When rainwater can't soak into the soil, because roofs and pavements are impervious, the results can be severe.

Permeable pavements -- roads, driveways, parking lots and sidewalks into which rain water can soak -- can change this dynamic, though, making cities more sustainable.

Ally John at Social Design Notes has an excellent overview of these new pavement possibilities:

"Permeable pavement allows rainwater to filter into the ground while providing a durable surface for vehicles to drive on. While gravel driveways and other pourous materials are a common form of this, other types composed of interlocking concrete blocks or plastic cell networks can allow vegetation to poke through.

"Permeable systems can cost more to lay than asphalt or poured concrete and, depending on the material, may require more maintenance. But the results are more aesthetically pleasing, more environmentally responsible, and may save money in the long run.

"By allowing rainwater to soak into the ground, permeable systems slow run-off and flooding the sewer systems. Allowing grass and plants to grow improves air quality and reduces the heat island effect."

Of particular note is Vancouver's Country Lanes project, about which our friends at Treehugger say:

"Residents fed up with getting their cars muddy paved over the dirt service lanes behind their homes in rainy Vancouver years ago. That didn’t help the city’s drainage problems: it forced rainwater into the sewers, where excess joined raw sewage and emptied into the Pacific. Lovely. Now Vancouver’s using Geoblock (shown) and Golpla structural grass [a system which supports lawns with a recycled plastic grid] to repave the back streets into Country Lanes right smack in the city. A few configurations are being tested out, but the goal is to use natural infiltration to lessen the load on the storm system. And to green the streets up a bit, making city life easier on the eyes and the lungs."

But Country Lanes is only one of many projects studying the use of new, more water-friendly surfaces: resin parking lots, greened railway lines, driveway pavers, even rainwater harvesting.

[We've also covered the ways in which relatively simple steps, like planting street trees, using lighter pavements, and painting roofs white can result in pretty dramatic energy savings by reducing the heat island effect.]

>"Residents fed up with getting their cars muddy

Well, there's the root of the problem. Because people don't want to have a muddy car, we should develop all sorts of new technologies and ways of making non-muddy roads?

Where I grew up (rural Louisiana), we just put down a layer of gravel anywhere that got too muddy. It's not very glamorous or high-tech, but it solves the drainage problem and the mud problem.

Posted by: jet on January 2, 2005 9:45 PM

For most roads its not an issue as the water just flows to the side of the road. Its only an issue when the water has to be directed into a drain and even there it can be dishcharged into a man made lake nearby so long as it doesnt run through the same pipes poop does;/

The fact tho is you want water around peoples homes to hit the drains because for 1 alot of it gets contamiated with oil and stuff and for anouther its the only thing keeping low flow toilets from clogging most older sewars.

In many cases what is realy needed is a MUCH larger catch basin to hold runoff till a treatment plant can process it.

Posted by: wintermane on January 2, 2005 10:50 PM

Gravel works fine on rural roads. In urban areas the volume of traffic is a lot higher. The gravel gets kicked off to the side, or pounded down into the mud, and pretty soon you're back to the same problems with washboard surfaces, potholes and mud. You can resurface with gravel every year or two, but that gets pricey and it's not so sustainable. Also, in the Pacific NW at least, gravel needs to be oiled in the summer to keep the dust down -- usually a somewhat toxic operation.

The new technologies last longer and are cheaper over the long run. They serve urban needs better, like rollerblades, wheelchairs, tricycles, and appearance/function that affects property values.

A new development that is using pervious paving on road shoulders is UniverCity in Barnaby, B.C. The paving is part of a comprehensive sustainable stormwater plan.

Posted by: Laurence Aurbach on January 3, 2005 3:37 PM

In Northeastern areas i can see the typical rather violent temperature changes causing significant damage when the water that hasn't quite worked its way through the semi-permeable surface begins to freeeze.

Posted by: daniel on January 3, 2005 5:58 PM

One big reason you wont see this "catch on" quickly is many cities and counties have thier own equipment for resurfacing and maintaining roadways that cost ALOT of money. They also have people trained only with using the old materials and methods.

They are far more likely to do test runs or to try to garner fed funds with a test project then anything else for the next 5-10 years.

Posted by: wintermane on January 4, 2005 12:04 AM