Dam

Dam

Overview
A dam is a barrier that impound
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

s water
Surface water
Surface water is water collecting on the ground or in a stream, river, lake, wetland, or ocean; it is related to water collecting as groundwater or atmospheric water....

 or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levee
Levee
A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...

s (also known as dikes) are used to manage or prevent water flow into specific land regions. Hydropower
Hydropower
Hydropower, hydraulic power, hydrokinetic power or water power is power that is derived from the force or energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as...

 and pumped-storage hydroelectricity
Pumped-storage hydroelectricity
Pumped-storage hydroelectricity is a type of hydroelectric power generation used by some power plants for load balancing. The method stores energy in the form of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost off-peak electric power is used to run the pumps...

 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.


The word dam can be traced back to Middle English
Middle English
Middle English is the stage in the history of the English language during the High and Late Middle Ages, or roughly during the four centuries between the late 11th and the late 15th century....

, and before that, from Middle Dutch
Middle Dutch
Middle Dutch is a collective name for a number of closely related West Germanic dialects which were spoken and written between 1150 and 1500...

, as seen in the names of many old cities.
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Unanswered Questions
Encyclopedia
A dam is a barrier that impound
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

s water
Surface water
Surface water is water collecting on the ground or in a stream, river, lake, wetland, or ocean; it is related to water collecting as groundwater or atmospheric water....

 or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levee
Levee
A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...

s (also known as dikes) are used to manage or prevent water flow into specific land regions. Hydropower
Hydropower
Hydropower, hydraulic power, hydrokinetic power or water power is power that is derived from the force or energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as...

 and pumped-storage hydroelectricity
Pumped-storage hydroelectricity
Pumped-storage hydroelectricity is a type of hydroelectric power generation used by some power plants for load balancing. The method stores energy in the form of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost off-peak electric power is used to run the pumps...

 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.

History



The word dam can be traced back to Middle English
Middle English
Middle English is the stage in the history of the English language during the High and Late Middle Ages, or roughly during the four centuries between the late 11th and the late 15th century....

, and before that, from Middle Dutch
Middle Dutch
Middle Dutch is a collective name for a number of closely related West Germanic dialects which were spoken and written between 1150 and 1500...

, as seen in the names of many old cities. Early dam building took place in Mesopotamia
Mesopotamia
Mesopotamia is a toponym for the area of the Tigris–Euphrates river system, largely corresponding to modern-day Iraq, northeastern Syria, southeastern Turkey and southwestern Iran.Widely considered to be the cradle of civilization, Bronze Age Mesopotamia included Sumer and the...

 and the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...

. Dams were used to control the water level, for Mesopotamia's weather affected the Tigris
Tigris
The Tigris River is the eastern member of the two great rivers that define Mesopotamia, the other being the Euphrates. The river flows south from the mountains of southeastern Turkey through Iraq.-Geography:...

 and Euphrates
Euphrates
The Euphrates is the longest and one of the most historically important rivers of Western Asia. Together with the Tigris, it is one of the two defining rivers of Mesopotamia...

 rivers, and could be quite unpredictable.

The earliest known dam is the Jawa Dam
Jawa Dam
The Jawa Dam is the remains of an ancient masonry gravity dam on Wadi Rajil at Jawa in Mafraq Governorate, Jordan, north of Azraq. It is the oldest known dam in the world, dating back to 3000 BC. The dam was part of a water supply system that eventually consisted of other smaller dams to support...

 in Jordan
Jordan
Jordan , officially the Hashemite Kingdom of Jordan , Al-Mamlaka al-Urduniyya al-Hashemiyya) is a kingdom on the East Bank of the River Jordan. The country borders Saudi Arabia to the east and south-east, Iraq to the north-east, Syria to the north and the West Bank and Israel to the west, sharing...

, 100 kilometres (62.1 mi) northeast of the capital Amman
Amman
Amman is the capital of Jordan. It is the country's political, cultural and commercial centre and one of the oldest continuously inhabited cities in the world. The Greater Amman area has a population of 2,842,629 as of 2010. The population of Amman is expected to jump from 2.8 million to almost...

. This gravity dam featured a 4.5 m (14.8 ft) high and 1 m (3.3 ft) wide stone wall, supported by a 50 m (164 ft) wide earth rampart. The structure is dated to 3000 BC. The Ancient Egypt
Ancient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...

ian Sadd-el-Kafara Dam at Wadi Al-Garawi, located about 25 km (15.5 mi) south of Cairo
Cairo
Cairo , is the capital of Egypt and the largest city in the Arab world and Africa, and the 16th largest metropolitan area in the world. Nicknamed "The City of a Thousand Minarets" for its preponderance of Islamic architecture, Cairo has long been a centre of the region's political and cultural life...

, was 102 m (334.6 ft) long at its base and 87 m (285.4 ft) wide. The structure was built around 2800 or 2600 B.C. as a diversion dam
Diversion dam
A diversion dam is the term for a dam that diverts all or a portion of the flow of a river from its natural course. Diversion dams do not generally impound water in a reservoir...

 for flood control, but was destroyed by heavy rain during construction or shortly afterwards. By the mid-late third century BC, an intricate water-management system within Dholavira
Dholavira
Dholavira is an archaeological site in Khadirbet in Bhachau Taluka of Kachchh district of Gujarat state in western India, which has taken its name from a modern village 1 km south of it. The site of Dholavira, locally known as Kotada timba contains ruins of an ancient Harappan city...

 in modern day India, was built. The system included 16 reservoirs, dams and various channels for collecting water and storing it.

Roman dam construction was characterized by "the Romans' ability to plan and organize engineering construction on a grand scale". Roman planners introduced the then novel concept of large reservoir dams which could secure a permanent water supply
Water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavours or by individuals, usually via a system of pumps and pipes...

 for urban settlements also over the dry season. Their pioneering use of water-proof hydraulic mortar
Mortar (masonry)
Mortar is a workable paste used to bind construction blocks together and fill the gaps between them. The blocks may be stone, brick, cinder blocks, etc. Mortar becomes hard when it sets, resulting in a rigid aggregate structure. Modern mortars are typically made from a mixture of sand, a binder...

 and particularly Roman concrete allowed for much larger dam structures than previously built, such as the Lake Homs Dam
Lake Homs Dam
The Lake Homs Dam is a Roman-built dam near the city of Homs, Syria, which is in use to this day.Contrary to an older hypothesis which tentatively linked the origins of the dam to Egyptian ruler Sethi , the structure dates to 284 AD when it was built by the Roman emperor Diocletian for irrigation...

, possibly the largest water barrier to that date, and the Harbaqa Dam
Harbaqa Dam
The Harbaqa Dam was a Roman gravity dam in the Syrian desert between Damascus and Palmyra, dating to the 2nd century AD. The dam was built of a concrete core faced on both air and water face with ashlar. The reservoir served for irrigation of nearby fields which supplied Palmyra....

, both in Roman Syria. The highest Roman dam was the Subiaco Dam near Rome
Rome
Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...

; its record height of 50 m (164 ft) remained unsurpassed until its accidental destruction in 1305.

Roman engineers made routine use of ancient standard designs like embankment dams and masonry gravity dams. Apart from that, they displayed a high degree of inventiveness, introducing most of the other basic dam designs which had been unknown until then. These include arch-gravity dam
Arch-gravity dam
An arch-gravity dam, curved-gravity dam or arched dam is a dam with the characteristics of both an arch dam and a gravity dam. It is a dam that curves upstream in a narrowing curve that directs most of the water against the canyon rock walls, providing the force to compress the dam...

s, arch dam
Arch dam
An arch dam is a type of dam that is curved and commonly built with concrete. The arch dam is a structure that is designed to curve upstream so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes...

s, buttress dam
Buttress dam
A buttress dam or hollow dam is a dam with a solid, water-tight upstream side that is supported at intervals on the downstream side by a series of buttresses or supports. The dam wall may be flat or curved. Most buttress dams are made of reinforced concrete and are heavy, pushing the dam into the...

s and multiple arch buttress dams, all of which were known and employed by the 2nd century AD (see List of Roman dams). Roman workforces also were the first to build dam bridges, such as the Bridge of Valerian in Iran.

