Riñihuazo
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The Riñihuazo is the name given to the
landslide dam A landslide dam or barrier lake is the natural damming of a river by some kind of landslide, such as a debris flow, rock avalanche or volcanic eruption. If the damming landslide is caused by an earthquake, it may also be called a quake lake. Some ...
ming of
Riñihue Lake The 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 ...
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, several
landslide Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...
s near
Tralcán Tralcán (Mapudungun for ''thunder'') is a triangular-shaped mountain, which is located near Riñihue Lake, Chile. It is located south of the outflow dividing western Riñihue in two arms. Despite having been sacred to the Huilliches for centuri ...
Mountain blocked the outflow of
Riñihue Lake The 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 ...
at (). Riñihue Lake is the lowest of the Seven Lakes chain and receives a constant inflow from the Enco River. The blocked San Pedro River, which drains the lake, passes through several towns and the city of
Valdivia Valdivia (; Mapuche: Ainil) is a city and commune in southern Chile, administered by the Municipality of Valdivia. The city is named after its founder, Pedro de Valdivia, and is located at the confluence of the Calle-Calle, Valdivia, and ...
before finally reaching
Corral Bay Corral Bay is a bay in the mouth of the Valdivia River, southern Chile. Its main towns are Corral and Niebla. The mouth of the bay is between Juan Latorre point and Morro Gonzalo, with a width of 5.5 km. All the year the bay is transited ...
. Because the San Pedro River was blocked, the water level of Riñihue Lake started to rise quickly. Each meter the water level rose was equivalent to 20 million cubic meters, which meant that 4.8 cubic kilometers of water would release into the San Pedro River (easily overpowering its flow capacity of 400 cubic meters per second) if it rose above the first, 26-meter-high dam.Operación Riñihue
/ref> This potential disaster would have destroyed all the settlements along the course of the river in less than five hours, and would have had more dire consequences if the dam had suddenly broken. The
Chilean Army The Chilean Army () is the land arm of the Chilean Armed Forces. This 80,000-person army (9,200 of which are conscripts) is organized into six divisions, an army aviation brigade and a special operations brigade. In recent years, and after sever ...
moved the Batallón Escuela de Suboficiales of San Bernardo south, a unit made mostly of young
conscript Conscription, also known as the draft in the United States and Israel, is the practice in which the compulsory enlistment in a national service, mainly a military service, is enforced by law. Conscription dates back to antiquity and it contin ...
s, south to Valdivia Province to aid in the relief efforts. Men of this battalion added to forces digging out the ditches west of Riñihue Lake. It became known as "Batallón de Hierro" (Iron Battalion) by grateful locals. About 100,000 people lived in the affected zone. Plans were made to evacuate Valdivia, and many people left. To avoid the destruction of the city, several military units and hundreds of workers from
ENDESA Endesa, S.A. (, originally an initialism for ''Empresa Nacional de Electricidad, S.A''.) is a Spanish multinational electric utility company, the largest in the country. The firm, a majority-owned subsidiary of the Italian utility company Enel, ...
,
CORFO The Production Development Corporation (CORFO, from ) is a Chilean governmental organization that was founded in 1939 by President Pedro Aguirre Cerda to promote economic growth in Chile. Originally, CORFO was responsible for the creation of ...
, and MOP started an effort, called the Riñihuazo, to control the lake. Twenty-seven
bulldozer A bulldozer or dozer (also called a crawler) is a large tractor equipped with a metal #Blade, blade at the front for pushing material (soil, sand, snow, rubble, or rock) during construction work. It travels most commonly on continuous tracks, ...
s were put into service, but they had severe difficulties moving in the mud near the dams, so dykes had to be constructed with shovels. A proposal by some US military to blow up the dams with missiles from a helicopter was rejected. The work was not restricted to the lake; drainages from other parts of the Seven Lakes were also dammed to minimize the flow into Riñihue Lake. These dams were removed later, with the exception of
Calafquén Lake Calafquén Lake (Mapudungun: Lake like a sea) is a lake of Chile, which straddles the border between the La Araucanía Region and Los Ríos Region. It is one of the Seven Lakes and forms part of the drainage basin of the Valdivia River The Vald ...
, which still retains its dam. By 23 May, the main dam had been lowered from 24 to 15 meters, allowing 3 cubic kilometers of water to leave the lake gradually, but still with considerable destructive power. The settlements of Los Lagos,
Antilhue Antilhue is a village () in Chile, South America. It is located in the commune of Los Lagos, Chile, Los Lagos on the shores of Calle-Calle River just east of Valdivia, Chile, Valdivia. Two petroleum-fueled power plants, Antilhue I Power Plant, An ...
, Pishuinco and the riverside areas of Valdivia were partially flooded. The team led by engineer
Raúl Sáez Raúl Sáez Sáez (16 February 1913 – 24 November 1992) was a Chilean civil engineer. He served as Minister of Finance in Chile in 1968, and as Minister of Economic Coordination under the military junta from 1974 to 1975. Early life and edu ...
finished two months after beginning the works.


References

{{DEFAULTSORT:Rinihuazo Landslides in Chile History of Los Ríos Region Presidency of Jorge Alessandri 1960 in Chile 1960 natural disasters 1960s landslides Landslide-dammed lakes Floods in Chile Mapuche language May 1960 in South America