What Is A Rain Garden And How Do I Build One?
Rachel Burris7-Minute Read
October 19, 2021
The sound of rain falling on your rooftop, driveway and road may be a pleasant one. But that soothing sound is often a symptom of a larger problem. These nonporous surfaces create stormwater runoff, as they prevent water from being absorbed into the soil. Stormwater runoff may not sound like such a bad thing, but as it accumulates, it can damage your property and have dangerous effects on the environment.
If you’ve noticed a large amount of stormwater runoff, it may be time to do something about it. Depending on the landscape of your property, creating a rain garden may be just the thing to keep your stormwater runoff in check. Before we get into how to grow a rain garden, let’s go over what a rain garden is and examine the problems with stormwater runoff, so you have a better idea of why you should create one. After reading this article, you’ll be able to do your part to help the environment and protect your home in the process.
What Is A Rain Garden?
Rain gardens are an environmentally friendly solution to stormwater runoff problems. Planted on downward-sloping ground, they use native plants to catch, hold and filter runoff. By creating these gardens, homeowners are able to minimize stormwater runoff, eliminate issues with water drainage and prevent pollutants from entering local bodies of water.
What Is Stormwater Runoff?
Stormwater runoff is rainwater that’s unable to be absorbed into the ground. As the rainwater flows off nonporous surfaces (like paved roads, driveways, patios and rooftops) and across flat ground, it collects several pollutants, like nitrogen, phosphorus, metals, oil, gas and pesticides. Instead of being soaked up by the soil or evaporated into the air, as is the case in forests, the massive amount of water eventually flows into local bodies of water.
Why Is Stormwater Runoff A Problem For Homeowners?
When it rains or snows, you may notice that your gutters overflow, your yard remains soggy or water pools in certain areas. These problems are often the result of stormwater runoff. When it’s left unmanaged, it can cause serious damage to your home, like a flooded basement, leaky roof or foundation issues. It can also lead mold and mildew to grow, septic systems to flood and water wells to become contaminated. Dealing with water damage can be time-consuming and costly, which is why it’s best to get ahead of the problem whenever possible.
Is Stormwater Runoff Bad For The Environment?
As more and more land has been developed, stormwater runoff has become a growing environmental concern. With the increasing amount of construction of both properties and paved roads, there is less soil for stormwater runoff to be absorbed into. When the water isn’t soaked up into the ground, it flows to local bodies of water, where it causes floods and erosion that disturb natural habitats.
Stormwater runoff is also referred to as polluted runoff because it picks up many pollutants and carries them into waterways. As the water collects sediment and heavy metals from building sites, oil, grease and toxins from automobiles, fertilizers and pesticides from yards and bacteria and viruses from septic systems, it travels through storm drains and is deposited into streams and rivers. The polluted water decimates wildlife populations and destroys local vegetation. Furthermore, it can also find its way into local sources of drinking water, making it dangerous to consume.
Now let’s get into the details about how rain gardens help with stormwater runoff and what you can do to create one on your property.
Rain Garden Benefits
To prevent costly damages to property and protect the environment, many homeowners are now building rain gardens. These gardens collect stormwater runoff and filter it through the soil before it has a chance to reach storm drains. Let’s go through how rain gardens work.
As stormwater runoff accumulates, it creates pools of water. Since rain gardens are built on sloped land, they prevent the water from traveling to the storm drain and instead allow the water to collect in the sunken planted area of the garden. By trapping the water in the depressed area, the runoff is given the time it needs to be fully absorbed into the soil. The absorption process usually takes about 12-48 hours.
Thanks to the vegetation planted in the depressed area, bioretention can take place. Bioretention is the process by which soil and plants filter out the pollutants within water. As the roots hold the water, the pollutants contained in the runoff are percolated through the soil. The sediment is retained by the stems, while the nitrogen and phosphorus are absorbed, enhancing the plants’ growth. The deeper the roots of the plants, the better the water is absorbed.
Planning Your Rain Garden Design
You can minimize the amount of stormwater runoff on your property by building your own rain garden. If you live on a modest plot of land, don’t worry – even very small rain garden designs can make a difference. This project will likely take a few days to complete, but it can be accomplished easily, especially if you choose to contract out the digging.
To determine the best place to build your rain garden, observe how water travels across your property. Ideally, it’s best to choose a spot that’s sloped below your house and just above where runoff accumulates.
