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Rain Gardens


Or further away so it catches water from your roof and your lawn ... If your lawn has a slope greater then 8% you will need to use some of the soil ... – PowerPoint PPT presentation

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Title: Rain Gardens

Rain Gardens
  • Landscaping for water quality
  • Presented by the Soil and Water Conservation
    District of Lake County

What is a rain garden?
  • A rain garden is a shallow depression in your
    yard that is planted with native flowers and
  • It is positioned in the yard to receive runoff
    from your roof, sidewalks, driveway and lawns
    allowing water to slowly soak into the ground

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Rain gardens a short history
  • Rain gardens are a relatively new concept
  • They emerged in 1993 in Maryland out of the need
    for low cost stormwater infiltration methods that
    would improve water quality
  • The idea of bioretention or holding and filtering
    stormwater in plant systems came about
  • The term was later refined as rain gardens as it
    was more attractive
  • Since then, the concept of rain gardens has been
    developed by other states especially Minnesota,
    Michigan and Wisconsin
  • A more widespread use of such gardens could
    dramatically improve water quality everywhere

Why are they important?
  • The conversion of land from forests, grassland
    and agricultural land to urban and suburban lots
    has reduced the natural ability rain water to
    infiltrate into the ground because of increased
    impervious surfaces
  • This results in stormwater runoff that carries
    pollutants from streets, parking lots and lawns
    into our local lakes and streams, degrading their
    water quality

Why are they important?
  • Urban areas are spreading rapidly...
  • Chicago (1970-1990)
  • 288,000 acres converted
  • 35 increase in developed land
  • 4 increase in population

Why are they important?
  • One way we can improve water quality right on our
    own properties, is by planting rain gardens, that
    can filter and re-direct rain water
  • Even though they are small in size, collectively
    they can make a big difference

Rain Garden Basics
  • Location
  • Your rain garden should be at least 10 feet away
    from your house
  • It can be placed close to your downspout so it
    only receives water from the roof
  • Or further away so it catches water from your
    roof and your lawn
  • Dont put it where water already ponds the idea
    is to encourage infiltration
  • Plants will grow easier in full sun than in shade
    or under a tree
  • A flat area of the yard will be easier to dig
    than on a slope

Picture courtesy of Wisconsin DNR
Picture courtesy of Wisconsin DNR
Rain Garden Basics
  • Size
  • You should choose a garden size that you can
    manage typical sizes are between 100 and 300
  • The depth can vary between 4 and 8 inches
  • A garden that is too small and too shallow will
    not have enough plant variety and will not
    provide appropriate infiltration
  • Similarly a garden that is too large and too deep
    will be hard to maintain, expensive and will
    resemble a hole in the ground filled with water

Rain Garden Basics
  • Size
  • To find the perfect size for your garden take
    into considerations a few things
  • Soil types
  • Drainage area that will feed into the garden
  • Depth of garden
  • Clayey soils drain slower that sandy and silty
  • The bigger the drain area, the bigger the garden
    should be
  • Depth of garden should be determined by the slope
    of the lawn

Rain Garden Basics
  • Determine soil type
  • The soaking test
  • The ribbon test
  • Determine the drainage area of your property
  • For gardens less than 30 feet from downspout
  • For gardens more than 30 feet from downspout
  • Determine the depth of the rain garden by
    determining the slope of the lawn

Determining slope
Picture courtesy of Wisconsin DNR
Rain Garden Size
  • Having determined soil types, drainage area and
    depth, you can now calculate the surface area of
    your garden
  • Use the table below to do that
  • Find the size factor for the soil type and rain
    garden depth.
  • Multiply the size factor by the drainage area.
    This number is the recommended rain garden area.
  • If the recommended rain garden area is much more
    than 300 square feet, divide it into smaller rain

Building Your Garden
  • Anytime before digging in your garden you should
    call JULIE (Joint Utility Locating Information
    for Excavators) at 1 800 892-0123
  • Recruit some friends to help you out so the work
    will take less time
  • Do some advanced prep work to lighten up the
    physical load

Building Your Garden
  • Start out by defining the shape of the garden
    with a string or a flexible hose
  • While you dig put the soil outside of the string
    you will use the displaced soil to build a berm
    or a low wall
  • If you are on an incline start out at the high
    end and work your way towards the low end make
    sure you know how deep your garden has to be
  • When you are done digging check to see that the
    bottom of your garden is flat you can eyeball
    it or use a 2x4 and a carpenters level

Building Your Garden
Building Your Garden
Picture courtesy of Wisconsin DNR
Building Your Garden
  • If your lawn has a slope greater then 8 you will
    need to use some of the soil you dig to level the
  • The rest of the soil will be used to build the
  • When you are done digging, rake the soil smooth
    and prepare for planting
  • For better plant establishment compost can be
    used you can mix it with your soil

Building Your Garden
Picture courtesy of Wisconsin DNR
Choosing plants
  • You should choose plants based on the sun/shade
    pattern and soil type to ensure proper growth
  • Native plants is they way to go due to their
    resilience and low maintenance needs
  • They come in different varieties and colors, they
    are drought resistant and they dont require
    fertilizer and pesticides

Root system of the prairie grasses
Picture Courtesy of Chicago Wilderness
Plants for full sun
Plants for full sun
Plants for partial shade
Plants for shady areas
  • You should come up with a pleasing design keeping
    in mind the height of the plants and color
  • Clump plants together for a visually enjoying
  • Do not exclude the rest of your property plan
    the rain garden as part of a whole
  • Native plants should be planted about 1 foot
    apart to allow roots to grow well
  • As soon as you finish mulch and water

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  • The first year after planting your rain garden is
    very important in terms of maintenance
  • It will determine how well your garden will do in
    the future
  • Two key components are watering and weeding
  • Second component cannot be emphasized enough
    since the plants and weeds are in powerful
    competition for resources
  • Once the garden is established (typically it
    takes 2-3 years for complete establishment) the
    amount of maintenance will reduce considerably

Alternative to Rain Gardens
  • If you feel that installing a rain garden is too
    much work, you can take advantage of rain barrels
  • They collect rain water from your roofs, which
    can be used for irrigation later
  • It is a cheap, easy alternative and requires no

Rain Barrels
  • Residential irrigation can account for 40 of
    domestic water consumption in a given
  • Rain barrels not only store water, they help
    decrease demand during the times when
    precipitation is scarce
  • Only 1/4 inch of rainfall runoff from the average
    roof will completely fill the typical barrel

Rain Barrels
  • Rain water is ideal for watering your gardens
    because it tends to have fewer sediments and
    dissolved salts than municipal water
  • Saving water in this manner will reduce your
    demand for treated tap water, and save money by
    lowering your monthly bill

Rain Barrels
Picture Courtesy of www.rainbarrelguide.com
  • One of the best resources is the booklet I used
    for this presentation Rain Gardens A How To
    Manual For Homeowners
  • The Soil and Water Conservation District of Lake
    County can help answering any questions about
    native plants
  • Also Applied Ecological Services can help with
    designs and planting ideas

Rain gardens
Rain gardens
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