Ifind myself writing this article while sitting in familiar standstill traffic caused by flooding. Perhaps there is no better place to begin a discussion about flooding than from inside it.
It is a situation Filipinos know all too well, particularly during the rainy months from June to November. Heavy rains arrive, streets disappear beneath floodwater, traffic comes to a halt, businesses are disrupted, and for many communities, the concern quickly shifts from inconvenience to safety.
What’s more worrying is that flooding is now occurring in places where, just 10 or 20 years ago, it was rarely a concern. And this is no longer a problem limited to poorly planned or developing cities. Cities around the world—from Tokyo to Copenhagen—are also experiencing increasingly intense rainfall and flooding.
Climate change is changing the equation. Warmer temperatures are contributing to more frequent and intense extreme weather events, putting pressure on infrastructure designed for a different climate.
When the city becomes a swimming pool
Rapid urbanization has transformed the natural landscape of our cities. Soil, vegetation, wetlands and open spaces have been replaced by buildings, roads and concrete pavements, reducing nature’s ability to absorb water.
Before cities became heavily urbanized, rainwater could penetrate the soil, be absorbed by vegetation, collect in natural depressions and wetlands, and make its way into rivers and groundwater. The landscape acted as a natural sponge.
Today, much of that sponge has been replaced by concrete. Rain that falls on roofs, roads and pavements quickly becomes surface runoff. When it exceeds the capacity of drainage systems, the water flows into streets and low-lying parts of the city.
In a sense, we have transformed our cities into giant swimming pools, with little natural ground left for the water to seep into.
But what if we changed the way we think about flooding? Instead of draining rainwater away as quickly as possible, what if we could redesign our cities to absorb, store, slow down and reuse it?
This is the idea behind the Sponge City.
Designing a city that works like a sponge
The Sponge City is an urban design approach that works with nature rather than against it.
The principle is simple: Allow the city to absorb rainfall where it falls, temporarily store excess water, slow its movement, let some infiltrate into the ground and reuse it when needed.
It is not a replacement for major flood-control infrastructure. Philippine cities will still need effective drainage networks, pumping stations, river management and large-scale flood-control projects. But what if every development, park and street could also become part of the city’s flood management system?
Turning parks into rain gardens
One of the simplest ways to introduce the Sponge City concept is to rethink our parks and open spaces.
Portions of parks can be designed as rain gardens, detention areas and retention ponds that temporarily hold stormwater during heavy rainfall. On normal days, these can function as gardens, playgrounds and public spaces. During extreme rainfall, they become temporary reservoirs.
These landscapes can also provide habitats for plants, birds, insects and other wildlife, helping restore biodiversity within increasingly urbanized environments.
In other words, flood infrastructure can also become beautiful public infrastructure.
Let the ground absorb water again
We also need to rethink the amount of impermeable surface we use in our cities.
Where appropriate, roads, sidewalks, parking areas and plazas can incorporate permeable paving, porous concrete and other water-sensitive materials that allow rainwater to infiltrate the ground rather than immediately becoming surface runoff.
This can also help replenish groundwater resources.
In areas where excessive groundwater extraction contributes to land subsidence, better groundwater management should be part of a broader strategy for addressing the problem of sinking cities.
More resilient
Another important element of the Sponge City is bringing nature back into the built environment.
Green roofs, rooftop gardens, planted terraces, pocket parks and landscaped open spaces can absorb and temporarily retain rainwater. When these interventions are multiplied across an entire city, they can make a meaningful contribution to reducing stormwater runoff.
Trees and vegetation also provide shade and cooling through evapotranspiration, helping mitigate the urban heat-island effect.
Catch the rain before it reaches the street
Rainwater harvesting should also become a more common part of building design.
Public and private developments can collect rainwater from roofs and store it for non-potable uses such as landscape irrigation, cleaning and other building needs.
This reduces the volume of water entering drainage systems while creating an alternative source during dry
periods. For the Philippines, this is particularly relevant as we can experience extreme rainfall during the wet season and water shortages during droughts associated with El Niño.
The beauty of the Sponge City concept is that the same water we want to get rid of during a typhoon can become a resource we need during the dry season.
Learning from other cities
Cities around the world are already showing how urban design can become part of flood management.
In China, landscape architect Kongjian Yu has championed the Sponge City approach, using wetlands, parks and other nature-based systems to absorb, retain and slow stormwater while creating public spaces.
Copenhagen has integrated climate adaptation into its streets, parks and public spaces, allowing them to manage extreme rainfall while maintaining their recreational and civic functions.
Closer to home, Bangkok’s Chulalongkorn University Centenary Park shows how landscape architecture can support urban flood management. The 11-hectares park uses slopes, green spaces and water-retention systems to temporarily store stormwater while serving the university and surrounding community.
These examples show that flood management does not always have to be hidden underground or rely only on massive engineering structures.
It can be visible. It can be green. And it can make the city better.
The city is the solution
The Sponge City is not a magic solution to Manila’s flooding problem. Our challenges are complex and require
coordinated action in watershed management, drainage, infrastructure, land-use planning and environmental protection.
But it gives us another way of thinking: How can we make the city itself part of the solution?
Every architect can incorporate rainwater harvesting. Every developer can preserve or introduce more green space. Every landscape architect can design areas that retain water. Every city can create more permeable public spaces. Every community can recognize the importance of protecting natural waterways and drainage paths.
Individually, these interventions may seem small. Collectively, they can transform how a city responds to rain.
Maybe the Manila of the future should not be a city that simply fights the rain, but a city that can absorb it, store it, use it—and ultimately, breathe with it.
The author is a senior partner and vice president at Visionarch.
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