However, it’s crucial that your rain garden is neither on top of your septic system nor less than 10 feet away from your house. If your rain garden is built too close to your foundation, it could cause flooding. Since creating your rain garden will require digging, you also want to ensure that you don’t place it above utility lines or under trees. If necessary, it’s possible to run a pipe through the area that directs the runoff to the garden.
This cost of this project will vary depending on the size and scope of your new rain garden. The average homeowner will typically spend $3-$4 per square foot on a rain garden. This price can vary, however, depending on the soil density and plants that you choose to utilize in your design.
Tools and Materials
The tools and materials that you’ll need for your rain garden design include:
- Sod cutter
- Rocks and boulders
- Native plants
- PVC piping
How To Build A Rain Garden
Although creating a rain garden necessitates more planning than your typical garden, it requires minimal maintenance once it’s fully set up. Let’s take a look at the five necessary steps for planning and establishing your rain garden.
1. Consider Your Plants
Before you begin building your rain garden, it’s important that you determine what you’ll be planting in it. Rain gardens typically have three different zones that each incorporate plants with different levels of water tolerance.
The first zone in the center of your rain garden is where most of the water will pool, so you’ll want to use plants that can withstand standing water. Native plants are recommended for this area because they have deeper roots that can absorb more water.
The second zone wraps around the perimeter of the first. This area should be filled with plants that can endure intermittent periods of standing water.
The third zone, which is the outermost ring or edge of the garden, should include plants that are drought tolerant. Plants that are accustomed to drier climates are preferable in this zone because they’ll receive the least amount of water. This is a great area for xeriscaping.
Speak to someone at a local gardening store to find out which plants are native to your area and how each species tolerates water.
2. Test Your Soil
After determining the location of your rain garden, you must test the soil to ensure that it can infiltrate the water fast enough. The ideal rate of infiltration is .5 inches per hour or higher. To test the rate of your soil, dig a two-foot deep hole in the desired area, time how long it takes for 8-12 inches of water to be absorbed and divide the amount of water by the number of hours.
For instance, if 10 inches of water is absorbed in 16 hours, the infiltration rate would be .63 inches per hour. If your rate is below .5 inches per hour, you’ll have to dig a deeper hole. If your rate is below .1 inches per hour, you’ll have to find a better site for your rain garden.
3. Cut Your Grass And Begin Digging
Once you’ve decided on the size and shape of your rain garden, mark the perimeter and remove the grass within the area. It’s best to do this with a sod cutter so you can sever the roots and roll large sections of the grass off the area. Then, it’s time to start digging.
Most rain gardens range from four to eight inches deep and consist of 100-300 square feet. As you dig, make sure to create a flat base in the center of the garden that’s at least 2 feet wide to ensure that the water can infiltrate uniformly. You’ll want the sides of the garden to be sloped so that it's shaped like a bowl. Just make sure the outer edge of the garden is high enough to keep the water from flowing out – shoot for at least six inches above the highest expected water level.
4. Add Soil, Plants And Mulch
When adding soil to the area, leave about 6-12 inches empty. For regular soil, combine it with compost before refilling, so it’s 65% soil and 35% compost. For clay soil, fill the area with 60% sand and 40% compost.
When you begin planting, make sure that you put the native plants that can withstand the most water in the center. Then, move to the middle ring, and plant the second most water tolerant plants along the slope of the garden. The drought-tolerant plants should be reserved for the edge of the garden. After everything has been planted, you’ll want to add three inches of mulch across the entirety of your rain garden.
As your plants begin to grow, you should water all of them, including the species in zone three, which require the least amount of water. This additional watering will ensure that all your plants live through the drier seasons.
Because you included compost in your soil, you will not need to fertilize your rain garden. However, you should add mulch on an annual basis to ensure that the mulch layer never gets below three inches. As time goes on, your rain garden will become mostly self-sufficient. Just be sure to weed and prune it regularly.
The Bottom Line: Good For Your Home, Good For The Planet
Stormwater runoff is detrimental not just to your home but also to our planet as a whole. If we want to eliminate pollution from our waterways, protect the wildlife in our communities and ensure the planet outlives us, we need to start taking measures to limit the amount of runoff that enters our storm drains. Creating a rain garden on your property is a fantastic way to start doing your part. Your rain garden will increase the amount of runoff that’s absorbed into the ground and add beauty to your yard.
If you think the rest of your land could use some sprucing, check out some other ideas for how you can elevate your landscaping.
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