سد - Dam

Dam

 A barrier or structure across a stream, river, or waterway for the purpose of confining and controlling the flow of water. Dams vary in size from small earth embankments for farm use to high, massive concrete structures for water supply, hydropower, irrigation, navigation, recreation, sedimentation control, and flood control. As such, dams are cornerstones in the water resources development of river basins. Dams are now built to serve several purposes and are therefore known as multipurpose (Fig. 1). The construction of a large dam requires the relocation of existing highways, railroads, and utilities from the river valley to elevations above the reservoir. The two principal types of dams are embankment and concrete. Appurtenant structures of dams include spillways, outlet works, and control facilities; they may also include structures related to hydropower and other project purposes. See also: Electric power generation; Irrigation (agriculture); Water supply engineering

 Fig. 1  John Day Lock and Dam, looking upstream across the Columbia River at Washington shore. In the foreground the navigation lock is seen, then the spillway beyond it, and then the powerhouse. The John Day multiple-purpose project has the highest single-lift navigation lock in the United States. (U.S. Army Corps of Engineers)

 

 

 

 

Dams have been built since ancient times, and improvements were made at varying intervals as engineering technology developed. However, very rapid advances occurred in the twentieth century as a result of developments in the use of concrete, soil mechanics, and construction equipment. In the early 1900s, concrete dams became thinner, and a new era of thin arch dams began. Earth and rock–fill embankment dams became economical during and after World War II. In 1980, an innovative method of using earth-moving and compacting equipment to place dry concrete (roller-compacted concrete) greatly improved the economics of concrete dams. As of December 1997, there was a total of 100,781 dams in the United States. Most of these are small recreational projects and farm ponds. Of this total, 6,389 dams have a height of 50 feet or more and 1,586 dams have a height of 100 feet or more. Numerous dams have been constructed in various countries worldwide (Table 1). Many dams possess considerable height, volume, and reservoir capacity (Table 2).

Purposes

 Dams are built for specific purposes. In ancient times, they were built only for water supply or irrigation. Early in the development of the United States, rivers were a primary means of transportation, and therefore navigation dams with locks (Fig. 2) were constructed on the major rivers. Dams have become more complex to meet large power demands and other needs of modern countries (Figs. 3 and 4). Although recreation is a popular purpose of small private dams, it is planned as a benefit with an assigned monetary value in federal projects in the United States. A typical summary of purposes of nonfederal dams is shown in Table 3.

 Features

In addition to the standard impounded reservoir and the appurtenant structures of a dam (spillway, outlet works, and control facility), a dam with hydropower requires a powerhouse, penstocks, generators, and switchyard. The inflow of water into the reservoir must be monitored continuously, and the outflow must be controlled to obtain maximum benefits. Under normal operating conditions, the reservoir is controlled by the outlet works, consisting of a large tunnel or conduit at stream level with control gates. Under flood conditions, the reservoir is maintained by both the spillway and outlet works.

 Fig. 2  Lock and Dam 1 on the Mississippi River between St. Paul and Minneapolis, Minnesota. Built in 1917 with a single lock to provide barge traffic to Minneapolis, the dam failed in 1929 and was rebuilt with twin locks in 1932. (U.S. Army Corps of Engineers)

 

  

The reservoir level of a flood control dam is maintained as low as possible to create the maximum amount of storage space for use in the flood season. For an irrigation project, the reservoir is filled as high as possible in the winter and early spring, and it is maintained at that level for maximum release of water during the dry season. The reservoir level of a hydropower dam is maintained as constant as feasible to create a uniform head for power generation. Water quality is an important ingredient in sustaining a balance in nature and is taken into account in modern dam design, construction, and operation. The chemical quality and temperature of the water are monitored in the reservoir. Intake ports at various depths allow selective withdrawal and mixing to produce the desired temperature and oxygen content, in order to enhance downstream environmental conditions. Fish ladders, that is, stepped series of elevated pools, are provided at many dams to allow free passage of fish upstream and downstream. Screens are used to keep fish out of the turbines. See also: Reservoir

