Types of dams include arch, gravity, buttress, rigid, non-rigid, timber, steel, concrete, masonry, embankment, earthen, rockfill, diversionary, tailings, weir, saddle, dry, coffer, debris, hydroelectric, detention, storage, underground, overflow, non-overflow, natural, and artificial dams.
These are classified based on structural design, composition, function, hydraulic performance, and mode of occurrence.
It is important to note that dams from different categories of classification can share some basic characteristics. Also, some dams can be built as a hybrid of more than one type.
The types of dams are discussed in this article, as follows;
-Types of Dams Based on Structural Design
1). Arch Dam as one of the Types of Dams
An arch dam is a type of dam which is designed with a curved geometry, so that its convex side faces the upstream segment of the water body in which it is built .
As a result of its curved design, the arch dam is able to deflect hydraulic pressure from the central portion of the dam to its abutments at both extremes of the dam .
What this implies is that the arch dam is protected from direct impact of excessive force from flowing water. It also implies that the abutments of this type of water dam must be resilient in both design and material-composition, to withstand the deflected force from the arch.
In locations where narrow canyons with resilient rock material are present, arch dam is especially suitable, as the canyon walls may serve as support for the abutments of the dam. The overall safety and reliability of the arch dam depend on the structural resilience of these abutments .
An example of arch dam is the Hoover Dam, located in the Black Canyon of Colorado River; United States. Arch dams may come in various designs and varying degrees of complexity, to include single-arch and double-arch subtypes.
They may also be built as a hybrid of multiple types of dams; such as the arch-gravity dam that combines the features of arch and gravity dams.
2). Gravity Dam as one of the Types of Dams
The gravity dam is designed so that its structural integrity, stability and resilience all rely on the force of gravity.
In order to remain stable, the components of the gravity dam must have optimal weight, geometry and positioning. These factors in turn depend on the size and purpose of the dam, and the hydraulic pressure from the water body.
Because the gravity dam is stabilized by gravity, it is important for its weight and foundation to both be resilient. Hard, impervious rock is usually suitable as foundation material, and an optimal weight should be sufficient to counteract and overcome the maximum hydraulic pressure from the water body.
Also, a triangular geometric design is usually applied when building gravity dams , as a means of maximizing the downward gravitational force on the structure.
Two major designs of the gravity dam are solid and hollow designs . While the solid design is more resilient and commonly-used, the hollow design is economical and may be used where suitable. Various materials can be used in building gravity dams, including masonry, concrete and steel.
3). Buttress Dam
Buttress dams comprise of a deck, barrier or slab which is supported by buttresses installed at intervals .
Various designs and models of buttress dams exist; all based on the same concept. Three major examples of the subtypes or models of buttress dams are massive-head, deck, columnar, and multiple-arch buttress dams .
The overall geometry of a buttress dam may be polygonal, arched or triangular. Intervals between the buttresses may range from 6 to 30 meters, although this range nay be exceeded, depending on the design and scale of the dam.
4).Rigid Dam as one of the Types of Dams
The concept of a rigid dam is similar to that of a rigid pavement in civil construction.
‘Rigid dam’ is itself a term that is used to describe a dam constructed using rigid components such as steel, concrete and masonry. Various designs can be employed when building a rigid dam, depending on the peculiar characteristics and requirements of the structure.
5). Non-Rigid Dam
Non-rigid dams are the structural counterparts of rigid dams.
These structures are generally built from materials that give them a degree of thermal and mechanical flexibility. Such materials include soil, rocks and asphalt material
As already implied, non-rigid dams have the advantage of greater thermo-mechanical flexibility than rigid dams, and are generally more reliable.
-Types of Dams based on Composition
6). Timber Dam
Timber dam is one of the most basic and primitive types of dams.
It is typically made out of coniferous wood, such as that derived from firs. After the basic framework of the dam is built out of these materials, the interior is filled with earth and rocks to provide structural and mechanical support.
Timber dams are relatively unreliable and have a short lifespan. The use of these dams was more common at the onset of the industrial era, when they were constructed as temporary structures for flood control and other purposes.
Because of the relative structural weakness of timber dams, they have a limited height and retention capacity, and may therefore be effective only under low-head (water level) conditions.
