The major causes for landslide dams investigated by 1986 are landslides from excessive
precipitation and
earthquakes, which account for 84%. Volcanic eruptions account for a further 7% of dams.[3] Other
causes of landslides account for the remaining 9%.
Consequences
The water impounded by a landslide dam may create a
dam reservoir (
lake) that may last for a short time, to several thousand years.[2]
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.[2]
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.
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.[2]
After forming, the dam leads to
aggradation of the valley upstream, and dam failure leads to aggradation downstream.[2]
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.
Examples
The highest known landslide dam of historic times is the
Usoi Dam in modern
Tajikistan created by a landslide triggered by an
earthquake on February 18, 1911. It dammed the
Murghab River to the height of 570 m (1,860 ft) to impound
Sarez Lake 505 m (1,657 ft) deep.[2]
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.[4]
Attabad Lake in Pakistan was formed by a landslide in 2010. (100 m (330 ft) high)
The Red Lake (Romanian: Lacul Roşu) is a barrier lake in the
Eastern Carpathians chain in Harghita County, Romania. The name of "Lacul Roşu" 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 devastating landslide dam, (60 m (200 ft) high).
The
Lynmouth Flood of 15-16 August 1952 was partly the result of the formation and subsequent failure of a landslide dam on the
East Lyn River, sending a wave of water and debris into the town and killing 34 people.
Quake Lake, created in Montana in 1959, (58 m (190 ft) high).
The
Tangjiashan Lake, a dangerous "quake lake", was created as a result of the
2008 Sichuan earthquake. It was located in the extremely rugged terrain of Tangjiashan Mountain.
Chinese engineers, scientists, and soldiers were involved in the digging of a
sluice to alleviate the dangers of this one of 34 landslide dams created by the magnitude 8.0
Sichuan earthquake.[5] On June 10, 2008, the lake started to drain via the sluice, flooding the evacuated town of Beichuan.[6] (52 m (171 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.[7]
^
abcdefRobert B. Jansen (1988) "Advanced Dam Engineering for Design, Construction, and Rehabilitation",
ISBN0-442-24397-9
^R.B. Jansen refers to Schuster R.L. and Costa J.E., "A Perspective on Landslide Dams", in Landslide Dams by the American Society of Civil Engineers, 1986, pp. 1–20.
^Offer, R.E. (Robert) (1997). Walls for Water: Pioneer Dam Building in New Zealand. Palmerston North: The Dunmore Press Ltd.
ISBN978-0-86469-313-6.
^Schuster, R.L. and G. F. Wieczorek, "Landslide triggers and types" in Landslides: Proceedings of the First European Conference on Landslides 2002 A.A. Balkema Publishers. p.66
^National Geophysical Data Center (1972).
"Significant Earthquake Information AZERBAIJAN: GYZNDZHA". ngdc.noaa.gov. National Geophysical Data Center / World Data Service (NGDC/WDS): NCEI/WDS Global Significant Earthquake Database. NOAA National Centers for Environmental Information.
doi:
10.7289/V5TD9V7K. Retrieved 4 June 2021.