The World’s 18 Strangest Dams

The World’s 18 Strangest Dams

 

Whether its builder is a beaver or a person, a dam is always used for the same purpose: to manage, direct and prevent water flow. There an estimated 845,000 dams in the world; here are our picks for the 18 strangest.

Three Gorges Dam

Where: Sandouping, China–Yangtze River

Why It’s Unique: China’s Three Gorges Dam is not only the world’s largest hydroelectric dam, it’s also the world’s single largest source of electricity. The construction of the dam has been convoluted: Preliminary plans began as far back at 1932 but construction but didn’t start until late 1994; the dam isn’t scheduled to be completely finished until 2011. The structure’s estimated life is as short as 70 years; that was deemed long enough to justify the displacement of 1.24 million people.

Itaipu Dam

Where: On the border of Brazil and Paraguay–Parana River

Why It’s Unique: The Itaipu Dam, a partnership between Brazil and Paraguay, generated over 90,000 gigawatt hours of power in 2000—then a world record for hydroelectric generation. With a height of more than 196 meters, the dam stands as tall as a 65-story building. Its construction used enough steel to build 380 Eiffel Towers, along with 12.3 million cubic meters of concrete.

Guri Dam

Where: Bolivar State, Venezuela–Caroni River

Why It’s Unique: The Guri Dam in Venezuela not only boasts sky-high walls and powerful generators, it also has artistic flair. Artist Carlos Cruz Diez decorated one of the plant’s machine rooms in mind-bending pattern of colorful vertical bars, while Alejandro Otero built an enormous rotating kinetic sculpture nearby. The dam produces the energy equivalent of approximately 300,000 barrels of oil per day.

Grand Coulee Dam

Where:Grand Coulee, Washington–Columbia River

Why It’s Unique: Washington state’s Grand Coulee Dam is the largest in the United States. Nearly a mile long and 503 meters wide, its base area is large enough to hold all the pyramids of Giza. At 115 meters high, the dam is more than twice the height of Niagara Falls. The dam also has a memorable role in folk music history—a governmental energy organization commissioned Woody Guthrie to write songs about the dam in the early 1940s, including “Roll On, Columbia, Roll On” and “Grand Coulee Dam.”

Sayano-Shushenskaya Dam

Where: Khakassia, Russia–Yenisei River

Why It’s Unique: Russia’s Sayano-Shushenskaya Dam may not hold any records for its electricity generation, but other dams are no match for its sheer strength—the structure’s stated ability to withstand 8.0-magnitude earthquakes has earned it a spot in the Guinness Book of World Records. Still, not even the world’s strongest dam is immune to problems—a 2009 accident in which a turbine exploded resulted in the deaths of 75 people and 40 tons of oil spilled into the river.

Krasnoyarsk Dam

Where: Divnogorsk, Russia–Yenisey River

Why It’s Unique: Although the Krasnoyarsk dam has operated without the notoriety of its Russian neighbor, this concrete gravity dam has troubles of its own. The plant and its reservoir have apparently wrought changes on the local climate, causing the area to experience warmer and more humid weather conditions than the norm, and reducing ice cover in the area, which is in Siberia. Russia shows off the engineering feat on its 10-ruble bill.

Robert-Bourassa Dam

Where: Quebec, Canada–La Grande River

Why It’s Unique: Situated over Canada’s La Grande River, the Robert-Bourassa dam reaches 140 meters below the surface, making it the world’s largest underground plant. The dam’s centerpiece is a unique “giant’s staircase”—each step is the size of two football fields—that sweeps water downward.

Sand Dams

Where: Kenya

Why It’s Unique: Since 1995, Kenya has constructed more than 500 sand dams, which are usually about 50 meters long and 2 to 4 meters high. Unlike larger dams, which usually are used for hydroelectric power, these smaller structures are designed to store water during the wet season so dry communities have a water reservoir when the rain stops. These dams, which store water buried in silt, do a better job than surface water dams of keeping water from evaporating and maintaining water quality.

Redridge Steel Dam

Where: Redridge, Michigan–Salmon Trout River

Why It’s Unique: Located in Houghton County, Mich., this flat slab buttress dam is one of only three steel dams in the United States. Built in 1894, the dam’s spillway broke in 1941 and was partially repaired in 2001.

Timber Dams

Where: Japan

Why It’s Unique: To limit carbon dioxide emissions from steel and concrete dam construction, northern Japan’s Akita Prefecture started a project to build small-scale dams out of the country’s abundant supply of cedar. The dams serve mainly to minimize the effects of landslides and mud flows in the mountains.

Inguri Dam

Where: Jvari, Georgia–Inguri River

Why It’s Unique: At 892 feet in height, the Inguri Dam is the world’s tallest concrete arch dam. Completed in 1978, it was repaired in 1999 at a cost of 116 million euros.

