As global warming accelerates, the oceans are rising faster than ever, threatening the lives and livelihoods of millions of people who live in coastal cities around the world. In India, a recent study has found that Chennai and Kolkata are at particular risk due to sea-level rise, which could exacerbate existing social and environmental problems and pose new challenges for urban planners and policymakers.

Understanding the Science of Sea-Level Rise

Sea-level rise is caused by the thermal expansion of seawater as it warms up and the melting of glaciers and ice sheets, which adds more water to the oceans. According to the latest report by the Intergovernmental Panel on Climate Change (IPCC), the global mean sea level has already risen by about 20 cm since 1900 and is projected to rise by another 30-110 cm by the end of this century, depending on how much greenhouse gases we emit and how much we can adapt to the changing climate.

However, the impacts of sea-level rise are not uniform across the world, as local factors such as land subsidence, sedimentation, storm surge, and tides can amplify or mitigate the effects. For example, some parts of India’s coast are sinking due to natural and human causes, such as groundwater extraction, while others are rising due to tectonic uplift. Moreover, the vulnerability of coastal communities depends on their exposure, sensitivity, and adaptive capacity, which vary widely depending on their social, economic, and ecological characteristics.

Examining the Risks and Impacts for Chennai and Kolkata

To assess the risks and impacts of sea-level rise for Chennai and Kolkata, a team of researchers from India and the United States analyzed various datasets and models of climate, hydrology, geology, and society. Their findings are summarized below.

Exposure: How Much of the Coastline is at Risk?

In Chennai, the researchers found that about 60% of the coastline is exposed to a sea-level rise of 1 meter by 2100, which is the upper end of the IPCC’s scenario range. This includes densely populated areas such as Adyar, Besant Nagar, and Thiruvanmiyur, where more than 1 million people live and work. In Kolkata, the exposure is lower, but still significant, with about 30% of the coastline at risk.

Sensitivity: How Vulnerable are the People and Places?

In Chennai, the researchers identified several factors that increase the sensitivity of the people and places to sea-level rise, such as poverty, informal settlements, inadequate infrastructure, water scarcity, and pollution. For example, many of the slums and low-lying areas in the city are already prone to flooding and waterlogging, which could worsen with sea-level rise. Moreover, the groundwater resources are already overexploited, which could lead to saltwater intrusion and other ecological impacts.

In Kolkata, the sensitivity factors are different but equally important. The researchers found that the city’s historical and cultural heritage, as well as its port and shipping activities, are at risk from sea-level rise. For example, the iconic Howrah Bridge, which spans the Hooghly River, could be affected by higher tides and storm surges. Moreover, the Sundarbans, the largest mangrove forest in the world, which is located downstream of Kolkata, is already under threat from climate change and sea-level rise, which could affect the livelihoods of millions of people who depend on its resources.

Adaptive Capacity: How Able are the People and Institutions to Cope?

In Chennai and Kolkata, the researchers identified several examples of adaptive capacity, which could help the people and institutions to cope with sea-level rise. For example,

In Chennai, some of the adaptive measures include the construction of seawalls and groynes, the desilting of stormwater drains, and the restoration of wetlands and mangroves. Moreover, some of the communities have developed their own coping mechanisms, such as building raised platforms and using boats to navigate flooded streets. However, these measures are often limited in scope and effectiveness, and require more support and coordination from the government and other stakeholders.

In Kolkata, some of the adaptive measures include the dredging of the riverbed and the construction of embankments and sluice gates, as well as the relocation of some of the vulnerable communities to safer areas. Moreover, some of the NGOs and research institutes have developed innovative solutions, such as floating gardens and rainwater harvesting systems, to address the water and food security challenges. However, these measures also face various obstacles, such as lack of funding, technical expertise, and political will.

Recommendations for Addressing the Risks and Impacts

Based on the findings of the study, as well as the broader literature and policy discourse on climate adaptation and urban resilience, we recommend the following actions to address the risks and impacts of sea-level rise for Chennai and Kolkata:

1. Enhance the scientific knowledge and communication of sea-level rise and its local effects, by conducting more research and outreach on the causes, consequences, and uncertainties of the phenomenon, as well as the options for reducing the risk and increasing the resilience.
2. Strengthen the institutional and governance frameworks for climate adaptation and urban resilience, by developing and implementing policies and plans that integrate the risks and impacts of sea-level rise into various sectors, such as land use, water management, transportation, energy, and public health, as well as involve the participation and feedback of the local communities and stakeholders.
3. Invest in the infrastructure and services that can reduce the exposure, sensitivity, and adaptive capacity of the people and places, by prioritizing the funding and implementation of the measures that have the greatest benefits and co-benefits, such as green and blue infrastructure, smart and inclusive mobility, and low-carbon and circular economy.
4. Promote the social and environmental justice and equity, by ensuring that the climate adaptation and urban resilience strategies and actions do not exacerbate the existing inequalities and injustices in the society, but rather address them in a transformative and participatory manner, that empowers the marginalized and vulnerable groups and promotes the public goods and common goods.

Conclusion: Collaborating for a Sustainable and Resilient Future

In conclusion, the risks and impacts of sea-level rise for Chennai and Kolkata are significant and complex, but can be addressed through a comprehensive and collaborative approach, that combines the best available science, policy, and practice. By working together, across different disciplines, sectors, and scales, we can create a more sustainable and resilient future, for ourselves and for the generations to come.