 

Fig. 3  Guri Dam, Venezuela, showing construction under way on the second stage of the concrete gravity dam. Embankment dams are shown on the left and right abutments. The concrete batch plant is shown at left with a trestle for transporting concrete shown on the downstream face of the dam. The second powerhouse with an excavated outlet channel is shown at the center of the photo. (C.V.G. Electrification del Caroni, C. A. EDELCA, Caracas, Venezuela)

 

 

 

 

 

 

Fig. 4  Itaipu Dam, on the Paraná River between Brazil and Paraguay. An operating spillway with a flip bucket on the Paraguay side of the river is shown at left. The hollow concrete gravity dam with powerhouse construction at the downstream toe is shown at center.(G. S. Sarkaria, International Engineering Company, Inc.)

 

 

 

 

The discharge from modern dams must be managed carefully and continuously. During floods, reservoir inflows may exceed maximum discharges and cause reservoir levels to rise. To prevent dams from overtopping and possibly failing, spillways are provided to pass floodwater safely. They are commonly built at elevations just below dam crests and without gates. These uncontrolled, ungated spillways are designed to allow all of the excess water to pass. In other cases, spillways are constructed at even lower levels and contain gates that are operated from the control facilities. The tops of these gates are lower than the dam crests, thus allowing some control of floodwater.

Penstocks (usually steel pipes or concrete-lined tunnels) are used to convey water from the reservoir through or around the dam to the powerhouse. The penstocks are connected to the turbines, and the water flow is controlled by valves. The number and size of the penstocks vary, depending on the number of generators and amount of water needed.

All the features of a dam are monitored and operated from a control room. The room contains the necessary monitors, controls, computers, emergency equipment, and communications systems to allow project personnel to operate the dam safely under all conditions. Standby generators and backup communications equipment are necessary to operate the gates and other reservoir controls in case of power failure. Weather conditions, inflow, reservoir level, discharge, and downstream river levels are also monitored. In addition, the control room monitors instrumentation located in the dam and appurtenant features that measures their structural behavior and physical condition.

 

 Fig. 5  Aerial view of North Fork Dam, a combination earth-and-rock embankment of the North Fork of Pound River, Virginia. The channel-type spillway (left center) has a simple overflow weir. (U.S. Army Corps of Engineers)

 

 

 

 

 

Requirements

All dams are designed and constructed to meet specific requirements. First, a dam should be built from locally available materials when possible. Second, the dam must remain stable under all conditions, during construction, and ultimately in operation, both at the normal reservoir operating level and under all flood and drought conditions. Third, the dam and foundation must be sufficiently watertight to control seepage and maintain the desired reservoir level. Finally, it must have sufficient spillway and outlet works capacity as well as freeboard to prevent floodwater from overtopping it.

 

Types

 Dams are classified by the type of material from which they are constructed. In early times, the materials were earth, large stones, and timber, but as technology developed, other materials and construction procedures were used. Most modern dams fall into two categories: embankment and concrete. Embankment dams are earth or rock-fill; other gravity dams and arch and buttress dams are concrete.

Earth-fill dam

Earth is the predominant material in this type of embankment dam. Earth dams are further classified by the construction method: hydraulic-fill or rolled-fill. A hydraulic-fill dam is one in which the soil is excavated, transported, and placed by flowing water. A large dredge operating in the river or other borrow area pumps a slurry of earth and water to the damsite. Here the coarse-grained materials settle on the outside portion of the embankment, and the remaining slurry is allowed to pond at the center, where the very fine-grained clay-size particles settle to form the impervious portion of the dam.

 Fig. 6  Plan and sections of North Fork of Pound Dam, Virginia. 1 ft = 0.3 m. (U.S. Army Corps of Engineers)

 

 

 

Advances in earth-moving construction equipment during World War II led to widespread construction of rolled-earth-fill dams. Economic advantages of this type of embankment often include the use of material available from the site excavation as embankment material, and the ready availability of fill material at or near the damsite. Other advantages of earth-fill dams include their adaptability to a wide variety of site configurations and their tolerance of weak foundations.

