Why did the sensors fail during the recent floods?

The state government’s attempt to install sensors in different parts of Bengaluru to get flood alerts suffered a major setback as heavy rains recently pounded the city throughout the night.

In less than 12 hours, half of the city, especially the outskirts, was flooded and many places resembled an archipelago in a sea of water. Still, none of the places where the sensors were implanted to get the alerts had worked, contrary to the government’s claim, raising serious doubts over the project’s workability.

Anticipating the monsoon fury, the BBMP had identified 211 areas and as many as 58 severely vulnerable places prone to urban floods across Bengaluru.

Revenue Minister R Ashoka had previously said that sensors have been installed in 21 stormwater drains (SWDs) and they will send out alerts if the drains fill up 75 per cent.

However, the overnight rains not only exposed the BBMP’s lack of preparedness to tackle the floods, but also the snag in the sensor project, jointly implemented by the Karnataka State Natural Disaster Monitoring Cell (KSNDMC) and IISc under central funding.

Defending the project, B N Prahalad, Chief Engineer, SWD, said the experiment is still in its nascency.

“We, along with experts from KSNDMC, are studying the mechanism. But what happened in the first week of September was similar to a cloud burst and an exception. But the same can be averted by incorporating corrective measures in our experiment to match such a sudden inflow of water,” he said.

Dr Shubha Avinash, scientist (Hydrology), KSNDMC, said the sensors worked well. “As it was installed on a pilot basis and set on test mode, only the chief engineer (SWD) was alerted about the imminent floods. The 26 sensors that are currently in place are only to check if the system is working properly. It is still in the R&D phase,” she said.

Regarding the flooding of Manyata Tech Park, Dr Shubha said the flooding happened upstream before the water reached downstream where the sensors were installed.

“The locations are very different even if there is a distance of 500-600 meters,” she said.

'Will be ready to tackle floods in 2021'

Promising that the entire process of instrumentation procurement and installation of the remaining 105 sensors will be completed by November 2020, Dr Shubha said, “The system will be ready to tackle urban floods by next year.”

Prahalad also added that soon a command centre will be set up at the BBMP to monitor SWDs in all the eight zones. “Real-time water levels in these drains can be seen on the screens so that our officials can take up rescue and relief operations immediately,” he revealed.

But every year, new areas are getting flood-prone in Bengaluru. Earlier, floods were common in Bommanahalli, RR Nagar, and Bengaluru South, but this time, Dasarahalli and areas in the Hebbal Valley falling within the East and Mahadevapura zones also witnessed floods.

Engineers also blamed encroachments of SWDs as a reason for the sudden flooding. Of the 2,626 SWDs, encroachments have been identified in 2016, while nearly 736 encroachments are yet to be removed.