Dam

The English word "dam" is found in Middle English, and traces back to the word dam in Germanic languages Middle Low German, Middle Dutch and Old Norse. Roots of the word include Gothic faur-dammjan ('to stop up'), and the Indo-European base *dhē- ('to set, put in place'). ==History==

in Spain was built by the Romans, and has been in use for almost two millennia. dam in Iran was built in the 3rd century CE. was built around 1350 CE. in Spain was the first true arch dam built in Europe since Roman times. tested the limits of how thin a dam could be. Antiquity The earliest known dam is the Jawa Dam near Amman Jordan, built around 3000 BCE. This embankment dam was part of an elaborate irrigation system, and was wide and high. Around 2600 BCE, Egyptians built the Sadd el-Kafara embankment dam near Cairo, although it failed about the time its construction completed. Some of the stone blocks weighed . The Sabaean peoples built a series of dams across the Wadi Danah, located in modern Yemen, starting around 1500 BCE, culminating in the Great Dam of Marib dam (built around 500 BCE) which was long and high. The Hittite Empire built several dams between the 17th and 13th centuries BCE, including the Eflatun Pınar dam and spring temple near modern Konya, Turkey. An early dam in Chinabuilt by engineer Sunshu Ao around 580 BCEimpounded the Afengtang Reservoir which is still in existence today. In Sri Lanka, several damsincluding Tissa Wewawere build around 370 BCE to create reservoirs; some of the dams were several kilometers long. Roman era The Roman empire constructed major water worksincluding aqueducts and tunnelsstarting in the 5th century BCE, but they did not begin building significant dams until the first century CE. Roman dams were typically masonry gravity dams with vertical faces on both upstream and downstream sides, although some were reinforced on the downstream side with buttresses or rock embankments. The Romans were the first to use cement as a construction material, which could be mixed with small rocks to form concrete, or mixed with sand to form mortar to join bricks or stones. Some Roman cements, particularly those containing volcanic ash, were waterproof. One of the earliest dams built by the Romans was also the tallest they built: the Subiaco dam, built around 60 CE, stood tall and wide. The Romans built about 80 dams in Hispania (modern Spain), including the Proserpina Dam, which impounded 6 million m of water. The dam was still operational in 2026. Roman dam technology was applied by neighboring countries: after Persian king Shapur I defeated Roman emperor Valerian, he put defeated Romans to work building the Band-e Kaisar dam, which also functioned as a 40-arch bridge spanning the Karun River. Post-classical Asia and Middle Ages One of the earliest dams built in Japan was the Sayama embankment, built near Osaka in 380 CE, and long. The Kurit Damthe world's first large, thin arch damwas built in Persia (modern-day Iran) around 1350 CE. Its height was initially and was later raised to ; it remained the world’s tallest dam until the start of the 20th century. Dams in India were typically earthen dams with steep faces faced in stone. A notable example is the Veeranam Dam built around 1020 CE in Tamil Nadu, long. In Europe, dams were used to power water wheels for milling and mining. An early example was the Bazacle weir built around 1170 CE in France. Dams to create fish ponds were common in Europe, and hundreds were built in Bohemia during the 15th and 16th centuries, creating ponds covering a total of 1,800 km. Dams for irrigation included the Almansa Dama gravity/arch dam built in 1384 in Spain; and the Elche Dam (built in 1640 and still standing)the first true arch dam built in Europe since Roman times. Several dams were built to supply Istanbul with water, including one designed by Mimar Sinan in 1560 to bring water from Belgrad Forest. Another purpose for canals was transportation: the Saint-Ferréol Dam was built in France in 1675 to provide water for the Midi Canal. It remained the highest earthen dam in the world for over a century. Several books on the subject of dam design and construction were published in the 1600s and 1700s, by authors including Jacob Leupold, Albert Brahms, Johann Silberschlag, and Oliver Evans. Industrial Revolution In the late 18th century, the process of designing dams began to transform from an informal practice based on experience, to an engineering discipline rooted in science. Important figures that contributed to this evolution included French scientist Charles-Augustin de Coulomb who, in 1776, created a formula that described how soil reacts under stress, a theory that was later given practical application to dams by Alexandre Collin. Claude-Louis Navier developed the theory of elasticity in 1826. In 1847, François Zola became the first engineer to design an arch dam based on an analytical consideration of stresses. French engineer J. Augustine DeSazilly established that the best cross-section for a gravity dam was a triangle, with a vertical face on the upstream side. Scottish physicist William John Macquorn Rankine developed a theory governing retaining walls in the 1850s which was applicable to dams. These scientific foundations led to safer, larger dams of all types. The Glencorse Dam in Britain (1824) was a high embankment dam that contained a clay core and had gently sloping faces. In France, the Gouffre d'Enfer masonry gravity dam (1866) was tall. The world's first large buttress dam was Mir Alam Dam (1804) in India. In Australia, an arch damthe Parramatta Dam (1856)tested the limits of how thin a dam could be. Modern era in China In the first half of the 20th century, many large dams were built, particularly in western Europe and the US. After WW II, the availability of power construction machinery such as bulldozers, dump trucks, and scrapers contributed to an explosion in the number of large dams. The 1933 invention of grout curtain technologies enabled dams to be safely built on top of porous soils. This enabled the Aswan High Dam to be built across the Nile river, which has a deep, sandy riverbed: grout was pumped deep into the riverbed (spanning 57,000 m), preventing water from flowing underneath the dam. Notable dams built in the modern era include: • Afsluitdijk (Netherlands, 1932) A 32 km long causeway that is a major component of Netherlands' flood management system. • Hoover Dam (US 1936) Enabled the development of the US Southwest. • Grand Coulee Dam (US, 1942) Provided irrigation for a large portion of northwest US. • Aswan High Dam (Egypt, 1970) Revolutionized Egyptian society by providing a reliable water supply. • Tarbela Dam (Pakistan, 1976) One of the largest earth-filled dams in the world. • Nurek Dam (Tajikistan, 1980) One of the tallest dams in the world. • Itaipu Dam (Brazil/Paraguay, 1984) An example of international cooperation. • Three Gorges Dam (China 2006). One of the world’s largest hydropower projects. • Baihetan Dam (China, 2022) Employs some of the most powerful turbines. • Grand Ethiopian Renaissance Dam (Ethiopia, 2025) Marked a major shift in political power in northeast Africa. The modern era also saw the emergence of arguments against dam construction, starting as early as the 1870s with objections to the Thirlmere Dam in Britain. In 1906, a seven-year battle was fought over the construction of the Hetch Hetchy dam in California, which was eventually built and flooded a valley in Yosemite National Park that opponents claimed was as scenic as the famed Yosemite Valley. After climate change became a global concern, debates emerged arguing whether the electricity produced by dams was as clean as solar power or wind generation. Although hydroelectricity itself is clean, dam opponents argue that adverse environmental impacts cancel any benefits. Number of dams in the world The number of large dams in the world in 2025 was 62,362, according to the International Commission on Large Dams (ICOLD). The total number of reservoirs (large and small) in 2011 was estimated to be 16.7 million. These reservoirs store an estimated 8,070 km of water, which is about 10% of the volume of the earth's natural freshwater lakes. The reservoirs cover about 305,000 km of the planet's surface, which is about 7.3% of the area covered by natural lakes. About 7.6% of the world's rivers are significantly impacted by reservoirs; and 46.7% of large rivers are affected. In 2015, the number of hydropower dams planned or under construction was 3,700, with most in China (highest total generation capacity), Brazil (highest number of planned dams), and India. == Types==

