What is a raingarden

Raingardens are specially designed garden beds which filter stormwater runoff from surrounding areas or stormwater pipes. They're also called bio-retention systems as they provide biological treatment of stormwater using soil, plants, roots and microbes.

Raingardens are designed to stop excess stormwater, nutrients, rubbish and sediment from polluting our waterways, bays and oceans. They can even be positioned to capture overflow from a rainwater tank.

How do raingardens work

A raingarden lets water collect and settle on the garden surface then soak through the plants and filter media. Rubbish and sediment is trapped on the surface. Nutrients dissolved in the stormwater are used by the plants and toxins stick to the soil. The soil and plant roots work together to naturally filter the water and remove pollutants.

Test the filter media before installation to check it meets standards for hydraulic conductivity and plant growth and holds adequate soil moisture to support the plants.

The image below shows a cross section of a raingarden.

raingarden cross section depicting the layered construction 

 

 

 

 

 

 

 

 

 

See raingardens in action

This video explains what raingardens do and how they work, and includes some backyard landscaping ideas.

 

What are the different types of raingardens

There are many different types of raingardens you can choose to build at home.

Type​ ​Description

Planter box

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.

Inground​

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.

Infiltration​

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.

Swale​

A slight depression in the landscape which can be either grassed or planted with other vegetation.

Green roof​

When the roof of a building is covered in vegetation and soil to assist with the filtration of stormwater.

Downpipe diversion​

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.

Porous paving​

A permeable material, often brick like, that allows water to penetrate through into the surrounding soil.

Rainwater tank diversion

Similar to a downpipe diversion only the d-shape mechanism is fitted to the overflow of the rainwater tank.

Vegetable​

​A vegetable raingarden is sub-irrigated, which means that the water enters at the base of the garden.  This helps to prevent the vegetables being submerged after heavy rain and water is used more efficiently as there is less evaporation from the surface.

Other

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.

 

 

Tips

All property and drainage amendments must comply with state and local regulations. A certified plumber must be used for stormwater connections and modifications.

 

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