11-07-2025
Nature-based solutions can help Kolkata tackle urban flooding
Written by Soumit Pandey, Ranjana Ray Chaudhuri and Sukanya Das
As Kolkata braces for another monsoon, scenes of waterlogged streets and overwhelmed drainage systems return with grim familiarity. Urban flooding is now an annual ordeal, disrupting lives, damaging infrastructure, and straining public health systems. Natural buffers, like canals, wetlands, and lakes, that once helped manage excess rainwater are now clogged, concretised, or encroached. Amid growing climate threats, Kolkata must consider a sustainable alternative: Nature-Based Solutions (NBS).
NBSs are interventions that work with natural systems, like restoring wetlands, planting native vegetation, or reviving water bodies to mitigate environmental hazards. Unlike conventional grey infrastructure (concrete embankments, pumps, stormwater tunnels), NBSs provide multiple benefits. They absorb rainwater, recharge groundwater, improve biodiversity, and offer green public spaces. Critically, they are cost-effective and inclusive, especially when communities are involved in their design and upkeep.
Our recent study from the TERI School of Advanced Studies assessed the socio-economic viability of NBSs in two contrasting areas: Maheshtala and Rabindra Sarobar Lake. Using household surveys and ex-ante cost-benefit analysis (CBA), we explored public awareness, perceived benefits, and the long-term financial feasibility of NBS interventions.
In Maheshtala, a flood-prone municipality with ten irrigation canals connected to the Hooghly River, we proposed a localised version of the Dutch 'Room for River' model. Restoration activities such as canal dredging, waste removal, and rainwater harvesting aim to reduce waterlogging and improve water quality. More than 70 per cent of surveyed households expressed willingness to pay higher municipal taxes for these interventions. The project showed a positive net present value (NPV) of Rs 22.4 million at a 2 per cent social discount rate, reflecting a long-term outlook that values sustainability and resilience.
At Rabindra Sarobar, a prominent urban lake in southern Kolkata, we proposed ecological restoration including de-siltation, tree planting, de-concretisation, and local rainwater harvesting. While better maintained, the lake faces issues like declining water levels and pollution. About 60 per cent of respondents, primarily educated visitors, were willing to voluntarily contribute to conservation efforts. The intervention had a positive NPV of Rs 3.3 million at a 19 per cent social discount rate, indicating strong short-term returns, likely due to the lake's visibility and recreational value.
Despite differences, both sites showed strong public recognition of NBSs as effective flood solutions. In Maheshtala, daily struggles with flooding drove support; around Rabindra Sarobar, the emphasis was on ecological preservation. The common thread was public willingness to support sustainable infrastructure.
However, implementing NBS citywide comes with challenges. Land acquisition, bureaucratic coordination, and public scepticism can delay progress. Our study also found that perceived risks, such as displacement, significantly reduced willingness to pay. Transparent planning and early community involvement are, therefore, essential.
The case for NBSs in Kolkata is not just ecological; it's economic and strategic. Climate change is intensifying extreme rainfall, exposing the limitations of outdated grey infrastructure. NBSs can bridge this gap. By integrating them into urban planning through tax incentives, zoning reforms, and civil society partnerships, Kolkata can become more resilient and livable. Kolkata is still green; we need to preserve the green corridors to enhance the city's resilience.
As climate risks escalate, the question is no longer whether to act, but how. The answer lies in nature. By investing in NBSs today, we can create a safer, greener Kolkata, one that is prepared not just for the next monsoon, but for the future.
Pandey is a Junior Research Associate at Ashoka Centre for a People-Centric Energy Transition (ACPET). Ray Chaudhuri is Associate Professor & Head, Department of Regional Water Studies and Department of Natural and Applied Sciences, TERI School of Advanced Studies, New Delhi. Das is Professor, Department of Policy and Management Studies, and Dean (Research & Partnerships), Teri School of Advanced Studies, New Delhi