Eflatun Pınar is a Hittite dam and spring temple near Konya, Turkey. It's thought to be from the time of the Hittite empire between the 15th and 13 century BC.

The Kallanai is constructed of unhewn stone, over 300 m (984.3 ft) long, 4.5 m (14.8 ft) high and 20 m (65.6 ft) wide, across the main stream of the Kaveri river in Tamil Nadu
Tamil Nadu
Tamil Nadu is one of the 28 states of India. Its capital and largest city is Chennai. Tamil Nadu lies in the southernmost part of the Indian Peninsula and is bordered by the union territory of Pondicherry, and the states of Kerala, Karnataka, and Andhra Pradesh...

, South India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

. The basic structure dates to the 2nd century ADand is considered one of the oldest water-diversion or water-regulator structures in the world, which is still in use. The purpose of the dam was to divert the waters of the Kaveri across the fertile Delta region for irrigation via canals.

Du Jiang Yan is the oldest surviving irrigation system in China that included a dam that directed waterflow. It was finished in 251 B.C. A large earthen dam, made by the Prime Minister
Prime minister
A prime minister is the most senior minister of cabinet in the executive branch of government in a parliamentary system. In many systems, the prime minister selects and may dismiss other members of the cabinet, and allocates posts to members within the government. In most systems, the prime...

 of Chu (state)
Chu (state)
The State of Chu was a Zhou Dynasty vassal state in present-day central and southern China during the Spring and Autumn period and Warring States Period . Its ruling house had the surname Nai , and clan name Yan , later evolved to surname Mi , and clan name Xiong...

, Sunshu Ao
Sunshu Ao
Sun Shu-Ao was an ancient Chinese court minister serving the administration of King Zhuang of Chu during the Eastern Zhou Dynasty. During his governmental career, SUN Shu-Ao was given notice by King Zhuang, who had him promoted to the rank of Prime Minister in the State of Chu...

, flooded a valley in modern-day northern Anhui
Anhui
Anhui is a province in the People's Republic of China. Located in eastern China across the basins of the Yangtze River and the Huai River, it borders Jiangsu to the east, Zhejiang to the southeast, Jiangxi to the south, Hubei to the southwest, Henan to the northwest, and Shandong for a tiny...

 province that created an enormous irrigation
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

 reservoir 62 mi (99.8 km) in circumference), a reservoir that is still present today.

In Iran
Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

, bridge dams such as the Band-e Kaisar were used to provide hydropower
Hydropower
Hydropower, hydraulic power, hydrokinetic power or water power is power that is derived from the force or energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as...

 through water wheel
Water wheel
A water wheel is a machine for converting the energy of free-flowing or falling water into useful forms of power. A water wheel consists of a large wooden or metal wheel, with a number of blades or buckets arranged on the outside rim forming the driving surface...

s, which often powered water-raising mechanisms. One of the first was the Roman-built dam bridge in Dezful
Dezful
Dezful is a city in and the capital of Dezful County, Khuzestan Province, Iran. At the 2006 census, its population was 228,507, in 55,711 families.The city houses a bridge that dates back to 300 BC.In 2006, the city had 235,819 inhabitants.-History:...

, which could raise water 50 cubit
Cubit
The cubit is a traditional unit of length, based on the length of the forearm. Cubits of various lengths were employed in many parts of the world in Antiquity, in the Middle Ages and into Early Modern Times....

s in height for the water supply
Water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavours or by individuals, usually via a system of pumps and pipes...

 to all houses in the town. Also diversion dam
Diversion dam
A diversion dam is the term for a dam that diverts all or a portion of the flow of a river from its natural course. Diversion dams do not generally impound water in a reservoir...

s were known. Milling
Mill (grinding)
A grinding mill is a unit operation designed to break a solid material into smaller pieces. There are many different types of grinding mills and many types of materials processed in them. Historically mills were powered by hand , working animal , wind or water...

 dams were introduced which the Muslim engineers
Muslim Agricultural Revolution
The Arab Agricultural Revolution is a term coined by the historian Andrew Watson in his influential 1974 paper postulating a fundamental transformation in agriculture from the 8th century to the 13th century in the Muslim...

 called the Pul-i-Bulaiti. The first was built at Shustar on the River Karun
Karun
The Kārun is Iran's most effluent, and the only navigable, river. It is 450 miles long. It rises in the Zard Kuh mountains of the Bakhtiari district in the Zagros Range, receiving many tributaries, such as the Dez and the Kuhrang, before passing through the capital of the Khuzestan Province of...

, Iran
Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

, and many of these were later built in other parts of the Islamic world. Water was conducted from the back of the dam through a large pipe to drive a water wheel and watermill
Watermill
A watermill is a structure that uses a water wheel or turbine to drive a mechanical process such as flour, lumber or textile production, or metal shaping .- History :...

. In the 10th century, Al-Muqaddasi
Al-Muqaddasi
Muhammad ibn Ahmad Shams al-Din Al-Muqaddasi , also transliterated as Al-Maqdisi and el-Mukaddasi, was a medieval Arab geographer, author of Ahsan at-Taqasim fi Ma`rifat il-Aqalim .-Biography:Al-Muqaddasi, "the Hierosolomite" was born in Jerusalem in 946 AD...

 described several dams in Persia. He reported that one in Ahwaz
Ahvaz
-History:For a more comprehensive historical treatment of the area, see the history section of Khūzestān Province.-Ancient history:Ahvaz is the anagram of "Avaz" and "Avaja" which appear in Darius's epigraph...

 was more than 3000 ft (914.4 m) long, and that and it had many water-wheels raising the water into aqueduct
Aqueduct
An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....

s through which it flowed into reservoir
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

s of the city. Another one, the Band-i-Amir dam, provided irrigation for 300 villages.

In the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

, a low-lying country, dams were often applied to block rivers in order to regulate the water level and to prevent the sea from entering the marsh lands. Such dams often marked the beginning of a town or city because it was easy to cross the river at such a place, and often gave rise to the respective place's names in Dutch. For instance the Dutch capital Amsterdam
Amsterdam
Amsterdam is the largest city and the capital of the Netherlands. The current position of Amsterdam as capital city of the Kingdom of the Netherlands is governed by the constitution of August 24, 1815 and its successors. Amsterdam has a population of 783,364 within city limits, an urban population...

 (old name Amstelredam) started with a dam through the river Amstel
Amstel
The Amstel is a river in the Netherlands which runs through the city of Amsterdam. The river's name is derived from Aeme stelle, old Dutch for "area abounding with water"....

 in the late 12th century, and Rotterdam
Rotterdam
Rotterdam is the second-largest city in the Netherlands and one of the largest ports in the world. Starting as a dam on the Rotte river, Rotterdam has grown into a major international commercial centre...

 started with a dam through the river Rotte, a minor tributary of the Nieuwe Maas
Nieuwe Maas
The Nieuwe Maas distributary of the Rhine River, and a former distributary of the Maas River, in the Dutch province of South Holland. It runs from the confluence of the rivers Noord and Lek, and flows west through Rotterdam. It ends west of the city where it meets the Oude Maas , near Vlaardingen,...

. The central square of Amsterdam, covering the original place of the 800 year old dam, still carries the name Dam Square
Dam Square
Dam Square, or simply the Dam is a town square in Amsterdam, the capital of the Netherlands. Its notable buildings and frequent events make it one of the most well-known and important locations in the city.- Location and description :...

or simply the Dam.