Based on structure and material used, dams are classified as easily created without materials, arch-gravity dams, embankment dams or masonry dams, with several subtypes. Embankment dam is an earthen embankment dam in North Carolina Embankment dams are made of compacted earth, and are of two main types: rock-fill and earth-fill. Like concrete gravity dams, embankment dams rely on their weight to hold back the force of water. Gravity dam is an example of a solid gravity dam. 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 the dam's weight wins that contest. In engineering terms, that is true whenever the resultant of the forces of gravity acting on the dam and water pressure on the dam acts in a line that passes upstream of the toe of the dam. The designer tries to shape the dam so if one were to consider the part of the 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. The shape that prevents tension in the upstream face also eliminates a balancing compression stress in the downstream face, providing additional economy. For this type of dam, it is essential to have an impervious foundation with high bearing strength. Permeable foundations have a greater likelihood of generating uplift pressures under the dam. Uplift pressures are hydrostatic pressures caused by the water pressure of the reservoir pushing up against the bottom of the dam. If large enough uplift pressures are generated there is a risk of destabilizing the concrete gravity dam. On a suitable site, a gravity dam can prove to be a better alternative to other types of dams. When built on a solid foundation, the gravity dam probably represents the best-developed example of dam building. Since the fear of flood is a strong motivator in many regions, gravity dams are 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. The solid form is the more widely used of the two, though the hollow dam is frequently more economical to construct. Grand Coulee Dam is a solid gravity dam and Braddock Locks & Dam is a hollow gravity dam. Buttress dam Arch dam , Tasmania, is an arch dam. 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 and arch action will depend upon the stiffness of the dam in a vertical and horizontal direction. When the upstream face is sloped the distribution is more complicated. The normal 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 or canyon 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. , Quebec, is a multiple-arch buttress dam. 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, in Canada, is a constant radius dam. In a constant-angle dam, also known as a variable radius dam, this subtended angle is kept constant and the variation in distance between the abutments at various levels is taken care of by varying the radii. Constant-radius dams are much less common than constant-angle dams. Parker Dam on the Colorado River 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, Québec, Canada. The multiple-arch dam does not require as many buttresses as the hollow gravity type but requires a good rock foundation because the buttress loads are heavy. Hybrid and other is an example of an arch-gravity dam. A gravity dam can be combined with an arch dam into an arch-gravity dam for areas with massive amounts of water flow but less material available for a pure gravity dam. The inward compression of the dam by the water reduces the lateral (horizontal) force acting on the dam. Thus, the gravitational force required by the dam is lessened, i.e., the dam does not need to be so massive. This enables thinner dams and saves resources. of Nepal is an example of a barrage dam. A barrage dam is a special kind of dam that 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, and are often used to control and stabilize water flow for irrigation systems. An example of this type of dam is the now-decommissioned Red Bluff Diversion Dam on the Sacramento River near Red Bluff, California. Barrages that are built at the mouths of rivers or lagoons to prevent tidal incursions or use the tidal flow for tidal power are known as tidal barrages. Not man-made , a landslide dam. At 567 metres (1,860 ft) high, it is the tallest dam in the world. In addition to man-made dams described above, dams can also be created by natural factors such as landslides, lava flows, and beavers. Landslidessome caused by earthquakesfrequently create landslide dams in mountainous regions with unstable local geology. Historical examples include the Usoi Dam in Tajikistan, which blocks the Murghab River to create Sarez Lake. At high, it is the tallest dam in the world, including both natural and man-made dams. A more recent example would be the creation of Attabad Lake by a landslide on Pakistan's Hunza River. Lava dams are formed when lava flows, often basaltic, intercept the path of a stream or lake outlet, resulting in the creation of a natural impoundment. The eruptions of the Uinkaret volcanic field about 1.8 million–10,000 years ago, which created lava dams on the Colorado River in northern Arizona in the United States. The largest such lake grew to about in length before the failure of its dam. Glacial activity can also form natural dams, such as the damming of the Clark Fork in Montana by the Cordilleran Ice Sheet, which formed the Glacial Lake Missoula near the end of the last Ice Age. Moraine deposits left behind by glaciers can also dam rivers to form lakes, such as at Flathead Lake, also in Montana (see Moraine-dammed lake). Beavers create dams 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. == Uses ==

