The hot new trend in sustainable landscape design, raingardens are taking off all over the country, particularly in areas of high rainfall.

Also called bioretention systems, they comprise beds of free-draining soil with sand underneath, planted with species that thrive even when dry for long periods then saturated during times of heavy rain.

A raingarden acts as a living filter for stormwater.

The plants draw nutrients from organic matter and fertilisers in the water that would have ended up in rivers and creeks, and the sandy soil collects oil and particulate waste, reducing the sediment and other pollutants in our waterways.

In addition to the rain that runs off our roofs, stormwater is washed from driveways, roads, paved areas and other hard surfaces.

This runoff can contain pollutants ranging from oil and biological waste like animal droppings and leaf litter to nitrogen, phosphorus and fertilisers.

It is directed into the stormwater system and finds its way to rivers and creeks, where it harms aquatic animals and promotes excessive algae growth, reducing oxygen levels in the water.

National bodies are keen to get behind the concept, with Melbourne Water providing a dedicated website on why and how to build a raingarden (raingardens.melbournewater.com.au).

The benefits of a raingarden

Even if you already have a rainwater tank installed, a raised raingarden is great for draining the first-flush diverter, and is invaluable for those times when the rainfall exceeds the capacity of the tank.

Runoff from hard surfaces like a driveway, patio or paving that doesn’t make it into the tank can also be used.

An inground raingarden can be fed by the drainage channel that collects this runoff and positioned to divert overflow to the stormwater system.

It also makes an attractive, functional border for the downhill edge of a patio and is the ideal feature to replace a lawn that gets boggy.

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