At various stages during excavation and placement of the fill, the moisture content of the soil may be adjusted by wetting or drying in order to optimize its performance in the finished embankment. The soil is spread on the embankment in uniform layers 8–12 in. (20–30 cm) thick and compacted with sheepsfoot or rubber-tired rollers. The rollers make from four to eight passes, depending on the desired density. Typical dry densities for rolled earth fill range 100–130 lb/ft3 (1602–2083 kg/m3).

Seepage control is an important aspect of earth-dam design. In early times, earth embankments were homogeneous, and seepage would emerge on the downstream slope just above ground level. If uncontrolled, such seepage can move soil particles and cause failure. In 1940, filter criteria were developed after careful scientific tests on all types of soil and on the sands and gravel to be used as filter material. These criteria allow engineers to design internal drains to collect and remove seepage. When an earth dam is built on a site where bedrock is at considerable depth, the foundation must be treated to control seepage. Typical treatment includes one or a combination of several things: upstream impervious blanket, cutoff wall, drainage blanket, gravel drains excavated into the foundation at the downstream toe, and relief wells. See also: Foundations

Earth-fill dams are by far the most popular type in the world. They make up 78%, or 27,260, of all those dams at least 50 ft (15 m) high. The earth dam's spillway is usually located in adjacent terrain rather than in the dam itself. The outlet works are either a conduit in the valley or a tunnel in one of the abutments (Figs. 5 and 6). Excavation for the spillway and outlet works usually produces large quantities of rock. As a result, the use of both earth and rock in an embankment is a common practice.

 

Rock-fill dam

 A rock-fill dam is a rolled fill embankment composed of fragmented rock with an impervious zone or membrane located on the upstream face or incorporated in the center of the embankment. The impervious membrane is typically a concrete slab or asphalt layer on the upstream face. The impervious zone is typically a thin internal core of earth fill. The earth core is separated from the rock shell (the structural mass of the dam) by zones of small rock fragments or gravel, to prevent the earth from washing into the rock fill, and a drain to control seepage. In Europe, it is common to use asphalt for the impervious zone.

Rock-fill dams require solid rock foundations and sites where large quantities of rock are available. Seepage through rock foundations is prevented or minimized by grout curtains. Rock-fill dams are usually more economical than concrete gravity dams at sites having wide valleys and adequate foundations. Spillways and outlet works are at locations similar to those of earth-fill dams. The primary advantage of rock-fill dams is that they require less material. Rock fill has a higher shear strength than earth fill and therefore permits steeper exterior slopes.

Rock for the embankment is normally excavated by drilling and blasting. Hole spacing and powder charges are set to produce a particular gradation of rock fragments for the dam. The rock is placed and spread in the same manner as earth but in thicker layers, 18–36 in. (45–90 cm). The material is normally compacted by weighted or vibratory steel drum rollers. Dry densities of rock fill are normally in the range 110–145 lb/ft3 (1762–2323 kg/m3).

Rock-fill dams became popular in the United States during the California gold rush in the 1860s and 1870s, when many dams were built in remote locations to store water for use in hydraulic sluicing. Of the 34,780 dams in the world that are at least 50 ft (15 m) high, 1590 are rock-fill embankments.

 

Concrete gravity dam

Concrete gravity dams are massive structures, characterized by vertical or near-vertical upstream faces and steep downstream faces (Figs. 7 and 8). They are designed with enough weight to resist being overturned or moved by the force of the water in the reservoirs. They are economical only at sites with shallow, high-strength rock foundations. Because of the large volumes of concrete involved, adequate sources of high-quality aggregates must be available near the sites. Concrete is composed of water, cement, pozzolan, aggregates, and entrained air. These ingredients are proportioned to produce concrete of the desired workability, durability, and strength as economically as possible. The density of concrete in dams typically ranges 140–160 lb/ft3 (2243–2563 kg/m3). An important feature of gravity dams is the simplicity with which safe spillways and outlet works can be provided. See also: Concrete

