Kerala floods
Vehicles move through a waterlogged road following incessant rainfall in Changanassery Road, Kerala on Monday. Image Credit: ANI

The south Indian state of Kerala has been witnessing regular floods for the past few years. The state has once again witnessed landslides and floods triggered by heavy rains, claiming the lives of more than 35 people, this weekend. Several people are reportedly missing. Residents were cut off in parts of the state as the rains, which started from Friday, swelled rivers and flooded roads. The military flew in emergency supplies as the rescuers scoured muddy debris for survivors. The army, navy and air force have assisted with flood relief and rescue operations.

Thousands of people have been evacuated and around 100 relief camps have been set up. The Indian Meteorological Department said the heavy rains were caused by a low pressure area over the south-eastern Arabian Sea and Kerala.

Indian Prime Minister Narendra Modi tweeted his condolences and said authorities were working to help those who were affected by the deluge.

The latest weather forecast, which has now come out predicts heavy rains to lash the state starting Wednesday. It all started with the century's biggest floods in 2018 and since then every year, Kerala has seen heavy rains and flash floods. In 2018, nearly 500 people were killed in Kerala when it was ravaged by the worst floods to hit the state in almost a century.

Meanwhile several Indian expats in the UAE have expressed fear and anxiety about the safety of their families in Kerala. Aged parents, water-clogged roads, damage to properties - their fears are many.

What is causing frequent Kerala floods?

Though the state has been experiencing frequent floods for several years now, there are different versions for the causes of it. Some experts consider the ‘cloudburst' phenomenon as one of the reasons for frequent floods. Some experts point out the illegal stone-quarrying activity in Kerala as the reason for landslides and floods.

A study, conducted by Cochin University of Science and Technology (CUSAT), Miami University, Indian Meteorological Department and the Indian Institute of Tropical Meteorology said that cloudburst causes regular floods in Kerala. Cloudburst phenomenon is a pattern of rain that causes heavy rain over a limited area. It was termed the factor for the landslides that occurred in Kavalappara and Puthumala three years ago.

The study was based upon the pattern of rain received in Kerala since 2018.

Pictures: Heavy rains create havoc in Kerala

2021 floods: Mini cloudburst behind Kerala rains

The brief, intense rain spells in a couple of regions in Kerala indicated mini cloudbursts, a factor that also led to casualties, damage and loss of properties, a scientist at the Cochin University of Science and Technology (CUSAT) claimed.

Citing more than 5 cm rain received in two hours in worst affected areas of Idukki and Kottayam districts, S Abhilash of the Department of Atmospheric Sciences, CUSAT said it was a "mesoscale mini-cloudburst type of event".

Mini cloud bursts are marked by intense short spells, which may not exceed 10cm in one hour-a classical definition by India Meteorological Department, he noted.

Changes in Kerala's climate received more attention during recent times as evident from back-to-back drought conditions during 2015 and 2016. In 2017 Kerala was hit by the cyclonic storm "Ockhi" and catastrophic flood and landslide episodes followed during 2018, 2019 and 2020, he has claimed. However, IMD Director General Mrutyunjay Mahapatra has ruled out cloudburst phenomenon for the heavy rains in Kerala. He said low pressure system and wind caused heavy rains.

Rescue workers carry the body of a victim after recovering it from the debris of a residential house following a landslide caused by heavy rainfall at Kokkayar village in Idukki district in the southern state of Kerala, India, October 17, 2021. Image Credit: Reuters

What is a cloudburst?

A cloudburst is defined as an extreme amount of precipitation in a short period of time. It is sometimes accompanied by hail and thunder and is capable of creating flood conditions, like in the case of Kerala. Cloudbursts can quickly dump large amounts of water, according to experts.

Most cloudbursts occur in connection with thunderstorms. In these storms there are violent uprushes of air, which at times prevent the condensing raindrops from falling to the ground.

According to the India Meteorological Department (IMD), it is a weather phenomenon with unexpected precipitation exceeding 100mm/h over a geographical region of approximately 20-30 square km.

On July 28 this year, at least seven people were killed, 17 injured and over 35 missing after a cloudburst hit a remote village of Jammu and Kashmir, according to a report in Indian Express. Recently, cloudbursts have been reported from several places in J&K, Union Territory of Ladakh, Uttarakhand and Himachal Pradesh. A 2017 study of cloudbursts in the Indian Himalayas noted that most of the events occurred in the months of July and August.

