Thodupuzha: Experts have warned that Sunday’s extremely heavy rain and flooding in rain shadow areas such as Vattavada, which have not traditionally experienced major rain-related disasters, could be an indication of changing climate patterns.

Located along the Tamil Nadu-Kerala border on the eastern side of the Western Ghats, Vattavada generally receives less rainfall than other parts of the region. However, meteorological experts say the sudden, intense rainfall was caused by cumulonimbus clouds (dense clouds that develop vertically) forming over the mountains as moist air moved in from the east amid rising atmospheric temperatures associated with climate change.

The impact of climate change on rain shadow regions is a cause for concern. Strengthening local monitoring systems in Kerala is essential to identify sudden episodes of extremely heavy rainfall, said Prof. S. Abhilash, director of the CUSAT Advanced Centre for Atmospheric Radar Research.

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An orange alert was issued for Idukki on Sunday, along with a warning of heavy rainfall of up to 115 mm. Although light rain had been reported in the district from Sunday morning, such intense rainfall was not expected in areas such as Vattavada. Around 4.30 pm, cloud formations began developing over the Kottakamboor region. Two people died in landslides triggered by the sudden rainfall.

Scanty monitoring system

The exact amount of rainfall received in Vattavada, where the accident occurred on Sunday, could not be ascertained due to the lack of adequate monitoring infrastructure.

The Meteorological Department has rain gauges at only six locations in the district. Some taluks also have automatic rain gauges installed by the Disaster Management Authority. In addition, rainfall is monitored at estates in Elappara, Peerumedu and Bison Valley.

Sudden heavy rainfall has caused accidents in several parts of the district since 2017. On August 1, a homemaker died in a landslide of a similar nature in Kudayathoor.

Cumulonimbus clouds can produce intense rainfall over highly localised areas. However, many panchayats have not been paying adequate attention to such localised weather events, experts said.

Rain shadow region

When moist winds hit the mountains, they rise upwards and cool, resulting in cloud formation and heavy rainfall on one side of the mountain range. By the time the air crosses the mountains and reaches the other side, much of its moisture has been lost. The descending air then becomes warmer and drier, making it difficult for rain-bearing clouds to form.

Vattavada, Marayoor, Kanthalloor and Chinnar are among the rain shadow areas located on the eastern slopes of the Western Ghats in Kerala.