Front Yard Blitz #02 – 10% Stormwater Runoff

So we’ve managed to get the overhead wires underground – what’s the next step in our green street refurbishment? There are a few options but it’s good practice to work from underground upwards, so let’s sort out our stormwater situation.

A few facts before we go on;

  • Rainwater = generally defined as ‘rain’ that has fallen but contains little or no dissolved matter or soil – so it’s generally what we can catch on roofs;
  • Stormwater = essentially rainwater that is running off over land, and the main source of downstream water pollution;
  • Sewage = from toilets and the like. In Australia the sewer and stormwater mains are required to be physically separated.

A typical residential neighbourhood will see around 55% of all of its rainfall leaving as stormwater runoff. In more built up urban areas it reaches up to 95%.  This runoff picks up contaminants along the way, sending everything to the nearest waterways. Two major problems here; loss of a valuable resource, and the downstream pollution (which can’t be fixed downstream).

Reducing our stormwater runoff to 10% (and you can aim even lower) requires a series of interventions, all of which add some value for homeowners (and I’ve chosen some dowdy images simply to demonstrate how easy some of the interventions can be);

Rainwater Harvesting – Adding a rainwater tank pulls out a certain amount of the total water flow – plumbing this back into landscape irrigation or toilet flushing saves you some water costs and adds value to your landscape (worth up to 10% of your home’s value). There are so many tank types around now that you could fit one almost anywhere. Keep using the water! This effectively increases the tank’s capacity.


Rain Gardens and Swales – rather than sending your excess rainwater off-site (and usually into the street gutters), slow it down and let it soak into the ground (more landscape benefits). Rain-gardens alone can strip out the majority of the stormwater runoff, and will take most of the pollutants out as well. When approached with design intent these gardens can become great additions to a landscape scheme – you might need help with ensuring that you don’t set up local flooding instead! (inlet-outlet invert levels etc.). Think of a ‘rain garden’ as a planted pond that only fills up during rain, and a ‘swale’ as a planted open spoon drain.


Street Rain Gardens – a great way to re-vegetate the public space and treat almost all of the stormwater. Check these out; rain garden retrofit and green streets for a cleaner harbour.

Soft Kerbs – ever watched all that stormwater running down the street in the gutters and wondering if there’s a better way? Soft kerbs can be suitable as part of the street rain garden retrofit, allowing stormwater an easier path into soft ground. This one requires considerations around traffic & safety and is typically only suited to local low-traffic streets, but streets with soft kerbs often have that something ‘special’ about them.

soft kerbs

These first two Blitz steps go hand-in-hand – removing the overhead wires allows us to get some serious planting into the street, and the stormwater bounty supports a much richer landscape.

Our next instalments will cover street trees and traffic calming.


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