Disasters & Failures - Dams

Dam

barriers across stream, river, waterway to confine and control flow of water; vary in size from small embankments (farm use) to high massive concrete structures (water supply, hydropower, irrigation)

Dam Uses

reservoirs to suppress floods, water for irrigation, consumption, industrial use, and aquaculture and navigability, hydroelectric

History of Dams

oldest built for water control, some diversion dams for flood control (Egypt), regulate water levels, prevent sea intrusion, water retention during rainy season & distribution during dry season, source of water for aqueducts that ran into cities

Jawa Dam

oldest known dam, in northern Jordan, water supply system & deflection dams, built across Wadi Rajil, masonry gravity dam constructed between 3500-3400 BC

Sadd el Kafara Dam

built across Wadi al-Garawi southeast of Cairo Egypt, built between 3000-2800 BC (possibly Pharoah Khufu), rubble and masonry used for flood control, never completed (destroyed by flood), not a lot of silt

Kallanai Dam

built by ruler of Chola dynasty around 150 AD in India, oldest water diversion structure in India still in use, used to promote irrigation, made of unhewn stone and remodeled over the years

Roman-Built Dams

mostly built in semi-arid regions of the empire (North Africa, Near East, and Spain), reached extraordinary height and remained unsurpassed until late Middle Ages, most earth/rock-filled embankment dams and masonry gravity dams, waterproof hydraulic mortar, relied on heavy weight to hold back water, first to use arches and buttresses, introduced 1.) arch-gravity dams 2.) arch dams 3.) buttress dams, 4.) multiple-arch dams

Middle Ages

communities still used old Roman dams, any new dams built were small/local for farming/agriculture, larger-scale dams built in Netherlands to block rivers and regulate water level to prevent sea from entering the marshlands, place-names used for area around dams (Amsterdam, Rotterdam)

Industrial Revolution

by early 1800s engineering skills/construction materials finally available to build large-scale dams, mostly built by British Empire in Europe, Canada, Australia, India

The Modern Era

“Era of Large Dams” began with construction of Aswan Low Dam across Nile in Egypt 1902, nothing of its scale had ever been attempted, largest masonry dam in the world, 1.21 miles long & over 118’ above riverbed, other examples 1.) Hoover Dam 2.) Daniel-Johnson Dam 3.) Grand Coulee Dam 4.) Jinping-1 Dam (tallest in world)

Three Gorges Dam

dams several branches of Yangtze River near Hubei China, largest hydroelectric dam in world, at capacity flooded with water weight = 42 billion tons, slowed Earth’s rotation by 0.06 microseconds, shifted the Pole positions by 20 cm/0.8 in, destroyed entire ecosystems and indigenous lands

Dam Structures

dams can be formed by natural human activity, natural causes, and intervention of wildlife (beavers), man-made dams can be classified according to size, intended purpose, or structure, structures: arch dams, gravity dams, arch-gravity dams, buttress dams, embankment dams, barrages

Arch Dams

dam wall arched to distribute hydrostatic pressure against abutments, most desirable place is a narrow canyon with solid rock walls, firm solid supports at abutments (safety depends on it)

Gravity Dams

force that holds dam in place against hydrostatic pressures is the Earth’s gravity pulling down on the mass of the dam, essential to have an impervious foundation with high bearing strength, when built on a solid foundation they represent the best-developed example of dam building

Arch-Gravity Dams

arch curves upstream, made of concrete/masonry

Buttress Dams

developed by Romans, wall either arched or straight, series of supports/buttresses on downstream side, prevent the dam from falling forward, used in wide valleys where solid rock is hard to find or too far underground

Barrages

dam that consists of a line of large gates that can be opened or closed to control the amount of water passing through the dam, gates are set between the piers that hold the weight of the dam, can also be built at the mouth of rivers or lagoons to prevent tidal incursions

Embankment Dams

made by placement and compaction of a mound of various compositions of soil or rock, 2 types: earth-filled and rock-filled, friction and interaction between the particles binds them together instead of cement, waterproof or natural

Malpasset Dam

Fréjus, France, 1959, killed 423, destroyed 2 villages and a highway construction site, causes: 1.) inadequate geological surveys (failed to find a large tectonic fault in the rock under the dam 2.) large storm (storm caused about 20 in of rain, adding to the forces behind the dam and seepage along the fault) dam failed released wall

Dale Dike Reservoir

Sheffield England, built 1859-64, was earth-filled embankment dam with a puddle clay core, used for a water source to power mills downstream and drinking water, March 11 1864, one day after full dam failed, over 690 million gallons of water came through center of town, destroyed over 5,000 properties and killed 244 people, dam was rebuilt about 980 ft upstream of the previous dam and is still in use, caused by large crack on outer slope of embankment, engineers let out more water to ease the stress but didn’t work, aftermath let to standards in engineering practices

Teton Dam

1976, built to control Snake River near Fremont Idaho, 1961=severe drought, 1962=severe flooding, it was an earthen dam 310 ft high holding back 17 mile long reservoir, completed 1975 and control-filled, 1976 engineers requested to double filling rate, june 4 1976 3 leaks spotted, then one big one developed june 5, then entire side wall gave out and emptied killing 11 people and over 16,000 head of livestock in valley below, emptied at rate of 2 million cubic feet per second, empty in less than 8 hrs, cause collapse of soil in the core and fractures in the rock at the abutments