Interactive Map

Daylighting a creek with water sensitive urban design features

The Pasadena Biodiversity Recreation Trail is an urban greening and cooling project that uses excess stormwater runoff as a resource to passively irrigate Grant Jacob and Sierra Nevada Reserves in the City of Mitcham. This innovative project brings one of the catchment’s three underground 900mm diameter pipes to the surface, effectively reinstating a pre-existing creek (commonly known as “daylighting” of the creek) to create a more natural environment. The stormwater runoff flow rate and discharge volume is reduced by diverting the water through a series of water sensitive urban design features, including detention basin, swales, rock riffles and infiltration trenches.

Outcomes sought by Stage 1 of the project include:

• significant increase in biodiversity through passive watering
• increased tree canopy coverage of over 50% of the total area of the reserve
• overall temperature reduction, providing a more resilient and useable open space
• improved stormwater quality
• greening of two reserves: Grant Jacob Reserve and Sierra Boulevard Reserve.

The master plan for this 3.5ha open space of the Pasadena Biodiversity Corridor seeks a climate resilient solution that includes a stormwater harvesting scheme within Branson Reserve (future stage) for the purpose of open space irrigation of the reserves and potential to supply Centennial Park Cemetery.

Detention Basin & Swale – Grant Jacob Reserve, east of Fiveash Drive

1. Inlet structure Underground stormwater is daylighted into Grant Jacob Reserve basin from neighbouring street catchment via a 900mm pipe with a headwall and concrete apron. The 1.1 megalitre basin stores peak flows during storm events and excess flows are directed back into the underground drainage network via the outlet structure.
2. Outlet structure The outlet chamber in the detention basin (concrete walled pit with steel grate lid 1000mm above base of basin) diverts low flows through the batter via a 200mm pipe to swale and soakage trenches. The chamber also allows high flows to re-enter the pre-existing underground system.
3. Spillway Extreme event flows are released via a spillway as overland flow to the stilling pond and vegetated swales towards Fiveash Drive
4. Swales Stormwater flows downstream from the stilling basin via vegetated and rock-lined swales.
5. Soakage trenches A network of over 180 metres of soakage trenches receive stormwater from the swale and the adjacent roads to passively water the reserves and trees when it rains. A 150mm slotted drainage pipe is laid at zero grade within a non-woven geofabric lined (BIDIM A34) 300mm x 300mm trench of 20mm aggregate. The soakage trenches are fed via PVC pipe inlets within the stilling basins. Soakage trench overflows are redirected into the swale to avoid soakage trench blowouts.
6. The flow splitting chamber (pit with steel lid and internal low flow weir) immediately upstream of Fiveash Drive directs low flows to the Sierra Nevada Reserve swale system under the road via a 250mm HDPE pipe, which includes a valve to control the flow rate.

Swales through Sierra Nevada Reserve, west of Fiveash Drive

7. Inlet surcharge pit The 250mm pipe feeds a surcharge pit that reduces the energy of the flow and captures sediment before feeding soakage trenches and the rock-lined swale.
8. Swale Flows are treated through a series of vegetated and rock-lined swales from the newly constructed playground for the length of the reserve – approximately 200 metres.
9. Outlet structure Any water that reaches the end of the swale is released onto Branson Boulevard via a 600mm long break in the kerb.

The swales meander through the reserve, and the corridor features remnant vegetation and 82 new trees, along with 3,800 native understorey and ephemeral plants that significantly increase biodiversity of the ecosystem. Plants were grown locally by a local native nursery, which ensured the quality of the plant stock and a very high survival rate.

Plant species

The detention basin was planted with a wider variety of species of plant that provide excellent ground cover to reduce weak cover and the need for slashing:

The swales have been planted with a biodiverse mix of species, including:

Design & construction

• Civil design: Water Technology
• Landscape design: Outerspace Landscape Architects with City of Mitcham and Water Technology
• Constructed by: Beltrame Civil (Contractors)

Funding partners

• City of Mitcham – $700,000
• Green Adelaide – $340,000
• Federal Government (Local Roads and Community Infrastructure Program – playground) – $200,000
• State Government (Open Space Grant Program) – $100,000