THOOTHUKUDI: The state disaster management machinery and the administration alike were caught off-guard during the recent flooding of Thamirabarani, which wreaked havoc in Tirunelveli and Thoothukudi districts. It is, however, noteworthy that the river has been prone to flooding, especially during the northeast monsoon, say the data available since the 19th century.
According to data from 200 years ago, three-fourth of the annual rainfall for the composite Tirunelveli district, consisting of Tirunelveli, Thoothukudi and Tenkasi, is received during the months of October, November, and December - or during the northeast monsoon season. With the exception of floods that occurred in April 1847, the calamities recorded in 1810, 1827, 1847, 1867, 1869, 1874, 1877, 1880, 1895, 1914, 1923, 1925, 1931 and 1992 took place during the NE monsoon.
The year of 1877, as per HR Pate’s Madras District Gazetteers — Tinnevelly Volume 1, witnessed a climactic catastrophe with Tirunelveli district recording two floods, a famine, and a cholera outbreak all in one year. Already reeling under the death of 54,000 people due to the famine and 14,400 to cholera, which had impacted the 1881 population census, a series of torrential rain in December exacerbated the situation.
The first spell of rain was recorded on December 5, followed by the second spell on December 17. Rains during the first episode saw water level rise up to 27 feet at Tirunelveli bridge, while another spell on December 17 recorded water level 15 inches higher than the first floods. This was the highest ever recorded.
The NE rains also fill tanks and satiate dry fields, Pate had observed 100 years ago noting that even though the Thamirabarani valley receives hefty rainfall, the district is one of the driest in the Madras Presidency. The average rainfall recorded in composite Tirunelveli district was 670.81 mm between 1871 and 1880, 689.86 mm in 1881-1890, 605.28 mm in 1891-1900, and 666.45 mm in 1901-1910.
Data from the ministry of earth and science show that Tirunelveli district has faced floods whenever rainfall has crossed the 300 mm mark in October, November and December. The region has been prone to flooding whenever NE monsoon exceeded 700 mm in Tirunelveli and 500 mm in Thoothukudi. Both regions witnessed flooding in 1914, 1923, 1925, 1931, and 1992. The month of December, in particular, has proved to be a critical period. Parallels can be drawn between the deluge in 1914 and 2023, since both witnessed breaching of major waterbodies in areas between Srivaikuntam and Authoor, and Alwarthirunagari to Tiruchendur, in addition to impacting agriculture. Communication between the remote areas and the mainland was also disrupted in 2023.
In 1914, Tirunelveli had recorded an annual average rainfall of 1,365.5 mm, while 1,353.3 mm was gauged in Thoothukudi in 2008 — the respective highest recorded rainfall. The average NE monsoon rain had doubled in 1914 in Tirunelveli, and in 1902, 1914 and 1940 in Thoothukudi district, the data revealed. Commenting on the developments, T Raja, a private weather researcher, told TNIE that the sea surface temperature was high in the Gulf of Mannar, Southeast Arabian Sea and Kanniyakumari sea.
“Being in the El Nino phase for the Indian ocean region, the air circulation moved towards southern Tamil Nadu due to positive Indian Ocean Dipole (IOD), that is, higher temperature in western Indian ocean region compared to the eastern Indian ocean”. Many rainfall that struck the southern peninsular has had the IOD impact in the past, said a weather researcher.
Raj Baghat, a geoanalytics expert, said extreme rains are inevitable. Dams have played a vital role in mitigating flood-induced damage in the 20th century, he said, adding, “The existing infrastructure is not capable of withstanding such extreme events.” Bhagat advises governments to have a long-term vision while formulating disaster management schemes.