Primary purposes The main purposes that dams serve are hydropower, water supply, irrigation, flood management, land reclamation, and inland navigation. Hydropower is a major source of electricity in the world. Many countries have rivers with adequate water flow, that can be dammed for power generation purposes. For example, the Itaipu Dam on the Paraná River in South America generates 14 GW and supplied 93% of the energy consumed by Paraguay and 20% of that consumed by Brazil as of 2005. Many urban areas of the world are supplied with water taken from rivers pent up behind low dams or weirs. Examples include London, with water from the River Thames, and Chester, with water taken from the River Dee. Other major sources include deep upland reservoirs contained by high dams across deep valleys, such as the Claerwen series of dams and reservoirs. Dams are often used to support irrigation, by controlling and stabilizing water flow, often for agricultural purposes and irrigation. 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. Many dams and their associated reservoirs are designed completely or partially to aid in flood protection and control. Many large dams have flood-control reservations in which the level of a reservoir must be kept below a certain elevation before the onset of the rainy/summer melt season to allow a certain amount of space in which floodwaters can fill. Dams (often called dykes or levees in this context) are used to prevent ingress of water to an area that would otherwise be submerged, allowing its reclamation for human use. Dams create deep reservoirs and can also vary the flow of water downstream. This can in return affect upstream and downstream navigation 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 weirs and locks are used. Other purposes Not all dams are created to support the primary purposes listed above: some dams support other purposes (often in addition to primary purposes). Dams that support other purposes include tailings dams, saddle dams, weirs, cofferdams, check dams, dry dams, diversionary dams, and underground dams. surrounds a pit used to store waste from mining activity. A tailings dam is typically an earth-fill embankment dam used to store tailings, which are produced during mining operations after separating the valuable fraction from the uneconomic fraction of an ore. 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 soil. 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, similar to a levee, which is a wall or embankment built along a river or stream to protect adjacent land from flooding. A weir is a low dam placed in a river channel. Other names (sometimes associated with specific purpose) include overflow dam, low head dam, and fixed-crest dam. Weirs are typically a straight, level and made of concrete. Some weirs are designed to maintain depth in the upstream channel to supportc navigation. They can pose risks to boaters who may travel over them, as they may be difficult to see and may create induced currents that are difficult to escape. during the construction of locks at the Montgomery Point Lock and Dam A cofferdam is a barrier, usually temporary, constructed to exclude water from an area that is normally submerged. Made commonly of wood, concrete, or steel sheet piling, cofferdams are used to allow construction on the foundation of permanent dams, bridges, and similar structures. When the project is completed, the cofferdam will usually be demolished or removed unless the area requires continuous maintenance. A check dam is a small dam designed to reduce flow velocity and control soil erosion. Conversely, a wing dam is a structure that only partly restricts a waterway, creating a faster channel that resists the accumulation of sediment. A dry dam, also known as a flood retarding structure, is 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. A diversionary dam is designed to divert all or a portion of the flow of a river from its natural course. The water may be redirected into a canal or tunnel for irrigation and/or hydroelectric power production. Underground dams are used to trap groundwater and store all or most of it below the surface for extended use in a localized area. In some cases, they are also built to prevent saltwater from intruding into a freshwater aquifer. Underground dams are typically constructed in areas where water resources are minimal and need to be efficiently stored, such as in deserts and on islands like the Fukuzato Dam in Okinawa, Japan. They are most common in northeastern Africa and the arid areas of Brazil while also being used in the southwestern United States, Mexico, India, Germany, Italy, Greece, France and Japan. ==Design==

