Should I Build A Rain Garden At The Bottom Of A Hill

Anthony enjoys spending time in the workshop, kitchen, garden, and out fishing. Many of his DIY projects are featured in his yard.

A patch of thirsty ferns

Anthony Altorenna

A Natural Filter for Stormwater Runoff

A well-designed rain garden is an organic and low-tech method for controlling the runoff from rainstorms and snowmelt. Runoff from rooftops, driveways, patios, and other nonporous surfaces is channeled and directed away from buildings and towards a low-lying section of the yard. As the rainwater and snowmelt runoff travels across the lawn and hardscape, fertilizers and pollutants are washed into the rain garden's natural filtration and cleansing system.

Dug into a shallow bowl shape, the rain garden retains stormwater run-off and helps to control soil erosion. The sunken planting beds capture the run-off and hydrate the landscape plants, and any excess water filters down through the soil. The organic cleansing action helps to remove salts and chemical residues before the runoff seeps deep below the surface into the underground aquifers.

Rain gardens are easy to maintain and can attract birds, butterflies, toads, and other wildlife into the backyard. The above photo was taken in early summer and highlights the native ferns. Other perennials, including Brown-Eyed Susan and Ajuga Bugle plants, add colorful blooms, while an Inkberry shrub and a dwarf conifer provide texture and visual interest during the winter season.

Why Assessing Location Is Important

Our property is situated on a hillside, and we get a lot of storm water runoff and snowmelt from the surrounding higher elevations and from the rooftop of our home. The photo (above) was taken in late winter, after this year's snowmelt is gone, but before the perennial plants have awoken from their winter slumber.

Located in the lowest section of the backyard, we dug into the bottom of the sloping lawn and directly in front of a berm that forms one side of our little pond. We buried a plastic drain pipe under the lawn and connected the other end of the pipe to the primary downspout for delivering runoff from the roof. A gentle swale sculpted into the lawn helps to steer more of the water runoff from rainstorms and snowmelt away from the house and into the planting bed.

Note: The planting bed at the bottom of the sloped yard is separated from the pond by a berm of soil and rock. Do not let the water runoff drain into your koi pond!

Creating Boundaries

We used pieces of fieldstone and rock to create a border and to define the bed's borders and edges. The fieldstone also helps to disguise and protect the plastic drain pipe from the roof gutters. A few strategically placed rocks in front of the drain pipe opening helps to diffuse the rushing water as it travels downhill from the roof and into the sunken garden. We do not apply any mulch, which would likely wash away from the drainpipe area and into the basin of the planting bed. Instead, a ground cover of Ajuga Bugle plants helps to control weeds.

Between rainstorms, the opening to the drain pipe and its surrounding rock cave is a favorite hangout for a large toad. Other welcomed visitors include insects, wood frogs, chipmunks, garter snakes, and an occasional box turtle.

Our rain garden fits well into our landscape, is simple to maintain, looks good, and is very effective at controlling large volumes of runoff from the roof and the sloped yard. Planted primarily with native Christmas ferns and cinnamon ferns, the plants help to control soil erosion on our hillside and act as a natural filter. The captured stormwater runoff soaks the soil and provides plenty of moisture for the ferns before the excess water seeps down into the ground. The water runoff is utilized by the plants rather than washing away into a storm drain.

Even after a significant rainstorm, the planting bed dries out within a day and does not leave any standing water. No standing water means there's no place for mosquitos to breed!

Tips for Creating a Rain Garden

Select a low-lying area or natural depression. Consider using an area that puddles naturally after a rainstorm or snowmelt.
Strategically locate an area near a downspout or at the bottom of a natural slope, but position the planting bed at least 10 feet away from the house foundation and other buildings.
Do not select a site that is over the septic tank or leeching field.
Avoid digging in areas near underground utilities including gas, electrical and water lines. If in doubt, check your local listings for the "Call Before You Dig" contact information.
Use hardy native plants that are suitable for planting in both wet and dry conditions. Add a few non-native plants for seasonal variety of height, foliage, texture and blooms. Avoid planting exotic and invasive species.
Until the plants become established, weed the planting bed often to remove the undesirable weeds. The established and matured perennials will crowd out the weeds, reducing the long-term maintenance needed to keep the rain garden looking good.

