During heavy storms, you can see and even hear floods of water rushing into that sewer, taking everything in its path. We call this runoff. Runoff not only contributes to flooding and erosion; it also plays a part in the contamination of our water supply.

Runoff occurs because traditional pavement is nonporous -- meaning it doesn't allow rainwater to settle back into the ground. Green pavement, a relatively new concept in green building, is a permeable and porous pavement (try saying that three times fast) that absorbs rainwater instead of repelling it. It allows water to return to the ground, which means the water doesn't wash into the sewer, along with oil, gas and pesticide residue.

Green pavement is a viable alternative for footpaths, driveways and parking lots, and one day it could revolutionize highway systems.