Conventional paving is impervious: rain runs straight off, overwhelming drains and causing urban flooding and pollution. Permeable (porous) pavements are a key Sustainable Urban Drainage System (SUDS) measure — they let water pass through the surface, managing stormwater where it falls rather than piping it away.
Working principle
The surface (porous asphalt, pervious concrete, or permeable block paving with gaps) lets water infiltrate into a coarse open-graded aggregate sub-base that acts as a temporary storage reservoir. From there water slowly infiltrates into the subgrade (recharging groundwater) and/or is released at a controlled rate via an underdrain. The aggregate and any geotextile also filter pollutants — oils, sediments, metals — improving runoff quality.
| Property | Conventional | Permeable |
|---|---|---|
| Runoff | High, fast | Reduced, delayed |
| Flood risk | Increases | Mitigates at source |
| Groundwater | No recharge | Recharges aquifer |
| Maintenance | Standard | Needs cleaning to avoid clogging |
Key limitationThe main maintenance issue is clogging: fine sediment fills the pores over time, so periodic vacuum sweeping is essential to preserve infiltration.
Applications
- Car parks, low-traffic roads and driveways
- Pedestrian areas, plazas and cycle paths
- Flood-resilient and sponge-city urban design
References & further reading
- Scholz & Grabowiecki, “Review of permeable pavement systems,” Building & Environment, 2007.
- Woods-Ballard et al., “The SuDS Manual (C753),” CIRIA, 2015.
- US EPA, “Permeable Pavements — Stormwater Best Management Practice,” 2021.