Event report: Flood-proofing homes and neighbourhoods

Key pointers from our first Citizen Clinic, where experts addressed specific concerns and questions from citizens on flooding and flood-proofing.

Citizen Matters has published in-depth articles and analyses on understanding the multiple causes of Bengaluru’s flooding this year. So it was only pertinent to engage with citizens to understand the issues they faced in their homes and apartment complexes during the floods, and give them a platform to raise their queries.

Challenges of rain-related problems, such as seepage, weakening foundations, damp basements, soil damage, not to mention potholed roads and footpaths, will predictably become more frequent as rainfall intensifies due to climate change. The first edition of Bengaluru Citizen Clinic, a format in which experts address specific questions from citizens face are address common issues raised by the latter, was conducted in an online meeting on November 4th. The session ‘flood-proofing homes and neighbourhoods’ had a panel of experts answer queries from residents, regarding rain-related problems affecting houses and apartment complexes.

Read more: Explainer: Why we have urban floods and how to stop that

The panelists

The panelists included Anjali Karol Mohan, an urban and regional planner with a PhD in e-governance; Vishwanath Srikantaiah, also known as the Zenrainman, a Bengaluru-based water expert and educator; and Captain Santhosh Kumar, lake activist and an environmental worker for the protection and promotion of rajakaluves (stormwater drains) in water bodies.

Arathi Manay was the moderator of the session.

The panelists gave invaluable insights into the causes of flooding. Climate change alone cannot be blamed for the flooding woes the city faced. Indiscriminate construction, lack of nature-based solutions, garbage dumping in stormwater drains, and faulty urban design were among the many reasons cited by the panelists.

The phenomenon of groundwater flooding

To a question on water seepage into basements and flooding of lower levels, Vishwanath said that a new phenomenon has been observed, not just in Bengaluru but also in Chennai and Hyderabad, which is groundwater flooding. “Typically there is surface water flooding, but now there is groundwater flooding or aquifer-based flooding.”

One solution he cited was to use the open well/aquifer during summers so that the aquifer is depleted, at least by 20% to 30%, in order for it to receive water when it rains heavily. He added that groundwater levels should be two metres below the lowest level of the building, so we need to start using aquifers instead of Cauvery water to reduce groundwater table.

Faulty road design

Anjali addressed a question of how Smart City work in Rhenius Street has elevated the road and affected the drains. This has led to flooding during heavy as well as not-so-heavy rains. “This is happening across cities, especially where there are white-topped roads,” Anjali said. “Road levels are going above house levels. When the roads are laid anew, the contractors need to strip the roads completely before the new road is made. But that does not happen. One possible solution is to increase the porous surfaces.”

Vishwanath added to Anjali’s point that stormwater drains are the most overlooked in road design. He said stormwater drains should be properly designed and should be deep enough to receive rain water.

Read more: Disaster management in Bengaluru: Temporary fixes touted as solutions as city floods again

Entry of sewage into lakes

One concern raised was that overflowing lakes are causing flooding, to which Captain Santhosh said that lakes are important because they are buffers. Whenever there is excess water it has to be stored somewhere, and lakes are important for this. He also said: “Whenever there is excess water, it is supposed to flow into another lake. But if catchment areas are blocked and lakes are not desilted, there will be problems.”

Read more: Study on cascading lakes in Hebbal explains why so many of them have dried up

Sewage entry into lakes is a problem across Bengaluru and Captain Santhosh said that this is because of rampant and irresponsible urbanisation. He said people are dumping garbage into stormwater drains. “You need to understand the difference between a rajakaluve and a sewage drain.”

He also said that there are no quick fix solutions to flooding and that knowledge of the basics is important. For example, it is crucial to maintain lake elevation. “When one lake flows into another lake it is based on elevation, not on pumping,” Captain Santhosh said.

Ensuring surface porousness

To a question on how public spaces should be designed to ensure flood mitigation, Anjali said that open spaces and campuses at the CBD level should be mapped and that only limited concretisation should be allowed. She added that it is important to maintain blue-green infra perspective at the ward level by looking into porous concrete, paver blocks, etc, and highlighted the need to increase surface porousness.

A collapsed drain after rains in October 2020
A collapsed stormwater drain after intense rains in October 2020. Pic: BBMP Commissioner/Facebook

She also spoke of the larger concept of ‘zero discharge’, which is prevalent in some cities, like Hyderabad and Gurgaon, specially in larger buildings where the rain water that falls into a campus is the responsibility of the specific campus, it cannot be discharged into the public drains.

Vishwanath added that rainwater harvesting should be implemented in all institutional and commercial campuses.

Apartments being affected by excessive rain

Addressing concerns around basement flooding, Vishwanath also mentioned that basement parkings have eaten away the aquifer. “We need to identify high groundwater zones.”

Captain Santhosh said that there have been instances of apartment flooding due to unscientific lake restoration and that this aspect needs to be looked into. He also emphasised that constructions are happening, especially in green belts, without proper approval from relevant authorities.

On the issue of garbage dumping into two stormwater drains near an apartment in Sarjapur, Captain Santhosh said, “Lake encroachment and garbage dumping are rampant in these areas. Residents must lodge formal complaints with Darjapur/Dommasandra panchayats for swift action.”

To a query of what can be done if BDA-approved layouts have roadside drains built as per approved plans, but there are no exits to these drains and water logs at the lowest area of the layout, Vishwanath recommended looking at the Dishaank app to check what the rajakaluves are leading to. While Captain Santhosh said BDA approvals also show data on rajakaluves and drains.

Anjali added that BDA/BBMP approvals only talk of roads and sites, not topography, which builders completely change and which affects water flow. What needs to be done is that there should be opening up maps to help people understand the lay of the land and that we have to put in place a process that includes topology in these approvals. She also emphasised the importance of adopting nature-based solutions.

The session concluded with a presentation by Captain Santhosh of a detailed map on how lakes and rajakaluves are interconnected. He explained how cleaning of drains and proper elevations can help prevent flooding. Conversations around lakes and stormwater drains cannot be in isolation, their upstream and downstream forms have to be considered.

Watch the full video here:

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