When people think about impervious pavements, they may immediately think of roads and parking lots, but another metaphorical funnel is right above our heads. Roofing is a big pusher of stormwater –and some of the most-traveled stormwater at that.

The connection is easy to make when considering water in roads and sewers, but much of that water –before it ever hits the ground– has moved over the surface of a roof, through a gutter and smacked down toward the ground, often upturning soil and dislodging many sediments (good for the ground, bad for the water).

A story last week in Scientific American summed up how the EPA is planning to address the stormwater problem nationwide. Resources like the Chesapeake Bay are at the head of concerns toward what ecosystems could be irreparably damaged by continued and/or amplified stormwater patterns.

In the story, David Beckman, co-director of the National Resource Defense Council’s national water program, explains the multitude of problems impervious surfaces pose for ecosystems that have grown and evolved with porous surfaces –the grass and forests.

The solution? Well, the EPA is considering a number of measures that several local governments have already taken toward stormwater runoff, including rain gardens, rain barrels, porous pavements and –that’s right– green roofs. Made of soil, grass and local plant life, green roofs look –and often serve– as lawns on top of buildings.

Green roofs, like the one pictured above, grab the rain before it can gain speed and chemistry. From there, the roof soaks up much of the water like a sponge, and acts as a filter for the water that runs through.

And cost? Depending on the company and breed of plants, a green roof can cost anywhere from $10 to $100 per square foot, according to estimates calculated online. But Beckman told SA green roofs will often pay for themselves in five to seven years because they help insulate buildings and thus reduce energy costs.