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 flooding, based on data collected by Indian Meteorological Department (IMD) between 1969 and 2019. In this 50-year period, Bengaluru Urban recorded 73 flood events while Bengaluru Rural district was not too far behind with 71 flood 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 flooding events. However, all these floods are not the same type, as some districts are on the coast while rivers flow through others.
Districts with most flooding events from 1969 - 2019
| Bengaluru Urban | 73 |
| Bengaluru Rural | 71 |
| Dakshina Kannada | 47 |
| Uttara Kannada | 40 |
| Ballari and Raichur | 36 |
| Kodagu and Kalaburagi | 34 |
Source: IMD
Urban flooding
What makes a landlocked city like Bengaluru vulnerable to flooding?
A senior IMD Bengaluru official explained that there are four types of flooding – coastal, riverine, urban and flash floods. Bengaluru faces urban flooding. “This type of flooding 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 find a route to reach various tributaries,” Mr. Prasad explained.
The other main reason for urban flooding 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 definitely cause flooding,” he said.
Cannot avoid flooding, only mitigate
The official said that avoiding urban flooding in Bengaluru is not a possibility. But, steps can be taken to mitigate its effects.
“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 effect 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 flood 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 identified high flood 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.
