Torrential rainfall and widespread flooding in Gujarat

Gujarat has been grappling with torrential rainfall and widespread flooding, resulting in the deaths of eight people and the displacement of hundreds of residents. On 26 August, the state received 91.3 millimetres of rainfall, which is 1,764 per cent above the average, according to data from the India Meteorological Department (IMD).

Districts in northern and northeastern Gujarat, such as Morbi, Vadodara, Anand, Panchmahal, Kheda, Kutch, Rajkot, Jamnagar, and Mahisagar, experienced heavy rainfall, making them some of the wettest areas. Morbi district recorded the highest rainfall at 206 mm, which is 9,264 per cent above the average for the day.

This extreme rainfall, along with the current floods in many parts of Gujarat and some areas of Rajasthan, has been attributed to a land-based deep depression, exacerbated by moisture influx from either the soil along its path or from the Bay of Bengal and the Arabian Sea.

A deep depression is a cyclonic system with wind speeds of 51-62 km/h that typically forms over the sea as one of the precursors to a tropical cyclone (which has wind speeds of 62-88 km/h). However, its formation and intensification on land is rare.

The rarity of a deep depression forming over land is due to the lack of abundant moisture required for the system to grow in size, generate winds, and accumulate rainfall, as compared to the sea. According to data from the IMD, analysed by Down To Earth, only six land-based deep depressions have formed over India in the last decade.

In the past month, there have been two land-based deep depressions. The first system formed as a cyclonic circulation on 31 July over West Bengal and tracked as far as Rajasthan, where it dissipated on August 6, causing flooding along its path. While the first system moved westward, which is typical for such depressions during the monsoon, the second system has moved southwestward after an initial westward movement, which is unusual.

“The formation of the deep depression is primarily due to the abundant moisture supply from the Arabian Sea, with soil moisture also playing a role in its intensification,” climate experts from the weather blog Vagaries of Weather told Down To Earth.

The state of Gujarat remains on red alert until August 29, with the IMD predicting further rainfall over the coming days.