‘Bengaluru most vulnerable to urban ooding’
Amongst all the districts in south India, except for a few in Kerala, Bengaluru Urban district is the most vulnerable (0.57 vulnerability index) to ¢ooding, based on data collected by Indian Meteorological Department (IMD) between 1969 and 2019. In this 50year period, Bengaluru Urban recorded 73 ¢ood events while Bengaluru Rural district was not too far behind with 71 ¢ood events.
Bengaluru Urban and Rural districts are followed by Dakshina Kannada (47), Uttara Kannada (40), Ballari and Raichur (36), and Kodagu and Kalburgi (34) when it comes to ¢ooding events. However, all these ¢oods are not the same type, as some districts are on the coast while rivers ¢ow through others.
What makes a landlocked city like Bengaluru vulnerable to ¢ooding?
A senior IMD Bengaluru o¡cial explained that there are four types of ¢ooding – coastal, riverine, urban and ¢ash ¢oods. Bengaluru faces urban ¢ooding. “This type of ¢ooding is very common in cities due to increased urbanisation,” A. Prasad, scientist, IMD Bengaluru told The Hindu.
“Due to increased demand for land and increasing population, urbanisation is on the rise in cities like Bengaluru. Due to this, rainwater often does not go where it is supposed to go, as it cannot nd a route to reach various tributaries,” Mr. Prasad explained.
The other main reason for urban ¢ooding in Bengaluru is thunderstorms accompanied by heavy rainfall. “Bengaluru generally gets heavy rainfall, along with thunderstorms in a short period of time. Such thunderstorms are reported most often in May and September. During an inundation episode in Bellandur in 2022, the city received 80 mm of rainfall in just one hour. This kind of rainfall will denitely cause ¢ooding,” he said.
‘Cannot avoid flooding’
The o¡cial said that avoiding urban ¢ooding in Bengaluru
is not a possibility. But, steps can be taken to mitigate its e¥ects.
“Instead of how the weather will be, we (IMD) have started issuing impact-based forecast as to what the weather will do, as the rain does not have the same kind of e¥ect in every region. We (IMD) issue warnings in advance, which can help in improving the response (to an event),” Mr. Prasad explained.
Experts agree that with factors like intensity of rain and crusting of the city increasing, strategic planning is necessary to keep ¢ood events at bay in the future.
“Karnataka State Natural Disaster Management Centre (KSNDMC), Bruhat
Bengaluru Mahanagara Palike (BBMP), and Indian Institute of Science (IISc.) have jointly conducted a study. They have identied high ¢ood areas along the storm water drains of both Vrushabhavathy and Dakshina Pinakini rivers. There are 250 hotspots that are currently in the red zone. The objective is to bring them to orange, and then green. Having adequate width of drainage to carry the water to a lake or river plays an important role in this strategy,” said S. Vishwanath, water conservation expert.
He stressed on the importance of recharging ground water. He suggests ensuring that rainwater harvesting laws are strictly followed.