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natural damming of a river by some kind of landslides
The water impounded by a landslide dam may create a dam reservoir (lake) 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 catastrophically 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 flooding: 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.
Profiles of the dam reservoir and groundwater upstream (the landslide dam is not shown in the figure)
Groundwater after dam failure downstream
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.
Lake Waikaremoana in New Zealand was formed by a 250 m (820 ft) 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 dam for power generation.
Attabad Lake in Pakistan was formed by a landslide in 2010. (100 m (330 ft) high)
The "Red Lake" (Romanian: Lacul Ro?u) is a barrier lake in the Eastern Carpathians chain in Harghita County, Romania. The name of "Lacul Ro?u" comes from the reddish alluvia deposited in the lake by the Red Creek.
The "Gros Ventre landslide" is an example of a huge, short-lived and disastrous landslide dam (60 m (200 ft) high).
Quake Lake, created in Montana in 1959. (58 m (190 ft) high)
Among the most destructive landslide lake outburst floods in recorded history occurred in the Sichuan province on 10 June 1786 when the dam on the Dadu River burst, causing a flood that extended 1,400 km (870 mi) downstream and killed 100,000 people.