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What is a Rain Garden?
Are you tired of that soggy area in the lawn that collects water any time it rains? Have you ever considered turning it into a rain garden? A rain garden is a depressed area that collects rainwater from a driveway, roof, or street. This type of garden allows excess rainwater to soak into the ground, improving your stormwater drainage. Grasses and flowering perennials are planted in rain gardens to make the soil more porous.
How does a rain garden work?
Rain gardens improve water runoff by increasing the absorption ability of the soil. High absorption is achieved by adding rocks, sand, compost, or plants. Since rain gardens are shaped like a bowl, rainwater will flow into your garden and filtrate through the soil.
What are the benefits of a Rain Garden?
Rain gardens can reduce flooding, filter pollution, protect the drinking water supply, and improve your surrounding landscape! They also reduce flooding by reducing the amount of water entering traditional stormwater systems. Rain gardens simulate the natural absorption of rainwater into the soil, which removes pollutants. By removing contaminants from the water, a rain garden will protect your drinking water supply and local bodies of water.
How to make a rain garden
Rain gardens perform best when integrated into your property’s water runoff pattern. Designing must begin with an analysis of the site and the stormwater loads on each system Stormwater load will affect the size, materials, and plants used in the garden. It will require an area for water to collect and filter into the ground.
Your rain garden will perform best at the bottom of a watershed slope. Observe your yard during heavy rain and map where the water flows. There are a few stipulations. Do not place your garden closer than 10 feet from a structure foundation. Also, do not place it near a septic tank or underground utility lines. Wrong placement will compound your water problems, not solve them!
Rain Garden Depth
To determine your rain garden depth, you will need to calculate your soil’s porosity. To measure it:
- Dig a hole in the ground and fill it with water.
- Time how long it takes for the water level to drop an inch.
- Divide that time by 24 to calculate how many inches of water your soil can absorb in a day.
That number is the ideal depth for your garden.
You will need to estimate the volume of water that will be flowing into your garden. To do this:
- Calculate the area that will bed shedding water.
- Multiply the runoff area by the inches of rainfall to calculate your water volume.
- Divide your water volume by the depth of your rain garden, and you will have your total rain garden size. It is ok to bend the rules.
- Make sure your rain garden’s size fits your other landscaping.
The soil used to filter the stormwater is called a substrate. Typically the substrate consists of 60% sand, 20% compost, and 20% topsoil. This mixture makes the substrate more porous than the surrounding soil. You can also line the basin with rocks to make the ground more permeable.
Rain gardens are often located near water drainage sources, like a roof drain pipe or a driveway. The porous soil allows the water to drain from the roof and provides groundwater to recharge. To increase drainage, you can add a french drain or sub-surface drainage to the bottom of the garden. Eliminating standing water prevents mosquito breeding and home flooding.
Rain gardens utilize plants to hold the soil together and improve drainage. Utilize vegetation that can withstand brief periods of flooding since rain gardens swing between extreme wet and dry spells. At the bottom of the bowl, grow vegetation that can withstand up to 6 inches of standing water. This area is called Zone One.
In Zone Two, the middle zone, plant vegetation can handle several inches of water during a storm. This zone will drain immediately after the rain. Zone three is the transition zone between the rain garden and the surrounding landscaping. What should be planted in Zone Three? Any common garden plant will work! Use this area to enhance your landscape design. Check out the lists below for plant ideas!
To learn more about the zones and the plants that grow best in each one, check out our blog on the best plants for softscape.
Zone One Plants
- Broad and Narrow leafed meadowsweet.
- Virginia Sweetspire
- Blue Star
- Mist Flower
- Red Maple
Zone Two Plants
- American Beautyberry
- Red-osier Dogwood
- Sweet Pepperbush
- Blue False Indigo
- Bottlebrush Grass
- Culvers Root
- Threadleaf Coreopsis
- Paw Maw
Zone Three Plants
- American Cranberry Bush
- Black Chokeberry
- Witch Hazel
- Sweet Pepperbush
- New Jersey Tea
- Blazing Star
- Anise Hyssop
- Butterfly Weed
- Calico Aster
- Staghorn Sumac
With the addition of remediation materials, your garden will filter pollutants out of the water. Typical contaminants found in stormwater include organic materials like animal waste, oils, heavy metals, and fertilizer nutrients.
These pollutants will cause the over-promotion of plants and algae if they drain into rivers and streams. Directing water to flow between soil and vegetation will capture the particles and trap them in the soil. Once those particles are trapped in the ground, they begin to break down.
Alternatives to a Rain Garden
While rain gardens are one of the best ways to handle stormwater runoff, other options exist. The options will vary depending on what type of runoff you are containing. Here are some alternatives.
Infiltration beds are well suited for large, flat spaces like meadows, lawns, or driveways. An infiltration bed is buried, so this drainage solution is invisible. To build an infiltration bed, we dig a trench and fill it with 3 -04 feet of stone. This stone will temporarily hold stormwater during a storm. These reservoirs will release the water over the next few days.
Have you considered a paver driveway? Driveways are usually made from materials that do not absorb any water. If you replace it with permeable pavers, the stormwater will be absorbed by your driveway instead of washing off. Reducing puddles will prevent floods, reduce the heat island effect, and naturally filter the water.
At Willowgates Landscaping we offer Permeable Driveway services, creating a driveway that is more durable than the standard driveway and offers benefits to the environment.
Rain Garden Contractor in Pennsylvania
We would love to help you with your stormwater management needs! Willow Gates Landscaping installs rain gardens, infiltration beds, and permeable driveways in Berks County and the surrounding areas. We have provided quality service to southeastern Pennsylvania since 2005.