Can ‘sponge’ pavement save us from urban flash floods?

The climate crisis is driving more extreme and unpredictable flooding, wreaking havoc from western Germany to China to Houston, Texas.

Aquipor, a startup specializing in urban stormwater systems, claims to have created a porous pavement to avert major damage which can run into billions of dollars.

A study, published last year in the journal Proceedings of the National Academy of Sciences, found that increased rainfall from 1988 through 2017, in part due to the climate crisis, cost the US an additional $2.5billion in flood damage.

One reason that flooding can be so devastating in cities is that concrete sidewalks, roads, and parking lots prevent water from being absorbed into the ground.

“Pavement has a use,” Greg Johnson, the CEO of Aquipor, told Fast Company. “But the problem is that we have too much of it in our cities.”

To help reduce floods, Aquipor created a material with tiny holes which allow rainwater to pass through. The pores are small enough to stop dirt in the rainwater filtering in, essential to stop the material becoming clogged up.

The company aims to get this material on to sidewalks and parking lots but for now are testing the material on private land.

Transforming cities with this material could be a cost-effective way to combat flooding. For example, the company claims it would cost around $5m to cover the mid-size city of Spokane, Washington in it. By comparison the cost of transforming a small city in an under-resourced country is around $20-$50m, according to the United Nations group UN-Habitat.

However while the porous pavement may help rainwater sink into the ground, it’s unclear if the pavement can offset increasingly heavier and more frequent rain.