With unpredictable weather becoming more frequent, having an effective water conservation and filtration system in your garden is more important than ever. If you have a garden drain that leads to the street or sewer, let me introduce you to a rain garden! This garden project allows you to disconnect your downspout from the sewer and instead allow rainwater to flow back into the ground.
While a rain garden may sound fancy, it is actually a Low maintenance system used to filter and release stormwater runoffThis helps water to be retained in the soil and streams, just as nature intended.
I live in a rainy climate where there is a lot of great work being done to research, build, and educate the public about rain gardens and why they are so important. It takes a while for these rain gardens to fill in, but they are beautiful when they are filled!
To test some of the established rain gardens, I took a walking tour with Deborah Jones from Cougar Creek Streamkeepers. They are an amazing group of volunteers dedicated to helping restore and maintain the health of Cougar Creek, a salmon stream in BC.
One of the important things they do is Create rain gardens to help reduce stormwater runoff. You can see the rain gardens I visited on this map (stops 13, 14, 15, 16, and 17). McCloskey Elementary School in particular has a beautiful rain garden. You can see the school’s rain garden in the photos in this post, along with the other stops.
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By the way, this is one of many projects featured in my latest book, Garden of Regeneration. Besides sustainable drainage systems and gardens, I also mention many other ways you can create a natural and self-sustaining garden. Be sure to check it out if you’re ready to take your garden further in the direction of sustainability.
What is a rain garden?
A rain garden is Any type of landscape that can receive, absorb, and filter stormwater runoff. Typically, this runoff comes from man-made surfaces such as sidewalks or roofs.
Without human intervention, all rainwater would naturally seep into the ground. But the more buildings, streets, and other urban areas we create, the more land we coverThis means that the area of land where rainwater can seep into the soil is becoming less and less.
Our solution is to create drainage systems such as gutters, storm drains and ditches. This is called urban flowThese drainage systems return water to streams and rivers, but they become extremely polluted. They carry waste, oil, fertilizers, gas, pesticides, and more.
A rain garden can help retain water in its natural place and filter all the runoff in the city. It will remove contaminants that would otherwise go down the drain.
In addition to their functional function, they can also be beautiful garden areas, provide habitat for local wildlife and even provide much needed shade during the warm season.
How do rain gardens work?
House gutters sometimes lead directly to the sewer system, carrying rainwater through the same treatment system as toilets, showers, and sinks. Not only is this treatment unnecessary, it can also cause the drainage system to overflow and flow directly into the nearest river, lake or ocean. This leaves local soil and water sources without the rainfall needed to stay healthy.
A rain garden’s reservoir is filled with moisture-loving plants that can act as biofilter for water purification. The upper drainage ditches contain drought-tolerant plants that like to grow deep roots and access groundwater when possible.
Designing a rain garden can be as simple as installing a Fill a gravel trough with gravel leading to the drain and build a garden bed around it to design more complex rain gardens that provide shelter for birds and insects.
Create a unique rain garden design
Every rain garden will look different but there are some rules you need to follow to get the right design!
The garden is built like a trench: a central depression of about 4-8 inches with soil banks around the perimeter to retain water. The central planting area should be level to avoid ponding. The garden is usually twice as wide as longwith the widest part located at the lowest point of the slope.
Locate an area Stay 5 to 15 feet away from buildings. At a minimum, the overflow drain must terminate 5 feet from structures without basements and 10 feet from structures with basements greater than 5 feet; add 2 feet for each additional foot of basement depth. Do not place the rain garden over underground utilities or large tree roots.
The location of rain gardens should be well back from buildings to Overflows flow directly out through the overflow drains into other gardens rather than back towards structures.; however, the garden itself should not have an overall slope of more than 5% (1 foot in 20 feet).
In rainy climates, the inner bottom of the garden should be 15% of the area of the overflow water source. So a 500 square foot tree stump needs a 75 square foot garden base (500×0.15=75).
These measurements were provided by Seattle Public Utilities’ RainWise Program and the King Country Wastewater Treatment Division.
How to build a rain garden
- Determine the location of the garden and extend the drain pipe down to the highest point of the garden. Choose a location that can handle large amounts of saturated water, away from a septic system, and away from trees, shrubs, or plants that do not like their roots wet.
- Use a garden hose or sprinkle flour to outline the shape of the garden.
- Dig the base 24 inches deep and use soil to build a bank around it.
- Fill the base with 12 inches rain garden soil mix (one-third compost and two-thirds garden soil). This leaves 12 inches of pond depth (the space from the base of the soil to the ground where water can accumulate during rains).
- At the lowest point of the garden edge, create an area filled with rocks. This allows water to run off without eroding the garden. Overflow water should be directed into the street drain.
- Planting rain garden design with water loving plant. Add optional overflow drains to other garden beds so overflow water can be used for irrigation.
Plants in rain garden
Choose plants that are suitable for the conditions of your garden. Suggested plants might be native or garden favorite plants thrive in your unique microclimate. The best place to find the right plants for your garden is at your local nursery, which carries both native and cultivated plants.
Plant in the garden, cover with 2 inches of compost, and water well. Water regularly to keep the plant growing for the first few years. Add more compost as an annual mulch.
Often The plants will move into the correct position in the garden.Like the drought-tolerant plants below, these have reestablished themselves in the basin of this area.
Rain Gardens FAQ
Find a high to low location where gravity can help drain water. You want an area that can handle a lot of saturated water.
Keep your rain garden away from large trees where their roots can invade, and near buildings and septic systems. Also consider the soil, as clay soils will require a larger rain garden to avoid ponding.
The best shape depends on your space, as you want to work with gravity rather than against it. Most rain gardens are designed to run from the gutter and down. People also design them along driveways or ditches for a longer, narrower design shape.
You want to maximize infiltration. Run water around or around the garden so it is filtered before it flows into the overflow.
Also, make sure you call your local authorities and map out utility lines on the property when designing your shape.
Arborist wood chips are great for improving water absorption as they prevent soil compaction. Regular addition of mulch will retain moisture in the soil and improve water retention and aeration.
Rocks do not absorb water, so use them sparingly and as a finishing touch. Once you are sure that the soil is loose and ready to absorb water, you can add rocks for aesthetic purposes or to protect the soil from erosion in areas with a lot of water flow. Keep the layer thin and don’t overdo it!
As you can see, creating a rain garden is quite simple and can provide lasting benefits for years to come. If you have any questions, please leave them in the comments section below!
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