What is a Rain Garden? ......and how to build one
A raingarden is a water saving garden that is similar to a regular garden bed, but is designed specifically to capture stormwater from hard surfaces such as driveways, patios and roofs via downpipes after it rains.
Raingardens are changing the way Australians think about gardening and are rapidly becoming an important part of garden design, particularly in Melbourne. They can even be positioned to capture overflow from a rainwater tank.
How do rain gardens work?
Beneath the raingarden are layers of sandy soil which help to slow the rate of stormwater entering our rivers and creeks. These layers also assist in the removal of pollution, such as nitrogen and phosphorus, fertilisers, dust, leaves and animal droppings, which are washed off these hard surfaces.
The plants in your raingarden help to further filter out pollution that would otherwise end up in our rivers and creeks.
By capturing stormwater, raingardens are self watering and are therefore easier to maintain and use less drinking water than regular gardens.
Raingardens are rapidly becoming an essential addition to any sustainable garden design, thanks largely to the fact that they come with a serious benefit to the environment and the health of local rivers and creeks.
What are the different types of raingardens?
There are many different types of raingardens you can choose to build at home. Any of these raingardens can be registered on our website to be included in the count towards our 10,000 raingardens target.
Planter box raingarden
This type of raingarden is positioned above the ground to collect stormwater from a diverted roof downpipe, allowing stormwater to filter through the raingarden before connecting to the stormwater system.
This type of raingarden is positioned in the ground to collect stormwater from hard surfaces or a diverted roof downpipe, allowing stormwater to filter through the raingarden before connecting to the stormwater system.
This type of raingarden is positioned in the ground to collect stormwater from hard surfaces or a diverted roof downpipe, allowing stormwater to filter through the raingarden and penetrate into the surrounding soil.
A slight depression in the landscape which can be either grassed or planted with other vegetation.
When the roof of a building is covered in vegetation and soil to assist with the filtration of stormwater.
A permeable material, often brick like, that allows water to penetrate through into the surrounding soil.
When a roof downpipe diverts roof water through a hose via a d-shape mechanism, allowing water to soak into the garden and surrounding soil.
Rainwater tank diversion
Similar to a downpipe diversion only the d-shape mechanism is fitted to the overflow of the rainwater tank.
You can be creative with how you utilise stormwater. You may have properly diverted a roof downpipe onto your garden, creating a frog bog or mini wetland for example*
* All property and drainage amendments must comply with state and local regulations
A certified plumber must be used for stormwater connections and modifications.
Raingardens are easy to design and build and come in many different shapes and sizes. Here is a simple outline of what is involved in designing and building your own raingarden. You can download more detailed instruction sheets below.
Step 1 – choose the right type of raingarden
Identify the location on your property where stormwater can be captured (i.e. from a downpipe, near to a driveway, patio or overflow from a rainwater tank).
Then select a suitable raingarden design for the location you have chosen. There are many different raingarden types you can choose from.
Instruction sheets are available for the following types of raingardens:
- Planter box raingarden - Building a raingarden instruction sheet (PDF, 744kb)
- Inground raingarden - Building a raingarden instruction sheet (PDF, 795kb)
- Inflitration raingarden - Building a raingarden instruction sheet (PDF, 805kb)
- Swale - Building a raingarden instruction sheet (PDF, 828kb)
- Downpipe diversion - Building a raingarden instruction sheet (PDF, 1.4mb)
- Porous paving - Building a raingarden instruction sheet (PDF, 1.97mb)
- Green roof - fact sheet (PDF, 1.98mb)
Some raingarden types are best suited to specific locations, depending on the soil type, depth and the steepness of the land. We have raingarden maps for City of Port Phillip, City of Kingston, City of Stonnington and City of Knox. These maps show which type of raingarden is best suited for different locations within these areas.
Step 2 – build your raingarden
Start by either constructing your planter box or excavating your trench, depending on the type of raingarden you have decided to build.
If you are building an inground style raingarden (including inground and infiltration raingarden or swale), dig the area with a gentle slope away from the house.
Determine if your raingarden needs to be lined with a PVC liner or if a perforated pipe at the bottom of your raingarden is required. Ensure an overflow pipe is installed to drain excess water during heavy rainfall.
Next, add your sandy soil layers one layer at a time. Attach a flow spreader to the end of your downpipe or rainwater tank overflow to evenly distribute water flow into your garden to limit erosion. At this point your raingarden is almost complete.
A certified plumber is required for any modifications and reconnections back to the stormwater system.
Step 3 – raingarden planting
Be creative with your raingarden design, using a variety of raingarden plants evenly spaced throughout the garden. Mulch your raingarden with gravel to keep the moisture in. Avoid using bark or straw mulch as it will float and wash back into the stormwater system.
A wide range of plants are suitable for raingardens. Your local nursery can guide you on what plants are suitable for your area. When choosing plants for your raingarden make sure that they are able to tolerate heavy rainfall as well as long dry periods. Native plants are usually more drought resistant and easier to maintain than introduced species.
Step 4 – register your raingarden
Register your raingarden and be part of the count towards building 10,000 raingardens across Melbourne to help our rivers and creeks.
Tips for a healthy raingarden
Raingardens are easy to maintain, especially when planted with native Australian plants. They don't need to be watered, mowed or fertilised. Follow these simple tips to make sure your raingarden functions well.
- Cover your raingarden with gravel mulch to retain moisture.
- Weed your raingarden until the plants have matured.
- Evenly distribute water flow into your raingarden to limit erosion from heavy rainfall. Strategically placed rocks may help with this.
- Inspect your raingarden - replace plants and repair erosion in your raingarden when necessary.
- Don't drive over or squash your raingarden as this will reduce its ability to work effectively.
Note - if it doesn't rain, water your raingarden until your plants have established in compliance with your local water restrictions.
Need help building your raingarden?
The easiest and cheapest way to build a raingarden is to do it yourself using our simple instruction sheets, available from this page. You could also contact an expert landscape gardener to help you build your raingarden and provide expert advice. A licensed plumber can assist you with any modifications and diversions to your stormwater.
Find an expert
If you want advice or assistance with building your raingarden from a qualified landscape gardener, you can contact Sustainable Gardening Australia . Look for this raingardens symbol to find an environmentally certified landscape industry professional who is qualified in designing and creating environmentally sustainable gardens.
You can also contact a plumber who has completed raingardens training in partnership with Melbourne Water and the Master Plumbers Association: