- May 19, 2011
POUNDING the PAVEMENT
About 19% of the average backyard in America is made up of impervious surfaces, including our rooftops, driveways, patios, and sidewalks. In fact, if you were to put all of America’s impervious surfaces together, you could almost pave the state of Ohio with it 1. The amount of impervious surface in the United States now exceeds the amount of water-purifying, carbon-storing herbaceous wetlands remaining in the lower 48 2. You may not think of your driveway or patio as having any habitat potential at all, but that idea just doesn’t hold water. The truth is that every type of landscaping has an implication for your backyard environment.
Just Passing Through
Gravel and pavement, although radically different kinds of groundcovers, are both used as sturdy surfaces for driving or walking. The big difference? Gravel is pervious (also called “permeable”), and pavement is usually impervious. What’s the big deal with impervious surfaces? Water can pass through permeable surfaces and make its way into the ground, where it is naturally filtered into our aquifers. When water hits an impervious surface, it runs into the nearest storm sewer or river, carrying pollutants with it. In general, a good rule of thumb is to minimize both paved or gravel areas, because they take up space that could otherwise support more biodiversity. However, don’t ditch the driveway quite yet. Having well-defined spaces for walking and driving helps minimize damage to plants and wildlife.
Paving the Way
Need to decide between laying concrete, asphalt, or gravel for a parking space or walkway?
- Gravel is highly permeable, which helps with water drainage; however, if you live in an area where snow removal is necessary, gravel could be problematic. Gravel or brick pavers are a good choice for garden paths.
- Porous concrete can bear heavier traffic and use than gravel, while also making snow removal more practical. Porous asphalt looks like conventional asphalt but is designed to improve infiltration of water; this can be a good alternative to traditional impervious asphalt.
- Porous paving systems can keep nearby trees and plants healthier by diverting salt and pollutants to special underground filtering reservoirs, and they are often safer than their conventional counterparts because water is less likely to pool.
If you are considering a paving project, think about how the space will need to be maintained, the water-retaining properties of your soil type, the intensity of use you expect, and any safety considerations. By choosing the most porous surface that you can, you will counteract local erosion and stormwater surges, both of which improve the environment and aesthetic appeal in your area. And if you can’t update your paved areas just yet, consider adding a rain garden, a rain barrel, or a green roof to help put clean water back into the ground.
Add your surface details to the map
The surfaces can be mapped using either the ground habitat (surface mostly bare of vegetation) or the pavement habitat (hard, man-made ground cover like a patio, driveway, deck, etc.).
Complete the characteristic for ground cover by clicking on the green info button and telling us what kind of ground cover is present.
Complete the characteristic for pavement by clicking on the green info button and telling us the pavement type as well as its permeability.