Climate Change

Karnataka flood trigger: Rainfall 3000% above normal in a single day

Downpour 3176% above normal in Mysuru, 2222% in Dharwad on Aug 8

By Akshit Sangomla
Published: Friday 09 August 2019

On August 8, Karnataka received nearly five times the rainfall it normally does, adding to the severity of the ongoing floods in at least 12 districts that have killed 20 people by August 9, 2019.

The rain has come at a time it normally does not. In some districts it has been multiple times more than the normal for this time of the year:

Mysuru in south Karnataka received 62.2 mm absolute rainfall in a day — 3176 per cent, or 32 times, the long-term average for that day. Dharwad in the north received 85.9 mm — 2222 per cent, or 22 times, above normal.

Kodagu, the worst hit, received 180.3 mm, some 700 per cent more than normal. The region is prone to flooding due to its hilly terrain and had suffered landslides and flash floods the same time last year as well. Coffee plantations there, accounting for 40 per cent of the country’s total production, was severely hit.

Absolute rainfall exceeded 30 mm — more than double the usual — in seven other districts.

The area weighted absolute rainfall for August 8 in these regions is much lower than what the India Meteorological Department (IMD) defines as very heavy rainfall (124.5 mm-244.4 mm) or as extremely heavy rainfall (greater than 244.5 mm). 

Similarly rainfall in the week (August 1-August 7) was 128 per cent more than normal, with many districts crossing the normal mark. Belagavi topped the list with rainfall 652 per cent above normal.

At the same time, Yadgir had a deficit, with only 48 per cent rainfall.

Excess rainfall stands out among the many possible factors that cause or intensify floods. Any particular region can manage rainfall only up to a point, based on its land use and soil holding. Once that is breached, it floods.

The current situation in Karnataka calls for a change in what constitutes ‘heavy’ and ‘very heavy’ rainfall for a particular region in a specific time period as the India Meteorological Department generates flood alerts based on this definition. There are instances where districts have been flooded despite there being no heavy rainfall. 

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