Rain Gardens
Credits- All images in this presentation are from the following manual:
Rain Gardens- A How-to Manual for Homeowners
Your Personal Contribution to Cleaner Water
Authors- 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?
• Increase the amount of water that filters into the ground-
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recharging groundwater supplies
Provide protection from flooding and drainage problems
Protect streams, lakes and rivers from pollutants
Channel water away from structures
Wildlife habitat
Page 5
Elements of a Rain Garden
• Diverse mix of flowering
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plants, sedges, rushes, and
grasses
Native plants a good choicerainfall patterns
Consider bloom time
Mix heights, shapes and
textures
Mulch- composted yard debris
and leaves
Add rocks, stones, gravel for
more texture and interest
Locating the Rain Garden
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At least 10 feet from house so water does not seep into foundation
Integrate into existing landscape
Locate next to outdoor gathering areas
Don’t locate over septic system or drainfield, or under a large tree
Locate in full or partial sun
Encourage additional water filtration- don’t locate in already low spot
Add plants to low spot and create new low spot with garden
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Size and Shape of Garden
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Kidney or teardrop shapes
Size depends on:
Type of soil
Size of roof and lawn area
to drain
• Depth of rain garden
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Type of Soil and Drainage Area
• Clay- slowest rate, so
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gardens must be
larger. Too much clay
is poor location
Sandy- highest rate,
smaller gardens
The larger the
drainage area the
larger the garden
Page 9
Calculating Drainage Area
• 10 to 30 feet from a downspout- almost all water
comes from roof- calculate portion of roof that drains
into garden
• More than 30 feet from downspout- measure length
and width of up lawn and add to roof area
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Depth of Rain Garden
• Typical- 4 to 8 inches
• Ground surface of the
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garden must be level
The slope of the lawn
determines the depth
of the garden
A steeper slope will
allow a deeper garden
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Calculating Slope
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• One stake at highest point- a second stake at low point –
about 15’ away
• Use a carpenter’s or string level
• Measure distance between stakes (width)
• Measure height from ground to string on downhill stake
Calculate Slope and Depth
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Calculate Square Footage
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Shape of the Garden
The long side of the garden should face uphill
The garden should be longer than it is wide
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Length and Width of the Garden
• Choose a width that fits the area- 10’ is typical, but no
more that 15’
• Should be wide enough for the water to spread evenly
over the whole bottom surface
• Provide enough space for a variety of plants
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Digging 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 Berm
• The berm should be as high as or slightly higher than
the uphill edge
• Compact the soil in the berm by tamping hard
• Have gently sloping sides and plant to integrate into the
rest surrounding garden
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Conclusion
• Rain gardens capture
stormwater
• Rain gardens:
– fit with the FloridaFriendly principle of
reducing runoff
– facilitate a positive
way to solve a
problem
• Reduced stormwater
equates to cleaner
water bodies