Landslide dam
Encyclopedia
A landslide dam, debris dam, or barrier lake is a natural dam
ming of a river
by some kind of mass wasting
: landslide
, debris flow
, rock avalanche or volcano
. If it is caused by earthquake
, it may also be called a quake lake. Some landslide dams are as high as the largest existing artificial dam.
and earthquake
s, which account for 84%. Volcanic eruptions account for a further 7% of dams. Other causes of landslides
account for the remaining 9%.
) that may last from short times to several thousand years.
Because of their rather loose nature and absence of controlled spillway
, landslide dams frequently fail catastropically
and lead to downstream flooding, often with high casualties. A common failure scenario is overflowing with subsequent dam breach and erosion by the overflow stream.
Landslide dams are responsible for two types of flood
ing: backflooding (upstream
flooding) upon creation and downstream flooding upon failure. Compared with catastrophic downflooding, relative slow backflooding typically presents little life hazard, but property damage can be substantial.
While the dam is being filled, the surrounding groundwater
level rises. The dam failure may trigger further catastrophic processes. As the water level rapidly drops, the uncompensated groundwater hydraulic pressure may initiate additional landslides. Those that fall into the dam reservoir may lead to further catastrophic spillages. Moreover, the resulting flood
may undercut the sides of the river valley
to further produce landslides downstream.
After forming, the dam leads to aggradation
of the valley upstream, and dam failure leads to aggradation downstream.
Construction engineers responsible for design of artificial dams and other structures in river valleys must take into account the potential of such events leading to abrupt changes in river's regimen
.
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
ming of a river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
by some kind of mass wasting
Mass wasting
Mass wasting, also known as slope movement or mass movement, is the geomorphic process by which soil, regolith, and rock move downslope under the force of gravity. Types of mass wasting include creep, slides, flows, topples, and falls, each with its own characteristic features, and taking place...
: landslide
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
, debris flow
Debris flow
A debris flow is a fast moving, liquefied landslide of unconsolidated, saturated debris that looks like flowing concrete. It is differentiated from a mudflow in terms of the viscosity and textural properties of the flow. Flows can carry material ranging in size from clay to boulders, and may...
, rock avalanche or volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
. If it is caused by earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
, it may also be called a quake lake. Some landslide dams are as high as the largest existing artificial dam.
Causes
The major causes for landslide dams investigated by 1986 are landslides from excessive precipitationPrecipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
and earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s, which account for 84%. Volcanic eruptions account for a further 7% of dams. Other causes of landslides
Causes of landslides
The causes of landslides are usually related to instabilities in slopes. It is usually possible to identify one or more landslide causes and one landslide trigger. The difference between these two concepts is subtle but important. The landslide causes are the reasons that a landslide occurred in...
account for the remaining 9%.
Consequences
The water impounded by a landslide dam may create a dam reservoir (lakeLake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
) that may last from short times to several thousand years.
Because of their rather loose nature and absence of controlled spillway
Spillway
A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...
, landslide dams frequently fail catastropically
Catastrophic failure
A catastrophic failure is a sudden and total failure of some system from which recovery is impossible. Catastrophic failures often lead to cascading systems failure....
and lead to downstream flooding, often with high casualties. A common failure scenario is overflowing with subsequent dam breach and erosion by the overflow stream.
Landslide dams are responsible for two types of flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
ing: backflooding (upstream
Source (river or stream)
The source or headwaters of a river or stream is the place from which the water in the river or stream originates.-Definition:There is no universally agreed upon definition for determining a stream's source...
flooding) upon creation and downstream flooding upon failure. Compared with catastrophic downflooding, relative slow backflooding typically presents little life hazard, but property damage can be substantial.
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
level rises. The dam failure may trigger further catastrophic processes. As the water level rapidly drops, the uncompensated groundwater hydraulic pressure may initiate additional landslides. Those that fall into the dam reservoir may lead to further catastrophic spillages. Moreover, the resulting flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
may undercut the sides of the river valley
Valley
In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...
to further produce landslides downstream.
After forming, the dam leads to aggradation
Aggradation
Aggradation is the term used in geology for the increase in land elevation due to the deposition of sediment. Aggradation occurs in areas in which the supply of sediment is greater than the amount of material that the system is able to transport...
of the valley upstream, and dam failure leads to aggradation downstream.
Construction engineers responsible for design of artificial dams and other structures in river valleys must take into account the potential of such events leading to abrupt changes in river's regimen
River regime
River regime can describe one of two characteristics of a reach of an alluvial river:* The variability in its discharge throughout the course of a year in response to precipitation, temperature, evapotranspiration, and drainage basin characteristics * A series of characteristic power-law...
.
Examples
- The highest known landslide dam of historic times is the Usoi DamUsoi DamThe Usoi Dam is a natural landslide dam along the Murghab River in the Central Asian country of Tajikistan. At high, it is the tallest dam in the world, either natural or man-made...
in modern TajikistanTajikistanTajikistan , officially the Republic of Tajikistan , is a mountainous landlocked country in Central Asia. Afghanistan borders it to the south, Uzbekistan to the west, Kyrgyzstan to the north, and China to the east....
created by a landslide triggered by an earthquakeEarthquakeAn earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
on February 18, 1911. It dammed the Murghab River to the height of 301 m (987 ft) to impound Sarez LakeSarez Lake-External links:****...
