Reduce Impervious Surfaces

Impervious surfaces include driveways, patios, and walkways. The more impervious surfaces on a site, the more run-off there is. The consequence of run-off is an increased speed of water flow, which cannot be absorbed into the ground as readily, increases erosion, and dumps an excessive amount of pollutants into one spot.

The goal, then, is to utilize surfaces that are "broken apart" and allow water to flow into the ground. In addition, in areas that freeze, this allows for the frozen ground to swell and then sink with the thaw, which eliminates cracks that form in wet laid patios, concrete and asphalt surfaces. Reducing impervious surfaces will help to minimize water velocity and run-off. It will aid the reduction of pollutants and sediment deposits in waterways and reduce estuarial water temperatures.

Utilizing planting swales instead of berms.
Planting areas within a parking lot should be in the form of swales versus berms. Swales gather water, which can then absorb into the groundwater system, while water on a berm simply runs off onto the paving. The swales are then planted with native grasses and trees that tolerate wet feet. Be sure that the soil in these swales is not compacted in the manner of the surrounding parking areas.

Narrow road width.
Narrow the width of roads, driveways and sidewalks within the local zoning regulations. If additional parking space is needed add an impervious paver or gravel expansion adjacent to the driveway. Shared driveways and parking lots are another easy way to reduce the amount of impervious surface on a site.

Parking lots can be greener by replacing unused parking spaces with planting beds. In addition to reducing the amount of impervious surface, it will decrease maintenance costs and create a more human-scaled environment.

Replace solid driveways with porous alternatives.
Replace solid concrete and asphalt driveways, with pavers, cobblestones, brick and turf stone, all of which will slow down the flow of water and allow it to settle into the ground. Another alternative is using impervious paths for the car tires with green plant material in between. Solid concrete can also be broken-up with decorative and functional paver inlays.

Porous paving or pervious pavement.
According to Central Concrete pervious pavement is a cement-based concrete product that has a porous structure allowing rainwater to pass directly through the pavement and into the soil at the rate of 8 to 12 gallons per minute, per square foot. This is achieved without compromising the strength, durability, or integrity of the concrete structure itself.

Green Spaces.
Design green spaces between hard surfaces (patios, walkways, and parking lots) and building edges. Not only will this help the aforementioned drainage issues, it will help to create a more welcoming and visually appealing site. Be sure that all paved areas are graded towards the planted areas.

Parking pullouts.
Since parking pullouts do not have a high level of wear and tear, asphalt and concrete are often not necessary. Substitute these impervious surfaces with gravel instead of asphalt or concrete.

Use dry laid patios and walk ways instead of wet laid.
Wet laid patios are set in concrete, which does not allow for any stormwater to be absorbed in that area. In contrast, dry laid patios are set in stone dust, which slows the velocity of sheet flow and allows for some absorption of storm water in that area. An additional benefit for regions that receive freezing temperatures is that dry laid patios will not crack like wet laid surfaces.

Interrupt walkways.
Small planting beds and creeping groundcovers, such as thyme, can be incorporated into the edges of walkways and patios. These planted areas will help to slow storm water flow and create a more aesthetic space.

Decking materials.
Treated wood, commonly used for decking, can be replaced with several alternatives. The first, and best alternative, is salvaged lumber. Salvaged lumber has been harvested from previously existing sites and is in good condition. Salvaged lumber can be attained in bulk from salvage shops.

A second alternative to using treated wood is lumber certificated sustainable by the Forest Stewardship Council (FSC). The Council utilizes region-specific forest-management standards to judge if a particular forest operations is in conformance with FSC standards. A certificate is issued, enabling the landowner to bring product to market as "certified wood," and to use the FSC trademark logo. This process is at the landowner's request.

A third option is plastic wood or products such as TREX, which is made from reclaimed plastics and woodwaste. Advantages of plastic wood include that it will not rot, does not need to be sealed, is resistant to moisture, bacteria growth and graffiti, and cleans up with soap and water. Guide to Plastic Lumber.

Use RubberSidewalks instead of concrete.
RubberSidewalks are made with recycled California tire rubber that is high-density, non-mushy, and tough enough to handle skateboards and women's high heels.

The rubber sidewalk gently bends when pushed from below by tree roots. It's also soft enough to cushion the landing of anyone unlucky enough to trip and fall on it. When the roots need trimming, the rubber panels can be popped out and then reused. In addition, rubber sidewalks come in a variety of colors. More information on RubberSidewalks.

Vegetated steps.
Utilize groundcovers and moss as the landing surface cover on steps that are located in low-traveled areas. A solid riser will still be needed to retain the integrity of the step.

Recycled concrete.
Use concrete from demolished walkways and driveways to build retaining walls and patios.

Green retaining walls.
Build small out-pockets and planters on the sides of retaining walls. Planting these planters with visually interesting material and vines will also help to absorb water and reduce run-off.