Rain Rain GardensGardens

Credits- All images in this presentation are from the following manual: Rain Gardens- A How-to Manual for Homeowners Your Personal Contribution to Cleaner WaterAuthors- City of Tallahassee Stormwater Management, TAPP- Think About Personal Pollution. www.TAPPwater.org. The original concept and illustrations were derived from the University of Wisconsin Extension Service

Why use Rain Gardens?Why use Rain Gardens?• Increase the amount of water that filters into the ground- Increase the amount of water that filters into the ground-

recharging groundwater suppliesrecharging groundwater supplies• Provide protection from flooding and drainage problemsProvide protection from flooding and drainage problems• Protect streams, lakes and rivers from pollutantsProtect streams, lakes and rivers from pollutants• Channel water away from structuresChannel water away from structures• Wildlife habitatWildlife habitat

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Elements of a Rain GardenElements of a Rain Garden

• Diverse mix of flowering Diverse mix of flowering plants, sedges, rushes, and plants, sedges, rushes, and grassesgrasses

• Native plants a good Native plants a good choice- rainfall patternschoice- rainfall patterns

• Consider bloom timeConsider bloom time• Mix heights, shapes and Mix heights, shapes and

texturestextures• Mulch- composted yard Mulch- composted yard

debris and leavesdebris and leaves• Add rocks, stones, gravel Add rocks, stones, gravel

for more texture and for more texture and interestinterest

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Locating the Rain GardenLocating the Rain Garden• At least 10 feet from house so water does not seep into foundationAt least 10 feet from house so water does not seep into foundation• Integrate into existing landscapeIntegrate into existing landscape• Locate next to outdoor gathering areasLocate next to outdoor gathering areas• Don’t locate over septic system or drainfield, or under a large treeDon’t locate over septic system or drainfield, or under a large tree• Locate in full or partial sunLocate in full or partial sun• Encourage additional water filtration- don’t locate in already low spotEncourage additional water filtration- don’t locate in already low spot• Add plants to low spot and create new low spot with garden Add plants to low spot and create new low spot with garden

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Size and Shape of GardenSize and Shape of Garden

• Kidney or teardrop shapesKidney or teardrop shapes

• Size depends on:Size depends on:

• Type of soilType of soil

• Size of roof and lawn area Size of roof and lawn area

to drainto drain

• Depth of rain gardenDepth of rain garden

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Type of Soil and Drainage Type of Soil and Drainage AreaArea• Clay- slowest rate, Clay- slowest rate,

so gardens must be so gardens must be larger. Too much larger. Too much clay is poor locationclay is poor location

• Sandy- highest rate, Sandy- highest rate, smaller gardenssmaller gardens

• The larger the The larger the drainage area the drainage area the larger the gardenlarger the garden

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Calculating Drainage Calculating Drainage AreaArea• 10 to 30 feet from a downspout-10 to 30 feet from a downspout- almost all almost all

water comes from roof- calculate portion of roof water comes from roof- calculate portion of roof that drains into gardenthat drains into garden

• More than 30 feet from downspout-More than 30 feet from downspout- measure measure length and width of up lawn and add to roof arealength and width of up lawn and add to roof area

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Depth of Rain GardenDepth of Rain Garden

• Typical- 4 to 8 inchesTypical- 4 to 8 inches

• Ground surface of the Ground surface of the garden must be levelgarden must be level

• The slope of the lawn The slope of the lawn determines the depth determines the depth of the gardenof the garden

• A steeper slope will A steeper slope will allow a deeper gardenallow a deeper garden

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Calculating Slope Calculating Slope

• One stake at highest point- a second stake at low point One stake at highest point- a second stake at low point – about 15’ away– about 15’ away

• Use a carpenter’s or string levelUse a carpenter’s or string level• Measure distance between stakes (width)Measure distance between stakes (width)• Measure height from ground to string on downhill stakeMeasure height from ground to string on downhill stake

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Calculate Slope and Calculate Slope and DepthDepth

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Calculate Square FootageCalculate Square Footage

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Shape of the GardenShape of the Garden

The long side of the garden should face uphill

The garden should be longer than it is widePage 14

Length and Width of the Length and Width of the GardenGarden• Choose a width that fits the area- 10’ is typical, Choose a width that fits the area- 10’ is typical,

but no more that 15’but no more that 15’• Should be wide enough for the water to spread Should be wide enough for the water to spread

evenly over the whole bottom surfaceevenly over the whole bottom surface• Provide enough space for a variety of plantsProvide enough space for a variety of plants

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Digging the Rain GardenDigging the Rain Garden

• Dig the depth of the garden at the uphill stake• Maintain the same depth across the bottom• Pile the dirt on the low side to create the berm

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Building the BermBuilding the Berm• The berm should be as high as or slightly higher The berm should be as high as or slightly higher

than the uphill edgethan the uphill edge• Compact the soil in the berm by tamping hardCompact the soil in the berm by tamping hard• Have gently sloping sides and plant to integrate Have gently sloping sides and plant to integrate

into the rest surrounding gardeninto the rest surrounding garden

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ConclusionConclusion• Rain gardens capture Rain gardens capture

stormwaterstormwater• Rain gardens:Rain gardens:

– fit with the Florida-Friendly fit with the Florida-Friendly principle of reducing runoffprinciple of reducing runoff

– facilitate a positive way to solve facilitate a positive way to solve a problema problem

• Reduced stormwater equates Reduced stormwater equates to cleaner water bodiesto cleaner water bodies