Timber dams are particularly an option where there is a plentiful supply of suitable wood biomass, and/or inaccessibility of other construction materials. They may be built in various structural designs, including arch, buttress and crib designs.
7). Steel Dam as one of the Types of Dams
A steel dam is a type of dam which is built primarily from steel components, such as beams, struts and plates.
The steel dam falls under the category of rigid dams, and may be built in various designs.
While it is considerably stronger and more reliable than the timber dam, steel dam is also a temporary structure, and is often built as a precursor to a permanent dam of another type.
Two main types of steel dams can be distinguished, based on how hydraulic pressure is managed by the structure. These are the cantilever and direct-strutted dams.
Cantilever steel dam resists hydraulic pressure from the water body by means of a lever mechanism between the deck and foundation of the dam. Pressure resistance for this dam is based on deflection and dissipation of force.
On the contrary, direct-strutted steel dams resist hydraulic pressure by transferring this pressure directly to a resilient foundation. While this is a simpler mechanism, it implies that the dam must be significantly stable and resilient to withstand maximum hydraulic pressure.
Cantilever dams may be expensive to construct due to the relative complexity of the structure and the brace-joints which must be designed to meet specific requirements.
While they were fairly common in the twentieth century, steel dams have become nearly obsolete.
8). Concrete Dam
Concrete dam is a rigid type of dam that is made primarily from concrete.
One of the major advantages of this type is that it is stronger than most alternative types of dams, having significant levels of mechanical resilience and structural capacity. Resultantly, major designs of various designs around the world are constructed with concrete.
Also, concrete hybrid dams can be built using a combination of concrete and other construction materials like rocks and asphalt. An example of these is the concrete-face rockfill dam (CFRD) which is simply a rockfill dam whose slabs are made of concrete .
Due to their prominence as one of the most common types of dams, concrete dams have been modified repeatedly to improve their performance and reliability.
9). Masonry Dam as one of the Types of Dams
As the name implies, masonry dam is a type of dam which is built from masonry components like rock material and bricks .
In some masonry dams, the aggregate materials are used without any binder, although others may be built with mortar, so that lime serves as the binder for the masonry materials.
Masonry dams may span across a broad range of sizes and capacities. They may also be differentiated on the basis of the geometry and composition of masonry materials.
A notable example of a masonry dam is the Nagarjunasagar Dam in India.
10). Embankment Dam
Embankment dam is a broad term used to describe all types of dams that are built from regolith and aggregate earth material.
The materials used to build embankment dams include soil, rocks, and suitable forms of solid waste.
Embankment dams are usually built where such materials are readily available, such as areas with large accumulations of excavated materials, and solid industrial waste.
In terms of composition, an embankment dam may be built from one or more types of materials, and may be described as homogeneous (built from one material), or zoned (more than one building material).
Because the two major materials used to build embankment dams are soil (earth) and rock, two subtypes of this dam can be distinguished. These are the earthen and rockfill (or rock-fill) dams.
11). Earthen Dam
Earthen dam is a sub-type of embankment dam that is built from soil or earth material.
This type of dam is usually constructed by compacting soil in layers to form a relatively durable structure . Where soil is the only component used, the dam can be described as a homogeneous earthen dam, or, on the contrary; a heterogeneous earthen dam.
The main advantage of earthen dams is their cost-effectiveness. This is due to the fact that soil is readily available in many regions, compared to masonry, steel or concrete.
However, the reliability and mechanical resilience of this dam are low, meaning that it cannot support significantly-large hydraulic weights.
12). Rockfill Dam as one of the Types of Dams
Rockfill (rock-fill, rock fill) dam is an embankment dam that derives most of its structural support from rock materials.
This type of dam is considered non-rigid, as the use of heterogeneous rock components provide a degree of thermal and mechanical flexibility.
When building rockfill dams it is ensured that the rocks used are suitable in terms of size and tensile strength. Also, an impermeable covering or membrane is often used  to protect the rock components from hydraulic inter-boundary stress.
Materials used to make the impermeable membrane include concrete and mortar, as well as timber and steel, although the latter are no longer used.
Another reason why a membrane is present in rockfill dams is to prevent or reduce seepage that may damage and disintegrate the dam.
