This monsoon, the civic body will get real-time updates on water levels in stormwater drains (SWDs) at most flood-prone spots. After the success of a pilot project, the Karnataka State Natural Disaster Monitoring Cell (KSNDMC) is all set to install telemetric flow gauges in 25 flood-prone SWDs across Bengaluru. Information from these gauges will help the Bruhat Bengaluru Mahanagara Palike (BBMP) act quickly to mitigate inundation.
Telemetric flow gauges are sensors installed along the retention walls of SWDs. They can monitor and send alerts on water flow level to a server every 15 minutes.
“After we analyse the topography of the area and the dimensions of the drain, we will fix a flood alert level. The device starts sending out messages as the water level approaches the flood level. These messages will be accessible through an app,” said Dr. G.S. Srinivasa Reddy, Director, KSNDMC. In times of heavy rain, they can be adjusted to send an alert every minute. As part of the pilot project, the disaster monitoring cell had installed seven flow gauges in SWDs connecting the Hulimavu lake system in 2018. The project was taken up after the floods of July 2016 when Hulimavu and Madiwala lakes overflowed.
Drain stretches are being categorised into red, orange and green zones based on their potential for overflowing and flooding. The KSNDMC and BBMP have identified 201 flood-prone points, of which 25 SWD stretches have been identified in the first phase.
Each flow gauge costs around ₹32,000. “The equipment will be placed in a house nearby. The house-owner will be paid ₹2,000/month towards electricity expenses. Round-the-clock power supply has to be ensured,” he said.
While the mechanism for timely alerts will help, residents in flood-prone areas, who saw their homes damaged in 2016, question whether agencies have a dynamic mechanism to manipulate water flow to prevent floods in real time.
The KSNDMC envisages restoring interconnection between lake systems and flood-gates to manipulate water levels. “Such a measure can help increase the water holding capacity of the city and mitigate flooding to a large extent. We are also recommending digging up recharge wells to ensure we use flood water as a resource to recharge the underground water table,” said Shubha Avinash, scientific officer, hydrology, KSNDMC.
Water conservationist S. Vishwanath said most of the large SWDs are unlikely to overflow. More often than not, inundation occurs when drains are blocked, especially by garbage.
“With a robust weather forecast and flow gauges, the BBMP needs to push as many SWD stretches from red and orange zones into green, which in effect will mitigate floods,” he said.
According to B.S. Prahlad, chief engineer, SWD, BBMP, the annual maintenance of SWDs had already been approved and work will be taken up. “The real-time rain forecast and water level updates will help us be better prepared,” he said, adding the civic body will soon launch a special drive to discourage citizens from dumping garbage in drains.