Rain Gardens

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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
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Why use Rain Gardens?

• Increase the amount of water that filters into
  the ground- recharging groundwater supplies
• Provide protection from flooding and drainage
  problems
• Protect streams, lakes and rivers from pollutants
• Channel water away from structures
• Wildlife habitat

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Elements of a Rain Garden

• Diverse mix of flowering plants, sedges, rushes,
  and grasses
• Native plants a good choice- rainfall patterns
• Consider bloom time
• Mix heights, shapes and textures
• Mulch- composted yard debris and leaves
• Add rocks, stones, gravel for more texture and
  interest

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Locating the Rain Garden

• At least 10 feet from house so water does not
  seep into foundation
• Integrate into existing landscape
• Locate next to outdoor gathering areas
• Dont locate over septic system or drainfield, or
  under a large tree
• Locate in full or partial sun
• Encourage additional water filtration- dont
  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

• 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 gardens must be larger.
  Too much clay is poor location
• Sandy- highest rate, smaller gardens
• The larger the drainage area the larger the garden

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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 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 carpenters or string level
• Measure distance between stakes (width)
• Measure height from ground to string on downhill
  stake

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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
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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 Florida-Friendly principle of
  reducing runoff
• facilitate a positive way to solve a problem
• Reduced stormwater equates to cleaner water
  bodies