Rising sea imperils India’s ports

By Soumya Sarkar

Water levels at India’s ports are rising much faster than elsewhere in the world, a marker of danger for the country’s infrastructure, coastal communities and ecosystems

Sea levels in some major ports in India are rising at a much faster rate than elsewhere in the world, endangering the ports, increasing the chances of coastal flooding in low lying areas and impacting livelihoods of millions of people who live near the sea shore and river deltas.

The water level at the Diamond Harbour port on the Gangetic delta in West Bengal has been rising at an annual average rate of 5.16 mm in the years between 1948 and 2004, the Ministry of Earth Sciences told Parliament on June 28.

This is almost five times higher than the average sea level rise of 1.3 mm per year along India’s 7,500 km coastline in the past 40-50 years, the ministry said. The global average is around 3.2 mm every year now, having accelerated since the 1990s, when the average rise every year was 2.5 mm.

Diamond Harbour in eastern India is not the only port where the sea level rise is higher than average. At Kandla port in Gujarat on the west coast, the rise has been 3.18 mm every year between 1950 and 2005. At Haldia, another major port on the Hooghly River near the Bay of Bengal coast, the average annual rise during 1972-2005 was 2.89 mm, the ministry said.

Rising sea levels can worsen the impacts of natural hazards such as storm surges, tsunamis, coastal floods and erosion in low lying areas, besides loss of land to sea. In India, where coastal communities number in the millions, accelerated sea level rise spells news of the worst kind. For instance, nearly half the villages in the deltaic fragile islands of the Sundarban Biosphere Reserve are vulnerable to storm surges induced by climate change. 

Relentless rise

Sea level rise is due to climate change. The global sea level has been rising at an average of 1.8 mm every year over the last century, according to the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC).

Ocean thermal expansion and melting ice near the earth’s poles, both attributed to human-caused global warming, have been the dominant contributors to global mean sea level rise since the 20th century, the report said. “The rate of global mean sea level rise during the 21st century will exceed the rate observed during 1971-2010,” the IPCC assessment said. “In the 21st century and beyond, sea level change will have a strong regional pattern, with some places experiencing significant deviations of local and regional sea level change from the global mean change.”

The rate of global sea level rise has been accelerating in recent decades, rather than increasing steadily, according to latest research based on 25 years of NASA and European satellite data. This increase in pace, driven by increased melting of ice in Greenland and Antarctica, could double the sea level rise expected by 2100 compared with estimates assuming a constant rate of sea level rise.

India expects sea level along its coast to rise by as much as 864 mm (2.8 ft) by the end of the century, according to a statement made by the Ministry of Environment, Forests and Climate Change in Parliament in December 2018. Citing studies by the Hyderabad-based Indian National Centre for Ocean Information Services, the government said that the most vulnerable stretches along the western Indian coast are the low lying Khambat and Kutch regions in Gujarat, Mumbai, India’s financial capital, and parts of the Konkan coast and southern Kerala.

Kerala’s coast is vulnerable to sea level rise of 1.75 mm per year, according to estimates by the National Institute of Oceanography. The impact of sea level rise in some parts of Kerala can be significant because of the inundation of the estuarine network along the coast, for instance, in and around the commercial city of Kochi. Even as storms become more intense due to climate change, walls along Kerala’s vulnerable shoreline are insufficient to protect the thickly populated coastal areas. 

Threatened rivers

“The deltas of the Ganga, Krishna, Godavari, Cauvery, and Mahanadi on the East Coast may be threatened, along with irrigated land and a number of urban and other settlements that are situated in them,” the then junior environment minister Mahesh Sharma said in reply to a question raised in Parliament on the threat to coastal villages.

The rivers mentioned by the minister are crucial sources of water in a country that is facing a severe scarcity. Sea level rise could imperil India’s food security as millions of people depend on these rivers, which might be adversely affected by seawater ingress.

The Sundarbans region in India and Bangladesh, home to more than four million people and the world’s biggest mangrove forest, is already showing the worst effects of climate change — coastal erosion, rising sea levels, unpredictable tidal surges, land salinity and more violent cyclonic storms. 

Some of the islands in the Sundarbans archipelago of 102 islands, out of which 54 are inhabited, have already sunk into the sea. Others like Ghoramara and Mousuni, which are thickly populated, are rapidly losing land, and it’s just a matter of time before they too will be lost. The situation is similar in many parts of the Bay of Bengal and Arabian Sea coasts of southern India.

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