Introduction of 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. Hence the dam fulfills two fundamental functions, namely it. There are different types of dam. let us discuss them.
- Develop a reservoir which has a capacity to store water and
- Builds up head and thus, potential for the river water
Types of Dam
Dams may be classified in various ways such as
b) construction material
c) structural load transfer mode
d) hydraulic condition
e) based on rigidity
Classification of dam based on its function
Based on the function, the dam is classified as storage dam, diversion dam, detention dam, debris dam and coffer dam
- Storage dam or conversion dam
Storage dam are constructed to impound water during periods of surplus supply for use during periods of deficient supply. These periods may be seasonal, annual or longer. Many small dams impound the monsoon runoff for use in the season. In the upstream of this dam a big reservoir is formed.
- Diversion dam
Diversion dam are ordinarily constructed to provide head ( raise water level ) for carrying water into ditches, canal, or other conveyance systems. The height of this of this dam is, therefore, relatively small as no reservoir is to be formed to store water. They are used for hydropower, irrigation and other developments, for diversion from a live stream to an off channel, tunnel or pipe location.
- Detention dam
Detention dam is constructed to store and detain flood water temporarily and to release it when flood subsided i.e. it retard flood runoff and minimize the effect of sudden floods. Detention dams consist of two main types.
Coffer dam are temporary dam constructed to divert water to construct the main dam.
B) Classification based on the construction material
Based on the material used for construction, the dam may be classififed as
- Concrete dam
They are made either from plain cement concrete or reinforced concrete. They may be gravity dams or may be in form of arch, butters or any other form of dams.
- Earthfill dam
Earthfill dam are the oldest types of dam. This dam structure consists of local soil mainly. This dam is not 100% impervious. Water percolates through the body of the dam but rate of percolation is kept under check and percolation line of hydraulic gradient line of percolating water is not allowed to get exposed anywhere. This dam does not require much of skill.
- Rockfill dams
These dam mostly comprise rock boulders. Only boulders cannot prevent the flow of water and as such some impervious layer is laid on the upstream face of the dam, which may be in form of cement concrete slab or earthfill covered by rip rap or any other arrangement. Rockfill provides the stability whereas impervious layer provides imperviousness to the dam to prevent flow of water through them.
- Masonry dams
They are made from stone masonry in cement mortar. They are mostly gravity dams.
- Steel dams
They are not used much. They are used for secondary purpose small dams.
- Timber dams
They are also of secondary nature and used for storing small amounts of water temporarily.
C) Classification based upon the structural load transfer mode
1) Gravity dam
Gravity dam resists all the forces acting on it, by the aids of its own weight and is considered as one of the most permanents dams. It requires very little maintenance. This is the most common type of dam, both for low heights as well as very large heights. Gravity dam may be made of either masonry or cement concrete.
2) Arch dam
An arch dam is curve in plain, arching between the abutment s of the river with convex face towards the flow of water. Self weight of this dam is quite less compared to the gravity dam and hence water pressure on upstream is resisted to a major extent by the arching action of the abutments.
3) Buttress dam
This dam consists of a numbers of piers that divide the total length of the dam into a number of spans. All the spans are then covered either with inclined concrete slab or arches on the upstream side of the piers. If spans are covered with flat inclined slab it is known as deck type buttress dam.
D) classification based on the hydraulic design
Based on the hydraulic design of dam, dam may also classified as overflow or non-overflow dams.
- Overflow dam
Overflow dam are designed to carry discharge over their crests or through spillways along the crest. The most common material used for this type of dam is concrete.
- Non-overflow dam
Non-overflow dams are those designed not to be overtopped. This type of design depends on the choice of materials to include earthfill and rockfill dams.
E) Classification based upon the head
Based on the hydraulic head available dam can be expressed as:
- Low head, H< 15 m
- Medium head, 15 m <H < 70 m
- High head, 70 m < H < 250 m
- Very high head, H > 250 m
F) Classification based on rigidity
According to rigidity, the dam may be
- Rigid dams
- Non-rigid dams
Rigid dams are those which are constructed of rigid materials like concrete, masonry, steel or timber. The dam made from materials like earth, earthfill etc are known as non-rigid dams.
I hope this article on “Different Types of Dam | Dam Classification based on materials, function etc.” remains helpful for you.