Coastal cities such as Mangaluru and Chennai need to urgently embrace nature-based solutions (NbS) such as wetland restoration, rooftop greening, and permeable pavements to address the escalating challenges of flooding, environmental degradation, and climate-induced vulnerabilities, according to a recent report by the Center for Study of Science, Technology and Policy (CSTEP), a Bengaluru-based think tank.

Titled Urban Greenprints: A Nature-based Solutions Feasibility Framework for Urban Coastal Regions, the report noted that both cities have witnessed a sharp decline in green cover and increased encroachments on natural water bodies. These changes, compounded by extreme weather events, have exposed the limitations of conventional grey infrastructure, such as stormwater drains and concrete embankments. This underscores the urgent need to adopt Nbs as part of a more sustainable and resilient urban strategy, the report noted.

Important findings

The study was conducted in 23 wards of Chennai and four wards of Mangaluru.

Among the main findings is the potential for rooftop greening, which could expand NbS-covered areas by 76% in Chennai and 80% in Mangaluru within the selected study regions. In both cities, the uptake of permeable pavements could enhance stormwater drainage capacity by 5%, reducing surface runoff and mitigating flood risks. Optimising existing waterbodies for flood mitigation, groundwater recharge, and biodiversity emerged as a particularly critical strategy.

”In cities like Chennai and Mangaluru, even modest ward-level investments in green infrastructure can yield substantial long-term savings and ecological benefits. As climate risks intensify, integrating nature-based solutions into urban planning is not just desirable—it is essential for building resilient, adaptive, and sustainable cities,” said Lakshmi Menon, Senior Analyst in the Adaptation and Risk Analysis group at CSTEP.

Economically viable

CSTEP’s cost–benefit analysis demonstrated that NbS interventions are not just environmentally sustainable but also economically viable. In the study area in Chennai, an investment of ₹2,203 crore for select NbS could result in annual savings of ₹505.31 crore in avoided flood damages, with a payback period of just over four years.

In study wards in Mangaluru, a smaller investment of ₹172.97 crore could still generate ₹11.62 crore in annual savings, breaking even within 15 years and becoming cost-positive by 2027.

To translate these insights into action, the report proposed a phased roadmap of urban NbS uptake, which involves engaging local communities, raising awareness, and initiating pilot projects to demonstrate the effectiveness against localised climate risks. The next step is to scale up interventions and align urban development policies with NbS objectives, it stated

The report recommended that policymakers in the study regions embed NbS within their core climate resilience strategies. This includes updating urban planning regulations to accommodate nature-based infrastructure, directing public funds toward NbS projects, and prioritising interventions in areas that are most vulnerable to climate stress. It also urged local governments to take the lead in piloting scalable NbS initiatives, leveraging data and technology for better decision-making, and fostering collaborations across sectors and stakeholders.