Roadside Guide to Clean Water: Porous and Permeable Paving Materials
Porous and Permeable Paving Materials at a Glance
Porous pavement and permeable pavers are types of paving materials intended to minimize flooding and stormwater runoff while armoring the land surface so it can carry the weight of foot or vehicle traffic. These pervious surfaces are designed to allow snowmelt and rain to drain through the hard, but porous, top surface. Traditional paving surfaces are considered impervious because rain and melting snow cannot pass through into the soils. Examples of porous and permeable paving materials include specially designed concrete, asphalt, and paving stones. To work properly, they must be installed over a carefully prepared subsurface. That might simply be graded washed stone, but it is likely to also include piping, storage tanks, and basins. Porous and permeable paving materials are more widely used in modern urban spaces and on commercial or industrial properties.
How Porous and Permeable Paving Materials Work
Permeable pavers and porous pavement help reduce stormwater runoff and prevent flooding. These engineered paving materials have large pore spaces that allow rainfall to pass through and be moved away from the site. This minimizes puddles, ice, and standing water directly on the surface. It also means less water is flowing off the surface and causing flooding downhill. The modified surface under the pavement can store water until it either absorbs into the soil below or is directed through pipes to a basin or other outlet. Pervious pavements must be maintained to keep them working properly. This includes regular cleaning to prevent clogging, often done through vacuuming.
Community Benefits of Porous and Permeable Paving Materials
- Stormwater: Reduces stormwater runoff
- Groundwater: Recharges groundwater
- Climate Change: Promotes climate change resiliency
- Flooding: Mitigates flooding
- Landscape: Beautifies the landscape
You can expect to find porous and permeable paving materials in urban and suburban settings.
How to Recognize Porous and Permeable Paving Materials
Pervious surfaces like porous concrete can provide drainage in low-traffic areas such as parking spaces. Photo by Scott Sjolander
Pervious surfaces can be designed to drain into vegetated areas such as rain gardens. Photo by Scott Sjolander
Under the pavers, pervious systems also include a stone drainage bed. Further engineered storage and piping may lie below. Photo by Anne Duggan, Kevcon.inc
Permeable pavers rely on the spacing between the pavers to allow water to drain into a storage or conveyance system below. Photo by Andy Yencha
The pervious paver system on the right side of this roadway collapsed under heavy truck traffic that it wasn't designed for, unlike the conventional concrete. Photo by Scott Sjolander
Some pervious pavers are meant to almost disappear into the landscape but allow cars to park in the grass without mud and erosion issues. Photo by Kristen Kyler
