Permeable pavement system is a stormwater management practice and pavement structure designed to allow water to pass through its surface and infiltrate into an underlying stone reservoir and, ultimately, the subsoil, rather than running off as surface flow. It is used to reduce runoff volume, promote groundwater recharge, and improve water quality by filtering pollutants.
A permeable pavement system typically consists of several integrated layers. The surface layer is made of permeable materials such as pervious concrete, porous asphalt, or permeable interlocking pavers, all of which contain void spaces that allow water to infiltrate. Beneath the surface is a bedding and base layer composed of uniformly graded, open-graded aggregate that provides structural support while also creating storage voids for temporarily holding stormwater. Below this reservoir layer, water either infiltrates into the native soil or is discharged through an underdrain system if infiltration is limited.
From a hydrologic standpoint, permeable pavement systems function by capturing rainfall where it lands and reducing the generation of overland flow. By allowing water to infiltrate, these systems decrease peak discharge rates, reduce total runoff volume, and help restore more natural watershed hydrology that is often disrupted by impervious surfaces.
In addition to quantity control, permeable pavement systems provide water quality benefits. As stormwater passes through the pavement and underlying aggregate, pollutants such as sediment, nutrients, metals, and hydrocarbons can be filtered, adsorbed, or biologically degraded, resulting in improved quality of infiltrated or discharged water.
These systems are commonly used in low-traffic areas such as parking lots, sidewalks, driveways, and plazas, although some designs can accommodate higher traffic loads. Proper design considerations include soil permeability, structural requirements, groundwater conditions, and maintenance needs.
Maintenance is essential to ensure long-term performance, particularly to prevent clogging of surface voids by sediment and debris. Regular vacuum sweeping and inspection are typically required.
Permeable pavement systems are a key component of green infrastructure and low impact development strategies, helping to manage stormwater at its source while providing both hydrologic and water quality benefits.