Dams are barriers that impound water and come in many types defined by their material, structure, size, and purpose. The main types include earth-fill dams, which are constructed from compacted earth and rock; arch dams, which are curved to exert outward pressure on the abutments; and gravity dams, which rely on their massive weight for stability. Dams are classified according to their material, structure, size, and purpose, with common purposes being water storage, diversion, or detention. Selection of the appropriate dam type depends on factors like the landscape, geology, construction materials, and project requirements.

1. DAMS

2. A dam is a barrier that impounds water or underground streams.
Dams generally serve the primary purpose of retaining water, while other structures
such as floodgates or levees (also known as dikes) are used to manage or
prevent water flow into specific land regions.
Hydropower and pumped-storage hydroelectricity are often used in conjunction with
dams to generate electricity.
A dam can also be used to collect water or for storage of water which can be evenly
distributed between locations.

3. A dam is a hydraulic impervious structure constructed across
a river to store water on its up-stream side.
Classification Of Dams By material
By structure a. Steel dams
1 Arch dams b. Timber dams
2 Gravity dams
3 Arch-gravity dams Other types
4 Barrages a. Cofferdams
5 Embankment dams b. Beaver dams
a. Rock-fill dams
b. Concrete-face rock-fill dams
c. Earth-fill dams
d. Asphalt-concrete core
By size
By use
a. Saddle dam
b. Weir
c. Check dam
d. Dry dam
e. Diversionary dam
f. Tailings dam

4. Classification of Dams
Dams are classified into different categories, depending on the purpose.
Types of Dams
Basis of classification Types Examples
According to Use 1. Storage dam Gravity dam, earth dam,
rock fill dam, arch dam etc.,
2. Diversion dam Weir, barrage
3. Detention dam Dike, water spreading dam,
debris dam
By hydraulic design 1. Overflow dam Spillway
2. Non overflow dam Gravity dam, earth dams,
rock fill dam
By materials 1. Rigid dams Gravity dam, earth dam,
buttress dam, steel dam, timer
dam
2. Non-rigid dams Earth dam, rock fill dam

5. A weir is a dam beneath the surface of a stream. In normal conditions the stream flows over the
weir but there is a pool of deeper quieter water behind the weir.

6. Earth-fill dams, also called earthen, rolled-earth or simply earth dams, are constructed as a
simple embankment of well compacted earth. A homogeneous rolled-earth dam is entirely
constructed of one type of material but may contain a drain layer to collect seep water. A zoned-
earth dam has distinct parts or zones of dissimilar material, typically a locally plentiful shell with
a watertight clay core. Modern zoned-earth embankments employ filter and drain zones to
collect and remove seep water and preserve the integrity of the downstream shell zone. An
outdated method of zoned earth dam construction utilized a hydraulic fill to produce a
watertight core.

7. Advantages
Earth-fill dams
1.Can be constructed on any type of
foundation.
2.Can be constructed rapidly
3.Skilled labor not required
4.Can be constructed with material
available nearby
5.Cheaper than other type dams
6.Height can be raised without any
difficulty
Earth-fill dams,
Disadvantages
1.More vulnerable to damage by floods and fail suddenly without any warning indications
2.Cannot be used as overflow dams.
3.Separate spillways have to be provided to avoid overflow and damage
4.Not suitable in places where heavy downpour rains are frequent
5.Maintenance is very high and requires constant supervision.

8. Advantages
Arch Dam Particularly adapted to gorges
It requires less material for
construction.
Construction cost is cheap
Due to less base width, the
problems of uplift
pressure are minor.
Small load of pressure load is
transferred to the
foundation by cantilever
action, therefore an
arch dam can be
constructed in moderate
foundations.
Disadvantages
It requires skilled labor and sophisticated form of work. It is a specialized design
construction.
Takes longer time for construction
Requires strong abutments of solid rock to resist the thrust of the arch.
Only few sites are suitable for this type of dam.

9. Multiple Arch Dam

10. Advantages
Gravity Dam It is a permanent dam.
It is a solid massive dam and
relatively more strong and
stable.
Particularly suited in gorges.
Requires less maintenance.
Well adapted for use as an
overflow spillway crest.
It can be constructed of any
height on strong suitable
rock foundations.
It suited to places where
there is no excessive or
likelihood of heavy
downpour.
It requires least maintenance
Disadvantages
Unsuitable on weak foundations or weak rocks and permeable
Failures of such dams is not
rocks. sudden and gives warning.
Initial cost is high. Deep set sluices are used to
Construction period will be more if proper infrastructure is not retard sedimentation or silt
available. deposition.
It requires skilled labor or mechanize plants for construction Trap efficiency is less
Difficult to raise the height of the dam unless specific compared to earth dams.
observations are made in the initial stage..

