Definition
Permeable paving and permeable surfacing are hardscape systems designed to allow rainfall to infiltrate through the surface into underlying layers, reducing runoff and supporting soil, water, and vegetation functions within urban environments.
What this strategy does
Replaces impermeable sealed surfaces with porous or permeable materials that manage stormwater at source and reduce soil sealing. Avoids fully impervious pavements that disconnect rainfall from soils and drainage systems.
Context
In New Zealand urban areas, high levels of surface sealing contribute to flash flooding, degraded freshwater quality, and loss of soil function. Permeable paving supports water-sensitive urban design objectives by improving infiltration, attenuating runoff, and reducing pollutant loads entering receiving environments.
Technical considerations
Design considerations
Permeability and hydrology
Design pavements to achieve infiltration rates appropriate to rainfall intensity, soil conditions, and loading, while maintaining structural stability and minimising long-term clogging.
Material and structure
Select permeable concrete, modular pavers, porous asphalt, or gravel systems based on pore structure, durability, and compatibility with soil biota and root growth.
Pollutant removal
Specify systems with demonstrated capacity to retain sediments, nutrients, heavy metals, and microplastics to avoid contaminant transfer to soils and waterways.
Vegetation support
Where vegetation is integrated, provide adequate rooting volume and select species tolerant of compaction, variable moisture, and local maintenance regimes.
Implementation considerations
Design priority
Integrate permeable paving early with stormwater, landscape, and structural design to avoid retrofitting constraints.
Key constraint
Performance is reduced in areas with high groundwater tables, low-permeability subsoils, or insufficient maintenance access.
Relevant tools or standards
Coordinate design with council-approved water-sensitive urban design guidance and pavement construction standards.
Issues and barriers
Clogging and maintenance
Sediment accumulation and surface wear can significantly reduce infiltration capacity without regular maintenance.
Pollutant accumulation
Captured pollutants may pose ecological risks if systems are not designed or maintained to manage long-term contaminant loads.
Hydrological limitations
In unsuitable soil or groundwater conditions, permeable pavements may deliver limited stormwater or ecological benefit.
Design and material constraints
Standardised pavement systems are often optimised for drainage performance rather than habitat value, limiting biodiversity outcomes.
Synergies and opportunities
Climate change
Reduces runoff volumes and peak flows during extreme rainfall and contributes to urban cooling through enhanced evaporation.
Human wellbeing
Improves local environmental quality by filtering pollutants and supporting greener, more permeable streetscapes.
Disaster risk reduction
Delays and attenuates stormwater flows, reducing flood risk and pressure on downstream infrastructure.
Financial case
Ecosystem services and performance value
Long-term cost savings
Reduced demand for conventional stormwater infrastructure and lower flood damage costs can offset higher upfront construction costs.
Cost-effectiveness
Investment logic
Where integrated with rainwater harvesting or distributed stormwater systems, permeable paving can deliver high water-use efficiency and favourable lifecycle economics.
Monitoring and evaluation metrics
Core metric
Surface and sub-surface infiltration rates to detect clogging and performance decline over time.
Advanced or long-term metrics
- Runoff volume and peak flow reduction compared with impermeable surfaces.
- Pollutant removal efficiency for sediments, nutrients, metals, hydrocarbons, and microplastics.
- Soil moisture, temperature, and related soil condition indicators beneath permeable systems.
- Vegetation cover and species richness where planting is incorporated.
Case study
Long Bay neighbourhood development
Related design strategies
- Biofilters
- Bioswales
- Building for biodiversity
- Rain water gardens
- Soil preservation
- Soil regeneration
- Stormwater planters
Additional resources or tools
Auckland Council Permeable Pavement Construction Guide
https://www.aucklandcouncil.govt.nz/content/dam/ac/docs/environment/permeable-pavement-construction-guide.pdf
Wellington Water Sensitive Urban Design Guide
https://wellington.govt.nz/-/media/environment-and-sustainability/water/files/wsud-guide.pdf
NZILA Permeable Pavements Overview
https://nzila.co.nz/media/user/PDF’s/Permeable%20pavements%20NZILA%20August%2017-reduced.pdf