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46-560: Gavins Point Dam is a 1.9-mile-long (3 km) embankment rolled-earth and chalk-fill dam which spans the Missouri River and impounds Lewis and Clark Lake . The dam joins Cedar County, Nebraska with Yankton County, South Dakota a distance of 811.1 river miles (1,305 km) upstream of St. Louis, Missouri , where the river joins the Mississippi River . The dam and hydroelectric power plant were constructed as

92-482: A bluff along the northern bank of the Missouri River named for an early settler, now within the western end of Lewis & Clark Recreation Area , which was to be the original location of construction of the dam. The location was moved and construction began further downstream along Calumet Bluff because this location offered a shorter span distance and less fill material needed for dam construction, although

138-418: A dam and the filling of the reservoir behind it places a new weight on the floor and sides of a valley. The stress of the water increases linearly with its depth. Water also pushes against the upstream face of the dam, a nonrigid structure that under stress behaves semiplastically, and causes greater need for adjustment (flexibility) near the base of the dam than at shallower water levels. Thus the stress level of

184-422: A drain layer to collect seep water. A zoned-earth dam has distinct parts or zones of dissimilar material, typically a shell of locally plentiful material with a watertight clay 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 An outdated method of zoned earth dam construction used a hydraulic fill to produce

230-513: A popular regional tourist destination for water-based recreational opportunities including boating and fishing, along with camping, hiking, and hunting opportunities managed by the State of South Dakota, State of Nebraska, and the U.S. Army Corps of Engineers. The lake is significantly impacted by sedimentation and siltation issues, diminishing the overall water surface area, water storage capacity, and recreational opportunities. Sediment carried by

276-462: A regression developed from water samples that are filtered, dried, and weighed), multiplying the concentration with the discharge as above, and integrating over the entire plume. To distinguish the spill contribution, the background turbidity is subtracted from the spill plume turbidity. Since the spill plume in open water varies in space and time, an integration over the entire plume is required, and repeated many times to get acceptably low uncertainty in

322-448: A rock-fill dam, rock-fill is blasted using explosives to break the rock. Additionally, the rock pieces may need to be crushed into smaller grades to get the right range of size for use in an embankment dam. Earth-fill dams, also called earthen dams, rolled-earth dams or earth dams, are constructed as a simple embankment of well-compacted earth. A homogeneous rolled-earth dam is entirely constructed of one type of material but may contain

368-404: A small sustained overtopping flow can remove thousands of tons of overburden soil from the mass of the dam within hours. The removal of this mass unbalances the forces that stabilize the dam against its reservoir as the mass of water still impounded behind the dam presses against the lightened mass of the embankment, made lighter by surface erosion. As the mass of the dam erodes, the force exerted by

414-686: A thick suspension of earth, rocks and water. Therefore, safety requirements for the spillway are high, and require it to be capable of containing a maximum flood stage. It is common for its specifications to be written such that it can contain at least a one-hundred-year flood. A number of embankment dam overtopping protection systems were developed in the early 21st century. These techniques include concrete overtopping protection systems, timber cribs , sheet-piles , riprap and gabions , Reinforced Earth , minimum energy loss weirs , embankment overflow stepped spillways , and precast concrete block protection systems. All dams are prone to seepage underneath

460-590: A watertight core. Rolled-earth dams may also employ a watertight facing or core in the manner of a rock-fill dam. The frozen-core dam is a temporary earth dam occasionally used in high latitudes by circulating a coolant through pipes inside the dam to maintain a watertight region of permafrost within it. Tarbela Dam is a large dam on the Indus River in Pakistan , about 50 km (31 mi) northwest of Islamabad . Its height of 485 ft (148 m) above

506-454: Is sometimes referred to by the ambiguous term " sediment pollution ", which can also refer to a chemical contamination of sediments accumulated on the bottom, or to pollutants bound to sediment particles. Although "siltation" is not perfectly stringent, since it also includes particle sizes other than silt, it is preferred for its lack of ambiguity. The origin of the increased sediment transport into an area may be erosion on land or activities in

