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 ( es, Lago Riñihue ) 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 con ...

on 22 May 1960, after a landslide caused by the

Great Chilean earthquake The 1960 Valdivia earthquake and tsunami ( es, link=no, Terremoto de Valdivia) or the Great Chilean earthquake (''Gran terremoto de Chile'') on 22 May 1960 was the most powerful earthquake ever recorded. Various studies have placed it at 9.4– ...

blocked its outflow. According to the chronicler Mariño de Lobera a similar event occurred after the

1575 Valdivia earthquake The 1575 Valdivia earthquake occurred at 14:30 local time on December 16. It had an estimated magnitude of 8.5 of on the surface wave magnitude scale and an estimated magnitude of 9.0+ on the Moment magnitude scale and led to the flood of Valdi ...

. During the

, several landslides near Tralcán Mountain blocked the outflow of

at (). Riñihue Lake is the lowest of the Seven Lakes chain and receives a constant inflow from the

Enco River The Enco River (Spanish: ''Río Enco'') is a river in Panguipulli commune in southern Chile. Flowing from Panguipulli Lake to Riñihue Lake, it carries the water of the six upper lakes of the Seven Lakes area into Riñihue, the last lake in the ...

. 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 Cau-Cau R ...

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 b ...

. 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 ( es, Ejército de Chile) is the land arm of the Military of Chile. This 80,000-person army (9,200 of which are conscripts) is organized into six divisions, a special operations brigade and an air brigade. In recent years, and ...

moved the Batallón Escuela de Suboficiales of San Bernardo south, a unit made mostly of young

conscript Conscription (also called the draft in the United States) is the state-mandated enlistment of people in a national service, mainly a military service. Conscription dates back to antiquity and it continues in some countries to the present day un ...

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 es, Corporación de Fomento de la Producción de Chile) is a Chilean governmental organization that was founded in 1939 by President Pedro Aguirre Cerda to promote economic growth in Chile. ...

, and MOP started an effort, called the Riñihuazo, to control the lake. Twenty-seven bulldozers 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 Vil ...

, 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 ( es, aldea) in Chile, South America. It is located in the commune of Los Lagos on the shores of Calle-Calle River just east of Valdivia. Two petroleum-fueled power plant A power station, also referred to as a power ...

Pishuinco Pishuinco is a hamlet ( es, caserío) in the commune of Valdivia, Chile. It lies at the northern end of the Calle-Calle River Calle-Calle River, also called Gudalafquén in Mapuche language, is a river in Valdivia Province, southern Chile. It dr ...

and the riverside areas of Valdivia were partially flooded. The team led by engineer Raúl Sáez finished two months after beginning the works.

References

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