Eco-Explainer: What is Porous Pavement?

Want to learn more about a no-brainer, effective method of addressing stormwater? Keep reading!

Technology that mitigates the impacts of climate change can take all shapes and forms, from green roofs to the type of paving below our feet and as increased stormwater flooding becomes more pronounced, the way we manage stormwater has never been more critical.

Green Stormwater Infrastructure in disguise

Porous pavement, aka permeable or pervious pavement, is a form of Green Stormwater Infrastructure (GSI) that works on the ground (literally) to combat flooding from supercharged storms.

The magic is in the mix, its composition has a significantly higher percentage of air voids, or bubbles, which allow it to soak up and slow down water as it meets the surface.

Essentially, it is a spongy form of asphalt that gives rapid moving water the chance to pass through and infiltrate into the subsoil, reducing the stormwater runoff volume from paved surfaces and “peak discharge rates” during storm events.

What exists beneath the surface that give it such powerful sequestering ability is a durable stone bed that stores water before it infiltrates the underlying soil, this simultaneously recharges groundwater levels which is important to maintain the barriers from saltwater intrusion that can corrode the ground beneath us.

Porous paving can replace traditional pavement anywhere, at homes, parking lots, highways, walkways, patios, plazas, driveways, and can make all the difference between a flooded intersection during a storm and a safe one. We can only imagine how differently our Vine Street Expressway might have looked post-Hurricane Ida if porous paving existed in a higher volume across Philly’s streets…

This type of GSI also plays an important role in capturing stormwater that would otherwise contribute to sewer overflows that have some nasty consequences for Philly’s water as well. Additionally, it helps to filter out pollutants that degrade water quality and helps slow the rate of litter that is swept away into our storm drains.

How Porous Pavement helps beyond stormwater

Outside of heavy storm events, porous paving can also help reduce runoff from melting snow and ice, as it allows snowmelt to seep through the surface down to underlying layers of soil and gravel and off the roads. Porous roads are much less likely to become icy in the winter because snow melts right through it. This both reduces the need for road salt which has its own host of environmental consequences, but also can act as a measure to support road quality. That is because the porous pavement is credited as being more durable not only in extreme storms, but extreme heat and cold as well (pressure that most of Philly’s streets literally crack under), due to its flexible and spongy composition.

Less flooding and potholes sound like a fantasy to many of us navigating Philly’s streets currently, but the Philadelphia Water Department is not only making this type of GSI more of a reality but more accessible to residents across the city as well. PWD’s Rain Check program allows residents to join in on the flood curbing, healthy water effort.

The program began in 2012 with the goal of giving residents the resources needed to manage stormwater and contribute to the health of our waterways. It offers resources to see what stormwater tools such as porous repaving can be suited for your home.

This program is a part of PWD’s “Green City Clean Waters” comprehensive plan to improve stormwater management, improve the quality of our waterways, and to inform residents on why exactly stormwater management is so critical in today’s climate.

Cover photo: Heron Playground Porous Basketball Court. Louis Cook for PWD

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