Socio-economic viability of nature-based solutions: a case study in Kolkata

Urban flooding in Kolkata, intensified by climate change and rapid urban development, has been presenting critical challenges, particularly in low-lying areas like Maheshtala and ecologically sensitive zones such as Rabindra Sarovar Lake. This study examines the feasibility and community support for Nature-Based Solutions (NBS) as flood mitigation strategies through Contingent Valuation (CV) to gauge willingness to pay (WTP), and Cost–Benefit Analysis (CBA) to determine socio-economic viability. Maheshtala and Rabindra Sarovar serve as study sites, with a CV survey assessing WTP across three NBS improvement scenarios. Principal Component Analysis (PCA) was utilized to reduce the dimensionality of survey data, identifying core environmental concerns and future expectations that influence community preferences for NBS. The results have shown that issues like poor canal conditions and frequent flooding in Maheshtala, and low water level of the lake and land (including concretization of the park area) and water pollution in Rabindra Sarovar Lake strongly influence the respondents’ willingness to pay for improvements. Further, a Bivariate Probit model was used to assess respondents’ preferences across the three scenarios. In Maheshtala, respondents with frequent exposure to flooding and environmental degradation showed a greater WTP for larger interventions, whereas, in Rabindra Sarovar, higher education levels of the visitors positively correlated with a willingness to contribute to ecological restoration efforts. The CBA identified a positive net present value (NPV) of approximately 22.4 million INR for Maheshtala, indicating long-term viability with a 2% social discount rate. Rabindra Sarovar Lake’s project, however, showed an NPV of around 3.3 million INR, justifying investment at a 19% social discount rate, indicating immediate gains over future. These outcomes emphasize the economic and social feasibility of NBS as flood mitigation strategies in Kolkata. NBS provides a community-supported alternative to conventional flood management. Integrating NBS into urban planning frameworks in Kolkata and similar flood-prone cities could enhance flood resilience and conserve natural ecosystems, promoting sustainable urban development.