The design of a concrete gravity dam is controlled by stability considerations and internal stresses. The structure must be able to resist water, sediment, and ice pressures from the reservoir, as well as earthquake forces. Computers permit rapid solutions of complex equations for determining the magnitude and distribution of internal stresses. These dams are built in monolithic units by using the block method of construction (Fig. 9). This promotes dissipation of heat produced by hydration of the cement (chemical combination with the water) and thus helps minimize the volume changes associated with overheating that cause tensile stresses and cracking. The blocks are separated by construction joints. In building a block, the concrete is placed in horizontal layers and vibrated to eliminate voids. The monoliths are cast on top of firm rock foundations that have been cleaned with water and treated by placement of cement and water slurry or grout in the cracks and joints.

A concrete gravity dam usually contains an internal gallery large enough to allow for physical inspection and for collection of drainage from downstream drain holes drilled into the foundation. Grout holes to reduce seepage in the foundation are also drilled from the gallery in the vertical or upstream direction. The grout is injected under pressure to force it into all joints and openings encountered at depth.

 

Arch dam

The arch dam is a thin concrete dam that curves upstream from each abutment (Figs. 10 and 11). Such dams are classified as thin, medium, or thick arch, depending on the ratio of structural height to base thickness. The ratio is 0.2 or less for a thin arch, 0.25 for a medium arch, and 0.3 or greater for a thick arch. The arch transmits the water pressure and other loads directly to the abutments and foundation. It contains significantly less concrete than a concrete gravity dam of the same height and length. Relatively narrow canyons favor the use of arch dams.

 Fig. 7  Green Peter Dam, a concrete gravity type on the Middle Santian River, Willamette River Basin, Oregon. A gate-controlled overflow-type spillway is constructed through the crest of the dam; the powerhouse is at the downstream toe of the dam. (U.S. Army Corps of Engineers)

 

 

 

 

The shape of early arch dams was controlled by construction materials available at the time, and by less sophisticated understanding of structural behavior and the way that loads were transmitted through the curved structures to the foundations. As a result, arches were simple masonry structures with curved alignments and near-vertical upstream faces. This type was popular among water companies supplying domestic and irrigation water.

Beginning in the 1900s, improved structural analysis and actual performance records led to the use of variable-thickness arch dams. Varying the thickness can reduce the volume of concrete required. Measurement of the physical properties of concrete began in the late 1920s. This led to improved design procedures and measurement of actual performance with such instruments as strain gages. The concept of working stresses emerged in the late 1920s. The double-curvature shape (curved top to bottom as well as transversely) emerged in the mid-1950s. Vertical curving and shaping of the arch improves stress distribution. Making the compressive stresses levels throughout the dam as close as possible to the maximum allowable stress results in the minimum volume of concrete. A symmetrical profile is desirable. This may require excavation on one abutment if the canyon is not symmetrical. The economic upper limit of the length-to-height ratio of an arch dam lies between 4:1 and 6:1.

 

 

Fig. 8  Plan and sections of Green Peter Dam. 1 ft = 0.3 m, 1 in. = 2.5 cm. (U.S. Army Corps of Engineers)

 

 

 

 

 

 

Buttress dam

The buttress dam consists of two principal structural elements: a sloping upstream deck that retains the water, and buttress walls that support the deck and transmit the loads to the foundation. Traditionally, buttress dams have been classified into three categories: flat slab, multiple arch, and massive head. The flat-slab type consists of a reinforced concrete flat slab inclined at about 45° and connected to buttresses. The multiple-arch type is a series of concrete arches spanning the buttresses. The massive-head type has a large mass of concrete in the section upstream from the buttresses.

