Permeable Surfaces
Key Benefits
- Water Management: Reduces surface runoff volume and peak flows; Improves water quality via filtration; Recharges groundwater; Reduces risk of surface flooding. (C753 Ch 20)
- Climate Regulation: Can reduce surface temperatures compared to impermeable asphalt/concrete.
- Biodiversity: Can provide some habitat potential in joints or within grass systems.
- Amenity: Provides usable surfaces (parking, paths) while managing water.
- Metrics: Rainwater Runoff Retained: 47-76%; Stormwater Runoff Delay: 59%; Water Quality Improvement (TSS, NO3, P - variable); Property Value Uplift (Nearby Water): 0.9-3.6%. (Placeholder - specific metrics vary widely)
Technical Guidance
Site Suitability (C753 S20.4)
Assess ground conditions (infiltration potential - C753 Ch 25), contamination risk, groundwater levels, slopes (<5% recommended for most types), and traffic loading requirements.
Design & Construction (C753 S20.5 - S20.9)
Design sub-base layers for structural support (traffic load) AND water storage/infiltration. Choose appropriate permeable surface type (concrete blocks, porous asphalt/concrete, gravel, reinforced grass) based on use and aesthetics. Ensure correct layer depths, materials (e.g., specific aggregate gradings), and construction techniques to maintain permeability.
Consider edge restraints, inflow/overflow connections, and potential need for underlying geomembranes or underdrains depending on infiltration capacity and site constraints.
Maintenance (C753 S20.12)
Essential to maintain permeability. Regular sweeping/vacuuming to remove sediment/detritus that can clog pores. Prevent soil/mud being tracked onto surface. Occasional deeper cleaning may be required. Manage vegetation if using grass systems.