A project to help alleviate rainwater flooding at the Royal Botanic Garden in Edinburgh could be expanded and replicated to work on agricultural land by farmers experts say.
Kirsty Wilson from The Royal Botanic Garden Edinburgh (RBGE) and Dr David Kelly from Heriot-Watt University installed the raingarden in an area prone to localised flooding at the site which was affecting the surrounding area.
The result may be attractive to visitors, but it could play an important role in the agriculture sector as climate change brings more extreme weather patterns.
A raingarden is a sustainable solution to managing stormwater. As demands for environmentally sustainable agriculture systems grow, it is a nature-based answer to flooding designed to act as a sponge.
Any rainwater run-off from a large storm can be directed to towards the raingarden, which intercepts and holds the rainwater in place.
The key feature of the raingarden is its shape. It is created as a basin in the ground and contains amended soil to be more infiltrating, including mixing in sand, fine gravel and compost.
Another key component is planting on top of the basin.
Kirsty, who is also presenter on BBC’s Beechgrove Garden programme said the project has intercepted run-off at the raingarden site completely and the system could be deployed on farm.
She said: “Farmers could also use a raingarden to harness the water and upscale the raingarden to use the water for crops. It can also be filtrated into a pond.
“We are getting such intense rainfall and then drought it’s case of trying to capture that water and hold it in a raingarden and use it later.
“In our agriculture sector, we have lost 97% of our wild flower meadows in the countryside, so if we could have native planting established in raingardens in a countryside setting then it could benefit wildlife and biodiversity going forward.
“In buffer strips and field margins, if you can add in these native species then it’s really good for wildlife.”
Dr Kelly said raingardens are flexible and can work small, narrow spaces but can also be adapted for much larger areas.
He said: “We are really looking for the components of higher infiltrating soil and a well thought through planting system that adds biodiversity to those areas, so you’re helping local wildlife including insects, pollinators and birds.”
The RBGE project started with a topographical survey of the affected area using open source software, but Dr Kelly was keen to stress the process does not need to be as specialised or scientific as that.
He said: “Lookat the area you want to take the run-off water from and the space you have for a raingarden and assess the amount of rainfall you expect to have.
“This can be done by going to the Met Office website and looking at the average rainfall and then the volume of rain you can expect to see can be calculated from there.
“Any size of raingarden would be beneficial and while the RBGE project has been designed to cope with a particular size of storm, no matter the size of available space, simply adding a raingarden with the extra capacity to hold and intercept the rainfall will be an improvement on what was there before.”
The RBGE raingarden was designed with a dip in the middle to allow for ponding, while the outer part holds the water in place to prevent water escaping.
In addition, planting is another important part of the system and can include trees, shrubs, herbaceous perennials or wild flowers.
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