Design process Geological assessment and site selection Specifications and Standards Aesthetics A dam's appearance can be a factor when evaluating potential designs. Bridges with some curvature, such as arch dams, tend to be perceived as more attractive than those designed with entirely straight lines. The advent of concrete after WWII as material for building bridges gave designers more flexibility to create pleasing bridge designs. Some dams such as the Hoover Dam and the Bratsk Damserve as objects that inspire admiration and pride, and can act as a symbol or icon of a community. Swiss dam engineer Niklaus Schnitter maintains that it is impossible to objectively determine if a dam and its reservoir will improve or detract from the pre-dam landscape, maintaining that it is a matter of taste. Materials Earthen Concrete and masonry Other Some dams are made of steel. Others are made of timber. 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 sawtooth flow patterns caused by releases followed by no releases. Water releases from a reservoir including that exiting a turbine usually contain 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 was a contributor to sand bar erosion. Older dams often lack a fish ladder, which keeps many fish from moving upstream to their natural breeding grounds, causing failure of breeding cycles or blocking of migration paths. Even fish ladders do not prevent a reduction in fish reaching the spawning grounds upstream. In some areas, young fish ("smolt") are transported downstream by barge during parts of the year. Turbine and power-plant designs that have a lower impact upon aquatic life are an active area of research. At the same time, however, some particular dams may contribute to the establishment of better conditions for some kinds of fish and other aquatic organisms. Studies have demonstrated the key role played by tributaries in the downstream direction from the main river impoundment, which influenced local environmental conditions and beta diversity patterns of each biological group. Both replacement and richness differences contributed to high values of total beta diversity for fish (average = 0.77) and phytoplankton (average = 0.79), but their relative importance was more associated with the replacement component for both biological groups (average = 0.45 and 0.52, respectively). Such changes may be explained by the fact that the fish obtained "different feeding habits, with almost all species being found in more than one group. Large reservoirs formed behind dams have been indicated in the contribution of seismic activity, due to changes in water load and/or the height of the water table. However, this is a mistaken assumption, because the relatively marginal stress attributed to the water load is orders of magnitude lesser than the force of an earthquake. The increased stress from the water load is insufficient to fracture the Earth's crust, and thus does not increase the severity of an earthquake. Dams are also found to influence global warming. The changing water levels in reservoirs are a source for greenhouse gases like methane. While dams and the water behind them cover only a small portion of earth's surface, they harbour biological activity that can produce large quantities of greenhouse gases. Social impact Dams' impact on human society is significant. Nick Cullather argues in ''Hungry World: America's Cold War Battle Against Poverty in Asia'' that dam construction requires the state to displace people in the name of the common good, and that it often leads to abuses of the masses by planners. He cites Morarji Desai, Interior Minister of India, in 1960 speaking to villagers upset about the Pong Dam, who threatened to "release the waters" and drown the villagers if they did not cooperate. The Three Gorges Dam on the Yangtze River in China is more than five times the size of the Hoover Dam (U.S.). It creates a reservoir long to be used for flood control and hydropower 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, and significant ecological change. During the 2010 China floods, the dam held back a what would have been a disastrous flood and the huge reservoir rose by 4 m (13 ft) overnight. In 2008, it was estimated that 40–80 million people worldwide have been displaced from their homes as a result of dam construction. Economic impact Construction of a hydroelectric plant requires a long lead time for site studies, hydrological studies, and environmental impact assessments, and are large-scale projects in comparison to carbon-based power generation. 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 lines. Hydroelectric generation can be vulnerable to major changes in the climate, including variations in rainfall, ground and surface water levels, 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 a clean energy 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. == Auxiliary structures ==

