What Caused Heavy Rains and Landslides in South Kerala in October?

The IMD has found that Kerala has already received 84% of its share of what should have been the northeast monsoon.

(Photo: The Quint)

After two years, rain fury has returned to flood several parts of central and southern Kerala districts. The incessant rainfall has caused flash floods and landslides, with at least 27 dead and hundreds displaced.

The Indian Meteorological Department (IMD) has warned of more rains this week.

The torrential rains have brought back memories of the devastating August floods of 2018 and 2019. But why is this havoc being wreaked in mid-October?

What Caused the Havoc?

On 14 October, a low-pressure system developed in the east-central Arabian Sea and began moving closer to Kerala coast. Since then, Kerala has been receiving heavy to very heavy rainfall ranging from 115.5mm to 204.4mm in 24-hours, and extremely heavy rain (over 204.4mm in 24hours).

On Saturday, between 12 pm and 6 pm, Thodupuzha received 145 mm rainfall, Cheruthoni 142.2 mm, Konni 125 mm, Thenmala 120.5 mm, Vyanthala 95 mm, Kottarakara 77 mm, and Pallurthy 66 mm.

The IMD has found that Kerala has already received 84% of its share of what should have been the north-east monsoon.

Is the SW or NE Monsoon the Cause?

The IMD has not yet announced the retreat of the south-west monsoon from Kerala, nor the setting in of the north-west monsoon.

The south-west monsoon in Kerala should have ended by the end of September. October to December is the time of the north-east monsoon. This year, the pattern seems to have been disrupted because the south-west monsoon has not yet retreated, and the north-east monsoon has not yet set in.

Usually, the south-west monsoon begins to retreat from Rajasthan by 17 September and from the southern states by 15 October. Meteorologists noted that this year south-west monsoon retreated from Rajasthan quite late, only by 6 October .

However, it is interesting to note that neither is the cause of the rain.

This is also not because of tropical cyclones that usually happen in October and November.

Unexpected Rains Caused by Heating Up of Arabian Sea

Meteorologists have concluded that the rainfall is mainly a localised phenomenon triggered due to the low-pressure system formed in the Arabian Sea.

Research director and professor of Bharti Institute of Public Policy and Indian School of Business Dr Anjal Prakash, who has been studying the rise in unexpected cyclonic activity in the southern coast for the past five years, attributed the cause to the warming up of the Arabian Sea.

"A study has revealed that global warming has led to the sinking of the ocean. Because of the increase in carbon emissions, the ocean is warmer and acidic. This warming of the ocean has led to an increase in cyclonic activity. We have found that over 38% of the population is vulnerable to the impact of this increase in sea temperature," he told The Quint.

The heating of the Arabian Sea is linked to the southern Indian Ocean, which in turn is connected to the Pacific Ocean system.

"Earlier, we used to hear about cyclones in Andhra Pradesh or the Odisha coast, but never in the Arabian Sea. In the past two-four years, the surface temperature in the Arabian Sea is increasing and that is why the coast that was not prone to such extreme conditions is now witnessing a number of cyclones," said senior journalist K A Shaji.

Lack of Response to Scientific Reports Calling for Immediate Action Worrying: Experts

This is the fourth successive year that we are seeing flash floods and incessant rains in the state.

What is worrisome is the lack of response to scientific reports calling for immediate action, opined weather experts.

Prakash explained that the staggered delay in the monsoons and variability in rainfall is a direct consequence of climate change.

When we studied the ecological impact of the Western Ghats, we found that the highest number of vulnerable zones are in Kerala. There are 44 major rivers and tributaries flowing through Kerala, of which 10 have been identified as most vulnerable to flooding. We have the knowledge, but the action plan needs to be drafted, corroborating with the scientific knowledge we already have," he added.

"Many are calling this a consequence of climate change and so we can't do anything about it. But that is not true. You cannot control the rains. But it is the unplanned urbanisation and deforestation that has blocked the flow of water. The dams are not able to work efficiently because of soil erosion, which has been triggered by deforestation and destruction of wetlands. If there is no large-scale afforestation, then Kerala is in serious trouble," said Shaji.

A senior meteorologist said that the state and central government have been quite lethargic in their attitude and need to address the issue at the earliest "before Kerala is submerged in water and debris".

Environment activists demanded that a separate ministry be set up to address climate change in the country.