What is low pressure?
Low-pressure areas are places where the atmosphere is relatively thin. Winds blow inward toward these areas. This causes air to rise, producing clouds and condensation. Low-pressure areas tend to be well-organised storms.

Where does cloudburst happen?

Cloudburst is basically a rainstorm and occurs in high-altitude areas due to the formation of a low-pressure area on the top of a mountain. The low-pressure zone attracts clouds to the top of the mountain with great force. When they hit the peak, the moisture content is released in the form of rain. In some cloudbursts, up to 13 centimeters of rain can fall in an hour, often in the form of extremely large droplets. All heavy rains are not necessarily cloudbursts.

They are called 'bursts' probably because it was believed earlier that clouds were solid masses full of water. So, these violent storms were attributed to their bursting.

Why is a cloudburst dangerous?

Cloudbursts are dangerous, especially if it lasts for several hours, due to their ability to cause heavy flash floods as well as landslide events. It can cause rivers and lakes to swell to critical levels. Flash floods are extremely forceful events and cause massive destruction in their paths.

Why are cloudbursts hard to predict?

There is no satisfactory technique for anticipating the occurrence of cloud bursts because of their small scale. According to an explainer by the IMD on its website, "It is very difficult to predict cloudbursts due to its very small scale in space and time. To monitor or nowcast (forecasting few hours lead time) the cloudburst, we need to have dense radar network over the cloudburst-prone areas or one need to have a very high resolution weather forecasting models to resolve the scale of cloudburst." "Cloudbursts do occur at plains, however, mountainous regions are more prone to cloud bursts due to orography."

However, a very fine network of radars is required to be able to detect the likelihood of a cloud burst and this would be prohibitively expensive. Only the areas likely to receive heavy rainfall can be identified on a short-range scale. Much of the damage can be avoided by way of identifying the areas and the meteorological situations that favour the occurrence of cloud bursts.

Mini cloudburst caused 2019 floods in Kerala

The extreme heavy rainfall of August 2019, which caused heavy landslide and mudslide leading to flooding of downstream areas, was a ‘mesoscale cloudburst (MsCB)’, normally seen in north India and a very rare and unheard of phenomenon in Kerala, says a study published in Elsevier ScienceDirect. On August 2019, due to heavy rainfall in the monsoon season, severe flood affected Kerala. Thousands of people have been evacuated to safer places and relief camps. A total of 121 people have died due to rain-related incidents as of 19 August 2019.

A man stands next to damaged cars after a landslide caused by torrential monsoon rains at Puthumala near Meppadi, Wayanad district, in the southern state of Kerala, India, August 14, 2019. Image Credit: Reuters

What’s mesoscale cloudburst?

The study found that the extreme heavy rainfall of August 2019, which caused heavy landslide and mudslide leading to flooding of downstream areas, was a ‘mesoscale cloudburst (MsCB)’. The phenomenon is normally seen in north India and a very rare in Kerala, the study pointed out.

Researchers at the CUSAT, said that a rainfall exceeding 50mm in two hours was reported in many places of the state from 8am to 10pm on August 8, 2019.

“We looked at 2018 and 2019 heavy rainfall events recorded by multiple sources. In terms of the number of casualties and areas affected, the 2018 Kerala flood is considered a major flood and the flood in 2019, a minor one. However, we suggest that the latter must be looked at as a far more convincing evidence of the regional impact of ongoing global climate change. While the 2018 flood partly resulted from a large excess of monsoon rainfall accumulated throughout the season up to mid-August, the rain pattern that caused the 2019 floods is different,” S Abhilash, director, ACARR- CUSAT was quoted as saying in Times of India.

Gadgil environmental report warnings

According to the study by Western Ghats Ecology Expert Panel (WGEEP), which was constituted by the Government of India under eminent ecologist Madhav Gadgil, several regions in Kerala were classified as ecologically sensitive zones where floods and landslides have been common. The report based on data from the ground and satellite imagery, the Gadgil panel submitted its report in September 2011. The panel suggested strict curbs on mining, timber felling, quarrying and on the use of land for non-forest purposes. However, there was opposition from almost all political parties in Kerala against the report and it has never been implemented.

The Union Environment Ministry later appointed another panel, headed by eminent space scientist K. Kasturirangan, to “examine” the Gadgil committee report in a “holistic and multidisciplinary” manner. The Kasturirangan committee submitted its report in 2013 but watered down the recommendations of the Gadgil panel. The Kasturirangan panel suggested that only a third of the Western Ghats need be identified as ecologically sensitive. It differentiated between natural landscapes and “cultural landscapes. Gadgil said the Kasturirangan panel “destroyed the spirit of his panel’s report”.