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552-516: Is the most downstream dam on the Missouri River, being 811.1 river miles upstream of St. Louis where the river meets the Mississippi River . The next dam upstream is Fort Randall Dam . During the 2011 Missouri River Flood , the dam released a record water flow of 160,200 cfs , topping the previous record of 70,000 cfs in 1997. During the 2011 flood, the debris damaged the dam and a significant portion of rocks were dislodged from its upstream side. The U.S. Army Corps of Engineers soon began repairs to

598-490: The earth-filled dam (also called an earthen dam or terrain dam ) made of compacted earth, and the rock-filled dam . A cross-section of an embankment dam shows a shape like a bank, or hill. Most have a central section or core composed of an impermeable material to stop water from seeping through the dam. The core can be of clay, concrete, or asphalt concrete . This type of dam is a good choice for sites with wide valleys. They can be built on hard rock or softer soils. For

644-475: The offshore dumping of material dredged from harbours and navigation channels. The deposition may also be to build up the coastline, for artificial islands , or for beach replenishment . Climate change also affects siltation rates. Another important cause of siltation is the septage and other sewage sludges that are discharged from households or business establishments with no septic tanks or wastewater treatment facilities to bodies of water. While

690-455: The sediment in transport is in suspension , it acts as a pollutant for those who require clean water, such as for cooling or in industrial processes, and it includes aquatic life that are sensitive to suspended material in the water. While nekton have been found to avoid spill plumes in the water (e.g. the environmental monitoring project during the building of the Øresund Bridge ), filtering benthic organisms have no way of escape. Among

736-766: The Gavins Point Project from 1952 to 1957 by the United States Army Corps of Engineers as part of the Pick-Sloan Plan . The dam is located approximately 4 miles (6.4 km) west or upstream of Yankton, South Dakota . Gavins Point Dam was constructed as a part of the Pick–Sloan Missouri Basin Program , authorized by the Flood Control Act of 1944 by Congress . The dam is named after Gavins Point ,

782-484: The Missouri River and Niobrara River is slowed and trapped within the reservoir due to the dam impounding and thus stopping the natural river flow. Studies show approximately 5.1 million tons of sediment are deposited in the lake each year, which contributes to the lake's increasing size of delta area on the western portions of the lake. Approximately 60% of the sediment comes from the Nebraska Sandhills via

828-554: The Niobrara River. As of 2016, approximately 30% of the lake's overall surface area has diminished due to sedimentation deposits, and some figures project by 2045 approximately 50% of the lake will be diminished due to sedimentation deposits. Presently, there is no plan or solution to remove or slow the progression of the siltation within the lake. [REDACTED] Media related to Gavins Point Dam at Wikimedia Commons Embankment dam Embankment dams come in two types:

874-451: The U.S. Bureau of Reclamation Siltation Siltation is water pollution caused by particulate terrestrial clastic material, with a particle size dominated by silt or clay . It refers both to the increased concentration of suspended sediments and to the increased accumulation (temporary or permanent) of fine sediments on bottoms where they are undesirable. Siltation is most often caused by soil erosion or sediment spill. It

920-637: The asphalt make such dams especially suited to earthquake regions. For the Moglicë Hydro Power Plant in Albania the Norwegian power company Statkraft built an asphalt-core rock-fill dam. Upon completion in 2018 the 320 m long, 150 m high and 460 m wide dam is anticipated to be the world's highest of its kind. A concrete-face rock-fill dam (CFRD) is a rock-fill dam with concrete slabs on its upstream face. This design provides

966-549: 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 concept originated during the California Gold Rush in the 1860s when miners constructed rock-fill timber-face dams for sluice operations . The timber was later replaced by concrete as

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1012-406: The core is separated using a filter. Filters are specifically graded soil designed to prevent the migration of fine grain soil particles. When suitable building material is at hand, transport is minimized, leading to cost savings during construction. Rock-fill dams are resistant to damage from earthquakes . However, inadequate quality control during construction can lead to poor compaction and sand in

