1979 Machchhu dam failure

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The Machchhu dam failure or Morbi disaster is a dam-related flood disaster which occurred on 11 August 1979. The Machchu-2 dam, situated on the Machchhu river, failed, sending a wall of water through the town of Morbi (now in the Morbi district) of Gujarat, India. Estimates of the number of people killed vary greatly ranging from 1,800 to 25,000 people.

The Machchu II dam
The first dam on the Machchhu river, named Machchhu I, was built in 1959, having a catchment area of 730 km2. The Machchhu II dam was constructed downstream of Machchhu I in 1972, and has a catchment area of 1929 km2.

It was an earthfill dam. The dam was meant to serve an irrigation scheme. Considering the long history of drought in Saurashtra region, the primary consideration at the time of design was water supply, not flood control. It consisted of a masonry spillway of 206 m consisting 18 sluice gates across the river section and long earthen embankments on both sides. The spillway capacity provided for 5663 m3/s. The embankments were of 2345 m and 1399 m of length on left and right side respectively. The embankments had a 6.1 m top width, with upstream and downstream slopes 1:3 (V:H) and 1:2 respectively; and a clay core extending through alluvium to bedrock. The upstream face consisted of 61 cm small gravel and a 61 cm hand packed rip-rap. The dam stood 22.6 m above the river bed and its overflow section was 164.5 m long. The reservoir had a storage capacity of 101020 dam3.

Failure
The failure was caused by excessive rain and massive flooding leading to the disintegration of the earthen walls of the four kilometre long Machchhu-2 dam. The actual observed flow following the intense rainfall reached 16,307 m3/s, thrice what the dam was designed for, resulting in its collapse. 762 m of the left and 365 m of the right embankment of the dam collapsed. Within 20 minutes the floods of 12 to 30 ft height inundated the low-lying areas of Morbi industrial town located 5 km below the dam.

Around 3.30 pm the tremendous swirling flow of water struck Morbi. Water level rose to 30 ft within the next 15 minutes and some low lying areas of city were under 20 ft of water for the next 6 hours.

The Morbi dam failure was listed as the worst dam burst in the Guinness Book of Records (before the death toll of the 1975 Banqiao Dam failure was declassified in 2005). The book No One Had A Tongue To Speak by Tom Wooten and Utpal Sandesara debunks the official claims that the dam failure was an act of God and points to structural and communication failures that led to and exacerbated the disaster. There was great economic loss. The flood damaged farmland, leading to a decrease in productivity of crops.

The book by Wooten and Sandesara gives vivid first person accounts of many survivors. It narrates how people scrambled for rooftops, hilltops, and other safe grounds in order to save themselves. Over a hundred people took shelter in Vajepar Ram Mandir but later the deluge submerged them with the temple. Women were compelled to drop their babies into the furious surge in order to save themselves and people lost their loved ones in a flash.

During reconstruction of the dam the capacity of the spillway was increased by four times and fixed at about 21,000 m3/s.

Popular culture
The Gujarati disaster film Machchhu is based on the Machchhu dam failure.