We are starting to recognize the significant role that streets play in creating community: the Complete Streets movement recognizes that streets are public spaces and that they need to accommodate mobility of all kinds (walking, biking, etc.). Streets also make up a large portion of the built landscape and therefore can have a great impact on the environment. Through these means it is possible to reduce a total impervious area of 50% to an effective impervious area of 10% or less. This is especially true for storm water management and quality; in aggregate, streets create huge expanses of impermeable surface which collect and direct huge volumes of untreated storm water. The streets are huge collectors of so-called non-point source pollutants, especially particulates from automobile exhaust and materials for winter road maintenance. For these reasons it is essential to put streets at the center of the green infrastructure strategy.
Bio-Swale Street Edge
The health of watersheds is compromised when the impervious area exceeds 10% of an entire watershed. Reducing the width of streets will reduce impervious surface area, while using the roadside area to clean and absorb rainwater will minimize the impact of remaining impervious surfaces.