In one spell lasting a few hours, the city got as much rain as it did through the whole monsoon season so far.
Between midnight and dawn on Tuesday, the city centre received 128.7 mm of rainfall — the highest for August in more than a decade. This figure matches the rainfall the city received till Monday after the monsoon began, shows Indian Meteorological Department observations.
The numbers, however, hide the localised intensity of rainfall. Figures released by the Karnataka State Natural Disaster Monitoring Centre (KSNDMC), which manages 91 rain gauges in the city, show that rainfall was particularly intense in south Bengaluru where 10 stations recorded rainfall exceeding 124.4mm. The highest was at Bilekahalli where the gauge measured 182 mm while the area stretching from Kumaraswamy Layout to HSR Layout recorded more than 120mm.
In contrast, north Bengaluru remained relatively dry, with Nagawara, Nandini Layout, Sanjaynagar, Horamavu and Yelahanka receiving less than 20mm of rain.
Why south Bengaluru?
Last July, Madivala, B.T.M. Layout and Silk Board junction were inundated. In 2014, Anepalya, J.P. Nagar, Nagarbhavi saw heavy flooding. Is south Bengaluru prone to heavy rains as compared to the rest of the city?
G.S. Srinivasa Reddy, Director, KSNDMC, says, “There is a clear temperature gradient towards the south compared to the north because of the high built-up area in south Bengaluru. This allows for convective movement of water-bearing clouds. Moreover, the city receives much of its rain from depressions in the Bay of Bengal, for which the gateways are the southern and eastern areas.”
G.S. Bhat from the Centre for Atmospheric and Oceanic Sciences at the Indian Institute of Science agrees. Comparative studies have shown that IISc. receives 30% less rain than the centre of the city. “There are multiple factors at play, including heat island effect and wind direction, which is south-west during this season. Moreover, north Bengaluru is at a higher altitude than south Bengaluru. So, rainfall in the north tends to drain out while water stagnates in low-lying areas of Koramangala,” he explained.
More intense rainfall
What meteorologists agree is that extreme weather events — whether in the form of excess, intense rainfall or period of extreme heat — is bound to increase as the effects of climate change become more apparent. “Extreme events have been observed, but the frequency and probability of these occurring are on the rise,” says Prof. Bhat.
