Living with floods

The recent severe flooding in Central Luzon that affected 163,634 families and cost P230 million in damage to agriculture is yet another reminder of the vulnerability of our towns and cities to climate change. It shows that traditional infrastructures, such as the dikes and seawalls that the government has built over the years, have not solved the problem. It makes clear the need to creatively solve more than one infrastructure or climate change issue at a time.

The solution to flooding does not lie in expanding traditional infrastructures such as inlets, concrete pipes, and culverts. It’s the surface of communities that need to be upgraded—and the streets are a primary target. When building roads, for example, cities can make road surfaces to directly absorb rainwater and flooding through climate-adaptive design.

Composing roughly 30 percent of a city’s surface, city streets, as well, as parking lots need to be retrofitted to behave more like a sponge by integrating nature-based design technologies such as permeable pavements and rain gardens. The importance of this cannot be overstated as climate-related flooding occurs disproportionately in our food-producing communities.

In recent years, green architecture and infrastructure have gained wider interest. An increasing number of people don’t necessarily want more underground infrastructure to solve flooding. They want green infrastructure, built at the surface of their neighborhoods with a concentration on the streets’ right-of-way to address their low-lying geography. They want all of the health and wellbeing benefits of green infrastructure for their communities by creating greenways and being able to enjoy the cooling effects of vegetated streets and commercial areas.

Although traditional underground gray infrastructure has been a backbone for managing drainage, those underground pipes and culverts are limited, single-function technology. They are also expensive and slow to adapt to climate change. Where water can’t get to the inlets, this leads to localized flooding, often in streets. Where there is an undercapacity of pipes and culverts, additional clogs and bottlenecks occur, creating sewage back-ups and overflows into adjacent waterways.

Rain doesn’t easily flow or fit into underground pipes and culverts. Rain’s natural propensity is to seep into the immediately surrounding environment where it falls. This is what underlies natural systems and climate adaptation strategies—embracing rainwater, not trying to get rid of it.

A transition from gray to green infrastructure is especially critical for older cities with ageing, often combined drainage-sewer infrastructure that, while novel a century ago, today needs rethinking and reinvention. Streets with inlets are the de-facto unnatural “tributaries” to these underground conveyance pipes. Rather than repave streets or increase the size of underground pipes and culverts, nature-based solutions can replace part of the street surface to allow water to infiltrate naturally.

But the shift from gray to green isn’t just a technological fix, it’s also a social one. Polluted waterways and flooding occur when the river system and the wider urban area become inundated by more frequent and intense rainfall. Historically, Central Luzon’s urban areas have struggled to keep pace with urbanization through their drainage and sanitation infrastructure. The area’s combined drainage-sewer infrastructure overflows every time it floods, polluting its rivers, creeks, and other water bodies.

While the government is spending billions of pesos on enormous gray infrastructure, this still won’t capture larger rainfall, and flooding will continue. This is because rain and urban areas must be designed together—to limit the flow of rainwater into these combined drainage-sewer pipes and strengthen resilience. By thinking interdependently with rainwater, the climate-adaptive design employs a broad knowledge of regional ecology, soils, the seasons, and the land itself as a natural-systems infrastructure that is centered on community and ecological health.

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Nathaniel von Einsiedel ([email protected]) is a Fellow of the Philippine Institute of Environmental Planners and Principal Urban Planner of CONCEP Inc.