Rain Ready: How to Design a Water-Wise Rain Garden
With just a little bit of prep work, you can design a rain garden that’s ready to capture every drop—saving water, reducing runoff, and keeping your plant babies thriving and happy.
October 23, 2024
Dominique Zamora, LA Waterkeeper Development & Communications Manager
Photo Credit: Garden Soft
Fall is here, which means now is the perfect time to start prepping your yard for the rainy season ahead. With just a little bit of prep work, you can design a rain garden that’s ready to capture every drop—saving water, reducing runoff, and keeping your plant babies thriving and happy.
Why Your Lawn Needs a Glow-Up (And How a Rain Garden Can Help)
We get it—grass lawns have been a go-to for decades. But the truth is, traditional lawns aren’t as eco-friendly as they seem. Grass lawns require a lot of water to stay green, especially in places like LA, where water is already a precious resource. Much of the water used on grass evaporates or runs off, never reaching the roots where it’s needed.
What’s worse, when it does rain, that precious water flows right off our roofs and lawns, often carrying fertilizers, pesticides, and other harmful chemicals into our storm drains. From there, the runoff travels to our rivers, streams, and eventually, the ocean. It’s a terrible cycle that not only wastes water but also negatively impacts the health of our environment.
The good news? By making just a few changes, you can transform your yard from a drab water-guzzling landscape into a sustainable lifescape that captures rainwater, reduces runoff, and helps restore our local ecosystems.
Photo Credit: Garden Soft
How to Set Up Your Rain Garden
So, what is a rain garden, anyway? Think of it as a shallow, bowl-shaped spot in your yard that’s designed to catch water. When rainwater collects there, it slowly sinks into the ground instead of running off. No more wasted rain, just a happy garden soaking up all the goodness.
Here’s how to get started: Look for an open, sunny spot in your yard that’s at least 10 feet away from your house (we don’t want water messing with your foundation). You’ll also want it to be at least 3 feet from sidewalks, and avoid placing it under big trees—they won’t love having their roots soaked all the time. Once you’ve got your spot, you can start redirecting water from your roof to collect there. You can even get fancy with multiple rain gardens or cascading setups if you’re feeling ambitious!
Calculating the Right Size for Your Rain Garden
Image Credit: LADWP
Now, before you start digging, you’ll need to figure out how big your rain garden should be. Don’t panic—it’s just a little math!
The first step is to measure the area of your roof that drains into the garden. This might not be the total area of your roof—just the section connected to the downspout(s) directing water to your rain garden.
You can use Google Earth’s Measure tool to get an overhead view and calculate the area of the roof that drains into your garden. If that sounds a bit too technical, you can also measure the length and width of the section manually by walking the perimeter of your house and using a tape measure. Multiply those two numbers to get the square footage.
Now, take that area and multiply it by 1 inch of rain (a typical LA rainfall) and 0.62 (to convert the area into gallons of water). This tells you how much rainwater will flow off your roof during a storm.
Finally, divide that number by 7.48 to convert gallons into cubic feet, which tells you how big your rain garden needs to be.
Example:
If the roof area draining into your garden is 600 square feet, multiply it by 1 inch of rain and 0.62 to get 372 gallons of water. Then divide by 7.48 to convert that into cubic feet:
372 ÷ 7.48 = about 50 cubic feet.
So, your rain garden would need to be able to hold about 50 cubic feet of water to handle runoff from your roof!
By following these steps, you’ll be well on your way to creating a rain garden that not only saves water but also helps your yard thrive in a sustainable, eco-friendly way!
Photo Credit: Garden Soft
Maximizing Rain Capture with Cisterns and Rain Barrels
Want to level up your rain capture even further? Consider adding a rain barrel or cistern to your setup. These handy gadgets let you store extra water from your roof, so when the rains come, you’ll have a backup supply to keep your garden happy during dry spells. Plus, once your rain barrel is full, the overflow will spill right into your rain garden, giving you double the water-saving power.
Even better - the City of LA offers a rebate if you install a rain barrel, so you can save money while saving water. Check out the LADWP website for all the details on how to snag one of these rebates.
Now that you’ve got your rain garden design mapped out, you’re one step closer to transforming your yard into a water-saving superstar.
Stay tuned for Step Three, where we’ll dive into the dirty work—removing that thirsty turf and getting your yard prepped for its rain garden makeover!
