Pervious Pavement
Urbanization has greatly increased the amount of impervious surfaces creating an imbalance in our watersheds. Large quantities of water that previously were allowed to infiltrate into the ground and collect in small pools now flow quickly, through storm sewer systems, to our lakes and streams. This short-term increase in water flow has exacerbated flooding and erosion problems, as well as delivering large amounts of sediments, pollutants, and excess nutrients. Low Impact Development is a multi-directional approach to reduce the impacts of urbanization. A large component of LID is reducing runoff by increasing infiltration. This can be accomplished in many ways, including the use of; rain gardens, vegetated swales, rain barrels, and pervious paving.
Pervious paving systems are those that allow water to percolate into the ground through small openings in the material. Pavements can be made of:
Porous concrete or asphalt
15-25% open space. High durability allows for use in parking lots, driveways, and low traffic streets.
Paving stones
Modular blocks with pervious joints. Often used for patios, walkways, and driveways.
Open cell pavers
Concrete or plastic cells with large open spaces. The cells provide structural support and prevent compaction of soil. Grass can be planted in open spaces. Often used for paths, fire lanes, overflow / event parking, driveways, and utility access.
All of these materials have been used for at least 20 years and are as resilient as conventional paving materials. These paving materials may have open space of 15-40%. This allows for:
- Increase infiltration of water, up to 5 gallons per minute, reducing amount of runoff, flooding.
- Higher resistance to freeze-thaw cycles and related cracking, due to large open space.
- Lower temperature due to greater heat exchange with ground, reducing temperature of runoff.
- Decreased need for additional stormwater management strategies, less land required for retention ponds
- Groundwater is recharged
Open-cell pavers filled with sand and gravel. Pavers may also be planted with grass. The cells protect roots from compaction.
