Underground transport in an uncertain climate

Authors: Roberto Pantoja Porro & Zili Li, University College Cork, Ireland (In collaboration with John O’Donovan, Gavin & Doherty Geosolutions, Ireland)

Roberto Pantoja Porro, Zili Li and John O’Donovan examine infrastructure design in an age of uncertainty.

When we picture climate change impacts, we often imagine flooded streets, scorched forests, or collapsing coastlines. However, what we don’t usually consider is what lies beneath our feet – the hidden world of underground transport.

From the London Underground to metro systems in Shanghai and New York, these subterranean networks are the lifeblood of our cities, moving millions of people daily. They protect us from traffic jams, storms, and heatwaves – but they are not immune to the changing climate.

In my recent review, The impact of climate change on underground transport infrastructure, published in Geotechnical Research, my co-authors and I explored how rising sea levels, extreme weather, groundwater shifts, and temperature extremes are reshaping the environment around underground systems. The conclusion was clear: climate change is not a distant threat – it’s already here, and it’s accelerating.

A changing risk landscape

When the article was written, our focus was on understanding the mechanisms: how sea level rise increases hydrostatic pressure, how torrential rains overwhelm drainage, and how temperature swings can crack tunnel linings.

Since then, the urgency has only grown. In 2024, global average temperatures hit record highs, extreme rainfall events broke historical records, and urban flooding incidents – many affecting underground transport – occurred in cities across Asia, Europe, and the Americas.

What’s become clearer is that we are designing in an age of deep uncertainty. Past climate patterns no longer predict the future. We need infrastructure that can adapt to unknowns.

The big four threats beneath our feet

1. Sea Level Rise (SLR): Higher seas raise groundwater tables, increasing pressure on tunnels and letting saltwater seep in, corroding steel and weakening concrete.

Example: In Washington, DC, and Shanghai, saltwater intrusion is accelerating tunnel deterioration, demanding costly retrofits.

2. Extreme Weather Events (EWEs): Heavy rainfall and storm surges can flood stations and tunnels within minutes, while heatwaves stress materials and ventilation systems.

Example: London’s low-lying Underground sections near the Thames have faced recurrent flooding; in Taipei, intense storms have caused dangerous water ingress.

3. Groundwater Fluctuations: Changes in water levels affect soil strength, leading to settlement, deformation, and seepage –  especially in cities built on soft soils.

Example: In Milan, groundwater recovery after reduced pumping submerged older metro tunnels not designed for wet conditions.

4. Temperature Extremes: Heatwaves can warp tracks and crack linings; freeze-thaw cycles in colder regions destabilise surrounding soils.

Example: In Norway, frost heave has damaged tunnel linings; in Singapore, heat retention has created comfort and safety challenges.

From risk to resilience

The mission, “Can we build a future we can’t predict?”, is exactly the question underground infrastructure faces.

We can’t know the exact rainfall totals in 2050 or how quickly seas will rise. But we can:

• Design for flexibility – allowing systems to be upgraded as risks evolve.
• Plan for extremes, not averages – building in capacity to handle rare but devastating events.
• Monitor in real time – using sensors to track movement, seepage, and temperature changes, enabling proactive maintenance.

Nature-based solutions also have a role: green infrastructure, permeable surfaces, and restored wetlands can reduce runoff into underground systems.

What still needs to change

• Design standards must move from historical data to climate projections.
• Funding must prioritise resilience upgrades before catastrophic failures occur.
• Collaboration across disciplines – engineers, climate scientists, and urban planners – must become the norm.

The road ahead

Future research needs to go beyond individual hazards. We must study compound events – like heavy rain coinciding with high tides – and understand their combined effects on underground systems.

As cities expand their metro networks, especially in coastal zones, the opportunity is now to integrate climate resilience from day one. Retrofitting later will cost far more – financially and socially.

A call to action

Underground transport may be invisible to most, but it is central to how cities function. Protecting it is not just an engineering challenge – it’s an investment in the safety, mobility, and economic resilience of urban life.

In the face of uncertainty, we can’t afford to stand still. We must design, upgrade, and monitor with the expectation that the future will surprise us, and build systems ready to adapt when it does.

“The conclusion was clear: climate change is not a distant threat – it’s already here, and it’s accelerating”

Read the full paper: The impact of climate change on underground transport infrastructure
 

Author

• Roberto Pantoja Porro and Zili Li, University College Cork, in collaboration with John O’Donovan, Gavin & Doherty Geosolutions.