 Fig. 9  Block method of construction on a typical concrete gravity dam. (U.S. Army Corps of Engineers)

 

 

 

 

In 1918, the flat-slab design was patented in the United States. About 200 buttress dams of all three categories have been built in the United States. Many are less than l50 ft (45 m) high. Some landmark buttress dams are the Daniel Johnson in Canada (1986), 702 ft (214 m) high, the world's highest multiple-arch buttress dam; and the José M. Oriol in Spain (1969), 426 ft (130 m), the world's highest flat-slab buttress dam.

 

Site and type selection

The type of dam for a particular site is selected on the basis of technical and economic data and environmental considerations. In the early stages of design, several sites and types are considered. Drill holes and test pits at each site provide soil and rock samples for testing physical properties. In some cases, field pumping tests are performed to evaluate seepage potential. Preliminary designs and cost estimates are prepared and reviewed by hydrologic, hydraulic, geotechnical, and structural engineers, as well as geologists. Environmental quality of the water, ecological systems, and cultural data are also considered in the site-selection process.

Factors that affect the type are topography, geology, foundation conditions, hydrology, earthquakes, and availability of construction materials. The foundation of the dam should be as sound and free of faults as possible. Narrow valleys with shallow sound rock favor concrete dams. Wide valleys with varying rock depths and conditions favor embankment dams. Earth dams are the most common type. See also: Engineering geology; Fault and fault structures

 

Construction process

 

Hydraulic-fill operations over a 4-year period at Fort Peck Dam, on the Missouri River, the largest embankment by volume in the United States (Fig. 12), dredged 156,000,000 yd3 (119,340,000 m3) of material. Of this volume, 122,000,000 yd3 (93,333,000 m3) was retained in the embankment. Large conventional excavation operations can produce hourly volumes of 2000–3000 yd3 (1530–2293 m3). Processing, hauling, placement, and compaction operations for earth or rock result in daily placement rates that vary from as low as 2500 yd3 (1911 m3) on small dams to 6500 yd3 (4969 m3) on larger dams.

The materials and construction procedures for concrete dams evolved gradually from the early dams in Asia and Europe to the modern massive concrete dams. Prior to 1900, portland cement used in the United States was imported from England. Thus, the early concrete dams built in the United States were masonry. Generally, the concrete was mixed and transported in wheelbarrows. In the case of cyclopean masonry, large irregular blocks of rock with mortar, small derricks were erected, and the maximum rate of placement approached a few hundred cubic yards a day. There was no attempt to cure the concrete. Between 1900 and 1930, concrete was placed by towers and chutes. Portland cement had become available in the United States, and placement rates improved. However, little attention was given to the mix design, and wet mixes that could easily flow in chutes were widely used.

 Fig. 10  East Canyon Dam, a thin-arch concrete structure on the East Canyon River, Utah. There is an uncontrolled overflow-type spillway through the crest of the dam at the right. (U.S. Bureau of Reclamation)

 

 

 

 

 

 

Fig. 11  Plan and sections of East Canyon Dam, Utah. 1 ft = 0.3 m. (U.S. Army Corps of Engineers)

 

 

 

 

Hoover Dam, on the Colorado River, was a major turning point in both the design and construction of concrete dams. Its unprecedented size, 4,400,000 yd3 (3,363,800 m3), led to the introduction of mass concrete placement. Average placement rates of 10,000 yd3 (7645 m3) per day were achieved. Advances in design resulting from the Hoover project led to the construction of Grand Coulee, on the Columbia River, 10,585,000 yd3 (8,099,000 m3). Two large concrete plants were used that supported a maximum placement of 20,680 yd3 (15,810 m3) per day and an average rate over the construction period of 6000 yd3 (4587 m3) per day.

Since 1980, the technology of placing dry concrete with paving equipment and compacting it with rollers has gained wide acceptance (Fig. 13). This construction method is known as roller-compacted concrete. By 1997, 30 dams at least 50 ft (15 m) high had been constructed in the United States using the roller-compacted concrete method. As of January 1998, there were 16 RCC dams in the world having a height of 100 m or greater. This method produces the high placement rates usually associated with earth-fill construction and results in economical structures. It was initially used in 1975 in the tunnel repairs at Tarbela Dam, Pakistan, and placement reached a maximum rate of 24,000 yd3 (18,343 m3).