French engineer Benoît Fourneyron
Benoît Fourneyron
Benoît Fourneyron was a French engineer, born in Saint-Étienne, Loire. Fourneyron made significant contributions to the development of water turbines....

 developed the first successful water turbine
Water turbine
A water turbine is a rotary engine that takes energy from moving water.Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. They harness a clean and renewable energy...

 in 1832. The era of large dams was initiated after Hoover Dam
Hoover Dam
Hoover Dam, once known as Boulder Dam, is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the US states of Arizona and Nevada. It was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President...

 was completed on the Colorado River
Colorado River
The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...

 near Las Vegas in 1936. By 1997, there were an estimated 800,000 dams worldwide, some 40,000 of them over 15 m (49.2 ft) high.

Types of dams


Dams can be formed by human agency, natural causes, or even by the intervention of wildlife such as beaver
Beaver
The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...

s. Man-made dams are typically classified according to their size (height), intended purpose or structure.

By structure


Based on structure and material used, dams are classified as timber
Timber
Timber may refer to:* Timber, a term common in the United Kingdom and Australia for wood materials * Timber, Oregon, an unincorporated community in the U.S...

 dams, arch-gravity dam
Arch-gravity dam
An arch-gravity dam, curved-gravity dam or arched dam is a dam with the characteristics of both an arch dam and a gravity dam. It is a dam that curves upstream in a narrowing curve that directs most of the water against the canyon rock walls, providing the force to compress the dam...

s, embankment dam
Embankment dam
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...

s or masonry dam
Masonry dam
Masonry dams are dams made out of masonry; mainly stone and brick. They are either the gravity or the arch type.The largest masonry dam of the world is Nagarjunasagar Dam in India....

s, with several subtypes.

Arch dams



In the arch dam, stability is obtained by a combination of arch and gravity action. If the upstream face is vertical the entire weight of the dam must be carried to the foundation by gravity, while the distribution of the normal hydrostatic pressure between vertical cantilever
Cantilever
A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...

 and arch action will depend upon the stiffness
Stiffness
Stiffness is the resistance of an elastic body to deformation by an applied force along a given degree of freedom when a set of loading points and boundary conditions are prescribed on the elastic body.-Calculations:...

 of the dam in a vertical and horizontal direction. When the upstream face is sloped the distribution is more complicated. The normal
Surface normal
A surface normal, or simply normal, to a flat surface is a vector that is perpendicular to that surface. A normal to a non-flat surface at a point P on the surface is a vector perpendicular to the tangent plane to that surface at P. The word "normal" is also used as an adjective: a line normal to a...

 component of the weight of the arch ring may be taken by the arch action, while the normal hydrostatic pressure will be distributed as described above. For this type of dam, firm reliable supports at the abutments (either buttress
Buttress
A buttress is an architectural structure built against or projecting from a wall which serves to support or reinforce the wall...

 or canyon
Canyon
A canyon or gorge is a deep ravine between cliffs often carved from the landscape by a river. Rivers have a natural tendency to reach a baseline elevation, which is the same elevation as the body of water it will eventually drain into. This forms a canyon. Most canyons were formed by a process of...

 side wall) are more important. The most desirable place for an arch dam is a narrow canyon with steep side walls composed of sound rock.
The safety of an arch dam is dependent on the strength of the side wall abutments, hence not only should the arch be well seated on the side walls but also the character of the rock should be carefully inspected.


Two types of single-arch dams are in use, namely the constant-angle and the constant-radius dam. The constant-radius type employs the same face radius at all elevations of the dam, which means that as the channel grows narrower towards the bottom of the dam the central angle subtended by the face of the dam becomes smaller. Jones Falls Dam
Jones Falls Dam
Jones Falls Dam is a dam on the Rideau Canal located in Rideau Lakes, Leeds and Grenville United Counties, Ontario, Canada, that was built in 1831 and completed in 1832 to tame the mile-long series of rapids and falls that runs through the Jones Falls....

, in Canada, is a constant radius dam. In a constant-angle dam, also known as a variable radius dam, this subtended angle is kept a constant and the variation in distance between the abutments at various levels are taken care of by varying the radii. Constant-radius dams are much less common than constant-angle dams. Parker Dam
Parker Dam
Parker Dam is a concrete arch-gravity dam that crosses the Colorado River downstream of Hoover Dam. Built between 1934 and 1938 by the Bureau of Reclamation, it is high, of which are below the riverbed, making it "the deepest dam in the world". The dam's primary functions are to create a...

 is a constant-angle arch dam.

A similar type is the double-curvature or thin-shell dam. Wildhorse Dam near Mountain City, Nevada in the United States is an example of the type. This method of construction minimizes the amount of concrete necessary for construction but transmits large loads to the foundation and abutments. The appearance is similar to a single-arch dam but with a distinct vertical curvature to it as well lending it the vague appearance of a concave lens as viewed from downstream.

The multiple-arch dam consists of a number of single-arch dams with concrete buttresses as the supporting abutments, as for example the Daniel-Johnson Dam
Daniel-Johnson Dam
The Daniel-Johnson Dam , formerly known as Manic-5, is a multiple arch buttress dam on the Manicouagan River which creates Manicouagan Reservoir. The dam is composed of 14 buttresses and 13 arches and is north of Baie-Comeau in Quebec, Canada...

, Québec, Canada. The multiple-arch dam does not require as many buttresses as the hollow gravity type, but requires good rock foundation because the buttress loads are heavy.

Gravity dams


In a gravity dam, the force that holds the dam in place against the push from the water is Earth's gravity pulling down on the mass of the dam. The water presses laterally (downstream) on the dam, tending to overturn the dam by rotating about its toe (a point at the bottom downstream side of the dam). The dam's weight counteracts that force, tending to rotate the dam the other way about its toe. The designer ensures that the dam is heavy enough that gravity wins that contest. In engineering terms, that is true whenever the resultant of the forces of gravity and water pressure on the dam acts in a line that passes upstream of the toe of the dam.

Furthermore, the designer tries to shape the dam so if one were to consider the part of dam above any particular height to be a whole dam itself, that dam also would be held in place by gravity. i.e. there is no tension in the upstream face of the dam holding the top of the dam down. The designer does this because it is usually more practical to make a dam of material essentially just piled up than to make the material stick together against vertical tension.

Note that the shape that prevents tension in the upstream face also eliminates a balancing compression stress in the downstream face, providing additional economy.

The designer also ensures that the toe of the dam is sunk deep enough in the earth that it does not slide forward.

For this type of dam, it is essential to have an impervious foundation with high bearing strength.

When situated on a suitable site, a gravity dam can prove to be a better alternative to other types of dams. When built on a carefully studied foundation, the gravity dam probably represents the best developed example of dam building. Since the fear of flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...

 is a strong motivator in many regions, gravity dams are being built in some instances where an arch dam would have been more economical.

Gravity dams are classified as "solid" or "hollow" and are generally made of either concrete or masonry. This is called "zoning". The core of the dam is zoned depending on the availability of locally available materials, foundation conditions and the material attributes. The solid form is the more widely used of the two, though the hollow dam is frequently more economical to construct. Gravity dams can also be classified as "overflow" (spillway) and "non-overflow." Grand Coulee Dam
Grand Coulee Dam
Grand Coulee Dam is a gravity dam on the Columbia River in the U.S. state of Washington built to produce hydroelectric power and provide irrigation. It was constructed between 1933 and 1942, originally with two power plants. A third power station was completed in 1974 to increase its energy...

 is a solid gravity dam and Itaipu Dam is a hollow gravity dam.

Arch-gravity dams



A gravity dam can be combined with an arch dam into an arch-gravity dam
Arch-gravity dam
An arch-gravity dam, curved-gravity dam or arched dam is a dam with the characteristics of both an arch dam and a gravity dam. It is a dam that curves upstream in a narrowing curve that directs most of the water against the canyon rock walls, providing the force to compress the dam...

 for areas with massive amounts of water flow but less material available for a purely gravity dam.

