Tide flooding in Indian lakes demands a permanent solution

Since December, Lapel Abraham has struggled to deal with life in his flooded home on the shore of Lake Venbanad in Etta, southern India.

He is one of the thousands of people facing severe flooding around India’s longest lake due to seawater invasion caused by a local phenomenon called “Kalakkadal,” meaning “a sea that arrives like a thief.”

“The past four months have been… hellish for us,” Abraham told Scidev.net.

Karakkadal, a term used by Fisher Fork in Kerala after official approval by UNESCO in 2012, is currently adopted for scientific use.

Researchers define kalakkadal as a flood during the premonsoon season (April to May) caused by the expansion waves that produce waves thousands of kilometers away in the Indian Ocean. They say the swell waves can reach 2-6 meters tall.

However, current water levels on Lake Bembanad have remained high since December last year, much before the Karakkadal season.

Another local resident, Rajendran Thavanakkadavu, says people living in the lakeside settlement were forced to abandon their homes due to floods and move them to rental accommodation elsewhere.

Abraham believes that the government’s temporary shelter offer to affected communities will only make the situation worse because of a lack of suitable facilities.

“We want a lasting solution,” he says.

In response to local protests, state government officials held a meeting to discuss the implementation of short-term and long-term projects to avoid flooding. During the meeting, local officials and experts agreed to highlight flooding as a climate change radioactive fallout.

However, experts say that predicting the arrival of swell waves is difficult.

M. Balakrishnan Nair, director of the National Maritime Information Services Centre for India at the Ministry of Earth Sciences, says researchers have recently discovered that Swells have reached Indian coasts from a distance from the Atlantic Ocean.

“Swelling in the ocean is not caused by local winds, but by distant weather systems such as storms, hurricanes and long periods of strong winds,” explained Sanjay Balachandran, a researcher in Kerala Fisheries and Marine Research.

“During these storms there is a significant movement of energy from the atmosphere to the ocean, creating large waves.”

The waves could travel thousands of kilometers before reaching the Kerala coast, shocking the coastline all the way through the storm, adding Balachandran.

The water rises

Previously, scientists believed that Karakkadal was confined to the Kerala-Tamilnadu coast. But now they have noticed that it is happening in various places on the eastern and west coast. It has also been reported in Bangladesh.

N. Sanjeevan, former director of the Indian Ministry of Earth Sciences’ Centre for Marine Biological Resources and Ecology, says the expansion waves caused by ocean currents, rising sea water temperatures and thermal expansion of water in the Arabian Sea contribute to rising seawater levels in Lake Venbanada.

“The water levels at Lake Bembanad remain high as they are not discharged into the ocean,” he explained.

“The difference between the tide amplitude, or the level of tide rave, which stood at one metre in the coastal area, rose to 1.6 metres, flooding around the lake,” Sanjeevan added.

According to Kerala Fisheries and Marine Research, around 400 million cubic meters of silt accumulated in Lake Benbanad, significantly reducing the storage capacity to 385 cubic meters from 2,678 cubic meters in 1930 in 2020.

In 1900, the lake, which covers an area of ​​365 square kilometers, was reduced to 206.4 square kilometers. Its average depth dropped from 8 to less than 3 meters.

The disappearing beach

Predicting the arrival of a surge in swells in the Indian Ocean is “a painless task,” the researchers said in a study published in 2021. They found that implementing altimeter assimilation in local wave prediction systems significantly improves swell prediction.

However, measures to reduce damage are urgently necessary.

Sanjeevan says he doesn’t think that removing silt from the lake is a solution, as it leads to higher invasion of seawater.

KV Thomas, director of the Department of Marine Sciences at the National Center for Geosciences, was the first person to report the phenomenon of Karakkadal in 1984.

“The disappearance of the beach caused chaos on the coast, leading to the invasion of kalakkadal, flash floods and seawater into the lake,” Thomas told Scidev.net.

“Reproducing natural beaches and building dunes is one of the solutions to consider.”