New Cornelia Mine Tailings Dam

Where: New Cornelia Mine Tailings Dam

Why It’s Unique: In terms of sheer volume, the 7.4 billion cubic foot New Cornelia MineTailings Dam is the country’s largest dam structure. But this dam isn’t used for water—it’s used for mining. Mine tailings (loose collections of crushed rock left over from the mining process) were dumped here before the mine was shut down in 1983.

Syncrude Tailings Dam

Alberta, Canada


The Syncrude Tailings Dam holds the highest volume of material of any dam in the world: 540,000,000 cubic meters. This dam holds tailings from oil sands extraction; 500,000 tons of tailings are produced each day.

Verzasca Dam
Where: Ticino, Switzerland

Why It’s Unique: The Verzasca Dam, completed in 1965, is renowned for its beauty and its slender concrete arch. The design used less concrete than comparable dams, resulting in lower construction costs. When its reservoir was filled, small earthquakes were triggered.

Santee Cooper Dam System

Where: Pinopolis, South Carolina—Santee River

Why It’s Unique: Built to create jobs in the region during the Great Depression, the Santee Cooper Dam system boasts a reservoir area of 186,000 acres. The dam system, 42 miles in total, survived the third worst earthquake in U.S. history and was subsequently redesigned and stabilized for future quakes. The Pinopolis Dam, which is part of the Santee Cooper system, has the highest single-lift lock in the world for raising and lowering boats between different levels of water.

Roosevelt Dam

Where: Phoenix, Arizona—Salt River

Why It’s Unique: Italian stonemasons crafted this dam, hand-cutting all the stones for the project. In recent years, the dam’s height was raised 23 meters to increase water storage space by 20 percent, and it was completely resurfaced in concrete, changing its appearance.

Chalk Hills Dam

Where: On the Border of Wisconsin and Michigan—Menominee River

Why It’s Unique: The power house connected to this dam resembles a cathedral, complete with stained-glass windows celebrating the engineers and bankers involved in the original construction, and small multi-colored terrazzo tile. The structure was completed in 1927.

World’s Largest Beaver Dam

Where: Wood Buffalo National Park—Alberta, Canada

Why It’s Unique: Google Earth found the largest beaver dam in Alberta, Canada at 850 meters long–the closest size relative exists in Montana at 652 meters. Viewers think two beaver families constructed this massive piece of architecture, which contains two separate beaver lodges inside. The entire dam is surrounded by wetlands, common of more sizable beaver creations.

Choice of site and type of dam

Choice of site and type of dam

 

Dam types can be classified in different categories according to the material used in construction and how they withstand the thrust of water:
  • homogeneous drained earthfill dams, either zoned or with a man-made impervious element;
  • gravity dams, whether concrete or RCC;
  • arch dams;
  • and buttress or multiple arch dams (not dealt with here).
Fill dams are flexible structures while the other types are rigid.The main parameters to be taken into account in choosing a dam site and type are the following:
  • topography and inflow in the catchment area;
  • morphology of the river valley;
  • geological and geotechnical conditions;
  • climate and flood regime.
In many cases, after consideration of all these aspects, several types of dams will remain potential candidates. Economic considerations are then applied to rank the available alternatives.

1. TOPOGRAPHY AND INFLOW IN THE CATCHMENT AREA

If we ignore the case of lakes for recreational purposes and small dams for hydroelectric power generation, reservoir storage is the main factor influencing the entire dam design. The objective is in fact to have a volume of water  available for increasing dry weather river flow, irrigation or drinking-water supply, or free storage capacity to attenuate flooding.
The first task therefore consists in calculating the volume of water that can be stored in a basin, possibly at several different sites. A first approximation can be achieved using a 1/25 000 scale map with contour lines every 5 or 10 metres, except for reservoirs with storage of several tens of thousand cubic metres. The second task will then be to check whether conditions in the catchment area are such that the reservoir will be filled and to calculate the risk of shortfall.

2. MORPHOLOGY OF THE RIVER VALLEY

 

A dam is by nature linked to an environment. The morphology of the river valley therefore plays a vital role in the choice of a dam site and the most suitable type of dam.
Of course, the ideal and most economical location will be a narrow site where the valley widens upstream of the future dam, provided that the dam abutments are sound (i.e. a narrowing with no zones prone to rockfall or landslide).
Such a site is rarely found, either because the natural structure of a valley does not offer any point of narrowing or because the choice of the site is not solely dependent on engineering considerations.
As a first approach, a wide valley will be more suitable for construction of a fill dam.
A narrow site will be suitable for a gravity dam as well, and a very narrow site will be suitable for an arch. In every case, of course, provided that the foundation is acceptable.

3. GEOLOGY AND FOUNDATION CONDITIONS

The nature, strength, thickness, dip, jointing and permeability of the geological foundations at the site are a set of often decisive factors in selection of the dam type.

