Rain is the most ordinary of things. It should nourish crops, fill reservoirs and cool the air. Yet, for millions of people living in the world’s big cities, rain has become something to fear.
When the clouds open, traffic stalls, homes flood, and smelly, brown water fills the streets. The sound of rain, once comforting, now signals the opposite.
This is the new face of climate change — not the distant threat of melting ice or rising seas, but the very local, immediate problem of water with nowhere to go.
When Cities Do Not Breathe
Water, by nature, must go somewhere. In the countryside, it soaks into the soil, seeps through roots, collects in ponds, and trickles toward streams and rivers. But in many big, modern cities, the ground is sealed beneath asphalt, concrete and tile. The soil can no longer breathe, and rain can no longer penetrate.
In Bangkok, for example, the city’s storm drains — designed more than half a century ago — can handle only a fraction of today’s rainfall.
When the downpours exceed their limits, which they often do, the water backs up, streets turn into canals, motorbikes and cars stall, and shops flood. For days afterwards, the stink of stagnant water lingers in the air.
This pattern repeats itself elsewhere, too. Jakarta, Mumbai, Lagos, New York — very different cities, same story. As climate change intensifies, rain is falling harder and faster than ever before.
The problem is not only the quantity of water but also the speed at which it arrives, overwhelming drainage systems and our patience.
The Lost Sponge
Once, nature managed. Wetlands, forests and floodplains acted as vast sponges, absorbing excess rainfall and releasing it slowly.
But in our rush to urbanise, we drained the wetlands, filled swamps and paved forests to build housing, industrial estates and parking lots.
Without these natural buffers, rainwater has nowhere to go. It rushes across smooth surfaces, collecting pollutants and debris before finding the city’s lowest points — often the poorest neighbourhoods — and settling there.
In China, urban planners have revived an ancient idea to address this: the sponge city. Rather than treating water as an enemy, a sponge city, if not welcoming it, at least accommodating it. Parks, gardens and permeable pavements allow the water to soak into the ground. It’s a principle as old as nature itself: let the earth do the heavy lifting.
Concrete as the Enemy
Look down from your aeroplane window at any big city — Bangkok, Manila, São Paulo, Los Angeles — and what you see is not green but grey. Highways, rooftops and car parks go on and on. Such impermeable surfaces repel rain like glass, funnelling it into drains and canals that now can’t cope.
By design, cities aim to keep water out, and so, today, cannot take it in. Urban flooding is not an act of nature — it often results from bad urban design.
We Can Design Our Way Out
The story need not end in wet feet and flooded streets. If poor design helped to create the problem, better design can help to solve it. Around the world, urban planners are today trying to build urban landscapes that work with, not against, climate change-driven rising rainfall.
Some solutions are large-scale, costly and structural. Expanding storm drain networks, improving canal management and installing underground reservoirs can make a difference. Unfortunately, these measures may come with high financial and, too often, environmental costs.
Other solutions are smaller, greener and surprisingly effective. Trees, for example, are natural. Their roots hold soil, their canopies intercept rain, and their trunks and roots store water.
A single mature tree can absorb hundreds of gallons of rainfall in a day. Multiply this across thousands of trees and you have a natural, living defence against urban flooding.
Rethinking a City’s Surface
Permeable pavements, whether open-grid concrete, porous asphalt, or biochar-infused surfaces, allow water to pass through rather than race away. In some European cities, small streets and roads are being replaced with grass-covered pedestrian walkways and lanes that can double as paths for water drainage and infiltration.
Green roofs are another powerful tool. Across Bangkok, tens of thousands of flat rooftops could be transformed into living landscapes, absorbing rain, cooling buildings and slowing runoff. In Singapore, Seoul and Copenhagen, such “sky gardens” are already standard features.
At ground level, rain gardens, bioswales, and retention ponds can capture runoff, while also providing beauty and supporting biodiversity. These elements, collectively known as green infrastructure, turn cities into living ecosystems rather than lifeless shells of concrete.
The Human Element
Urban flooding poses not only an engineering challenge; it sets a cultural one, too. For decades, modern development has equated progress with pavement and, in effect, productivity with impermeability. Wetlands were seen as wasted land, and rivers were necessarily channelled into concrete boxes.
But as climate change exposes the weaknesses of such thinking, urban planners are being forced to reconsider their approach to water. Perhaps the most effective adaptation strategy is not to build more, but to restore what was lost.
At the Warm Heart Foundation in northern Thailand, where I work, we have seen firsthand how local action, reforesting degraded hillsides, creating small wetlands and improving soil health with added water-absorbing biochar can reduce downstream flooding. What works for a village ought to work for a city as well.
Living with Rain
No intervention will prevent the kind of catastrophic floods recently seen in Pakistan and India. Collectively, however, measures such as these can reduce flood frequency and severity, giving cities breathing room.
Imagine a future Bangkok where the rain arrives and the city sighs, not panics. Water pools briefly in parks and gardens, then seeps quietly into the earth. Streets stay passable. The air smells clean.
That future is not a dream. It is a design choice, a matter of how we rebuild and reimagine the places we live.
Too often, cities fight against water, seeing it as an enemy to be contained. The future demands the opposite approach: to embrace water as a partner in design, a reminder that even in the heart of concrete, nature still matters.
If we have learned anything from the floods that now plague our cities, it is that water always wins in the end. The only question is whether we choose to go with the flow or live with wet feet.