Barrages


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
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

 or utilize the tidal flow for tidal power
Tidal power
Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity....

 are known as tidal barrage
Tidal barrage
A tidal barrage is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tidal forces....

s.

Embankment dams



Embankment dams are made from compacted
Soil compaction
In Geotechnical engineering, soil compaction is the process in which a stress applied to a soil causes densification as air is displaced from the pores between the soil grains. When stress is applied that causes densification due to water being displaced from between the soil grains then...

 earth, and have two main types, rock-fill and earth-fill dams. Embankment dams rely on their weight to hold back the force of water, like the gravity dams made from concrete.
Rock-fill dams

Rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

-fill dams are embankments of compacted free-draining granular earth with an impervious zone. The earth utilized often contains a large percentage of large particles hence the term rock-fill. The impervious zone may be on the upstream face and made of masonry
Masonry
Masonry is the building of structures from individual units laid in and bound together by mortar; the term masonry can also refer to the units themselves. The common materials of masonry construction are brick, stone, marble, granite, travertine, limestone; concrete block, glass block, stucco, and...

, concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

, plastic membrane, steel sheet piles, timber or other material. The impervious zone may also be within the embankment in which case it is referred to as a core. In the instances where clay is utilized as the impervious material the dam is referred to as a composite dam. To prevent internal erosion of clay into the rock fill due to seepage forces, the core is separated using a filter. Filters are specifically graded soil designed to prevent the migration of fine grain soil particles. When suitable material is at hand, transportation is minimized leading to cost savings during construction. Rock-fill dams are resistant to damage from earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

s. However, inadequate quality control during construction can lead to poor compaction and sand in the embankment which can lead to liquefaction of the rock-fill during an earthquake. Liquefaction potential can be reduced by keeping susceptible material from being saturated, and by providing adequate compaction during construction. An example of a rock-fill dam is New Melones Dam
New Melones Dam
New Melones Dam is an earth and rock filled dam across the Stanislaus River creating New Melones Lake. Situated between Calaveras and Tuolumne County, California in the Sierra Nevada foothills near Jamestown, the dam was completed in 1979 replacing the old Melones Dam.-Background:The dam was...

 in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

.
Concrete-face rock-fill dams

A concrete-face rock-fill dam (CFRD) is a rock-fill dam with concrete slab
Concrete slab
A concrete slab is a common structural element of modern buildings. Horizontal slabs of steel reinforced concrete, typically between 10 and 50 centimeters thick, are most often used to construct floors and ceilings, while thinner slabs are also used for exterior paving.In many domestic and...

s on its upstream face. This design offers the concrete slab as an impervious wall to prevent leakage and also a structure without concern for uplift pressure. In addition, the CFRD design is flexible for topography, faster to construct and less costly than earth-fill dams. The CFRD originated during the California Gold Rush
California Gold Rush
The California Gold Rush began on January 24, 1848, when gold was found by James W. Marshall at Sutter's Mill in Coloma, California. The first to hear confirmed information of the gold rush were the people in Oregon, the Sandwich Islands , and Latin America, who were the first to start flocking to...

 in the 1860s when miners constructed rock-fill timber-face dams for sluice operations. The timber was later replaced by concrete as the design was applied to irrigation and power schemes. As CFRD designs grew in height during the 1960s, the fill was compacted and the slab's horizontal and vertical joints were replaced with improved vertical joints. In the last few decades, the design has become popular.
Currently, the tallest CFRD in the world is the 233 m (764.4 ft) tall Shuibuya Dam
Shuibuya Dam
The Shuibuya Dam is a concrete-face rock-fill embankment dam on the Qingjiang River in Badong County, Enshi, Hubei Province, China. The purpose of the dam is mainly hydroelectricity but it also promotes flood control, navigation, tourism and fishery...

 in China which was completed in 2008.
Earth-fill dams


Earth-fill dams, also called earthen, rolled-earth or simply earth dams, are constructed as a simple embankment
Embankment dam
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...

 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
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

 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
Hydraulic fill
A hydraulic fill is an embankment or other fill in which the materials are deposited in place by a flowing stream of water, with the deposition being selective...

 to produce a watertight core. Rolled-earth dams may also employ a watertight facing or core in the manner of a rock-fill dam. An interesting type of temporary earth dam occasionally used in high latitudes is the frozen-core dam, in which a coolant is circulated through pipes inside the dam to maintain a watertight region of permafrost
Permafrost
In geology, permafrost, cryotic soil or permafrost soil is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of...

 within it.

Tarbela Dam
Tarbela Dam
Tarbela Dam on the Indus River in Pakistan is the second largest dam in the world by structural volume. It is located in Haripur District, Khyber Pakhtunkhwa, about northwest of Islamabad.The dam is high above the riverbed. The dam forms the Tarbela Reservoir, with a surface area of approximately...

 is a large dam on the Indus River
Indus River
The Indus River is a major river which flows through Pakistan. It also has courses through China and India.Originating in the Tibetan plateau of western China in the vicinity of Lake Mansarovar in Tibet Autonomous Region, the river runs a course through the Ladakh district of Jammu and Kashmir and...

 in Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...

. It is located about 50 km (31.1 mi) northwest of Islamabad, and a height of 485 ft (148 m) above the river bed and a reservoir size of 95 sq mi (246 km²) makes it the largest earth filled dam in the world. The principal element of the project is an embankment 9,000 feet (2743 meters) long with a maximum height of 465 feet (143 meters). The total volume of earth and rock used for the project is approximately 200 million cubic yards (152.8 million cu. Meters) which makes it the largest man made structure in the world , except for the Great Chinese Wall which consumed somewhat more material.

Because earthen dams can be constructed from materials found on-site or nearby, they can be very cost-effective in regions where the cost of producing or bringing in concrete would be prohibitive.
Asphalt-concrete core

A third type of embankment dam is built with asphalt concrete
Asphalt concrete
Asphalt concrete is a composite material commonly used in construction projects such as road surfaces, airports and parking lots. It consists of asphalt and mineral aggregate mixed together, then laid down in layers and compacted...

 core. The majority of such dams are built with rock and/or gravel as the main fill material. Almost 100 dams of this design have now been built worldwide since the first such dam was completed in 1962. All asphalt-concrete core dams built so far have an excellent performance record. The type of asphalt used is a viscoelastic-plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

 material that can adjust to the movements and deformations imposed on the embankment as a whole, and to settlements in the foundation. The flexible properties of the asphalt
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...

 make such dams especially suited in earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

 regions.

By size


International standards (including International Commission on Large Dams
International Commission on Large Dams
The International Commission on Large Dams, or ICOLD, The International Commission on Large Dams, or ICOLD, The International Commission on Large Dams, or ICOLD, The International Commission on Large Dams, or ICOLD, The International Commission on Large Dams, or ICOLD, The International Commission...

, ICOLD) define large dams as higher than 15 meters and major dams as over 150 meters in height. The Report of the World Commission on Dams also includes in the large category, dams, such as barrage
Barrage
Barrage may refer to:In music* Barrage , a Canadian violin ensemble, or* Barrage , their self-titled debut albumIn engineering...

s, which are between 5 and 15 meters high with a reservoir capacity of more than 3 million cubic meters.

The tallest dam in the world is the 300-meter-high Nurek Dam
Nurek Dam
The Nurek Dam is an earth fill embankment dam on the Vakhsh River in the central Asian nation of Tajikistan. Construction of the dam began in 1961 and was completed in 1980, when Tajikistan was still a republic within the Soviet Union. At it is currently the tallest dam in the world...

 in Tajikistan
Tajikistan
Tajikistan , officially the Republic of Tajikistan , is a mountainous landlocked country in Central Asia. Afghanistan borders it to the south, Uzbekistan to the west, Kyrgyzstan to the north, and China to the east....

