Rain gardens
Creating habitat for wildlife, reducing flooding and cleaning water.
Rainfall flows down rooftop into gutter
Rain water enters rain garden from downpipe
This rain garden is a ‘planter’ so it’s above the ground, but you can also build them into the ground! Didyou know?
Water filters through the rain garden before entering watercourses
Why make a rain garden?
Lots of hard surfaces, like roads and roofs, cause flooding problems during heavy rain. As water runs off into drains, it can also wash pollutants into rivers, damaging the animals and plants that live there.
Soil, sand and compost mixture
Flooding and pollution is likely to increase with climate change as more frequent heavy rainfall occurs. Adding more trees and plants into towns and cities can help by collecting some of this water and filtering out pollutants, reducing what goes into waterways.
Rain gardens add this much needed vegetation to urban areas while naturally cleaning water and creating food sourc shelter for insects like bees and butterflies.
Slotted pipe
Overflow pipe
Gravel
Geotextile
Example of planter-style rain garden
How do I make a rain garden?
Choose the right location
Rain gardens are best located at low points where surface water will flow. However, the location might be determined by the downpipes from your guttering, ideally below a downpipe and near an existing drain
How big should my rain garden be?
The bigger the better, but any size rain garden will help Ensure you construct an overflow pipe at least 100mm above the top of the mulch and 100mm below the top of the garden to remove excess water.
Construction
Hand digging is best when constructing a sunken garden to ensure you don’t hit any buried existing services. If constructing a planter-style rain garden, ensure there is a solid bottom to retain water. Work out exact quantities based on the size of your planter using these percentages.
Planting
Consider how much sunlight your garden will get and how much water it will receive. Plant shrubs such as dogwood, guelder rose, yellow flag iris, ferns, sedges and grasses. Native plants are preferred if possible and hardy plants will last longer. Plant water tolerant plants by your downpipe.
Maintenance
Follow your plants guidance on pruning. Occasionally some plants might need replacing - keep an eye on what thrives. Keep checking your overflow pipes to make sure they are draining freely and not blocked up.
Example of shallow depression rain garden
As illustrated, rain gardens can be either a planter or shallow depression. They are designed to capture rain water flowing off roofs and slow the flow of water back into drains and eventually watercourses.
Rain gardens can help to reduce flooding by storing rain water and reduce pollution by filtering it through, whilst also allowing you to create a wildlife-friendly feature that often waters itself. You can even grow some edible or sensory plants for something different!
Rain gardens by Gloucestershire Wildlife Trust
We’ve built a variety of rain gardens over the years. Using different materials, methods and designs, we ’ ve slowed the flow of water across the whole county. We’ve worked with local communities to reduce the impact of flooding in their area, while improving water quality and boosting wildlife biodiversity.