Hydropower and electric generator , hydroelectric power, mostly from dams, supplies some 19% of the world's electricity, and over 63% of renewable energy. Much of this is generated by large dams, although China uses small-scale hydro generation on a wide scale and is responsible for about 50% of world use of this type of power. 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. Gates Locks Penstocks, inlets, and outlets Fish ladder ==Construction ==

Cofferdams and diversion of river Preparation, grouting, and foundations Building the dam Filling Hydropower facilities ==Operation and maintenance==

Management procedures Maintenance, leaks, and repairs Inspection and monitoring Sedimentation of reservoir Dam removal Water and sediment flows can be re-established by removing dams from a river. Dam removal is considered appropriate when the dam is old and maintenance costs exceed the expense of its removal. Some effects of dam removal include erosion of sediment in the reservoir, increased sediment supply downstream, increased river width and braiding, re-establishment of natural water temperatures and recolonisation of habitats that were previously unavailable due to dams. As a result, the delivery of sediment and wood to the downstream river and delta were re-established. Approximately 65% of the sediment stored in the reservoirs eroded, of which ~10% was deposited in the riverbed. The remaining ~90% was transported to the coast. In total, renewed sediment delivery caused approximately 60 ha of delta growth, and also resulted in increased river braiding. == Safety and Failures==

Risk analysis and mitigation methods Failures failed in 1976 in the US. failed in 1959 in France. Dam failures are generally catastrophic if the structure is breached or significantly damaged. Routine deformation monitoring 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 grouting – pressure pumping Portland cement slurry into weak fractured rock. The main causes of dam failure include inadequate spillway capacity, piping through the embankment, foundation or abutments, spillway design error (South Fork Dam), geological instability caused by changes to water levels during filling or poor surveying (Vajont, Malpasset, Testalinden Creek dams), poor maintenance, especially of outlet pipes (Lawn Lake Dam, Val di Stava Dam collapse), extreme rainfall (Shakidor Dam), earthquakes, and human, computer or design error (Buffalo Creek Flood, Dale Dike Reservoir, Taum Sauk pumped storage plant). Since 2007, the Dutch IJkdijk foundation is developing, with an open innovation model, an 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. == Society and culture ==

International geopolitics Profession and regulation Most countries with large dams have statutes or regulations regulating dam construction and inspection practices. The regulations vary widely across the countries. Some nations have an government agency responsible for inspecting dams, but many do not. Some countries regulate dams at a federal level, but others regulate at a province/state level. For example, Germany has no federal regulations, instead each state has its own statutes; dam owners are required to inspect their dams periodically, with supervision by the government. The regulations of most nations do not specify particular dam design parameters, but instead require compliance with “recognized rules of technology” or “state of the art in science and technology”. Art and culture Wartime During an armed conflict, a dam is to be considered as an "installation containing dangerous forces" due to the massive impact of possible destruction on the civilian population and the environment. As such, it is protected by the rules of international humanitarian law (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 consisting of three bright orange circles placed on the same axis is defined by the rules of IHL. A notable case of deliberate destruction of a dam was the Royal Air Force 'Dambusters' raid on Germany in World War II (codenamed "Operation Chastise"), in which three German dams were selected to be breached in order to damage German infrastructure and manufacturing and power capabilities deriving from the Ruhr and Eder rivers. This raid later became the basis for several films. == References==