1979 Machchhu dam failure
Failed earthen embankment of Machchhu II dam
|Location||Morbi and villages of Rajkot district, Gujarat, India|
The Machchhu dam failure or Morbi disaster was a dam-related flood disaster which occurred on 11 August 1979, in India. The Machchu-2 dam, situated on the Machhu river, burst, 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 1800 to 25000 people. This dam was built near Rajkot in Gujarat, India, on River Machhu in August, 1972, as a composite structure. It consisted of a masonry spillway in river section and earthen embankments on both sides. The embankment had a 6.1 m top width, with slopes 1 V : 3 H and 1 V : 2 H respectively for the upstream and downstream slopes and a clay core extending through alluvium to the rocks below. The upstream face had a 61 cm small gravel and a 61 cm hand packed riprap. The dam was meant to serve an irrigation scheme. Its, storage capacity of 1.1 × 108 m3. The dam had a height of 22.56 m above the river bed, a 164.5 m of crest length of overflow section, and a total of 3742 m of crest length for the earth dam. The failure was caused by excessive rain and massive flooding leading to the disintegration of the earthen walls of the four kilometer long Machchhu II dam. The spillway capacity provided for 5663 m³/s. The actual observed flow following the intense rainfall reached 16307 m³/s, thrice what the dam was designed for, resulting in its collapse. Within 20 minutes the floods of 12 to 30 ft (3.7 to 9.1 m) height inundated the low-lying areas of Morvi industrial town located 5 km below the dam. During reconstruction of the dam the capacity of the spillway was increased by 4 times and fixed at about 21,000 m³/s.
The Morbi dam failure was listed as the worst dam burst in the Guinness Book of Records (before the death toll of the 1975 Banquiao 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 the farmland, leading to a decrease in productivity of crops.
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