ROCK FOUNDATIONS

Except for severely jointed rock or rock with very mediocre characteristics, rock foundations are suitable for construction of any type of dam, provided that suitable measures are taken to strip off severely weathered materials and, if necessary, treat the foundation by grouting. Fill dams will always be suitable. For the other types, requirements are more severe for RCC, still more for conventional concrete, and finally most stringent for arch dams. The most important aspect is cracking (faults, joints, schistosity).

GRAVEL FOUNDATIONS

Provided that they are sufficiently compacted, gravel foundations are generally suitable for earth or rockfill dams, at least in terms of mechanical strength. Leakage must be controlled by suitable impervious barriers and drainage systems. In practice however, this type of foundation essentially is found on rivers with high flows. The dam must
therefore be able to discharge high floods, which precludes earthfill dams. Very small concrete dams may also be suitable provided precautions are taken with leaks and seepage (risk of piping) and with differential settlement.

SANDY-SILT FOUNDATIONS

Silt or fine sand foundations can be suitable for construction of earthfill dams, and even, in exceptional cases, for very small concrete gravity dams provided strict precautions are taken.

CLAY FOUNDATIONS

Clay foundations almost automatically impose the choice of a fill dam with slopes that are compatible with the mechanical characteristics of the geological formations.

4. AVAILABLE MATERIALS

 

Availability, on the site or near it, of suitable materials to build the dam has a considerable influence and one that is often decisive in choosing the type of dam:
  • soil that can be used for earthfill,
  • rock for rockfill or slope protection (rip-rap),
  • concrete aggregate (alluvial or crushed materials),
  • cementitious materials (cement, flyash, etc.).
If it is possible to extract the materials from the reservoir itself, reservoir storage can be increased. This also usually keeps the cost of transport and restoring borrow areas to a minimum.
As a general rule, if silty or clay soil of satisfactory quality (fines content, plasticity, condition) and quantity (1.5 times or twice the volume of fill required) is available, a dam construction alternative using homogeneous earthfill or quarry-sorted materials – setting aside the coarsest materials for the downstream shoulder – will be the most economical provided that the flood flows to be discharged are moderate.
If only a limited quantity of impermeable materials, and coarse or rockfill materials as well, is available, the possibility of a zoned earthfill dam or a rockfill dam with a watertight core can be considered. The disadvantage of this alternative is placement in zones, which is all the more complicated when the site is narrow, hindering movement of the machinery.
If only coarse materials are available, they can be used to build a homogeneous embankment with a watertight diaphragm wall built in the centre of the dam, by grouting after the fill has been placed or by an upstream watertight structure (concrete or bituminous concrete facing).
If only rockfill is available, a compacted rockfill dam with external watertight structure (geomembrane, hydraulic concrete or bituminous concrete facing) on the upstream face, will be suitable. A concrete alternative, especially RCC, can also prove to be competitive provided the foundation is good enough (rock or compact ground) with no need for excessive excavation.

5. FLOODS AND FLOOD DISCHARGE STRUCTURES

The cost of flood discharge structures depends on the hydrological characteristics of
the catchment area.
When the catchment area is large and floods are likely to be high, it may be advantageous to combine the dam and spillway functions and build an overspill dam.
On the other hand, if the spillway can be kept small, a fill dam will be preferred if all other conditions are equal.
When construction of the spillway would require significant excavation, the possibility of using the excavated materials will also be a factor in favour of building a fill dam.
When a tunnel is required for temporary diversion of the river during the work, it can usefully be incorporated into the flood discharge structures, if necessary increasing its cross-section slightly.
The choice of an RCC dam can be attractive if it is a means of shortening construction lead time and removing the risk of damage from flooding of the site before construction is complete, a risk that, with any other alternative, would mean building costly diversion or protection structures.

6. ECONOMIC CRITERIA

In many cases, the considerations set out above will be sufficient to select several types of dam as potential alternatives. For example, if the foundation is rock, loose materials are available near the site and flood flows are high, the choice will be between an RCC dam and an earthfill dam with a costly spillway.
The studies must then be pursued for these two types of dam, taking care to refine the cost estimates as the studies progress. As soon as one of the dam types seems significantly more economical, it is preferable to waste no further time on the other option.

CONCLUSIONS ON SELECTING A TYPE OF DAM

The choice of a type of dam is imposed by natural conditions in many cases, with no need for in-depth investigations. For example, if the rock substratum is at a depth of more than 5 metres, the only reasonable alternative will be a fill dam, at least for any project less than 25 metres high. In some regions, the geological context is such that
only one type of dam is usually built.
In other cases, the choice of dam type will be a compromise between different aspects – type of foundation, availability of materials in the vicinity, hydrology – to arrive at the best option economically speaking.
However, it is always an advantage to make a decision as quickly as possible, as a rule after the feasibility studies.
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