Creating a Rain Garden for Stormwater Runoff

How to Construct a Rain Garden to Gather Rainwater

Rain Garden

What makes a rain garden built?
Mr. TAF and I were eager to turn our backyard into a garden as soon as we moved into our first home. Our initial objective was to lessen stormwater runoff from our house. This is due to the fact that one of the main reasons for water pollution in the US is stormwater runoff.


I recently discovered that the runoff from our roof collects debris, bacteria, and air pollutants along with bird droppings, sending them into the storm drain that drains into the nearby watershed.

Bad! especially when there are easy-to-implement methods, such as rain gardens, to collect runoff, filter it, and transform it into a valuable resource. This filtered water can refill the nearby watershed, help local wildlife, and irrigate a garden.

We hired a local because we had no idea how to design a rain garden at the time. He set up a quite nice system with three rain barrels outside our backyard patio.

We revamped the rain garden to better utilize the area after a few years, feeling more assured. Next, we developed our front yard into a second rain garden.

I gained a lot of knowledge about the procedure from creating all three rain garden ideas, which I'll discuss with you in this post.
What precisely is a rain garden?

A rain garden is a small earthen depression created to collect rainwater temporarily from an impermeable surface, like a parking lot, driveway, roof, or even rain barrel overflow.

It gathers water flowing down a natural slope by harnessing the force of gravity. Water is momentarily contained by a berm on the depression's downward side.

Rainwater can percolate into the ground in this gathering basin as opposed to running off. Plants with deep roots are cultivated in the basin to absorb surplus water.

Rainwater is slowed and filtered by plants and dirt in nature. It replicates the hydrological processes seen naturally on Earth. Stormwater harvesting done right "becomes an on-site asset rather than a liability," according to Rainwater Harvesting for Drylands and Beyond author Brad Lancaster.

In a permaculture setting, where the emphasis is on utilizing resources and interacting with nature, a rain garden is a logical addition.

Designed correctly, a stormwater basin is neither a mosquito factory nor a marsh. As a short-term collection basin, it empties in a day or two.

Are you set to create a stunning rain garden of your own?
Ten Steps to Building a Rain Garden

#1: It's all about the location.
A rain garden should be planted where the earth slopes away from a structure. Choose a location that is at least 10 feet away from structures and 18 feet away from the edge of a steep slope or a septic drain field.

Test for infiltration to make sure the water will drain in a day.

#2: Determine the rain garden's dimensions and mark them.
Determine the size of the driveway, roof, or other surface that will be used to direct water into the rain garden first. I've measured in square feet for this exercise.

Note: Just the portion of the roof that allows water to enter the downspout you want to use for your rain garden should be identified. For instance, my 1,200-square-foot roof's 600 square feet are dedicated to my backyard rain garden.

Next, multiply that figure by...08 to determine how many cubic feet your rain garden can retain during a one-inch downpour.

For my project, I calculated the volume in cubic feet by multiplying 600 square feet by.08.

Third, calculate the surface area in square feet by dividing the volume by 1.1.

I have to demarcate an area of roughly 44 square feet in my example.

Your site's conditions and slope will determine the design of your rain garden. The most typical shapes are kidney or circular shapes.

In my case, the garden was roughly 4 feet in width and 11 feet in length due to the long and narrow layout of our space.
#3: Grade the area and excavate the depression.

Dig out 12 inches of earth inside the designated area to form the depression. Make soft, rounded corners all around.

Note: Set aside some of this soil; you'll need it for the next stage.

After the depression has been fully excavated, make sure the bottom is level by using a leveling tool.

#4: Create a berm on the incline.
A rain garden requires a berm on the downhill side to retain water because it is situated on a natural slope. Using the soil from step three, construct the berm now.

Note: Set aside some rich topsoil from the remaining soil for step seven. If not, scatter it somewhere else.

#5: Add air to the bowl's bottom.
For clay soil more than for other types of soil, this phase is crucial. Water and plant roots are encouraged to into the subsurface by aerating it. Make holes all over the bottom with a digging fork to loosen up any hardpan soil.

#6: Verify the infiltration rate once more.
To ensure that the water in your rain garden would drain correctly, you tested the infiltration of your site in step one. This stage involves making sure it drains to ensure you haven't produced a mosquito pond or put people's health at danger.

It's also crucial to make sure that the large amount of water you'll be directing into this region won't flood a nearby basement.

Once the bowl is completely filled with water, set a timer. Does it finish in a day or less? In that case, move on to step seven. Should it not, you will need to adjust the layout. It could be necessary to lower the height of the berm or add extra aeration to the bowl's bottom. Test again until the drainage is fixed.

Make plans for where the rain garden's overflow will go in the event that it fills up.

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Compost the soil before planting (#7).

It's time to get the rain garden ready for planting now. Fill the bowl with 6 to 9 inches of compost soil, adding any rich soil left over from stages three and four.

#8: Use native perennials when planting.
For a rain garden, deep-rooted prairie plants like grasses and wildflowers are ideal. Although it might seem that you should choose plants that appreciate moisture, the contrary is actually true. A rain garden will usually be dry after a rain, though it may occasionally become soggy.

For this reason, prairie plants are ideal for this use. When it rains, the extra water is absorbed by their deep roots. Those deep roots aid in locating underground water reserves during dry spells.

Along with a few edible perennials for moist soil, yarrow and echinacea are some of my favorite plants for rain gardens.
On the outside of the rain garden berm above, away from the runoff, is where kale and other annual crops are grown. See my post about my front yard rainwater catchment for additional details about this rain garden.


#9: Use good mulching.
Mulching retains moisture on the surface between rainstorms and helps shield your newly planted plants. There are many different kinds of mulch for the permaculture garden, but my favorites are wood chips and shredded leaves.

#10: Send the garden's water supply to it.
Now that everything is in place, your rain garden is prepared to formally gather water from its source! This can just entail pointing the downspout in the direction of the rain garden. If necessary, a PVC pipe length can be used to extend the downspout to the desired location.

To divert the water, a small trench may need to be dug. Using flat rocks to line a trench can assist stop erosion.