NASA Kerala Floods
Before [L] and After [R] images of Kerala after the floods in 2018 Image Credit: Nasa

Human intervention

In an interview with Frontline three years ago, Gadgil said: “Scientists have been saying that on account of global warming there has been an increased prevalence of extreme climatic patterns both in frequency and magnitude… excess and low rainfall. But the disaster in Kerala and probably in Kodagu has been also caused by major and unjustified human intervention in the natural processes, which has gone on unabated [for many years]. This human intervention has increased the magnitude of the damage, be it flooding or landslides, manifold. In Kerala, for example, the proliferation and quantum increase in illegal stone-quarrying activity has resulted in stones and rubble getting into streams and even the rivers, silting them up badly. There has also been large-scale construction, much of it illegal.

“In recent years, stone quarrying has become even more rampant, exceeding all limits. Quarrying and mining are taking place in a very improper fashion.

He said timber felling, improper tree cutting has also had an adverse impact. The forest department’s decision to replace natural forests with monoculture or forests of exotic species has also disturbed the hydrological balance.

Premature silting up of reservoirs

The report also highlighted the premature silting up of reservoirs, especially those in the steep valleys in the Western Ghats States.

“Dams have been unnecessarily constructed or planned to be constructed even where technically and economically unjustifiable. This has caused the drying up of streams and even waterfalls. Our report had strongly opposed the construction of the Athirappilly dam on the Chalakudy river in Kerala’s Thrissur district for these very reasons. Another reason for the flooding has been unscientific and improper water management. This poor management is a prescription for disaster. Reservoirs should be gradually filled up as the monsoon progresses not to the fullest the moment the monsoon starts. Water should be released from the dams into the river as an environment flow to protect river life and systems,” Gadgil said.

Gadgil also pointed out illegal construction as a factor for the disasters. “Kerala has the wetland protection Act [the Kerala Conservation of Paddy Land and Wetland Act, 2008]. But it has not been able to prevent construction of houses and other building in paddy fields and even riverbeds. Paddy fields would act as sponges, but now this water is getting into and flooding concrete houses. The water has nowhere to go,” he said.

‘This could happen again’

While talking about the Kasturirangan report, Gadgil said: “Our report emphasises taking good care of water resources, streams and rivers. The Kasturirangan report ignores this. This will cause havoc on the environment as has been seen in Kerala. The Kasturirangan report has been carried out in an opaque way. It was written for the forest bureaucracy and in a way to increase their [forest bureaucracy’s] powers. Then again, the Kasturirangan report categorises land under the Forest Department as natural landscapes while that under private ownership as cultural landscapes. This is absurd. The ecological system is not confined to or dictated by the ownership of the land.”

When asked whether he foresees such disasters happening again in the state, Gadgil said: “Yes, this could happen again unless there is a drastic reorientation in the way society operates. Right now the greed for enormous profits has resulted in governments being lax in implementing environmental norms. The Central government has in fact been bending over backwards to make sure that the National Green Tribunal does not function properly.”

2018 floods: How dams failed to prevent catastrophe

In August 2018, Kerala experienced one of its worst monsoons, with incessant rains devastating several homes and establishments, killing over 450 people and displacing thousands. All districts were placed on red alert and the Government of India declared the floods a “calamity of severe nature”. According to reports, this was the worst flood since the great flood of 99 which was encountered in 1924. In 1924, 3368 mm rainfall and in the year 2018, 2086 mm rain was received by Kerala.

As the rain intensified in mid-August state authorities were forced to release water from 35 dams to manage rising waters in reservoirs, many of which are used to generate hydroelectricity.

Those living near the banks of Kerala's biggest river, the ‎244 km Periyar, say the sudden opening of dam gates without proper warnings to those living downstream was a big factor in the devastation.

More than half a dozen experts who Reuters consulted were divided on the extent to which dam water spills contributed to the flooding, but almost all, including India's Central Water Commission (CWC), say reservoirs levels were too high ahead of the disaster.

Experts are divided on the extent to which dam water spills contributed to the flooding, but almost all say reservoirs levels were too high ahead of the disaster. The release of dam water, sharply criticised by some water management experts, has put a focus on dam safety practices and the need for better flood mapping and warning systems in India.

State government officials say the severity of the flooding was due to a once-in-a-century storm that could not reasonably have been prepared for, and that the spilling of dam water had little impact.

