Building a rain-garden to keep stormwater in the catchment

On 27 and 28 March 2010, The Little Stringybark Creek project team descended on a willing household in Mt Evelyn, and built an infiltration system (in the distance, down the hill) and a rain-garden (in the foreground) in their front garden. This series of photos compresses about 20 hours of hard labour into 1 minute. Both systems have deep stores filled with scoria (to hold lots of water and allow it to filter into the surrounding soils), sprinkled with woodchips (to promote denitrification). Over the top of the scoria, thin layers of fine gravel, coarse sand and fine sand were lain (to prevent fine sediment seeping into the scoria), finally topped by a layer of sandy loam into which we planted lots of wetland plants. When it rains, the raingarden fills up through the pits,and water soaks through the sandy loam down into the deeper layers. When the rain-garden fills up, water overflows into the stormwater pipe down the hill where it flows into the infiltration system. When that system fills up, the water drains off to the stormwater drain on the street.

The systems will retain almost all of the runoff from the house in most years, keeping it out of the stormwater system, allowing a lot of the water to go back to the air through the plants, and treating some of it, allowing it to filter slowly to the creek, helping restore lost dry-weather flows. We're funding the construction of a whole lot more of these systems in the coming year, and hope to effect the restoration of poor old Little Stringybark Creek back to good ecological health. For more information see www.urbanstreams.unimelb.edu.au.

Category:

Science & Technology

Tags:

• Raingarden
• bifiltration system
• Stormwater runoff retention