Urban greenprints: Developing a nature-based solutions feasibility framework for Indian cities

This report serves as the primary document that offers a structured methodology for decision-making around nature-based solutions (NbS) in Indian urban coastal regions.

Report structure:
• Main Report (core document)
• Addendum 1 (overview of the policy and governance contexts within which NbS operate)
• Addendum 2 (detailed justification for the NbS decision matrix)

How to navigate this report:
• For policymakers and urban planners: Focus on the Main Report for key findings, policy implications, and strategic recommendations
• For technical experts and researchers: Refer to the Addenda and Appendices for detailed analyses, methodological insights, and ward-level assessments
• For practitioners and project implementers: Use the NbS decision matrix and case studies to inform site-specific interventions and implementation strategies

The Compendium of Nature-based Solutions for Coastal Adaptation complements this report by offering a structured knowledge base for scaling up NbS in urban coastal regions. It aligns NbS strategies with Sustainable Development Goals (SDGs) and existing policy frameworks while providing case studies, implementation insights, and policy recommendations.

Together, this report, addenda, and compendium serve as essential resources for cities aiming to mainstream NbS into climate adaptation and urban resilience planning. Readers are encouraged to engage with these documents holistically to develop science-backed, context-specific NbS interventions that support climate-adaptive and sustainable urban growth.

Summary

This study proposes a nature-based solutions (NbS) feasibility framework to help Indian cities, particularly urban coastal regions, systematically assess and implement climate resilience strategies. Chennai (Tamil Nadu) and Mangaluru (Karnataka) were selected as case studies because of their exposure to flooding, sea level rise (SLR), and extreme weather events.

Overall, 23 wards covering 64.35 sq km in Chennai and 4 wards spanning 15.75 sq km in Mangaluru were analysed for their NbS potential using land use and land cover (LULC) mapping. Key intervention zones included residential areas, public spaces, transportation corridors, and blue-green infrastructure. Rooftops in residential zones present major opportunities for green infrastructure, with a potential increase in NbS areas of 76% in Chennai and 80% in Mangaluru. Permeable pavements in transport corridors could improve urban drainage, offering a 5% increase in NbS areas in both cities. Additionally, water bodies in select wards can be fully leveraged for wetland restoration and buffer zones.

A decision matrix ranked 13 NbS types based on ecosystem benefits, land requirements, and effectiveness of urban coastal adaptation. High-ranking solutions include mangroves and bioretention areas, while green roofs and permeable pavements offer practical options for space-constrained areas.

A cost–benefit analysis was conducted for two interventions: intensive green rooftops and permeable pavements. The results estimate that investing INR 2,203 crore in NbS for Chennai could yield INR 505.31 crore in annual avoided damages, paying for itself in just over 4 years. Without intervention, Chennai risks INR 10,000 crore in climate-related damages over the next 2 decades. In Mangaluru, an NbS investment of INR 172.97 crore could prevent INR 11.62 crore in damages annually, breaking even in 15 years and turning cost-positive by Year 27 owing to smaller-scale interventions. While Mangaluru’s payback period is longer, the long-term benefits in resilience, flood mitigation, and sustainability make NbS a sound investment.

While the findings present a conservative estimate of benefits, they highlight the potential for significant long-term gains. As climate change intensifies, NbS will play a crucial role in mitigating risks and fostering sustainable urban development. Policymakers, urban planners, and stakeholders must prioritise NbS to maximise their ecological and socio-economic benefits, ensuring climate-adaptive urban growth.