Water Sensitive SA

Infiltration – Benefits

Benefit 1 - Protect downstream stormwater drainage network and streets (minor drainage system) from flooding (reduce the total volume of stormwater runoff)

Example | George Whittle Reserve: An 11m x 3m x 1m infiltration trench filled with 40mm aggregate was designed to ensure the 1-in-5 year ARI (0.18 AEP) design storm did not result in increased stormwater runoff from a 1500m2 of hard surfaces on the 3750m2 site (40% impervious) from entering City of Prospect’s stormwater network.

 

Benefit 2 – Protect urban waterways from erosion (reduce total volume of stormwater runoff)

Benefit 3 - Increase soil moisture to sustain tree health

Example | Dorset Avenue, Colonel Light Gardens, City of Mitcham: A 9000 x 750 x 750 mm infiltration trench delivers over 100,000 litres of water to the verge soils to passively irrigate street trees in an average year.

Source: Johnson T, Lawry D and Sapdhare H (2016) The Council verge as the next wetland: TREENET and the Cities of Mitcham and Salisbury investigate. In: Acta Horticularturae 1108: pp 63-70.

Dorset Avenue, Colonel Light Gardens - demonstration of canopy density and shade benefits of infiltration system: Left-hand side tree receives no infiltration, right-hand side tree with infiltration. Source: City of Mitcham.
Dorset Avenue, Colonel Light Gardens – demonstration of canopy density and shade benefits of infiltration system: Left-hand side tree receives no infiltration, right-hand side tree with infiltration. Source: City of Mitcham.

 

Example | The Strand, Colonel Light Gardens, City of Mitcham: An infiltration system consisting of 66 m of 525mm slotted drainage pipe buried within a 20mm single sized aggregate filled trench (900mm wide x 965mm deep) diverts a minimum of 1megalitre per annum, in a dry year, from the stormwater network into the verge subsoil to passively irrigate trees.

The Strand, Colonel Light Gardens - trees in Peragini Park. Source: City of Micham
The Strand, Colonel Light Gardens – trees in Peragini Park. Source: City of Micham

 

Benefit 4 - Remove pollutants from stormwater runoff

Expected pollutant removal from infiltration systems

Expected pollutant removal from infiltration systems. Source: Auckland Regional Council 2002
Source: City of Auckland (2002) Stormwater management devices: design guidelines manual (revision to Technical Publication 10). Auckland, New Zealand: Auckland Regional Council.

 

Benefit 5 - Replenish groundwater and therefore dry weather base flows to waterways

Example | Newenham ecological sponges: Small-scale wetlands manage (detain) frequent flow events up to the 1.5-year average ARI from a 6 hectare urban catchment, incorporating gravel filled infiltration wells at 2-3m depth that are integrated into the wetland liner to enable low flow, sub surface releases to the creek to encourage baseflows.

Newenham development ecological sponges, Mount Barker

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.