressure is the weight of the dam itself.
All major and critical gravity dams are inbuilt concrete.
Gravity dams of concrete might be straight or curved within the plan.
Concrete Buttress Dam:
This type of dam consists of a number of piers or buttresses which are broken in a number of spans, dividing the space.
Panels are constructed within the form of horizontal arches or flat slabs to retain water between the buttresses.
A dam whose main load bearing structural elements are made of wood are mainly coniferous varieties such as pine and fir.
Timber dams are built for small heads (2–4 m or, rarely 4–8 m) and usually have sluices.
Merits of timber dams:
- There is a great speed in construction.
- These dams are suitable for any type of foundation
- It has a low initial cost.
- These dams are more suitable in places where only temporary dams are to be constructed.
Demerits of Timber Dam:
- The life of such a dam is short.
- This requires high maintenance costs.
- There is great seepage loss through the body of such a dam.
- These dams are suitable only for small elevations.
A steel dam is a type of dam made of steel instead of common earthquake, concrete or wood building material.
Merits of steel dams:
- These dams are cheaper as compared to rigid dams.
- The construction speed is high.
- These dams are not affected by frost action.
- The stresses in steel dams are more firm.
- It has great flexibility to resist uneven settlements without excessive leakage.
Demerits of steel dams:
- It requires continuous maintenance compared to concrete.
- Steel dams are lightweight therefore do not absorb shock from the vibrations of the circulating water.
- The life of a steel dam is shorter than concrete dams.
- It is difficult to anchor the foundation.
The dams which are constructed from clay material like clay sand, silt and clay are called Earthen Dam.
They are trapezoidal in shape and relatively small in height and broad at the base.
Earthen dams are built where foundations or underlying materials or rocks are vulnerable to support a masonry dam or where suitable competent rocks are at greater depths.
Merits of Earthen Dam:
- Use of locally available materials.
- Design and construction is relatively simple and easy.
- Such types of dams have high resistance to settlements and movement under the ground.
- The equipment and plant required are simple and small.
Demerits of earth dams:
- Non-availability of material at or near the dam site.
- Higher maintenance costs than a good concrete dam.
- Earthen dams are unsuitable for spillways.
Rock fill dam:
Rockfill Dam is a type of embankment called Earth-Rock Dam, it is a water-holding barrier.
It is composed of three major parts: fill with a loose rock by dumping or roller compaction, an impermeable membrane made of masonry, concrete, asphalt concrete, steel sheet piles, wood or other materials and a transition layer.
Merits of earth and rockfill dams:
- These dams can be constructed over any available foundation.
- These dams are generally economical compared to other types.
- They can be constructed more rapidly and with unskilled labor.
- These camps can be constructed from locally available materials.
- The height of these dams can be increased without much difficulty in future.
Demerits of earth and rockfill dams:
- These dams can be damaged by floods.
- These dams can fail suddenly without any prior warning.
- It needs heavy maintenance costs.
- This requires constant supervision.
- These dams cannot be used as overflow dams, so separate spillways have to be provided.
- Not suitable in places where heavy recession is more common.
Before constructing the dam, the site selection and preliminary investigation is a vital factor whereas designing the dam and the selection of the types of dams is also depending on the soil condition at the dam site.