Water is the enemy of pavement. It gets into cracks, freezes, expands, and makes bigger cracks. It makes the ground beneath roads soggy and soft. Drive some heavy trucks over those roads and they can give way, forming potholes and ruts. Even when it’s not destroying the road, water pools on the surface, turning cars into dangerous hydroplanes and splashing buckets of filthy water onto windshields and pedestrians.
Water is the enemy of pavement—unless that pavement is permeable.
Permeable pavement is pocked with pores that allow the water to trickle through it like a rock-based rice crispy treat. In freezing temperatures the water has room to expand inside the pores without cracking the material. Potholes are less of a problem because the pavement is laid on top of a bed of gravel, which allows water to drain through to the absorbent soil below while maintaining a firm foundation under the road surface. There’s no standing water puddling on top of the road causing sliding and splashing.
And permeable pavement helps solve the top two problems created by polluted runoff: dirty stormwater that poisons streams and lakes, and the tsunamis of water that gush through creeks and flood buildings. Permeable pavement cleans the water as it trickles through it into the soil, and it helps the dirt soak up the water, recharging pockets of buried groundwater.
But just how does a simple roadway shrink our stormwater woes and make streets safer to drive, bike, and walk on? Here’s how.
