Unchecked urban expansion has resulted in significant land-use and land-cover changes, leading to deforestation and reduction in green spaces. These factors exacerbate the impacts of climate change, particularly in India's coastal cities, where effects are more intense and widespread.
For instance, the loss of vegetation and wetland ecosystems in urban areas have intensified the urban heat island effect, increasing communities' vulnerability to flooding and water scarcity. It disproportionately affects marginalised groups, especially those living in informal settlements without adequate infrastructure or access to resources, thereby worsening socio-economic inequalities.
The Center for Study of Science, Technology, and Policy (CSTEP), a Bangalore-based policy think tank, conducted granular analyses of India’s coastal cities, Chennai and Mangalore, to strategise on investments and the implementation of nature-based solutions (NbS).
CSTEP’s study, "Urban Greenprints: A Nature-based Solutions Feasibility Framework for Urban Coastal Regions," identified areas for NbS intervention in coastal cities to effectively address climate risks. These solutions are cost-effective and offer both environmental and social benefits.
The NbS approach is defined as actions that protect, sustainably manage, and restore natural or modified ecosystems that address social needs and simultaneously benefit people and nature.
Over a period, coastal cities like Chennai and Mangalore have experienced a sharp decline in green cover and increased encroachments on natural water bodies. The conventional grey infrastructure, such as stormwater drains and concrete embankments, revealed their limitations in mitigating disasters.
The report’s 27 ward-level analyses pinpointed areas within wards where comprehensive NbS strategies that effectively utilise both aquatic and terrestrial resources are needed.
The CSTEP report analysed the climate vulnerabilities of India’s coastal cities, focusing on 23 wards of Chennai and four of Mangaluru.
Researchers micro-analysed each ward area and recommended NbS interventions. For instance, open spaces in the Kathivakkam ward in Chennai constitute approximately 2% of the area, and were identified as having potential for NbS implementation.
Further, researchers analysed that 46% of the ward areas are residential. They underline the NbS opportunity, such as rooftop greening in 39.30% areas and permeable pavement in 6.93% asphalt areas. Transportation-related land use accounts for 7.11% of the wards, and green areas comprise a small portion of around 0.16%.
A similar detailed evaluation was conducted for 27 wards in Chennai and Mangaluru. This analysis highlights the potential for integrating NbS interventions, especially in residential and open spaces, to enhance urban resilience against flood risks.
The study evaluates the feasibility and impact of NbS interventions. Among its main findings is the significant 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 implementation of permeable pavements could enhance stormwater drainage capacity by 5%, thus reducing surface runoff and mitigating flood risks.
The report states these recommendations can also be implemented in other Indian coastal cities too. These cities have significant potential to implement NbS activities, such as rooftop greening and the installation of permeable pavements, which can help mitigate climate risks in the long run.
In addition, the study emphasises the need to optimise existing water bodies for flood mitigation, groundwater recharge, and biodiversity, identifying this as a critical strategy that should be adopted.
Finally, it recommends integration of NbS into urban planning to counter the escalating challenges of flooding, environmental degradation, and climate-induced vulnerabilities. It underscores the urgent need to adopt NbS—like wetland restoration, rooftop greening, and permeable pavements—as part of a more sustainable and resilient urban strategy.