An outstanding example of the rapid construction achieved by using roller-compacted concrete is Copperfield Dam in Australia. This 131-ft-high (40-m) dam contains 183,000 yd3 (140,000 m3) and required only 10 months from initial design to completion. The project was originally designed as an earth- and rock-fill dam, but it was switched to roller-compacted concrete for greater economy.

 

River diversion during construction

The designers of a dam must consider the stream flow around or through the damsite during construction. Stream flow records provide the information for use in determining the largest flood to divert during the selected construction period. One common practice for diversion involves constructing the permanent outlet works, which may be a conduit or a tunnel in the abutment, along with portions of the dam adjacent to the abutments, in the first construction period. In some cases, a temporary channel is built at a preferred diversion location, and levees are built to control the flow of water through the damsite. After the outlet works and main dam are completed to an appropriate level, the stream is diverted into the outlet works by a cofferdam high enough to prevent overtopping during construction. A downstream cofferdam is also required to keep the damsite dry. In the final construction period, the entire dam is brought to full height. See also: Cofferdam

 Fig. 12  Fort Peck Dam, Missouri River, Montana, the largest embankment dam by volume in the United States, 125,628,000 yd3 (95,625,000 m3). A hydraulic-fill dam, it was built between 1935 and 1939 for flood control, hydropower, irrigation, and navigation. (U.S. Army Corps of Engineers)

 

 

 

 

 

 

Fig. 13  Galesville Dam, Oregon, showing roller-compacted concrete construction; completed in 1985, it has a height of 157 ft (48 m) and a volume of 161,000 yd3 (123,100 m3).

 

 

Operation and maintenance

 

Personnel responsible for operation and maintenance of the dam become involved during the final design and construction to become familiar with design details that relate to operation. The operating instructions and maintenance schedule are published in a formal document for each dam. A schedule is established for collection and reporting of data for climatic conditions, rainfall, snow cover, stream flows, and water quality of the reservoir, as well as the downstream reaches. All these data are evaluated for use in reservoir regulation. Another schedule is established for the collection of instrumentation data used to determine the structural behavior and physical condition of the dam. These data are evaluated frequently.

Routine maintenance and inspection of the dam and appurtenant structures are ongoing processes. The scheduled maintenance is important to preserve the integrity of the mechanical equipment.

 

Periodic inspection and evaluation

 Upon completion of construction, the project is inspected in detail by a team made up of the designers, construction managers, operations personnel, and other experts. The purpose is to ensure that the dam has been built as designed and can safely impound water and that all systems are ready for the initial reservoir filling and operation. In addition, the same team conducts an in-depth inspection once a year for about 5 years after completion and at 5-year intervals thereafter. Design criteria and performance of the dam as measured by instruments are reviewed during the life of the dam, and structural reanalyses are made when necessary. Photographs are taken to record rates of deterioration.

The intake structure, trash racks, emergency gates, outlet conduit or tunnel, and stilling basin are normally under water and therefore require special procedures such as dewatering prior to the inspection. At normal velocity, the flowing water can severely erode soil and rock in the approach and discharge channels. High-velocity flow over small irregularities can cause a phenomenon known as cavitation, which can lead to rapid erosion of metal and concrete and can threaten the safety of the outlet works. See also: Cavitation

 Instrumentation

 As the technology of dam design and construction progressed, the need to measure performance and structural behavior became important in order to verify the design. Advances in instruments starting in the 1950s gave the designer a valuable tool. Instrumentation gave the engineer knowledge of how the temperatures from hydration in concrete varied and the effect on strength. Pressure cells were developed that gave information about the interaction between soil backfill and a concrete wall or structure as well as the actual load distribution. Piezometers (devices to measure water level), settlement plates, and slope indicators are used in measuring the performance of embankment dams. Plumb lines, strain gages, and uplift cells are used for the same purpose in concrete dams. In addition, instruments are used to measure vertical and horizontal movement, alignment and plumb, stresses, strains, water pressure, seismic effects, and the quantity and clarity of seepage.