.

Saddle dam


A saddle dam is an auxiliary dam constructed to confine the reservoir created by a primary dam either to permit a higher water elevation and storage or to limit the extent of a reservoir for increased efficiency. An auxiliary dam is constructed in a low spot or saddle through which the reservoir would otherwise escape. On occasion, a reservoir is contained by a similar structure called a dike to prevent inundation of nearby land. Dikes are commonly used for reclamation of arable land from a shallow lake. This is similar to a levee
Levee
A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...

, which is a wall or embankment built along a river or stream to protect adjacent land from flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...

ing.

Weir



A weir (also sometimes called an overflow dam) is a type of small overflow dam that is often used within a river channel to create an impoundment lake for water abstraction purposes and which can also be used for flow measurement.

Check dam



A check dam is a small dam designed to reduce flow velocity and control soil erosion. Conversely, a wing dam
Wing dam
A wing dam is a manmade barrier that, unlike a conventional dam, only extends partway into a river. These structures force water into a fast-moving center channel which reduces the rate of sediment accumulation, while slowing water flow near the riverbanks....

is a structure that only partly restricts a waterway, creating a faster channel that resists the accumulation of sediment.

Dry dam



A dry dam also known as a flood retarding structure, is a dam designed to control flooding. It normally holds back no water and allows the channel to flow freely, except during periods of intense flow that would otherwise cause flooding downstream.

Diversionary dam



A diversionary dam is a structure designed to divert all or a portion of the flow of a river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 from its natural course. The water may be redirected into a canal or tunnel for irrigation and/or hydroelectric power production.

Tailings dam


A tailings dam is typically an earth-fill embankment dam used to store tailings
Tailings
Tailings, also called mine dumps, slimes, tails, leach residue, or slickens, are the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore...

 — which are produced during mining
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...

 operations after separating the valuable fraction from the uneconomic fraction of an ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....

. Conventional water retention dams can serve this purpose but due to cost, a tailings dam is more viable. Unlike water retention dams, a tailings dam is raised in succession throughout the life of the particular mine. Typically, a base or starter dam is constructed and as it fills with a mixture of tailings and water, it is raised. Material used to raise the dam can include the tailings (depending on their size) along with dirt.

There are three raised tailings dam designs, the upstream, downstream and centerline, named according to the movement of the crest during raising. The specific design used it dependent upon topography, geology, climate, the type of tailings and cost. An upstream tailings dam consists of trapezoidal embankments being constructed on top but toe to crest of another, moving the crest further upstream. This creates a relatively flat downstream side and a jagged upstream side which is supported by tailings slurry
Slurry
A slurry is, in general, a thick suspension of solids in a liquid.-Examples of slurries:Examples of slurries include:* Lahars* A mixture of water and cement to form concrete* A mixture of water, gelling agent, and oxidizers used as an explosive...

 in the impoundment. The downstream design refers to the successive raising of the embankment that positions the fill and crest further downstream. A centerlined dam has sequential embankment dams constructed directly on top of another while fill is placed on the downstream side for support and slurry supports the upstream side.

Because tailings dams often store toxic chemicals from the mining process, they have an impervious liner to prevent seepage. Water/slurry levels in the tailings pond must be managed for stability and environmental purposes as well.

Steel dams


A steel dam
Steel dam
A steel dam is a type of dam that is made of steel, rather than the more common masonry, earthworks, concrete or timber construction materials.Relatively few examples were ever built...

 is a type of dam briefly experimented with in around the turn of the 19th-20th Century which uses steel plating (at an angle) and load bearing beams as the structure. Intended as permanent structures, steel dams were an (arguably failed) experiment to determine if a construction technique could be devised that was cheaper than masonry, concrete or earthworks, but sturdier than timber crib dams.

Timber dams



Timber
Timber
Timber may refer to:* Timber, a term common in the United Kingdom and Australia for wood materials * Timber, Oregon, an unincorporated community in the U.S...

 dams were widely used in the early part of the industrial revolution and in frontier areas due to ease and speed of construction. Rarely built in modern times because of relatively short lifespan and limited height to which they can be built, timber dams must be kept constantly wet in order to maintain their water retention properties and limit deterioration by rot, similar to a barrel. The locations where timber dams are most economical to build are those where timber is plentiful, cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

 is costly or difficult to transport, and either a low head diversion dam is required or longevity is not an issue. Timber dams were once numerous, especially in the North American west, but most have failed, been hidden under earth embankments or been replaced with entirely new structures. Two common variations of timber dams were the crib and the plank.

Timber crib dams were erected of heavy timbers or dressed logs in the manner of a log house and the interior filled with earth or rubble. The heavy crib structure supported the dam's face and the weight of the water. Splash dam
Splash dam
A splash dam was a temporary wooden dam used to raise the water level in streams to float logs downstream to sawmills. By impounding water and allowing it to be released on the log drive's schedule, these dams allowed many more logs to be brought to market than the natural flow of the creek allowed...

s were timber crib dams used to help float logs
Logging
Logging is the cutting, skidding, on-site processing, and loading of trees or logs onto trucks.In forestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard...

 downstream in the late 19th and early 20th centuries.

Timber plank dams were more elegant structures that employed a variety of construction methods utilizing heavy timbers to support a water retaining arrangement of planks.

Cofferdams




A cofferdam
Cofferdam
A cofferdam is a temporary enclosure built within, or in pairs across, a body of water and constructed to allow the enclosed area to be pumped out, creating a dry work environment for the major work to proceed...

 is a (usually temporary) barrier constructed to exclude water from an area that is normally submerged. Made commonly of wood, concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 or steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 sheet piling
Deep foundation
A deep foundation is a type of foundation distinguished from shallow foundations by the depth they are embedded into the ground. There are many reasons a geotechnical engineer would recommend a deep foundation over a shallow foundation, but some of the common reasons are very large design loads, a...

, cofferdams are used to allow construction on the foundation
Foundation (architecture)
A foundation is the lowest and supporting layer of a structure. Foundations are generally divided into two categories: shallow foundations and deep foundations.-Shallow foundations:...

 of permanent dams, bridges, and similar structures. When the project is completed, the cofferdam may be demolished or removed. See also causeway
Causeway
In modern usage, a causeway is a road or railway elevated, usually across a broad body of water or wetland.- Etymology :When first used, the word appeared in a form such as “causey way” making clear its derivation from the earlier form “causey”. This word seems to have come from the same source by...

 and retaining wall
Retaining wall
Retaining walls are built in order to hold back earth which would otherwise move downwards. Their purpose is to stabilize slopes and provide useful areas at different elevations, e.g...

. Common uses for cofferdams include construction and repair of off shore oil platforms. In such cases the cofferdam is fabricated from sheet steel and welded into place under water. Air is pumped into the space, displacing the water allowing a dry work environment below the surface. Upon completion the cofferdam is usually deconstructed unless the area requires continuous maintenance.

Beaver dams



Beavers create dams primarily out of mud and sticks to flood a particular habitable area. By flooding a parcel of land, beavers can navigate below or near the surface and remain relatively well hidden or protected from predators. The flooded region also allows beavers access to food, especially during the winter.

Power generation plant




As of 2005, hydroelectric power, mostly from dams, supplies some 19% of the world's electricity, and over 63% of renewable energy
Renewable energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...

. Much of this is generated by large dams, although China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 uses small scale hydro generation on a wide scale and is responsible for about 50% of world use of this type of power.

Most hydroelectric power comes from the potential energy
Potential energy
In physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...

 of dammed water driving a water turbine
Water turbine
A water turbine is a rotary engine that takes energy from moving water.Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. They harness a clean and renewable energy...

 and generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...

