Flooding that occurred in Kerala
On 16 August 2018, severe floods affected the south Indian state Kerala, due to unusually heavy rainfall during the monsoon season. It was the worst flood in Kerala in nearly a century. Over 483 people died, and about one million people were evacuated, mainly from Chengannur, Pandanad, Edanad, Aranmula, Kozhencherry, Ayiroor, Ranni, Pandalam, Kuttanad, Malappuram, Aluva, Chalakudy, Thrissur, Thiruvalla, Eraviperoor, Vallamkulam, North Paravur, Chendamangalam, Chellanam, Vypin Island, and Palakkad. All 14 districts of the state were placed on red alert. According to the Kerala government, one-sixth of the total population of Kerala was directly affected by the floods and related incidents. The Indian government declared it a Level 3 Calamity, or "calamity of a severe nature". It is the worst flood in Kerala after the great flood of '99 that took place in 1924.
Thirty-five out of the fifty-four dams within the state were opened for the first time in history. All five overflow gates of the Idukki Dam were opened at the same time, and for the first time in 26 years, five gates of the Malampuzha dam of Palakkad were opened. Heavy rains in Wayanad and Idukki caused severe landslides and had left the hilly districts isolated. The situation was regularly monitored by the National Crisis Management Committee, which also coordinated the rescue and relief operations. The dam openings disrupted many of those living nearby.
With the recurrence of flood events in the state in the subsequent years, several studies have attempted to explain the behavior.
Causes.
Rainfall from the southwest monsoon was 23% higher than normal in Kerala in 2018, with August seeing rainfall 96% above normal. On the evening of 8 August, Kerala received heavy rainfall which was 116% more than usual, resulting in dams filling to their maximum capacities. In the proceeding 48 hours, the state received of rain. Almost all dams had been opened since the water had risen close to overflow levels due to heavy rainfall, which flooded local low-lying areas. For the first time in the state's history, 35 of its 54 dams had been opened. The deluge is considered an impact of global warming.
Independent scientific studies conducted by hydrology experts from IIT Madras, Purdue University, and IIT Gandhinagar concluded that heavy downpour and dam management resulted in the floods. Based on a computer simulation of flood storage and flow patterns by a team of researchers from IIT Madras and Purdue University, it was found that the devastation wrought by the floods cannot be attributed to the release of water from dams. Further, the scientists added that the odds of such floods were 0.06% and no reservoir management could have considered such scenarios. A hydrology expert from IIT Gandhinagar, Vimal Mishra, identified four major factors for the floods: unexpected above-normal downpour, extreme rainfall events occurring almost across Kerala during the season, over 90% reservoir storage even before the onset of extreme rainfall events, and the unprecedented extreme rainfall in the catchment areas of major reservoirs in the state.
The prime reason for the anomalous rainfall in 2018 is the high-frequency mixed Rossby-gravity waves in the mid-troposphere triggered by the synoptic disturbances of the tropical Pacific. These high-frequency waves manifested as cyclonic and anticyclonic circulations and dilated the wind field to establish zones of convection in the tropics, as they propagated across the Indian Ocean basin. Although the Madden-Julian Oscillation phase with 20-to-40-day period has favored convection in the tropics, the high-frequency mode correlates better with the anomalous precipitation during the intervals of extreme events.
Expert bodies like the Central Water Commission have corroborated the findings by scientists from IIT Madras, Purdue University and IIT Gandhinagar.
A report by Adv. Jacob P. Alex, an advisor appointed by the Kerala high court, alleged that the devastating floods of 2018 were the result of bad dam management by the state government. All 79 dams in the state were maintained with the objective to generate hydroelectricity or irrigation and controlling flooding wasn't their purpose. "The major concern of the dam operators was to maximise reservoir levels, which conflicted with the flood control purpose for which the dams could be utilised. The 'flood cushion' of reservoirs – the storage space earmarked in dams to absorb unanticipated high flows – needed review as per the latest guidelines," Alex wrote in his report. "Sudden release of water simultaneously from different reservoirs, during extreme rainfall aggravated the damage," it said, adding that various alerts—blue, orange and red—had been issued not in accordance with the EAP guideline. "No proper follow-up action and effective precautionary steps (especially for evacuating people and accommodating them in safe location) were taken after issuance of Red Alert," it said. As of August 2024[ [update]], the high court of Kerala had not accepted the report.
The government of Kerala argued in the Supreme Court that the sudden release of water from the Mullaperiyar Dam by the Tamil Nadu government was one of the reasons for the devastating flood in Kerala. The Tamil Nadu government rejected the argument, saying that Kerala suffered the deluge due to the discharge of excess water from 80 reservoirs across Kerala, spurred by heavy rains from within the state; It also argued that the flood surplus from the Idukki dam was due mainly to the flows generated from its own independent catchment due to unprecedented heavy rainfall, while the discharge from the Mullaperiyar dam was significantly less.
Impact.
Over 489 people died, 15 are missing and 140 were hospitalized, while "The Economic Times" reported that 33,000 people were rescued. The Kerala State Disaster Management Authority had placed the state on red alert as a result of the intense flooding. A number of water treatment plants were forced to cease pumping water, resulting in poor access to clean water, especially in northern districts of the state. Over 3,274 relief camps were opened at various locations to accommodate the flood victims. It is estimated by the National Disaster Management Authority that 1,247,496 people found shelter in such camps. The flooding affected hundreds of villages, destroyed an estimated of roads, and thousands of homes have were damaged or destroyed. The government cancelled Onam celebrations and reallocated the funds to relief efforts.