1058-600: The dam and its spillway gates. Pressure sensors were also installed in concrete portion of the dam. The dam has a hydroelectric power plant with three generators, each having a nameplate capacity of 44,099  kW , for a total of 132.297  MW . The hydroelectric power plant provides enough electricity to supply 68,000 homes. The power generated is sold through the Western Area Power Administration . See main article: Lewis and Clark Lake Gavins Point Dam creates Lewis and Clark Lake,

1104-406: The dam must be calculated in advance of building to ensure that its break level threshold is not exceeded. Overtopping or overflow of an embankment dam beyond its spillway capacity will cause its eventual failure . The erosion of the dam's material by overtopping runoff will remove masses of material whose weight holds the dam in place and against the hydraulic forces acting to move the dam. Even

1150-490: The dam, but embankment dams are prone to seepage through the dam as well; for example, the Usoi landslide dam leaks 35-80 cubic meters per second. Sufficiently fast seepage can dislodge a dam's component particles, which results in faster seepage, which turns into a runaway feedback loop that can destroy the dam in a piping-type failure. Seepage monitoring is therefore an essential safety consideration. gn and Construction in

1196-456: 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, design has become popular. The tallest CFRD in the world is the 233 m-tall (764 ft) Shuibuya Dam in China , completed in 2008. The building of

1242-578: 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 in California or the Fierza Dam in Albania . A core that is growing in popularity is asphalt concrete . The majority of such dams are built with rock and/or gravel as

1288-429: The first line of defense is to maintain land cover and prevent soil erosion in the first place. The second line of defense is to trap the material before it reaches the stream network (known as sediment control ). In urban areas, the defenses are to keep land uncovered for as short a time as possible during construction and to use silt screens to prevent the sediment from getting released in water bodies. During dredging,

1334-410: The food gathering of filtering organisms, and the sediment accumulation on the bottom may bury organisms to the point that they starve or even die. It is only if the concentration is extreme that it decreases the light level sufficiently for impacting primary productivity. An accumulation of as little as 1 mm (0.039 in) may kill coral polyps. While the effect of the siltation on the biota (once

1380-455: The harm is already done) can be studied by repeated inspection of selected test plots, the magnitude of the siltation process in the impact area may be measured directly by monitoring in real time. Parameters to measure are sediment accumulation, turbidity at the level of the filtering biota, and optionally incident light. Siltation of the magnitude that it affects shipping can also be monitored by repeated bathymetric surveys. In rural areas,

1426-476: The most difficult conflicts of interest to resolve, as regards siltation mitigation, is perhaps beach nourishment . When sediments are placed on or near beaches in order to replenish an eroding beach, any fines in the material will continue to be washed out for as long as the sand is being reworked. Since all replenished beaches are eroding or they would not need replenishment, they will contribute to nearshore siltation almost for as long as it takes to erode away what

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1472-436: The most sensitive organisms are coral polyps. Generally speaking, hard bottom communities and mussel banks (including oysters) are more sensitive to siltation than sand and mud bottoms. Unlike in the sea, in a stream, the plume will cover the entire channel, except possibly for backwaters, and so fish will also be directly affected in most cases. Siltation can also affect navigation channels or irrigation channels. It refers to

1518-403: The original land-covering vegetation and temporarily creating something akin to an urban desert from which fines are easily washed out during rainstorms. In water, the main pollution source is sediment spill from dredging , the transportation of dredged material on barges, and the deposition of dredged material in or near water. Such deposition may be made to get rid of unwanted material, such as

1564-424: The primary fill. 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 material that can adjust to the movements and deformations imposed on the embankment as a whole, and to settlement of the foundation. The flexible properties of