Instrumentation for a dam is installed at first in the design phase to establish baseline data, then during construction and throughout the life of the dam as conditions warrant. The frequency with which instrumentation data are obtained is an extremely important issue and depends on operating conditions. Timely collection and evaluation of data are critical for periods when the loading changes, such as during floods and after earthquakes. Advances in applications of remote sensing to instrumentation have made real-time data collection possible. This is a significant improvement for making dam safety evaluations.

Safety

Throughout history there have been instances of dam failure and discharge of stored water, sometimes causing considerable loss of life and great damage to property. Failures have generally involved dams that were designed and constructed to engineering standards acceptable at the time. Most failures have occurred with new dams, within the first five years of operation.

As dam technology advanced with increasing knowledge of design principles and better understanding of foundation and material properties, dams became safer. There is no question that they can be built and operated safely. The major issue is to monitor deterioration as the structures and equipment get older. In earlier times, the sizes of spillways and outlet pipes had to be determined by judgment. As a result, overtopping was the main cause of dam failure. Little was known about soil mechanics and slope stability, and so slides and slope failures were common. Beginning in the 1930s, statistical methods were used to predict floods. Advances in soil mechanics in the later 1930s and early 1940s produced new methods of stability analysis that revolutionized the slope design for excavations and earth embankment dams. Historical data indicate that the causes of failure (in the order of their significance) are piping, overtopping, slope instability, conduit leakage (outlet works), and foundation failures. See also: Pipeline; Rock mechanics; Soil mechanics

It is estimated that about 150,000 dams around the world present a potential hazard to life or property; there have been 200 failures since 1900. Many of these have involved small dams. Table 4 lists some major failures that resulted in considerable loss of life.

Dam failures cause loss of life and property damage in downstream reaches that are beyond the control of the dam owner or local government. For this reason, and because dam safety practices should apply to all dams, national governments have become involved in order to provide supervision and standardize regulations. The United States government published “Federal Guidelines for Dam Safety” in June 1979. This initiated a coordinated effort in management practices among federal agencies and set an example for private organizations that own dams. The International Commission on Large Dams (ICOLD) was formed in 1928 by 6 countries with the purpose of developing and exchanging dam design experience, and it has grown to 76 member countries. In 1982 ICOLD established a committee on dam safety to define common safety principles, integrate efforts, and develop guidelines, and in 1987 ICOLD published “Dam Safety Guidelines.”

Bibliography

•  Federal Emergency Management Agency, Federal Guidelines for Dam Safety, FEMA 93, June 1979
• Ali Fazeli = egeology.blogfa.com
• International Commission on Large Dams, Dam Safety Guidelines, Bull. 59, ICOLD, 1987
• Ali Fazeli = egeology.blogfa.com
• International Commission on Large Dams, Dam Failures, Statistical Analysis, 1995
• Ali Fazeli = egeology.blogfa.com
• International Commission on Large Dams, World Register of Dams, 1997
• Ali Fazeli = egeology.blogfa.com
• International Commission on Large Dams, Dam Failures, Statistical Analysis, 1995
• Ali Fazeli = egeology.blogfa.com
• R. B. Jansen, Advanced Dam Engineering for Design, Construction, and Rehabilitation, 1988
• Ali Fazeli = egeology.blogfa.com
• R. B. Jansen, Dams and Public Safety, U.S. Department of the Interior, 1980
• Ali Fazeli = egeology.blogfa.com
• E. B. Kollgaard and W. L. Chadwick (eds.), Development of Dam Engineering in the in the United States, 1988
• Ali Fazeli = egeology.blogfa.com
• J. Sherard et al., Earth and Earth-Rock Dams, 1967
• Ali Fazeli = egeology.blogfa.com
• U.S. Bureau of Reclamation, Design of Small Dams, 3d ed., 1987
• Ali Fazeli = egeology.blogfa.com

 

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