Rain Garden at the University of Nebraska

The Benefits of Creating a Rain Garden

Controlling storm water runoff and reducing soil erosion.
Reducing the amount of runoff that enters the storm drains and municipal water treatment systems.
Protecting rivers and stream from property runoff that contains fertilizers, pesticides, and other chemical pollutants.
Filters storm water runoff while replenishing groundwater and aquifer reserves.
Attracts birds, butterflies and other wildlife.
Reduces lawn and gardening maintenance.

Do Rain Gardens Attract Mosquitoes?

This is a common misconception about rain gardens; they are not swampy bogs. A well-placed and properly planted area controls and utilizes the flow of stormwater, however, a well-designed sunken garden is not a bog and it does not stay wet all of the time (no standing water means no mosquitoes). Planted with native perennials, a typical rain garden drains well and dries out within a day or so, filtering the runoff before it enters into the groundwater system.

Consider a Rain Barrel

Rain barrels are another option for controlling stormwater runoff. We use a rain barrel to collect runoff from the roof in another area of our yard. Unlike a rain garden that uses the trapped water immediately to hydrate thirsty plants, a rain barrel collects and stores the rainwater for future use. Runoff from the roof is channeled through the gutter and downspout to an inflow point at the top of the barrel. When the barrel is full, an overflow value allows the excess water to escape. A spigot at the bottom of the rain barrel connects to a garden hose, making it easy to use the rainwater when and where it is needed, such as watering container plantings throughout the growing season.

How Do You Control Rainwater in Your Garden?

John Dove on November 03, 2017:

Hello Anthony--

Thank you for you rain garden article. I too have a very small rain garden, designed to collect rainwater flowing down a hardscape walkway at the side of our house. Someday I plan to write a Hub about my experience.

Thanks again for spreading the word about rain garders.

Joanie Ruppel from Keller, Texas on May 17, 2014:

I have a rain barrel - I swear my water bill is cheaper this spring and we have had less rain than normal.

Anthony Altorenna (author) from Connecticut on December 09, 2013:

@Lady Lorelei: Hi, and thank you for you comment. The water runoff does not actually run into the pond. The rain garden is located in front of the pond, and is separated by a berm. Rain water flows downhill into the rain garden, but cannot enter the pond.Rainwater runoff from the yard can contain fertilizer and pesticides, and should not be allowed to enter a fish pond.

Lorelei Cohen from Canada on February 04, 2013:

I would have never thought of creating a pond with the run off water from our roof. What a fantastic idea. Now to talk hubby into it.

AstroGremlin on January 21, 2013:

We don't get a lot of rain here in Southern California, but when we do it makes sense to charge the ground water instead of letting it run off.

GardenIdeasHub LM on October 24, 2012:

Your tips about creating a rain garden are really great!

julieannbrady on June 19, 2012:

I've been chatting recently with Pastiche about doing a rain garden in my back yard. I've got a schedule to have two large water oaks brought down and once that is complete, I will look seriously to this project. Good to know that they don't attract mosquitoes!

anonymous on June 04, 2012:

If I ever have a yard again, I think I must have a rain garden, I love the idea behind it and you do it so well!

KimGiancaterino on April 06, 2012:

We're on a slight grade and probably don't have room for a rain garden. I would love to get one or two of those barrels when we have our new gutters installed.

Renaissance Woman from Colorado on April 04, 2012:

Congrats on your feature (gardening monsterboard). Wish I had a need for a true rain garden. My part of Colorado gets less than 9 inches of rain per year. However, I do have a few rain and snow melt associated features. I have a couple of berms set up to create a temporary little pond during the time of year when water flows down the mountain. I do have a water catchment system set up to channel rain off of my roof into an underground cistern. Enjoyed seeing what you have done with your rain garden. I can tell it was thoughtfully and beautifully designed and constructed.

flicker lm on March 30, 2012:

Interesting idea! I collect rainwater from my roof in rain barrels, for use in my garden. But I also have runoff around the house from snowmelt in the spring, which I might be able to turn into a rain garden. Thanks!

anonymous on March 25, 2012:

Enviable work and a great showcase for a 'How to' page! I have to share this with friends who would be interested in this type of work for a garden! Enjoyed my visit too! :)

anonymous on March 23, 2012:

Great tip for conserving water, I love the idea of having a rain garden.

Einar A on March 23, 2012:

Looks like that garden really makes your yard a pleasant place to be, as well as controlling water runoff!