Maintain city’s lakes to prevent flooding, say experts

How does a “City of Lakes” flood so frequently even after short spells of brief rainfall? While there may be much wrong with the way the city has grown, a group of researchers are attempting to find a way to mitigate the disasters by using its natural terrain.

Veena Srinivasan, a Fellow at the Ashoka Trust for Research in Ecology and the Environment (ATREE), has been working with researchers from the Indian Institute of Science (IISc.), the Norwegian Embassy, and Oracle to study the lakes of the city, how they can prevent flooding, and help groundwater recharge under three different projects.

To understand the lakes and its integration with the water system, her team has initiated hydrological and water quality analyses in Jakkur, Rachenahalli, and Kaikondrahalli lakes, with funding from the Norwegian embassy. Sensors have been placed at the inlets and outlets of the lakes to study how the amount of lake water and treated sewage, untreated sewage, and rainwater changes over time. “We want to create a sustainable model of lake system which can address the water needs of the city in future and also prevent flooding,” Ms. Veena Srinivasan said.

One of the reasons for the widespread inundation is that what was once irrigation tanks carrying only rainwater now carry a significant amount of sewage. “During monsoon, when the storm-water drains bring in rainwater, the lake do not have the capacity to hold it, hence they overflow, flooding the surrounding areas. Adding to this, our rajakaluves are also not continuous or blocked at most places,” she said, adding that we need a two-prong approach — where we plug sewage inlets to the lakes and clear the drains and ensure they are continuous.

The study in collaboration with IISc. focuses on the Cauvery basin and links between lakes and groundwater. ATREE is also working to build a citizens’ dashboard, which will be an online information system of the lakes. “Until now, the debate around lakes have been devoid of data. We are trying to integrate the data collected through the sensors in the lakes into the system so that we can make informed decisions in future for better water and flood management,” said Ms. Veena Srinivasan. Agreeing that a scientific study of lakes is essential, Seema Garg, Chief Executive Officer, Karnataka Lake Conservation and Development Authority, said, “We need to study each lake and create a customised technical plan for it. Also, dredging of lakes needs to be taken up once in two years to prevent flooding.”

Ramprasad, co-founder and convener of Friends of Lakes, said if lakes have been rendered incapable of handling even small rains, the city will continue to witness large-scale inundation.

“The responsibility of the disaster must be shared between the authorities concerned and residents of the city. While the authorities have failed to take up the dredging of both lakes and drains before the monsoon, residents continue to dump garbage into the lakes,” he said.

Every year hundreds of crores of rupees meant for storm-water drains go down the drain. And the result: flooding. Encroachments and blockages of the rajakaluves (big storm-water drains) have spelt disaster for the city.

“The biggest issue is that these SWDs have either been diverted, reduced in width or encroached upon. In some places, natural drains have completely disappeared or reduced by 50%. As a result, the carrying capacity has drastically gone down, resulting in floods,” said A.R. Shivakumar, principal investigator, Karnataka State Council for Science and Technology. Stating that our waterways were once bigger than the roads, he said, today it is just the opposite. This is another reason for flooding. “The authorities concerned must remove the encroachments from SWDs and lake area and allow only fresh water to flow into them. Also, the cascading system of lakes needs to be revived and the lakes reconnected,” he said.

After last year’s flooding, the civic body started an encroachment clearance drive. But, work is progressing at a snail’s pace. Of the 81 acres identified as encroachment along the 800-km SWD, the Bruhat Bengaluru Mahanagara Palike cleared only 11.21 acres as on September 4. Of the 1,953 building identified as encroachments, action has been initiated against 1,225 buildings.

Residents say be it BBMP, BDA or BWSSB, they wake up only after a disaster. “These bodies are very good at disaster management, but not its prevention or mitigation,” said Vijayan Menon, a resident of Koramangala, one of the areas affected by flooding this year. He said unless the government accords as much priority to water management as it does to Metro, things will not change.

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Printable version | Jun 13, 2021 8:17:34 AM |

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