14 Million Indians at Risk: UN Warns of Permanent Inundation in Kolkata, Mumbai

Key Takeaways:

• More than 14 million people across the low-lying deltas of Kolkata, Mumbai and Dhaka face an immediate risk of losing their homes to permanent inundation, according to the UN.
• Global sea levels rose by an average of 4.7 mm per year from 2014–2023, before recording a 5.9 mm rise in 2024.
• Around 770 million people globally, or roughly one in ten, live less than five metres above the high-tide line.
• For Mumbai and Kolkata, rising baseline sea levels can compound the effects of high tides, coastal flooding, storm surges and other weather-driven hazards.

A terrifying warning has alarmed a large community of Indians living along river and sea coastlines, raising questions about the growing risk faced by nearly 11 million people. For families who have lived along the tidal edges of Kolkata and Mumbai for generations, the sea has always been a neighbour to be respected. A new United Nations report suggests that neighbour is now closing in faster than at any point in recorded history, and the numbers behind that warning are hard to ignore.

The UN Warning

A report from the UN Secretary-General, released this week, finds that more than 14 million people across the low-lying deltas of Kolkata, Mumbai, and Dhaka are at immediate risk of losing their homes to permanent inundation. The report frames this as a defining, human-scale impact of sea-level rise in South Asia, distinct from the trillion-dollar infrastructure losses projected for wealthier coastal cities like Miami, New York, and Guangzhou.

The pace driving this risk is itself accelerating. Global sea levels rose by an average of 4.7 millimetres a year between 2014 and 2023, and that rate jumped to a record 5.9 millimetres in 2024 alone, driven by warming oceans and melting glaciers. Zoomed out further, the UN estimates that around 770 million people, which is roughly one in ten people on Earth, already live less than five metres above the high-tide line, making this a global exposure problem with a distinctly South Asian front line.

Is Permanent Inundation Really Coming?

The honest answer is yes, but not the way headlines might suggest. "Immediate risk," as used in the report, describes severe and growing structural vulnerability — not an overnight submersion of entire cities. The report does not put a date on when, or if, these areas would be permanently underwater.

The real danger lies in compounding factors. Mumbai's reclaimed coastal land and Kolkata's low, delta-based geography make both cities unusually sensitive to the combination of rising seas, land subsidence, high tides, and intensifying monsoon storm surges — each factor amplifying the others rather than acting alone.

Long before any area is submerged around the clock, it can become functionally unlivable. Chronic tidal flooding, saltwater creeping into drinking-water sources, and drainage systems overwhelmed beyond repair can push people out of their homes well ahead of the water arriving for good.

The Skymet Perspective: Where Meteorology Meets the Coastline

From a meteorological standpoint, sea-level rise and monsoon behaviour now compound each other and are no longer separate stories. A high spring tide that once passed unnoticed can, when it coincides with an intensifying monsoon low or a cyclonic surge, push water levels into neighbourhoods that were dry a decade ago.

As baseline sea levels creep upward year after year, the threshold for "normal" high tide flooding keeps getting lower, meaning weather systems that once caused nuisance flooding are increasingly capable of triggering emergencies. And as a result, Coastal forecasting in cities like Mumbai and Kolkata now has to account for this shifting baseline.

Adaptation Still Matters

The report is clear that this outcome is not fixed. Seawalls, upgraded drainage, and nature-based defences such as mangrove and delta restoration can meaningfully slow or prevent full permanent submersion in many areas. The gap, however, is uneven: lower-income coastal neighbourhoods, which often have the least access to such protections, remain the most exposed unless adaptation funding and planning reach them directly.

For the fishing families of Kolkata's delta edges and the reclaimed shorelines of Mumbai, the sea isn't a distant climate statistic — it's the tide outside the door, rising a little further each year. Whether that rise stays manageable or becomes displacement on the scale the UN describes will depend less on the ocean itself than on how quickly cities act to meet it.