Water Sensitive SA

Permeable paving

Benefits
Allow water to filter through hard surface to increase soil moisture and sustain adjacent vegetation


Decrease excess stormwater runoff

  • Catchment outflow reductions of 67% are possible for rainfall events of less than 50 mm by using permeable paving built over clay subgrades (Collins, Hunt & Hathaway, 2008)
  • Permeable pavement appears to be an effective tool for hydrologic mitigation of storms from “every day events” up to the 10-year, 24-h average recurrence interval (ARI) or now referred to as 10% AEP (Fassman & Blackbourn, 2010)


Stormwater management solution when no underground drainage system exists

Avoid downstream drainage system upgrades

Case study: Kegworth Road, Melrose Park permeable paving project cost $30,000 more than resurfacing the road with asphalt. The project cost $200,000 in total, including permeable paving, leaky wells, and soakage and distributions systems in the nearby reserve. This was in comparison with the estimated $1.2 million cost of upgrading the conventional pit and pipe network to address a local flooding issue (Johnson & King, 2020)


Support maintenance of pre-development run-off rates and/or more natural hydrological cycle

Reduce stormwater ponding on surface of carpark, road or footpath

Reduce the need for stormwater pits and pipes (and associated cost)

Design tips
TIP 1 – Geofabric between bedding course and base layer almost redundant

If ratio of diameter of bedding layer to base course layer aggregate is less than 1:10, then no geofabric is required between the layers.

Why? The materials are close enough in size, ensuring that migration of smaller bedding course material into the voids of base course does not occur.


TIP 2 - To avoid clogging of permeable pavers

Ratio of contributing impervious areas to permeable paving area – no greater than 4:1

Ratio of contributing impervious areas : permeable paving area | No greater than 4: 1. Image: Concrete Masonry Association of Australia

Image: Concrete Masonry Association of Australia


TIP 3 – Avoid recycled concrete basecourse

Why? The limestone leaches out of the material and clogs the system.


TIP 4 – Always install an edge restraint or a concrete kerb

Why? To prevent movement, ensure load is spread across.

Edge restraint – pavement transition to concrete or other surface. Source: Interlocking Concrete Paving Institute


TIP 5 – When design is close to a footing or structure

ensure no water enters the subgrade by:

  • ensuring a minimum 1% grade of pavement to draw the water away from the structure/wall
  • installing an impermeable liner that redirects water away from the footing.

Permeable interlocking concrete pavement (PICP) adjacent to building structure. Source: Interlocking Concrete Paving Institute (ICPI), 2021


TIP 6 – Use permeable paving to protect significant trees

even if the tree is on an adjacent property.

 

TIP 7 – To preserve infiltration capacity

pervious pavement subgrades should not be compacted (Drake, Bradford & Marsalek, 2013).

 

Acknowledgement of Country

Water Sensitive SA acknowledges Aboriginal people as the First Peoples and Nations of the lands and waters we live and work upon, and we pay our respects to their Elders past, present and emerging. We acknowledge and respect the deep spiritual connection and the relationship that Aboriginal and Torres Strait Islander people have to Country.