932 ft (284.1 m) deep. - Lake WaikaremoanaLake WaikaremoanaLake Waikaremoana is located in Te Urewera National Park in the North Island of New Zealand, 60 kilometres northwest of Wairoa and 80 kilometres southwest of Gisborne. It covers an area of 54 km². From the Maori Waikaremoana translates as 'sea of rippling waters'The lake lies in the heart of Tuhoe...
in New ZealandNew ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
was formed by a 250m high landslide dam believed to be 2,200 years old. Between 1935 and 1950 the landslide was tunneled and sealed to stabilise it so it could be used for hydroelectric power generation. This appears to be the first example of modification of a natural landslide for power generation. - Attabad LakeAttabad LakeAttabad Lake, Gojal, also known as Gojal Lake, is a lake in the Hunza Valley of northern Pakistan created in January 2010 by a landslide dam. The lake was formed due to a massive landslide at Attabad village in Gilgit-Baltistan, upstream of Karimabad that occurred on January 4, 2010. The...
in Pakistan was formed by a landslide in 2010. (100m high) - The "Red Lake" (Romanian: Lacul Roşu) is a barrier lake in the Eastern Carpathians chain in Harghita County, RomaniaRomaniaRomania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...
. The name of "Lacul Roşu" comes from the reddish alluvia deposited in the lake by the Red Creek. - The "Gros Ventre landslideGros Ventre landslideThe Gros Ventre landslide is located in the Gros Ventre Wilderness of Bridger-Teton National Forest, Wyoming, United States. The Gros Ventre landslide is east of Jackson Hole valley and Grand Teton National Park....
" is an example of a huge, short-lived and disastrous landslide dam (60 m high). - Quake LakeQuake LakeQuake Lake is a lake in southwestern Montana, United States. It was created after a massive earthquake struck on August 17, 1959, which killed 27 people. Today, Quake Lake is 190 feet deep and six miles long...
, created in Montana in 1959. (58m high) - The Tangjiashan LakeTangjiashan LakeTangjiashan Lake is a landslide dam-created lake on the Jian River, which was formed by the 2008 Sichuan earthquake. Its name comes from the nearby mountain Tangjiashan. On May 24, 2008 the water level rose by in a single day, reaching a depth of , just below the barrier level...
, a dangerous "quake lake", was created as a result of the 2008 Sichuan earthquake2008 Sichuan earthquakeThe 2008 Sichuan earthquake or the Great Sichuan Earthquake was a deadly earthquake that measured at 8.0 Msand 7.9 Mw occurred at 14:28:01 CST...
. It was located in the extremely rugged terrain of Tangjiashan Mountain. Chinese engineers, scientists, and soldiers were involved in the digging of a sluiceSluiceA sluice is a water channel that is controlled at its head by a gate . For example, a millrace is a sluice that channels water toward a water mill...
to alleviate the dangers of this one of 34 landslide dams created by the magnitude 8.0 Sichuan earthquake. On June 10, 2008, the lake started to drain via the sluice, flooding the evacuated town of Beichuan. (52m high) - The RiñihuazoRiñihuazoThe Riñihuazo is the name given to the damming of Riñihue Lake on 22 May 1960, after a landslide caused by the Great Chilean Earthquake blocked its outflow. According to the chronicler Mariño de Lobera a similar event occurred after the 1575 Valdivia earthquake.During the Great Chilean Earthquake,...
begun on 22 May 1960, after a landslide caused by the Great Chilean EarthquakeGreat Chilean EarthquakeThe 1960 Valdivia earthquake or Great Chilean Earthquake of Sunday, 22 May 1960 is to date the most powerful earthquake ever recorded on Earth, rating 9.5 on the moment magnitude scale...
blocked Riñihue LakeRiñihue LakeThe Riñihue Lake is a lake of glacial origin in eastern Valdivia Province, southern Chile. It is surrounded by several mountains. The eastern side receives the waters of the Panguipulli Lake, by the Enco River its main contributor. It is the last of the Seven Lakes chain. In the west is it cut...
's outflow. According to the chronicler Mariño de Lobera a similar event occurred after the 1575 Valdivia earthquake1575 Valdivia earthquakeThe 1575 Valdivia earthquake was an earthquake in Chile that caused the subsequent flood of Valdivia much like the 1960 Valdivia earthquake caused the ensuing Riñihuazo flooding. It occurred at 14:30 local time on December 16, 1575. It had an estimated magnitude of 8.5 on the surface wave...
. (26m high)
- Among the most destructive landslide lake outburst floods in recorded history occurred in the SichuanSichuan' , known formerly in the West by its postal map spellings of Szechwan or Szechuan is a province in Southwest China with its capital in Chengdu...
province of ChinaChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
on 10 June 1786 when the dam on the Dadu River burst, causing a flood that extended 1400km downstream and killed 100,000 people.
- The largest landslide dam in Britain impounds Tal-y-llyn Lake (Llyn Mwyngil)Tal-y-llyn LakeTal-y-llyn Lake, also known as Talyllyn Lake or Llyn Mwyngil, is a large glacial ribbon lake formed by a post-glacial massive landslip damming up the lake within the glaciated valley...
beside Cadair IdrisCadair IdrisCadair Idris or Cader Idris is a mountain in Gwynedd, Wales that lies at the southern end of the Snowdonia National Park. The peak, which is one of the most popular in Wales for walkers and hikers, is composed largely of Ordovician igneous rocks, with classic glacial erosion features such as...
in Snowdonia National Park, WalesWalesWales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
. It was first recognised by E Watson in 1962. It is probably over 10,000 years old.