; to boost the power generation capabilities of a dam, the water may be run through a large pipe called a penstock
Penstock
A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. It is a term that has been inherited from the technology of wooden watermills....

 before the turbine
Turbine
A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...

. A variant on this simple model uses pumped storage hydroelectricity to produce electricity to match periods of high and low demand, by moving water between reservoirs at different elevations. At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine. (For example see Dinorwic Power Station.)


Spillways




A spillway is a section of a dam designed to pass water from the upstream side of a dam to the downstream side. Many spillways have floodgate
Floodgate
Floodgates are adjustable gates used to control water flow in flood barriers, reservoir, river, stream, or levee systems. They may be designed to set spillway crest heights in dams, to adjust flow rates in sluices and canals, or they may be designed to stop water flow entirely as part of a levee or...

s designed to control the flow through the spillway. Types of spillway include: A service spillway or primary spillway passes normal flow. An auxiliary spillway releases flow in excess of the capacity of the service spillway. An emergency spillway is designed for extreme conditions, such as a serious malfunction of the service spillway. A fuse plug
Fuse plug
A fuse plug is a collapsible dam installed on spillways in dams to increase the dam's capacity.The principle behind the fuse plug is that the majority of water that overflows a dam's spillway can be safely dammed except in high flood conditions. The fuse plug may be a sand-filled container, a...

 spillway
is a low embankment designed to be over topped and washed away in the event of a large flood. Fusegate elements are independent free-standing block set side by side on the spillway which work without any remote control. They allow to increase the normal pool of the dam without compromising the security of the dam because they are designed to be gradually evacuated for exceptional events. They work as fixed weir
Weir
A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...

 most of the time allowing overspilling for the common floods.

The spillway can be gradually eroded
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 by water flow, including cavitation
Cavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...

 or turbulence
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...

 of the water flowing over the spillway, leading to its failure. It was the inadequate design of the spillway which led to the 1889 over-topping of the South Fork Dam
South Fork Dam
The South Fork Dam was located on Lake Conemaugh, an artificial body of water located near South Fork, Pennsylvania, United States. On May 31, 1889, the South Fork Dam failed catastrophically and 20 million tons of water from Lake Conemaugh burst through and raced 14 miles downstream, causing the...

 in Johnstown
Johnstown, Pennsylvania
Johnstown is a city in Cambria County, Pennsylvania, United States, west-southwest of Altoona, Pennsylvania and east of Pittsburgh. The population was 20,978 at the 2010 census. It is the principal city of the Johnstown, Pennsylvania, Metropolitan Statistical Area, which includes Cambria County...

, Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

, resulting in the infamous Johnstown Flood
Johnstown Flood
The Johnstown Flood occurred on May 31, 1889. It was the result of the catastrophic failure of the South Fork Dam situated upstream of the town of Johnstown, Pennsylvania, USA, made worse by several days of extremely heavy rainfall...

 (the "great flood of 1889").

Erosion rates are often monitored, and the risk is ordinarily minimized, by shaping the downstream face of the spillway into a curve that minimizes turbulent flow, such as an ogee curve.

Common purposes

Function Example
Power generation Hydroelectric power is a major source of electricity in the world. Many countries that have rivers with adequate water flow, that can be dammed for power generation purposes. For example, the Itaipu Dam on the Paraná River
Paraná River
The Paraná River is a river in south Central South America, running through Brazil, Paraguay and Argentina for some . It is second in length only to the Amazon River among South American rivers. The name Paraná is an abbreviation of the phrase "para rehe onáva", which comes from the Tupi language...

 in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 generates 14 GW
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...

 and supplied 93% of the energy consumed by Paraguay
Paraguay
Paraguay , officially the Republic of Paraguay , is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to the east and northeast, and Bolivia to the northwest. Paraguay lies on both banks of the Paraguay River, which runs through the center of the...

 and 20% of that consumed by Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

 as of 2005.
Water supply Many urban areas of the world are supplied with water abstracted from rivers pent up behind low dams or weirs. Examples include London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 - with water from the River Thames
River Thames
The River Thames flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom. While it is best known because its lower reaches flow through central London, the river flows alongside several other towns and cities, including Oxford,...

 and Chester
Chester
Chester is a city in Cheshire, England. Lying on the River Dee, close to the border with Wales, it is home to 77,040 inhabitants, and is the largest and most populous settlement of the wider unitary authority area of Cheshire West and Chester, which had a population of 328,100 according to the...

 with water taken from the River Dee
River Dee, Wales
The River Dee is a long river in the United Kingdom. It travels through Wales and England and also forms part of the border between the two countries....

. Other major sources include deep upland reservoirs contained by high dams across deep valleys such as the Claerwen
Claerwen
The Claerwen reservoir and dam in Powys, Wales, were the last additions to the Elan Valley Reservoirs system built to provide water for the increasingly demanding city of Birmingham, in neighbouring England. Built mainly of concrete, the exterior of the dam face is dressed stone. The dam itself is...

 series of dams and reservoirs.
Stabilize water flow / irrigation Dams are often used to control and stabilize water flow, often for agricultural
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

 purposes and irrigation
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

. Others such as the Berg Strait dam can help to stabilize or restore the water levels of inland lakes and seas, in this case the Aral Sea
Aral Sea
The Aral Sea was a lake that lay between Kazakhstan in the north and Karakalpakstan, an autonomous region of Uzbekistan, in the south...

.
Flood prevention Dams such as the Blackwater dam of Webster
Webster, New Hampshire
Webster is a town in Merrimack County, New Hampshire, United States. The population was 1,872 at the 2010 census.- History :A part of Boscawen until 1860, the town takes its name from American statesman Daniel Webster.- Geography :...

, New Hampshire
New Hampshire
New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...

 and the Delta Works
Delta Works
The Delta Works is a series of construction projects in the southwest of the Netherlands to protect a large area of land around the Rhine-Meuse-Scheldt delta from the sea. The works consist of dams, sluices, locks, dikes, levees, and storm surge barriers...

 are created with flood control in mind.
Land reclamation Dams (often called dykes or levee
Levee
A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...

s in this context) are used to prevent ingress of water to an area that would otherwise be submerged, allowing its reclamation
Land reclamation
Land reclamation, usually known as reclamation, is the process to create new land from sea or riverbeds. The land reclaimed is known as reclamation ground or landfill.- Habitation :...

 for human use.
Water diversion A typically small dam used to divert water for irrigation, power generation, or other uses, with usually no other function. Occasionally, they are used to divert water to another drainage or reservoir to increase flow there and improve water use in that particular area. See: diversion dam
Diversion dam
A diversion dam is the term for a dam that diverts all or a portion of the flow of a river from its natural course. Diversion dams do not generally impound water in a reservoir...

.
Navigation Dams create deep reservoirs and can also vary the flow of water downstream. This can in return affect upstream and downstream navigation
Navigability
A body of water, such as a river, canal or lake, is navigable if it is deep, wide and slow enough for a vessel to pass. Preferably there are few obstructions such as rocks or trees to avoid. Bridges must have sufficient clearance. High water speed may make a channel unnavigable. Waters may be...

 by altering the river's depth. Deeper water increases or creates freedom of movement for water vessels. Large dams can serve this purpose but most often weir
Weir
A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...

s and locks are used.
Recreation and aquatic beauty Dams built for any of the above purposes may find themselves displaced by time of their original uses. Nevertheless the local community may have come to enjoy the reservoir for recreational and aesthetic reasons. Often the reservoir will be placid and surrounded by greenery, and convey to visitors a natural sense of rest and relaxation.

Location



One of the best places for building a dam is a narrow part of a deep river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 valley
Valley
In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...