An example of a rockfill dam is the Mica Dam which is located in British Columbia, Canada.
-Types of Dams based on Function or Purpose
13). Diversionary Dam
A diversion dam is a type of dam which is built for the purpose of diverting water from its natural flow-path in a river or stream, into a designated channel, conduit or canal .
In order to achieve its purpose, a diversionary dam is usually equipped with features that enable it to alter the natural fluid flow and cause diversion with minimal retention of water. These include small storage volume, low water head and inclined geometry.
Diverted water may be used for various purposes such as hydroelectricity generation and irrigation. The diversionary dam itself is common and relevant where there is need for soil conservation and similar practices.
14). Tailings Dam
A tailings dam is a type of earth fill embankment dam which is built primarily to store or manage tailings which are produced in the course of mining operations .
Tailings are themselves the byproducts of mining, which remain after the valuable materials are separated from the ore. They usually occur in the form of slurry.
Tailings dams are used for storing mine waste mainly because they are inexpensive and can be constructed as the mine is being operated, so that they are fully capable of storing all the waste that is produced.
Based on the changes in geometry of the tailings dam as it is further built using subsequent layers of mine waste, it may be described as a centerline, downstream or upstream-crest tailings dam.
The size of a tailings dam generally depends on the scale of mine-waste production. In cases where they are not capable of bearing the weight of tailings, these dams may pose significant risk in the form of hazards like landslides.
15). Weir Dam as one of the Types of Dams
The term ‘weir’ is used collectively to describe all types of dams which occur as a small barrier across a river or stream channel for impounding the water and altering the natural pattern of flow.
Aside its basic function of impoundment, a weir dam is also used for flow retardation and measurement; as well as abstraction and storage of water. When installed, a weir dam raises the water level on the upstream segment  so as to alter the height of the water body over a given area.
Size and geometry may differ depending in the size of the water body and the specific objectives of the structure.
It is important to note that weir dams are considered to be very different in their structural and operational characteristics than other, conventional types of dams. The main difference between a weir and a conventional dam is that the dam is designed to completely impound water within a given area, while a weir allows the water to flow over it.
As a result, while dams and barrages may be used to control flooding, a weir is used mainly to alter flow patterns.
When described in terms of hydraulic performance, a weir dam is alternatively referred to as an overflow dam.
16). Saddle Dam
A saddle dam is an auxiliary or subsidiary dam which is built within a topographically depressed area of a reservoir .
Saddles dams are built for any of various purposes. These include changing the water head or level within the reservoir, and increasing storage efficiency or capacity.
An alternative term used to refer to a saddle dam is ‘dike’, due to its role in protecting adjacent areas of land from flooding. Saddle dams usually support a larger dam and improve their performance.
17). Dry Dam
A dry dam is a category which includes all types of dams which are built mainly to control flooding in particular periods of time .
The function of a dry dam is restricted to periods of excessive stormwater formation. During these periods, the dam prevents or minimizes downstream flooding. At other times however, a dry dam does not affect the natural flow of water
18). Coffer Dam as one of the Types of Dams
Coffer dam (or cofferdam) is a temporary structure which is built to prevent the intrusion of water into an area that is usually submerged underwater .
This type of dam is most needed in construction projects within river beds or other water-submerged areas. Various materials, like wood, concrete and steel may be used to build a cofferdam.
In many cases, the cofferdam is used as a protective structure for hydraulic exclusion of the work area during the building of other permanent types of dams. The cofferdam may function like a diversionary dam, by diverting the flow of water from the excluded area.
19). Debris Dam
A debris dam is built to separate and retain materials like gravel, sand, solid waste and wood fragments from water as it flows downstream.
Based on the above definition, it can be said that a debris dam is used for waste management, as it ensures that unwanted materials are removed from water that flows downstream through it. Debris dams may act as an auxiliary structure to support the operation of a larger dam.
20). Hydroelectric Dam
Many types of dams can be categorized under this group. A hydroelectric dam is any dam which is a component of a hydropower facility.
The concept behind the use of dams in hydropower plants is basically to store and control water for electricity generation. In order to achieve this, the dam must have sufficient storage capacity, and internal water head to convert potential energy of stored water into kinetic energy as the water flows and falls downstream from an elevation.
