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Find out why and how to build your own rain garden, helping to clean storm water run off and beautify your community.


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Did you know…?


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Sixty six percent of all freshwater is found in solid form in ice caps & glaciers.

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97% salt

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That leaves only 1% of all the Earth's water in a form useable to humans and land animals.

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This small amount of fresh water is found in our lakes, rivers, streams, ponds, and in the ground.

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The Water Cycle

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When it rains in a natural, undisturbed environment about 50% of the rainwater infiltrates into the ground, 40% evaporates or is taken up by plants and only about 10% runs off the surface.

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Our activities and development on land alters how water naturally travels through the landscape. As we develop the land, we add roads, houses, parking lots, sidewalks, and driveways.

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These hard surfaces are called impervious surfaces, because water cannot pass through them as it does through soil, so the water is forced to evaporate or run off.

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At 30 to 50% impervious (such as suburban areas like Mandeville), runoff is tripled.

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Stormwater runoff is one of the biggest problems facing our waterways. Mandeville’s growing population has increased the impervious surfaces, which increases runoff and pollutants in our lakes, rivers, streams and oceans.

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Increased stormwater runoff leads to degraded water quality, loss of habitat and aquatic life, increased flooding and stream erosion.

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Building a rain garden (or a couple of rain gardens) in your own yard is probably the easiest and most cost efficient thing you can do to reduce your contribution to stormwater pollution.

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A rain garden is a shallow, constructed depression that is planted with deep-rooted, native plants & grasses. It is located in your landscape to receive runoff from hard surfaces such as a roof, a sidewalk and a driveway.

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Rain gardens slow down the rush of water from these hard surfaces, holds the water for a short period of time, and allows it to naturally infiltrate into the ground. A rain garden can be thought of as a personal water quality system because it filters the runoff from your roof and lawn and recharges the groundwater.

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Rain gardens are a beautiful and colorful way for homeowners, businesses and municipalities to help ease stormwater problems. There is a growing trend by municipalities and homeowners to incorporate natural processes to help relieve flooding and pollution, and we hope to continue that trend.

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Because rain gardens are dug 4" to 8" deep, and in some cases 1' - 2' deep, they hold larger quantities of rainwater, conserving the use of municipal water and making their overall construction more cost efficient than other green alternatives. Rain gardens also need less technical experience to install and can be installed without permits or heavy equipment.

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By capturing rainwater from your roof, driveway and sidewalks and diverting it into a great looking rain garden where it can slowly soak into the ground, filter contaminants and keep quantities of clean water from going down the sewer system, you'll have a great looking garden that puts water in its place.

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Rain gardens are an excellent way to reduce the impact of impervious surfaces and polluted runoff because they are low-tech, inexpensive, sustainable and esthetically beautiful, and in some areas, there may be grants available to subsidize the minimal costs of constructing a rain garden.

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Rain Gardens

Filter runoff pollution Recharge local groundwater Conserve water Improve water quality Protect rivers and streams

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Rain Gardens

Remove standing water in your yard

Reduce mosquito breeding Have water-cooling benefits

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Rain Gardens

Reduce potential of flooding Create habitat for birds &

butterflies Survive drought seasons Reduce garden maintenance

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Rain Gardens

Enhance sidewalk appeal Increase garden enjoyment Remove excess pollutants

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To start your own rain garden, you must first find the best location, test your soil, determine the size, dig or build your garden and plant your native plants.

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• Between the source of all the water runoff and its destination

• At least 10’ from your house or building• At least 25’ from a septic system• In a sunny place, if possible

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The soil is an important factor in your rain garden, so it would be great to first test your soil. The soil binds pollutants, preventing them from moving down into groundwater supplies.

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Soil Type

How This Type of Soil Behaves

Sand Will not form a ribbon of any length and has a non-sticky, grainy feel

Sandy Loam

Will form a ribbon less than a half-inch in length and feels gritty

Clay Loam

Will form a ribbon less than an inch in length and feels smooth and only slightly sticky

Clay Will form a ribbon longer than an inch in length and feels smooth and sticky

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Once you determine the soil type, you will need to test the infiltration rate of the soil by digging a 12 inch hole at the site and filling with water.

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Mark the water level with a stick or ruler then observe how long it takes the water to totally infiltrate the soil. Soil that drains completely in 24 hours is acceptable with minimal amendment of compost and sand. Soil that takes longer than 24 hours must be amended with compost or a mixture of compost and sand to make it more porous or a new site must be chosen.

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The next step would be to determine the path of stormwater in your garden. Try mimicking a rain event by using a hose in place of your downspout. The area where water collects is where you should plant your wet zone plants.

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Dig up the soil in the rain garden with a shovel to a depth of 4-6 inches and grade the area so there is a lower catch basin.

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Use the excess soil to create a small berm 6 to 12 inches tall on the lower side of the garden to help catch water runoff to pool in the heart of the rain garden. Cover this berm with the extra sod you removed from the hole. This will create your dry zone.

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Native Plant Suggestions

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• Does the garden receive adequate sunlight for the plants you select?

• Can your plants survive in times of drought or heavy rains?

• Will the plants blend in with the existing landscaping?

• Have you planned for seasonal timing of growth so that color and wildlife food are available year round?

• Have you thought about the height and width of full-grown plants?

• Have you thought of what species of wildlife you want to attract?

• Have you thought of specialized plants for each zone of the rain garden you will have: the hydrazone, hardiness zone, heat zone?

• Have you chosen a mixture of plants with different form and texture—woody and perennials?

Questions to Consider When Choosing Your Plants

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Once your plants have been chosen and placed according to zone, you are ready to finish your garden. Mulch the rain garden area after planting with a heavy hardwood mulch. Layer it two to three inches deep to cover all the exposed soil in the garden area. Avoid using lightweight mulches that will float or wash away once water runoff collects and pools in the rain garden.

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Water the garden thoroughly to remove any air pockets in the soil from planting. Add 3 to 5 inches of irrigation to all planted areas through the mulch.

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…and enjoy!

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