On 12 August, Cochin International Airport, India's fourth busiest in terms of international traffic and the busiest in the state, suspended all operations until 29 August, following runway flooding. All schools throughout the state were closed, and tourists were dissuaded or prohibited from some districts due to safety concerns. The Kochi Metro closed briefly on 16 August, and later offered free services to aid those affected by the flooding. Due to heavy rain and rising water levels the southern railway suspended train services on the Thiruvananthapuram-Kottayam-Ernakulam and Ernakulam-Shoranur-Palakkad sections.
Rescue Operations.
Government.
The central government launched a large search and rescue operation that included aircraft, boats, rescue and medical teams, and police. The government provided supplies to those who needed help and conducted many rescue operations.
Public.
WhatsApp groups sprung up as control centers that coordinated help and support across various areas. Many people volunteered to deliver supplies and materials, or donated money.
Rescue operation by fishermen.
According to the government, a total of 4,537 fishermen communities from Kollam and Thiruvananthapuram districts participated in the rescue operation with 669 fishing boats. They managed to rescue more than 65,000 people from various districts. Chief Minister Pinarayi Vijayan honoured the fishermen. Fisheries Minister J. Mercykutty Amma said that the government would provide financial aid to repair the fishing boats which were partially damaged in the rescue operations while new ones will be provided for those boats which were completely destroyed. According to estimates, seven boats were completely destroyed, while 452 were partially destroyed.
Response.
At a press conference on 11 August, Chief Secretary Tom Jose said, "Things are well under control. The government is on top of the situation." Prime Minister Narendra Modi conducted an aerial survey and offered federal support to Keralites. Chief Minister Pinarayi Vijayan described the floods as "something that has never happened before in the history of Kerala."
International.
The United States embassy urged its citizens to avoid traveling to the affected areas. The UAE embassy in India issues warning for its citizens regarding the flood. The embassy also said that the weather agencies in India had given warnings regarding heavy rainfall in the southern state of Kerala. UAE's President Sheikh Khalifa bin Zayed Al Nahyan ordered the formation of a national emergency committee to provide relief assistance to people affected by flash floods in the Indian state of Kerala.
A controversy arose from an offer of US$100 million in aid from the UAE. The Kerala Chief Minister's office wrote "CM Pinarayi Vijayan informed that the United Arab Emirates will provide Kerala an assistance of ₹700 Crore. Kerala has a special relationship with UAE, which is a home away from home for Malayalees. We express our gratitude to UAE for their support. #KeralaFloodRelief". The Ministry of External Affairs of India clarified that they received no such offer for financial help from any country, and the UAE Ambassador to India declared that no official announcement had been made.
Rainfall data.
Rainfall departures.
Week by week departures from normal:
Cumulative rainfall by district.
Percentage increase in rainfall compared to normal.
Analysis by Central Water Commission.
Kerala as a whole.
According to a study by the Central Water Commission, the average cumulative rainfall of 3 days from 15 to 17 August 2018 was about 414 mm. This was almost of the same order as that of rainfall of Devikulam which occurred during 16–18 July 1924. Assuming a runoff coefficient of 0.75, the runoff generated by 3 days of intense rainfall was estimated to be 12057 MCM for the entire state of Kerala. This huge runoff was beyond the carrying capacity of most of the rivers in Kerala, resulting in bank overflows from most of the rivers. The total catchment area tapped by dams in Kerala, excluding barrages is about . The runoff generated from the catchment tapped by these dams during the period 15–17 August 2018 was estimated at 2.19 BCM, out of a total runoff of 12 BCM for the whole of Kerala. As per the study, with a total live storage in the state of 5.8 BCM and assuming a live storage availability of 20% on 14 August 2018, the extent of available flood moderation would have only been 1.16 BCM against an estimated inflow of 2.19 BCM. It was therefore essential to make releases from the reservoirs.
The study stated that the dams in Kerala neither added to the flood nor helped in reduction of flood, as most of the dams were already at or very close to FRL on 14 August 2018. Even if the reservoirs had been a few feet below FL, the flooding conditions would not have changed much as the heavy rainfall continued for 3–4 days. It would have been necessary to release water from the reservoirs after the first day of heavy rainfall.
The study concluded it would be necessary to review the rule curves of all reservoirs in Kerala, especially those with a live storage capacity of more than 200 MCM. This would help to create a dynamic flood cushion for moderating floods.
Periyar Basin.
From 15 to 17 August 2018, the rainfall depth realized in the Periyar basin was 588 mm. The maximum discharge passing through the Periyar at Neeleeswaram was 8800 m3/sec, recorded at 16 August 15:00 hrs, according to the CWC's Neeleeswaram G&amp;D site. The major storage reservoirs in the Periyar basin are the Idukki reservoir (1.4 BCM) and the Idamalayar reservoir (1.1 BCM). The peak release on 16 August 2018 from the Idukki reservoir was 1500 m3/sec against an inflow of 2532 m3/sec, thus achieving a flood moderation of 1032 m3/sec. The release from Idamalayar on 16 August 2018 was 963 m3/sec against an inflow of 1164 m3/sec.
The discharge at Neeleshwaram on 17 August 2018 was 8600 m3/sec. The release from Idukki and Idamalayar reservoirs were 1500 m3/sec (with an inflow of 1610 m3/sec) and 1272 m3/sec (inflow of 1007 m3/sec). CWC's analysis found that the releases of water were controlled releases as the discharge capacity of Idukki and Idamalayar dams are 5013 m3/sec and 3012 m3/sec, respectively.
Immediate drought after the flood.
A few days after receiving one of the highest rainfalls in century, Kerala was caught under the threat of severe drought. Water level in wells, ponds and rivers recorded lowest levels and some wells even collapsed. Chief minister Pinarayi Vijayan directed the state council