Kerala’s terrain and climate make it ideal for hydroelectric power projects. The steep slopes of the Western Ghats mountain range that borders the state catch monsoon rain, which is stored in upstream reservoirs on dozens of rivers that flow across the plains into the Arabian Sea.

Dam water releases occurred from 35 dams on multiple rivers in Kerala during the heavy August rain, but it is the releases on the Periyar, the largest river in the state, that have created some of the most controversy.

Kerala floods
Image Credit: Seyyed de Llata/Senior Designer

How reservoirs filled and spilled

Water management experts note state authorities and the Kerala State Electricity Board (KSEB) issued an alert on Idukki's high water levels on July 31, when the reservoir was 92 percent full, but only began a slow release of water on August 9, when levels were at 98 percent. Data shows Idamalayar spills began only when it exceeded its full capacity on August 9.

A government official said blaming KSEB is unfair, as Kerala's dams only have the capacity to store less than a tenth of the state's annual rainfall, and even less in years of extreme rainfall. According to the official, flood warning systems are also not effective in Kerala, where most reservoirs are small in size and steep hills and relatively short river lengths leave no time to react to such freak rain as Kerala was hit.

India's Central Water Commission (CWC) also said the rain in Kerala would have led to flooding regardless of whether water had been spilled from the dams. "The release from reservoirs had only a minor role in flood augmentation," said CWC in a report.

The report noted however, that most of the dams were already "at or very close to" full reservoir levels just before the most intense rain, and it called for a review of water storage norms at all major reservoirs in Kerala. It also shows nearly half the outflows into the Periyar between the peak flood days of August 15 to August 17 were from within the catchment areas of big dams.

Blame game in Kerala

While opposition parties in Kerala have demanded a judicial probe into the release of dam water, state officials have blamed the India Meteorological Department (IMD) for poor forecasts and the release of water into Idukki reservoir from Mullaperiyar - a dam managed by next door Tamil Nadu state - for exacerbating the flooding.

KSEB said forecasts failed to predict the intensity of the rain. "If reliable forecasting is done in respect of very heavy and extremely heavy rainfall, we can manage dam operations very efficiently," said KSEB Chairman N.S. Pillai.

Nayan Sharma, an expert on river engineering and a former professor at IIT Roorkee, told Reuters that hydroelectric dams incentivise operators to stockpile water as turbines are most efficient at full reservoir levels. He advises these be converted to multipurpose dams with bigger storage buffers to mitigate such disasters.

The aftermath of nature’s fury in Kerala

The quaint towns and villages scattered between the lush forests and paddy fields bordering backwaters were turned into communities in despair. Ernakulam district, home to the historic city of Kochi, suffered major flooding, and its busy international airport was shut for nearly two weeks. The low-lying plains around Lake Vembanad were still flooded more than a week after intense rainfall forced KSEB to rapidly ramp-up releases of water from reservoirs. Many parts of Kerala, including Idukki district, were on high alert, and the state again received rainfall, in “large excess” of seasonal levels.

Causes of floods in Kerala

The extreme rains were triggered by a depression toss the Arabian sea resulting in intense convection over Kerala. Many parts of South Asia are hit by a period of heavy rains, especially monsoon, which usually fall between June and September annually. It is caused by a change of wind patterns over the region. Because of this phenomenon, there would be heavy rains in the summer but there would be long dry spells in other months. The monsoon generally provides 70 per cent of India's annual rainfall. However, with the rains being heavy, it can cause sudden flooding as well. With the rain fall being heavy, it can cause sudden flooding as well.

Mining operations are also being viewed as one of the major reasons for changes in environment. According to scientists who conducted studies on disaster-prone areas, soil-piping is a major cause for landslides. High ranges of Kerala will likely be worst hit as pointed out by major environmentalists.

Low pressure brings rain across India

The India Meteorological Department has notified that a western disturbance and formation of two lower pressure systems, one over the Arabian Sea and the other over the Bay of Bengal, will continue to cause rainfall in different parts of the country till October 21. The interactions and heavy wind was primarily the reason that led to torrential rainfall in Kerala in the past 48 hours. It is now expected that these systems, mainly easterlies, may trigger the onset of the northeast monsoon over the south Peninsula around October 26.

"The two low-pressure systems, one over the Bay of Bengal and another over the Arabian Sea for the current spell of rainfall across India, Mohapatra, IMD director general qouted as saying in Times of India. The IMD also updated that a western disturbance lying over Afghanistan and its neighbourhood was interacting with easterlies at lower levels from the Bay of Bengal.

With inputs from IANS, ANI, PTI, Reuters, American Geosciences