Saryu Dam

The Saryu Dam (沙流水坝) is an arch dam on the Puratalusugu River (青龍川) near Saryu County, in Bintamalu Prefecture, Surea. The main purpose of the project is hydroelectric power generation with additional purposes of flood control and irrigation. The dam is 88 metres tall and was constructed between 1953 and 1955.

Construction
In September 1952, planning for dams in the Puratalusugu River basin began and by January 1953, plans for the Saryu Dam were complete. In August 1956, construction on the dam began and excavation commenced the next month and continued until April of 1954, removing 790,000 cubic metres of rock and material. The same month that excavation was complete, concrete placement began and continued until September 1955. Earlier in August, the first generator was placed online and the rest were operational by the end of 1955. Originally, the dam support 6 x 10.5 MW generators but in 1986, they were upgraded to 16 MW each.

Design
The dam is a 283.5 metres long and 88 metres high double-curvature arch dam with a crest width of 3 metres and base width of 28 metres. The dam is composed of 145,000 cubic metres of concrete and contains nine openings on its surface to discharge water downstream. Each opening is 11.5 metres wide and 4 metres high with a discharge capacity of 141 cubic metres per second each. A 237 metres long discharge tunnel with a maximum capacity of 1,070 cubic metres per second is also built on the dam's right bank.

An axillary dam was built in conjunction with the project in order to protect low lying areas from the reservoir. It is located about 2 kilometres (1 mi) northwest of the main dam and is an embankment type. The dam is 34.7 metres tall and 220 metres long while having a structural volume of 370,000 cubic metres.

Failure
Reportedly, in the early morning of 22 March 2011, the dam failed due to the Bintamalu earthquake. Locals reported hearing a loud burst before seeing a flood.

The resulting flood waters caused a large wave, which was 10 kilometers wide and 8 meters high, to rush downwards into the plains below at nearly 50 kilometers per hour, almost wipe out an area 55 kilometers long and 15 kilometers wide, and create temporary lakes as large as 12,000 square kilometers. Five county seats, including Dongdu Metropolitan City, were inundated, as were thousands of square kilometers of countryside and countless communities.

Evacuation orders had not been fully delivered because of the damage from the quake. Telephones and internet failed, signal flares fired were misunderstood, and some messengers were caught by the flood. 3657 people reported dead while 360,500 people reported missing. These numbers are expected to rise as the water continues to flow into neighboring counties and cities.