; the valley sides can then act as natural walls. The primary function of the dam's structure is to fill the gap in the natural reservoir line left by the stream channel. The sites are usually those where the gap becomes a minimum for the required storage capacity. The most economical arrangement is often a composite structure such as a masonry
Masonry
Masonry is the building of structures from individual units laid in and bound together by mortar; the term masonry can also refer to the units themselves. The common materials of masonry construction are brick, stone, marble, granite, travertine, limestone; concrete block, glass block, stucco, and...

 dam flanked by earth embankments. The current use of the land to be flooded should be dispensable.

Significant other engineering
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...

 and engineering geology
Engineering geology
Engineering geology is the application of the geologic sciences to engineering practice for the purpose of assuring that the geologic factors affecting the location, design, construction, operation and maintenance of engineering works are recognized and adequately provided for...

 considerations when building a dam include:
  • permeability
    Permeability (fluid)
    Permeability in fluid mechanics and the earth sciences is a measure of the ability of a porous material to allow fluids to pass through it.- Units :...

     of the surrounding rock or soil
  • earthquake
    Earthquake
    An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

     faults
  • landslides and slope stability
    Slope stability
    The field of slope stability encompasses the analysis of static and dynamic stability of slopes of earth and rock-fill dams, slopes of other types of embankments, excavated slopes, and natural slopes in soil and soft rock...

  • water table
  • peak flood flows
  • reservoir silting
  • environmental impacts on river fisheries, forests and wildlife (see also fish ladder
    Fish ladder
    A fish ladder, also known as a fishway, fish pass or fish steps, is a structure on or around artificial barriers to facilitate diadromous fishes' natural migration. Most fishways enable fish to pass around the barriers by swimming and leaping up a series of relatively low steps into the waters on...

    )
  • impacts on human habitations
  • compensation for land being flooded as well as population resettlement
  • removal of toxic materials and buildings from the proposed reservoir area

Impact assessment


Impact is assessed in several ways: the benefits to human society arising from the dam (agriculture, water, damage prevention and power), harm or benefit to nature and wildlife, impact on the geology of an area - whether the change to water flow and levels will increase or decrease stability, and the disruption to human lives (relocation, loss of archeological or cultural matters underwater).

Environmental impact




Reservoirs held behind dams affect many ecological aspects of a river. Rivers topography and dynamics depend on a wide range of flows whilst rivers below dams often experience long periods of very stable flow conditions or saw tooth flow patterns caused by releases followed by no releases. Water releases from a reservoir including that exiting a turbine usually contains very little suspended sediment, and this in turn can lead to scouring of river beds and loss of riverbanks; for example, the daily cyclic flow variation caused by the Glen Canyon Dam
Glen Canyon Dam
Glen Canyon Dam is a concrete arch dam on the Colorado River in northern Arizona in the United States, just north of Page. The dam was built to provide hydroelectricity and flow regulation from the upper Colorado River Basin to the lower. Its reservoir is called Lake Powell, and is the second...

 was a contributor to sand bar erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

.

Older dams often lack a fish ladder
Fish ladder
A fish ladder, also known as a fishway, fish pass or fish steps, is a structure on or around artificial barriers to facilitate diadromous fishes' natural migration. Most fishways enable fish to pass around the barriers by swimming and leaping up a series of relatively low steps into the waters on...

, which keeps many fish from moving up stream to their natural breeding grounds, causing failure of breeding cycles or blocking of migration paths. Even the presence of a fish ladder does not always prevent a reduction in fish reaching the spawning
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...

 grounds upstream. In some areas, young fish ("smolt") are transported downstream by barge
Barge
A barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. Some barges are not self-propelled and need to be towed by tugboats or pushed by towboats...

 during parts of the year. Turbine and power-plant designs that have a lower impact upon aquatic life are an active area of research.

A large dam can cause the loss of entire ecosphere
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

s, including endangered
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 and undiscovered species in the area, and the replacement of the original environment by a new inland lake.

Large reservoir
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

s formed behind dams have been indicated in the contribution of seismic activity
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

, due to changes in water load and/or the height of the water table.

Human social impact


The impact on human society is also significant. Nick Cullather argues in Hungry World: America's Cold War Battle Against Poverty in Asia that dam construction requires the state
The State
The State is a daily morning newspaper published in Columbia, South Carolina, in the United States. Owned by The McClatchy Company and distributed in most of South Carolina's 46 counties, The State is the largest newspaper in the Palmetto State....

 to displace individual people in the name of the common good
Common good
The common good is a term that can refer to several different concepts. In the popular meaning, the common good describes a specific "good" that is shared and beneficial for all members of a given community...

, and that it often leads to abuses of the masses by planners. He cites Morarji Desai
Morarji Desai
Morarji Ranchhodji Desai was an Indian independence activist and the fourth Prime Minister of India from 1977–79. He was the first Indian Prime Minister who did not belong to the Indian National Congress...

, Interior Minister of India, in 1960 speaking to villagers upset about the Pong Dam
Pong Dam
The Pong Dam, also known as the Beas Dam, is an earth-fill embankment dam on the Beas River just upstream of Talwara in the state of Himachal Pradesh, India. The purpose of the dam is water storage for irrigation and hydroelectric power generation. As the second phase of the Beas Project,...

, who threatened to "release the waters" and drown the villagers if they did not cooperate.

For example, the Three Gorges Dam
Three Gorges Dam
The Three Gorges Dam is a hydroelectric dam that spans the Yangtze River by the town of Sandouping, located in the Yiling District of Yichang, in Hubei province, China...

 on the Yangtze River
Yangtze River
The Yangtze, Yangzi or Cháng Jiāng is the longest river in Asia, and the third-longest in the world. It flows for from the glaciers on the Tibetan Plateau in Qinghai eastward across southwest, central and eastern China before emptying into the East China Sea at Shanghai. It is also one of the...

 in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 is more than five times the size of the Hoover Dam
Hoover Dam
Hoover Dam, once known as Boulder Dam, is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the US states of Arizona and Nevada. It was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President...

 (U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

), and will create a reservoir 600 km long to be used for hydro-power generation. Its construction required the loss of over a million people's homes and their mass relocation, the loss of many valuable archaeological and cultural sites, as well as significant ecological change. It is estimated that to date, 40-80 million people worldwide have been physically displaced from their homes as a result of dam construction.

Economics


Construction of a hydroelectric plant requires a long lead-time for site studies, hydrological studies, and environmental impact assessment, and are large scale projects by comparison to traditional power generation based upon fossil fuel
Fossil fuel
Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...

s. The number of sites that can be economically developed for hydroelectric production is limited; new sites tend to be far from population centers and usually require extensive power transmission
Power transmission
Power transmission is the movement of energy from its place of generation to a location where it is applied to performing useful work.Power is defined formally as units of energy per unit time...

 lines. Hydroelectric generation can be vulnerable to major changes in the climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...

, including variation of rainfall, ground and surface water level
Water level
Water level or gage height or stage is the elevation of the free surface of a stream, lake or reservoir relative to a specified datum ....

s, and glacial melt, causing additional expenditure for the extra capacity to ensure sufficient power is available in low water years.

Once completed, if it is well designed and maintained, a hydroelectric power source is usually comparatively cheap and reliable. It has no fuel and low escape risk, and as an alternative energy
Alternative energy
Alternative energy is an umbrella term that refers to any source of usable energy intended to replace fuel sources without the undesired consequences of the replaced fuels....

 source it is cheaper than both nuclear and wind power. It is more easily regulated to store water as needed and generate high power levels on demand compared to wind power
Wind power
Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships....

, although dams have life expectancies while renewable energies
Renewable energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...

 do not.

