The 1970 Bhola cyclone, also known as the Great Cyclone of 1970 or simply the Bhola Cyclone, was the deadliest tropical cyclone on record, as well as one of the deadliest humanitarian disasters ever recorded. It struck East Pakistan (present-day Bangladesh) and India's West Bengal on 12 November 1970. At least 300,000 people died in the storm, possibly as many as 500,000, primarily as a result of the storm surge that flooded much of the low-lying islands of the Ganges Delta. The Bhola cyclone was the sixth and strongest cyclonic storm of the 1970 North Indian Ocean cyclone season.
The cyclone formed over the central Bay of Bengal on 8 November and travelled northward, intensifying as it did so. It reached its peak with winds of on 10 November, and made landfall on the coast of East Pakistan on the following afternoon. The storm surge devastated many of the offshore islands, wiping out villages and destroying crops throughout the region. In the most severely affected upazila Tazumuddin, over 45% of the population of 167,000 were killed by the storm.
The Pakistani government, led by junta leader General Yahya Khan, was criticized for its delayed handling of relief operations following the storm, both by local political leaders in East Pakistan and by the international media. The poor and discriminatory response from the West Pakistan government led to the increasingly widespread disillusionment from the East Pakistani people, allowing the opposition Awami League to gain a landslide victory in the province during the election that took place a month later as well as the Bangladesh Liberation War seven months later.
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Meteorological history
On 1 November, Tropical Storm Nora developed over the South China Sea, in the West Pacific Ocean. The system lasted for four days before degenerating into a remnant low over the Gulf of Thailand on 4 November, and subsequently moved west over the Malay Peninsula the next day. The remnants of this system contributed to the development of a new depression in the central Bay of Bengal on the morning of 8 November. The depression intensified as it moved slowly northward, and the India Meteorological Department upgraded it to a cyclonic storm the next day. No country in the region had ever named tropical cyclones during this time, so no new identity was given.
The storm further intensified into a severe cyclonic storm on 11 November and began to turn towards the northeast as it approached the head of the bay. It developed a clear eye and reached its peak intensity later that day, with three-minute sustained winds of , one-minute sustained winds of , and a central pressure of 960 hPa. The cyclone made landfall on the East Pakistan coastline during the evening of 12 November, around the same time as the local high tide. Once over land, the system began to weaken; the storm degraded to a cyclonic storm on 13 November, when it was about south-southeast of Agartala. The storm then rapidly weakened into a remnant low over southern Assam that evening. A large part of the population was reportedly taken by surprise by the storm. There were indications that East Pakistan's storm warning system was not used properly. The Pakistan Meteorological Department issued a report calling for "danger preparedness" in the vulnerable coastal regions during the day on 12 November. As the storm neared the coast, a "great danger signal" was broadcast on Radio Pakistan. Survivors later said that this meant little to them, but that they had recognised a No. 1 warning signal as representing the greatest possible threat.
Following two previously destructive cyclones in October 1960, which killed at least 16,000 people in East Pakistan, the Pakistani central government contacted the American government for assistance in developing a system to avert future disasters. Gordon Dunn, the director of the National Hurricane Center at the time, carried out a detailed study and submitted his report in 1961. However, the central government did not carry out all the recommendations Dunn had listed.
The Bhola cyclone is the deadliest tropical cyclone on record and also one of the deadliest natural disasters in modern history. A comparable number of people died as a result of the 1976 Tangshan earthquake, the 2004 Indian Ocean earthquake, and the 2010 Haiti earthquake, but because of uncertainty in the number of deaths in all four disasters, it may never be known which one was the deadliest.
Bangladesh
The meteorological station in Chittagong, to the east of where the storm made landfall, recorded winds of before its anemometer was blown off at about 2200 UTC on 12 November. A ship anchored in the port in the same area recorded a peak gust of about 45 minutes later. In the port at Chittagong, the storm tide peaked at about above the average sea level, of which was the storm surge. Several seagoing vessels in the ports of Chittagong and Mongla were reported damaged, and the airports at Chittagong and Cox's Bazar were under of water for several hours.
Over 3.6 million people were directly affected by the cyclone, and the total damage from the storm was estimated at US$86.4 million (US$701 million in 2024). The survivors claimed that approximately 85% of homes in the area were destroyed or severely damaged, with the greatest destruction occurring along the coast. Ninety percent of marine fishermen in the region suffered heavy losses, including the destruction of 9,000 offshore fishing boats. Of the 77,000 onshore fishermen, 46,000 were killed by the cyclone, and 40% of the survivors were affected severely. In total, approximately 65% of the fishing capacity of the coastal region was destroyed by the storm, in a region where about 80% of the protein consumed comes from fish. Agricultural damage was similarly severe with the loss of US$63 million worth of crops and 280,000 cattle.
India
The cyclone brought widespread rain to the Andaman and Nicobar Islands, with very heavy rain falling in places on 89 November. Port Blair recorded of rain on 8 November, and there were a number of floods on the islands. MV Mahajagmitra, a 5,500-ton freighter en route from Calcutta to Kuwait, was sunk by the storm on 12 November with the loss of all fifty people on board. The ship sent out a distress signal and reported experiencing hurricane-force winds before it sank. There was also widespread rain in West Bengal and southern Assam. The rain caused damage to housing and crops in both Indian states, with the worst damage occurring in the southernmost districts. but the survey found no evidence of an epidemic of cholera, smallpox, or any other disease in the region affected by the storm.
The totals from the second survey were likely a considerable underestimate, as several groups were not included— 100,000 migrant workers who were collecting the rice harvest, families who were completely wiped out by the storm, and those who had migrated out of the region in the intervening three months. Excluding these groups reduced the risk of hearsay and exaggeration. The survey concluded that the overall death toll was, at minimum, 224,000. The worst effects were felt in Tazumuddin, where the mortality was 46.3%, corresponding to approximately 80,000 deaths in the thana alone. The mean mortality throughout the affected region was 16.5%.
The results showed that the highest survival rate was for adult males aged 15–49, while more than half the deaths were children under age 10, who only formed a third of the pre-cyclone population. This suggests that the young, old, and sick were at the highest risk of perishing in the cyclone and its storm surge. In the months after the storm, the mortality of the middle-aged was lower in the cyclone area than in the control region, near Dhaka. This reflected the storm's toll on the less healthy individuals.