1610-656: The project kept the original name. The dam operations work in conjunction with the other Pick-Sloan Program Dams to assist with conservation, control, and use of water resources in the Missouri River Basin . The intended beneficial uses of these water resources include flood control , aids to navigation , irrigation , supplemental water supply , power generation , municipal and industrial water supplies , stream-pollution abatement , sediment control , preservation and enhancement of fish and wildlife , and creation of recreation opportunities . Gavins Point

1656-474: The proportion of fines in sediments typically increases in the offshore direction, the deposited sand will inevitably contain a significant percentage of siltation-contributing fines. It is desirable to minimize the siltation of irrigation channels by hydrologic design, the objective being not to create zones with falling sediment transport capacity, as that is conducive to sedimentation. Once sedimentation has occurred, in irrigation or navigation channels, dredging

1702-501: The reservoir begins to move the entire structure. The embankment, having almost no elastic strength, would begin to break into separate pieces, allowing the impounded reservoir water to flow between them, eroding and removing even more material as it passes through. In the final stages of failure, the remaining pieces of the embankment would offer almost no resistance to the flow of the water and continue to fracture into smaller and smaller sections of earth or rock until they disintegrate into

1748-474: The results. The measurements are made close to the source, in the order of a few hundred meters. Anything beyond a work area buffer zone for sediment spill is considered the potential impact area. In the open sea, the impact of concern is almost exclusively with the sessile bottom communities since empirical data show that fish effectively avoid the impacted area. The siltation affects the bottom community in two main ways. The suspended sediment may interfere with

1794-399: The river bed and 95 sq mi (250 km ) reservoir make it the largest earth-filled dam in the world. The principal element of the project is an embankment 9,000 feet (2,700 m) long with a maximum height of 465 feet (142 m). The dam used approximately 200 million cubic yards (152.8 million cu. meters) of fill, which makes it one of the largest man-made structures in

1840-409: The spill can be minimized but not eliminated completely by the way the dredger is designed and operated. If the material is deposited on land, efficient sedimentation basins can be constructed. If it is dumped into relatively deep water, there will be a significant spill during dumping but not thereafter, and the spill that arises has minimal impact if there are only fine-sediment bottoms nearby. One of

1886-445: The stream, by measuring the sediment concentration and multiplying that with the discharge ; for example, 50 mg/L (1.8 × 10  lb/cu in) times 30 m /s (1,100 cu ft/s) gives 1.5 kg/s (200 lb/min). Also, sediment spill is better measured in transport than at the source. The sediment transport in open water is estimated by measuring the turbidity , correlating turbidity to sediment concentration (using

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1932-409: The undesired accumulation of sediments in channels intended for vessels or for distributing water. One may distinguish between measurements at the source, during transport, and within the affected area. Source measurements of erosion may be very difficult since the lost material may be a fraction of a millimeter per year. Therefore, the approach taken is typically to measure the sediment in transport in

1978-404: The upstream face and made of masonry , concrete , plastic membrane, steel sheet piles, timber or other material. The impervious zone may also be inside the embankment, in which case it is referred to as a "core". In the instances where clay is used 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,

2024-400: The water. In rural areas, the erosion source is typically soil degradation by intensive or inadequate agricultural practices, leading to soil erosion , especially in fine-grained soils such as loess . The result will be an increased amount of silt and clay in the water bodies that drain the area. In urban areas, the erosion source is typically construction activities, which involve clearing

2070-414: The world. Because earthen dams can be constructed from local materials, they can be cost-effective in regions where the cost of producing or bringing in concrete would be prohibitive. Rock -fill dams are embankments of compacted free-draining granular earth with an impervious zone. The earth used often contains a high percentage of large particles, hence the term "rock-fill". The impervious zone may be on

2116-422: Was added, albeit with somewhat decreasing intensity over time. Since the leakage is detrimental to coral reefs, the practice leads to a direct conflict between the public interest of saving beaches, and preserving any nearshore coral reefs. To minimize the conflict, beach replenishment should not be done with sand containing any silt or clay fractions. In practice the sand is often taken from offshore areas, and since

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