Dam failure





Dam failures are generally catastrophic if the structure is breached or significantly damaged. Routine deformation monitoring
Deformation monitoring
Deformation monitoring is the systematic measurement and tracking of the alteration in the shape or dimensions of an object as a result of stresses induced by applied loads...

 and monitoring of seepage from drains in and around larger dams is useful to anticipate any problems and permit remedial action to be taken before structural failure occurs. Most dams incorporate mechanisms to permit the reservoir to be lowered or even drained in the event of such problems. Another solution can be rock grout
Grout
Grout is a construction material used to embed rebars in masonry walls, connect sections of pre-cast concrete, fill voids, and seal joints . Grout is generally composed of a mixture of water, cement, sand, often color tint, and sometimes fine gravel...

ing - pressure pumping
Pressure grouting
Pressure grouting involves injecting a grout material into generally isolated pore or void space of which neither the configuration or volume are known, and is often referred to simply as grouting. The grout may be a cementitious, resinous, or solution chemical mixture. The greatest use of...

 portland cement
Portland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...

 slurry
Slurry
A slurry is, in general, a thick suspension of solids in a liquid.-Examples of slurries:Examples of slurries include:* Lahars* A mixture of water and cement to form concrete* A mixture of water, gelling agent, and oxidizers used as an explosive...

 into weak fractured rock.

During an armed conflict, a dam is to be considered as an "installation containing dangerous forces" due to the massive impact of a possible destruction on the civilian population and the environment. As such, it is protected by the rules of International Humanitarian Law
International humanitarian law
International humanitarian law , often referred to as the laws of war, the laws and customs of war or the law of armed conflict, is the legal corpus that comprises "the Geneva Conventions and the Hague Conventions, as well as subsequent treaties, case law, and customary international law." It...

 (IHL) and shall not be made the object of attack if that may cause severe losses among the civilian population. To facilitate the identification, a protective sign
Protective sign
Protective signs are symbols to be used during an armed conflict to mark persons and objects under the protection of various treaties of International Humanitarian Law . While their essential meaning can be summarized as "Don't shoot!" or "Don't attack!", the exact conditions implied vary depending...

 consisting of three bright orange circles placed on the same axis is defined by the rules of IHL.

The main causes of dam failure include inadequate spillway capacity, piping through the embankment, foundation or abutments, spillway design error (South Fork Dam
South Fork Dam
The South Fork Dam was located on Lake Conemaugh, an artificial body of water located near South Fork, Pennsylvania, United States. On May 31, 1889, the South Fork Dam failed catastrophically and 20 million tons of water from Lake Conemaugh burst through and raced 14 miles downstream, causing the...

), geological instability caused by changes to water levels during filling or poor surveying (Vajont Dam
Vajont Dam
The Vajont Dam is a disused dam, completed in 1959 in the valley of the Vajont river under Monte Toc, 100 km north of Venice, Italy...

, Malpasset
Malpasset
Malpasset was an arch dam on the Reyran River, constructed approximately 7 km north of Fréjus on the Côte d'Azur, southern France, in the Var département. It collapsed on December 2, 1959, killing 421 people in the resulting flood. Various sources indicate death numbers of 361, 400, 423, 429 or 510...

, Testalinden Creek
Testalinden creek
Testalinda is an historic area, school, creek, and a dam south of the Okanagan town of Oliver, British Columbia. . The dam at Testalinden Lake burst June 13, 2010 at approximately 2:15 creating a debris torrent landslide that descended about a mile to the valley below destroying at least 5 homes...

 Dam), poor maintenance, especially of outlet pipes (Lawn Lake Dam
Lawn Lake Dam
Lawn Lake Dam was an earthen dam in Rocky Mountain National Park, United States that failed on July 15, 1982 at about 6 a.m. The sudden release of 220 million US gallons of water resulted in a flash flood that killed three people camping in the park and caused $31 million in damage to the town of...

, Val di Stava Dam collapse
Val di Stava Dam Collapse
The Val di Stava Dam collapse occurred on 19 July 1985, when two tailings dams above the village of Stava, near Tesero, Northern Italy, failed. It resulted in one of Italy's worst disasters, killing 268 people, destroying 63 buildings and demolishing eight bridges.The upper dam broke first, leading...

), extreme rainfall (Shakidor Dam
Shakidor Dam
Shakidor Dam was a small dam located near Pasni in Balochistan province of Pakistan. The dam is 485 metres long. It was constructed in 2003 at a cost of 45 million Pakistani Rupees to provide irrigation for nearby farms....

), and human, computer or design error (Buffalo Creek Flood
Buffalo Creek Flood
The Buffalo Creek Flood was a disaster that occurred on February 26, 1972, when the Pittston Coal Company's coal slurry impoundment dam #3, located on a hillside in Logan County, West Virginia, USA, burst four days after having been declared 'satisfactory' by a federal mine inspector.The resulting...

, Dale Dike Reservoir
Dale Dike Reservoir
Dale Dike Reservoir or Dale Dyke Reservoir , famous for causing the Great Sheffield Flood, is in the north-east Peak District, in the City of Sheffield South Yorkshire, England, a mile west of Bradfield, eight miles from the centre of Sheffield, on the Dale Dike, a tributary of the River...

, Taum Sauk pumped storage plant
Taum Sauk pumped storage plant
The Taum Sauk pumped storage plant is located in the St. Francois mountain region of the Missouri Ozarks approximately south of St. Louis near Lesterville, Missouri in Reynolds County. The pumped-storage hydroelectric plant, operated by the AmerenUE electric company, was designed to help...

).

A notable case of deliberate dam failure (prior to the above ruling) was the Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...

 'Dambusters'
No. 617 Squadron RAF
No. 617 Squadron is a Royal Air Force aircraft squadron based at RAF Lossiemouth in Scotland. It currently operates the Tornado GR4 in the ground attack and reconnaissance role...

 raid on Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 in World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 (codenamed "Operation Chastise
Operation Chastise
Operation Chastise was an attack on German dams carried out on 16–17 May 1943 by Royal Air Force No. 617 Squadron, subsequently known as the "Dambusters", using a specially developed "bouncing bomb" invented and developed by Barnes Wallis...

"
), in which three German dams were selected to be breached in order to have an impact on German infrastructure and manufacturing and power capabilities deriving from the Ruhr and Eder
Eder
The Eder is a 177 km long river in Germany, and a tributary of the Fulda River. It was first mentioned by the Roman historian Tacitus as the Adrana in the territory of the Chatti....

 rivers. This raid later became the basis for several films.

Since 2007, the Dutch IJkdijk
IJkdijk
The IJkdijk is a facility in the Netherlands to test dikes and to develop sensor network technologies for early warning systems. Furthermore the sensor network will be able to detect many water-related environmental factors that affect the health of humans such as pollution and biological changes...

 foundation is developing, with an open innovation
Open Innovation
Although the idea and discussion about some consequences date back at least to the 60s, open innovation is a term promoted by Henry Chesbrough, a professor and executive director at the Center for Open Innovation at the University of California, Berkeley, in his book Open Innovation: The new...

 model and early warning system for levee/dike failures. As a part of the development effort, full scale dikes are destroyed in the IJkdijk fieldlab. The destruction process is monitored by sensor networks from an international group of companies and scientific institutions.

See also


  • Canal lock
  • Grout curtain
    Grout curtain
    Grout curtains are barriers that protect a dam from seepage and can be used in initial construction or repair. Additionally, they can be used to strengthen foundations and contain spills.-Characteristics:...

  • Inflatable rubber dam
    Inflatable rubber dam
    Inflatable rubber dams are cylindrical rubber fabrics placed across channels, streams and weir or dam crests to raise the upstream water level when inflated. The membrane is a multi-layer fabric made of synthetic fibre and rubberised on one or both sides. The fabric is quite flexible and yet...

  • List of largest dams
  • List of reservoirs and dams
  • List of world's tallest dams
  • Bunding
    Bunding
    Bunding, also called a bund wall, is the area within a structure designed to prevent inundation or breaches of various types.-Liquid containment:...


External links