21). Detention Dam
A detention dam is a type of dam which is built primarily for flood-control .
The dam captures (detains) stormwater as it flows downstream, thereby protecting the downstream and adjacent land areas from flooding. Aside water capture, the dam helps the slow the rate of downstream flow.
Detention dams are typically installed at an elevation above the area which is prone to flooding . An example of this type of dam is the Los Banos Creek Detention Dam, located in California, United States.
22). Storage Dam as one of the Types of Dams
A storage dam is a type of dam that is built primarily to impound and store excess water in the upstream segment of a river during the rainy season .
Unlike other types of dams that serve to control the flow of water, a storage dam is often solely used for water storage. The stored water is subsequently released when river levels are relatively low and precipitation rates are reduced.
When released, water from a storage dam may be utilized for any of various purposes such as irrigation, domestic water supply, and hydropower generation.
On the basis of their capacity, storage dams may be sub-classified as small, medium and large, which have various thresholds of classification.
23). Underground Dam
An underground dam, as the name implies, is built within reach of groundwater reserves in the subsurface, and is used to impound and store this water .
Alternatively referred to as ‘submersible dam,’ this type of dam can be considered to be an innovative outcome of various efforts to achieve sustainable development.
Underground dams are built to conserve groundwater resources. This may be by preventing saltwater intrusion that can degrade water quality, or by reducing water losses through evaporation and other mechanisms.
As a tool for water resources conservation, underground dams are usually a component of an artificial underground reservoir alongside groundwater extraction facilities and artificial recharge facilities .
Based on construction and function, two types of underground dams exist, which include sand-storage and subsurface dams.
The sand-storage underground dam is a weir which is usually built across a river flow pathway, so that it acts as a barrier behind which sand accumulates over time, thereby reducing evaporation rates of groundwater in the subsurface, which can be accessed through wells.
Subsurface dams are built to cut directly across the flow path of groundwater, causing water to accumulate behind the barrier, and thereby raising groundwater levels within that area to make the water more accessible.
-Types of Dams based on Hydraulic Performance
24). Overflow Dam
An overflow dam is a type of dam which is designed such that water can flow over the crest of the structure .
Based on this description, it may be said that a weir is an overflow dam. Alternative terms used to refer to this dam include over-fall dam and spillway dam.
The mode of operation of overflow dams is different from that of most other types of dams. Scenarios where this type of dam is useful are mostly those where there is need to control the flow pattern of the water, in a low-head river. It may also be used alongside a reservoir.
25). Non-Overflow Dam as one of the Types of Dams
Non-overflow dams are those which do not allow the flow of excess water over their crest. These dams are constructed by making their height to exceed the maximum flooding level of the river or stream.
-Types of Dams based on Mode of Occurrence
26). Natural Dam as one of the Types of Dams
Natural dams are dams formed as a result of natural factors and processes.
Examples of processes by which these dams are formed include earthquakes, glaciation and volcanic eruption. And the dams may be composed of earth material (soil and rock), igneous deposits, and glacial material.
Because of the spontaneous nature of their occurrence, natural dams can pose a threat go regional safety, through their potential abrupt failure and capability to cause flooding.
27). Artificial Dam as one of the Types of Dams
Artificial dams are simply manmade barriers built across water bodies to alter natural flow.
All types of dams aside natural dams, fall within this category.
The types of dams are;
- Arch Dam
- Gravity Dam as one of the Types of Dams
- Buttress Dam
- Rigid Dam as one of the Types of Dams
- Non-Rigid Dam
- Timber Dam
- Steel Dam
- Concrete Dam
- Masonry Dam
- Embankment Dam
- Earthen Dam
- Rockfill Dam as one of the Types of Dams
- Diversionary Dam
- Tailings Dam
- Weir Dam as one of the Types of Dams
- Saddle Dam
- Dry Dam
- Coffer Dam as one of the Types of Dams
- Debris Dam
- Hydroelectric Dam
- Detention Dam
- Storage Dam as one of the Types of Dams
- Underground Dam
- Overflow Dam
- Non-Overflow Dam as one of the Types of Dams
- Natural Dam as one of the Types of Dams
- Artificial Dam as one of the Types of Dams
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