11. Advantages
It is a less massive dam than a gravity Buttress dam
dam.
Due to less foundation pressures it
can be constructed on foundations
where it doesn’t support gravity dam.
Water load acts normal to the inclined
deck stabilizing the dam against
overturning.
Buttress dam has a more safety factor
than for a gravity dam.
Ice pressure is relatively not important
as it slides down the slope.
Further raising of the dam height is
possible and convenient by extending Back of the upstream face and foundations between
the buttress and slab. the buttresses is accessible for periodic inspections
It is used where a future increase is and grouting, drilling of pressure relief holes.
contemplated.
The dam can be designed to accommodate
Power houses and water treatment
plants can be housed between the
moderate amounts of foundation movements
buttresses. without serious damages.
Concrete use is ½ or 1/3 less than that The reduction in concrete volume and increase in
of the gravity dam. the surface area to volume ratio provide for better
heat dissipation during construction.
Increase speed of construction due to larger
exposed area.

12. Disadvantages
Requirement of
skilled labor
Shuttering concrete
ratio > for solid dams
leading to higher
rates and this offsets
the saving of the
concrete quantity.
Deterioration of the
thin concrete surface
in the upstream has
serious effect on
buttress dam.
It is more susceptible
to willful damage
which depends on
the thickness of the
upstream face and
the facility for access
from the downstream
side.

13. Advantages
Higher speed of construction Steel dam
Cheaper than rigid dams.
Stresses are more
determinative can be
designed economically with
confidence.
Has greater flexibility to resist
to unequal settlement without
excessive leakage.
It is Frost resistant.
Leaky joints can be fixed very
effectively with modern
welding process.
Disadvantages
Steel dams are lighter and hence not adaptable to absorb shock from the spilling water.
Life is shorter than concrete dams.
Requires more constant maintenance.
Andhoring at foundations is difficult and precarious.
There is considerable concentration of bearing stresses.

14. A barrage dam is a special kind of dam which consists of a line of large gates that can be opened
or closed to control the amount of water passing the dam. The gates are set between flanking
piers which are responsible for supporting the water load. They are often used to control and
stabilize water flow for irrigation systems.
Barrages that are built at the mouth of rivers or lagoons to prevent tidal incursions or utilize the
tidal flow for tidal power are known as tidal barrages. [

15. An embankment dam is a massive artificial water barrier. It is typically created by the
emplacement and compaction of a complex semi-plastic mound of various compositions of soil,
sand, clay and/or rock. It has a semi-permanent waterproof natural covering for its surface, and
a dense, waterproof core. This makes such a dam impervious to surface or seepage erosion

16. Embankment dams come in two types: the earth-filled dam (also called an earthen dam or
terrain dam) made of compacted earth, and the rock-filled dam. A cross-section of an
embankment dam shows a shape like a bank, or hill. Most have a central section or core
composed of an impermeable material to stop water from seeping through the dam. The core
can be of clay, concrete or asphalt concrete. This dam type is a good choice for sites with wide
valleys. Since they exert little pressure on their foundations, they can be built on hard rock or
softer soils. For a rock-fill dam, rock-fill is blasted using explosives to break the rock.
Additionally, the rock pieces may need to be crushed into smaller chunks to get the right range
of size for use in an embankment dam.
Rock Fill Dam

17. Type of dam
Saddle dam
Rolled earth fill and
rock fill embankment

18. Check dam

19. Frame type
Timber dam timber dam
Rock filled timber crib dam

20. Rock filled
Advantages timber crib dam
1.Low initial cost
2.Suitable for any type of foundation
3.Suitable for temporarily required dams
4.Greater speed in construction
Disadvantages
1.Maintenance cost is high
2.Life of dam is short.
3.Not suitable for high dams
4.Greater seepage through the dam Beaver type timber dam
The beaver (genus Castor) is a primarily
nocturnal, large, semi-aquatic rodent.
Beavers are known for building dams, canals,
and lodges (homes). They are the second-
largest rodent in the world (after the
capybara). Their colonies create one or more
dams to provide still, deep water to protect
against predators, and to float food and
building material.

21. Timber dam

22. Debris dam

23. Factors affecting selection of type of dam
1.Topography
Low topography – earth dam with separate spill ways
Low narrow V shaped valley – arch dam
A narrow stream with U shaped valley – concrete overflow dam
Depending on the foundation rock conditions with reference to structure etc. other
suitable type of dams can be considered
2. Geology and Foundation conditions
Structural conditions and the type of rocks have to be studied in detail to go in for any
major construction of dam.
3. Materials of construction
Earth material, rocks, timber, concrete or combination of materials
4. Spillway size and location
For large spillway capacity – overflow gravity dam
Small spillway capacity – earth dam
Large discharges during construction of dam – concrete gravity dam
If no favourable location is available for spillway – a concrete gravity dam and
sometimes in inevitable conditions in earth dam with central overflow on the dam may be
provided

24. 5. Roadway
A roadway is to be provided – earth dam or gravity dam is preferred
6. Length and height of dam
Long length and low height – earth dam
Less length and higher height – gravity dam
7. Life of dam
Long life – concrete and masonary dams
Temporary dams – timber and debris dams for temporary storage of water
Intermediate life – earth dams or rockfill dams
Selection of site for a dam
1.Foundation
2.Topography
3.Site for spillways
4.Materials availability
5.Reservoir and catchment area
6.Communications
7.Locality
8.Land and population