From rare to routine: What’s next as Bangladesh stares at the rising tide of destruction?

Once considered rare and catastrophic, destructive storm surges in Bangladesh are set to become disturbingly frequent, according to a new study by researchers at the Massachusetts Institute of Technology (MIT). 

Published in the journal One Earth on 11 April, the research warns that what was once considered a "100-year event" could occur every decade, or even more often, by the end of the century. 

This shift could present an existential threat to one of the world's most climate-vulnerable nations.

Historically, these powerful storms have wrought destruction along the country's southern coast, where fertile agricultural lands and dense rural populations lie perilously close to sea level. 

Sai Czander Ravela, principal research scientist at MIT's Department of Earth, Atmospheric, and Planetary Sciences, worked on the project alongside his colleagues, postdoctoral researcher Jiangchao Qiu and Kerry Emanuel, professor emeritus of Atmospheric Science at MIT.

They used advanced climate modelling techniques to simulate tens of thousands of possible cyclones near Bangladesh under different future climate scenarios. Their approach combined high-resolution downscaling with dynamic storm tide modelling to capture how storms could behave in a warming world.

The outcome paints a sobering picture: in a future where fossil fuels continue to burn as they do today, not only will the most extreme storm tides occur more often, but their seasonal timing will also shift.

Tropical cyclones are projected to increasingly coincide with the country's monsoon season—an overlapping of hazards that could lead to back-to-back or even simultaneous flooding events. 

Until now, Bangladesh has been spared the worst-case scenario of overlapping disasters; the monsoon and cyclone seasons have mostly occurred at different times. But if heavy monsoon rains saturate the soil and a cyclone strikes soon after, the combined impact could be devastating. Communities would have no recovery window between two extreme events.

Of course. Bangladesh has made major strides in storm preparedness in recent years—upgrading early-warning systems, reinforcing village embankments, and expanding access to cyclone shelters.

Yet the models guiding these efforts, including those used in the Coastal Embankment Improvement Project (CEIP), still rely on limited historical data and fixed assumptions about tides and sea-level rise. Typically based on just 19 to 23 past cyclones, these models offer a narrow view of future risks, Ravela told The Business Standard.

By contrast, Ravela said, their study uses a far more expansive and dynamic approach.

They use high-resolution statistical-physical downscaling of CMIP5 (Coupled Model Intercomparison Project Phase 5) and CMIP6 climate models, implementing IPCC (Intergovernmental Panel on Climate Change) scenarios to simulate tens of thousands of plausible cyclone events. 

These account for changes in structure, intensity, and timing, and are coupled with detailed storm tide models that dynamically incorporate sea level rise and the full range of tidal cycles. 

This provides a more comprehensive view of flood risk, including phenomena such as cyclone–monsoon overlap, which Ravela and his team's results show is likely to increase as warming delays monsoon withdrawal and extends cyclone-favourable ocean conditions.

"The result is a clearer and more actionable picture of future extremes. Storm tides that are considered 100-year events today may occur every 10 years or less by the end of the century—not because cyclone frequency increases tenfold, but because rising seas and stronger storms amplify impacts," Ravela said.

That shift in recurrence, he warns, has far-reaching consequences.

"When extreme storm tides become decadal instead of centennial events, the baseline shifts," Ravela said. "What was once rare becomes routine."

The implications are structural, systemic, and deeply social. Infrastructure like embankments, polders, and drainage networks—often designed with 50 or 100-year return periods in mind—will be overwhelmed more often, not because they were poorly built, but because the assumptions they're based on no longer hold true.

"This isn't just a stressor," Ravela added. "It's a signal that chronic disruption is replacing episodic disaster."

Compressed recovery times mean communities cannot rebuild before the next shock hits. This fundamentally alters planning horizons for housing, agriculture, and water infrastructure. Crops may not recover. Saltwater intrusion could make freshwater sources unusable. Repeated inundations risk making entire coastal zones uninhabitable.

In a country where rice cultivation remains a livelihood for millions and seasonal migration patterns hinge on planting and harvest cycles, such disruptions are not abstract. They point toward a future in which traditional ways of life may no longer be viable in some regions.

Ravela advocates that the situation demands a shift in mindset—from resisting individual storms to adapting to a new pattern of persistent, interwoven threats. "We need to move away from deterministic design and toward risk-based, recurrence-resilient planning," he said.

When asked what kind of systemic or infrastructural rethinking is needed to prepare for compound events like cyclones overlapping with monsoons, Ravela was blunt: "That's the million-dollar question, isn't it?"

"If cyclones begin to overlap with the monsoon, you are no longer managing separate events," he said. "You're managing a single, cascading system failure. Saturated soils, full rivers, high tides, and storm surge all converge. Drainage backs up. Embankments fail under compound pressure."

In this scenario, single-hazard designs—like storm barriers or cyclone shelters—are no longer enough. Instead, Bangladesh will need adaptive, flexible systems that anticipate a range of overlapping hazards and respond in real time.

"It is not about building stronger walls. It is about building smarter systems," Ravela said. "Compound events don't just test infrastructure. They test how we think about risk. And that thinking needs to change."

"It will take many minds working together, but the shift to risk-based, cascade failure planning is no longer optional. It needs to begin now," Ravela concluded.