Permeable Paving

The concrete sea of the urban landscape is a vast impermeable surface contributing to massive flows of water runoff. Water that is unable to soak into the ground will quickly flow over asphalt parking lots, roads, rooftops, driveways, sidewalks, and residential streets into the local drainage network and low-lying areas. The amount of impervious surface within a watershed determines how great the change in runoff will be. Surface water runoff will double in areas with 10-20% impervious surface cover and triple in areas with 30-50% impervious surface cover. The majority of all surface water will result in runoff in urban areas with 75-100% impervious surface cover. This means that the process of urbanization dramatically increases surface water runoff because water is prevented from soaking into the soil.

Permeable Paving\Permeable paving is a broad term used to describe a diverse range of pavement technologies that allow water to seep through the surface material into a base layer for on-site water infiltration and filtration. Porous paving allows water to move through the surface material while permeable paving directs water around impervious brick pavers and into aggregate material in the joints between pavers.

 

These innovative paving methods can be utilized for roads, paths, driveways, parking lots, sidewalks, and other surfaces that are subject to light vehicular traffic. They are becoming increasingly popular for reducing runoff in urban centres because they maintain the functionality of a stable, load-bearing surface. Permeable paving systems utilize a wide variety of technologies for increasing soil infiltration capacity, including porous concrete or asphalt; porous turf; permeable interlocking concrete pavers; and resin bound paving made of recycled materials, such as glass, plastic, and rubber. Permeable paving is an effective strategy for low impact development at the neighbourhood scale. This strategy may be incorporated with innovations at the property scale to further enhance the utility of sustainable surface water management initiatives in urban areas.

The following examples of permeable paving technologies may be incorporated with innovations at the property and neighbourhood scale to further enhance the utility of sustainable surface water management and low impact development initiatives in urban areas.

Are Pervious, Permeable, and Porous Pavers Really the Same?

Pervious Concrete

Parking lot pavement made of pervious concrete allows rainwater to filter through to underlying base layers. Pervious concrete is a made up of a mixture of mainly coarse aggregate, cementing materials, and water. The reduced sand content results in a pavement with a high void content to allow water to freely move through the concrete surface.

Porous Asphalt

Porous asphalt is produced using the same methods as conventional asphalt concrete. It differs in that fine aggregates are omitted from the asphalt mixture. The remaining, large, single-sized aggregate particles leave open voids that give the material its porosity and permeability. Fiber or a polymer-modified asphalt binder may be used to ensure pavement strength. Porous asphalt pavements are generally designed with a subsurface reservoir that holds water that passes through the pavement, allowing it to evaporate or percolate into the surrounding soils.

Porous Pavers

Porous pavers are made up of plastic or concrete turfblock and are characterized by a cellular grid system filled with dirt, sand, or gravel. These systems provide grass reinforcement and ground stabilization while creating the effect of an open lawn.

Permeable Interlocking Pavers

Permeable interlocking pavers are made up of clay or concrete impervious units bonded with a permeable joint system to allow water to infiltrate into a base layer underneath the blocks.

Resin/Glass Bound Paving

A paving mixture of aggregate, such as stones, or post-consumer recycled materials, including glass; plastic; or rubber is adhered together by a bonding process. Aggregates are typically bonded together with a mixture of resins, pigments, and other binding agents.