One of the most popular features of the Friends of Piesse Lake Community Native Botanical Garden is the Rain Garden (also known as the Bog Garden).
It was so popular, in fact, that they are going to build two!
Below, Bev shares both what a Rain Garden is, and how you can build one in your own back yard!
Rain Gardens or Bioretention Systems are excavated basins or trenches filled with layers of stones and soil then planted with native plant species which tolerate periodic inundation.
The object of a Rain Garden is to retain stormwater on site where it is used by plants to create green areas which provide microclimate benefits, biodiversity and wildlife habitat.
Rain Gardens can be small or large depending on the area available and the amount of water to be retained. In public areas they can be used to remove pollutants from road stormwater, slow the flow which takes pressure off downstream infrastructure, and create green aesthetic areas for public enjoyment. The rain garden should be connected to the usual stormwater system so water from heavy rainfall events can be removed.
In private gardens, stormwater from gutters directed to a rain garden will cool the soil and increase water availability for the garden. There should be an outlet where excess water can be directed during a high rainfall event.
Rain Gardens make great habitat for frogs, beneficial bugs, and boggarts 🙂
MAKING YOUR OWN RAIN GARDEN
- Dig a trench or bed ideally about 50 cm deep.
If the soil is sandy a layer of clay gravel can be placed in the bottom to slow infiltration.
- Place a layer of rocks, blue metal or washed gravel in the bed.
The depth depends on the depth of your bed. The spaces between the rocks is your water storage.
- Next place coarse grained sandy soil mixed with a small amount of pine bark or wood chip material over the rock layer.
- Plant your choice of plants then cover the surface with blue metal, small stones, or washed gravel to act as mulch and protect the bed from erosion until the plants grow.
The depth of your bed will control the selection of plants. A very shallow bed is best planted with sedges or reeds.
For advice on plant selection, see the Monash University’s Vegetation Guidelines for stormwater biofilters in the south-west of Western Australia
UPDATE: Only a few plants were chosen to live directly in our Rain Garden, as listed below. The surrounding garden has a wide selection of natives, approximately 50+ species were used elsewhere.
– Isolepis nodosa
– Anigozanthos flavidus
- The edges of the bed can be planted with any vegetation.
Deeper rain gardens, especially those in public areas, can incorporate larger species particularly Melaleucas which tolerate periodic inundation.
Rain Gardens can be a beautiful addition to your landscape, and there are plenty of examples of how-to’s and photos across the web, though many examples are from North America. Here’s a sample of other instructions:
- Melbourne Water – http://www.melbournewater.com.au/getinvolved/protecttheenvironment/raingardens/Pages/How-do-I-build-a-raingarden.aspx (Australian) Shows multiple types of home-based rain gardens, and includes really informative videos. These are ‘lined’ rain gardens and most suitable for smaller blocks, but offer great practical advice.
- Woodland Stewards – http://www.woodlandstewardseries.com/landowner-information-for-managing-woodland/documents/HowtoCreateYourOwnBackyardStormwaterRainGarden.pdf (American)
Has some technical calculations for managing water volumes, but some of the content will probably not be applicable to Australian soils.
- Rain Garden Network – http://www.raingardennetwork.com/build.htm (American)
Has nice simple steps to follow, which are practical most anywhere.
- This Old House – http://www.thisoldhouse.com/toh/how-to/intro/0,,20517496,00.html (American)
I love This Old House. Though it’s American, their detailed step-by-step photos with clear instructions will really help those of us who like to know what to expect at each stage of the process.
If you are interested in getting a hands on lesson in building a Rain Garden, come along to the Friends of Piesse Lake Busy Bee this weekend – Sunday 12th July 2015 from 2-4pm – and work with Bev and the team building the second Rain Garden!
And just one more interesting link: http://watersensitivecities.org.au/robust-research-and-industry-bond-guides-a-new-generation-of-raingardens/
Author: Andrea Salmond
Andrea has been with Katanning Landcare since 2013 and is passionate about equipping people with the tools, skills and resources they need to make positive changes to our environment.