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Roger Bannerman's Rain Garden
Roger Bannerman is an environmental specialist with the Wisconsin
Department of Natural Resources. He says that a rain garden is
an easy, natural way of reducing the amount of water and trapping
pollutants that runoff our lawns and rooftops.
The Bannerman rain garden is in the Lake Wingra watershed. Phosphorus
running off the neighborhood lawns and rooftops contribute to
the excess plant growth in Lake Wingra. A lake in this condition
can be unpleasant to swim in, reduces the enjoyment of recreational
boating, and can suffer from odor problems. The Bannerman rain
garden is one small step in reducing the amount of phosphorus
and runoff water reaching Lake Wingra.
Here's how Bannerman
Built his Rain Garden
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Design
Goal
to infiltrate all the annual runoff from 1/3 (636 sq.
ft.) of the Bannerman rooftop. The infiltration rate in the
garden is about 7.0 inches/hour, while the rate in the nearby
turf is only 2 inches/hour.
Build
raingarden approx. 10 ft. from house.
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Dimensions
of the Rain Garden
The diameter of the half circle shaped rain garden is 22
ft. The surface area is about 190 sq. ft. A shovel was used
to hand dig the depth to about an average of 3.5 inches.
The garden area is 30 percent of the roof drainage area.
The volume of the garden is 55 cubic feet (1.56 cubic meters)
or about 411 gallons.
This
volume is equal to all runoff from the roof for a 1 inch
rainfall.
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Plant
Native Plants
Native plants are the best choice because they are adapted
to soil and by selecting the appropriate plants will tolerate
moisure. Here's what Bannerman used in his rain garden:
- Blue
False Indigo (early summer)
- Red
Milkweed (summer)
- Nodding
Pink Onion (summer)
- Prairie
Blazing Star (summer)
- Buttonbush
(summer)
- Square
Stemmed Sticky Monkey (summer)
- Sweet
Black-Eyed Susan (fall)
- Ohio
Goldenrod (fall)
- Prairie
Dropseed (all season)
The
plant arrangement was created by Jennifer Baker of Prairie
Nursery, (800-476-9453) and the construction was by
Keith Baker of Lawson Ridge Native Landscaping (608-296-3503).
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The cost of
Bannerman's rain garden was $1,400. This included construction
of the garden and purchase and installation of plants. The total
number of plants was 179. Of course, you can construct and plant
your own rain garden.
For more information
about rain gardens, contact Roger
Bannerman at 608-266-9278.
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