building your rain garden. garden location where does water flow from? where does water travel or...
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BUILDING YOUR RAIN GARDEN
Garden LocationGarden Location
Where does water Where does water flow from?flow from?
Where does water Where does water travel or collect?travel or collect?
Observe your yard during a rainfall eventObserve your yard during a rainfall event
“Pinch Point”
Garden LocationGarden Location
Place your garden Place your garden between runoff source between runoff source and destinationand destination
We want to intercept We want to intercept water before it reaches water before it reaches surface waters or low surface waters or low spots!spots!
Garden LocationGarden LocationSITING GUIDELINES:SITING GUIDELINES:
>10 feet from house >10 feet from house foundation or wellheadfoundation or wellhead
> 25 ft from septic system > 25 ft from septic system drain fielddrain field
Away from utility linesAway from utility lines
In full to partial sun if In full to partial sun if possiblepossible
Garden LocationGarden Location
Garden TimingGarden Timing
Add garden after Add garden after other construction other construction is finishedis finished
Planting best Planting best
done between done between November and November and AprilApril
Soil EvaluationSoil Evaluation
Soils and DrainageSoils and Drainage Signs of an impermeable soilSigns of an impermeable soil
Ponding waterPonding water Wetland soils – grey Wetland soils – grey
with areas of brown with areas of brown
colorcolor Water remains after Water remains after
two days of no rainfalltwo days of no rainfall
Design as a Backyard Wetland!
Wetland SoilsWetland Soils
Wetland SoilsWetland Soils
Backyard WetlandBackyard Wetland
What is it?What is it? An area where the soil is An area where the soil is
saturated or covered saturated or covered with water for 2-3 weeks with water for 2-3 weeks during the growing during the growing seasonseason
Located in spots where Located in spots where water collects much water collects much faster than it drains.faster than it drains.
Backyard Wetland Backyard Wetland Install in an area Install in an area
where there is a where there is a naturally occurring naturally occurring wet spot or drainage wet spot or drainage way.way.
Can be as simple as Can be as simple as installing wetland installing wetland plants in the wet areaplants in the wet area
Backyard WetlandBackyard Wetland
Backyard WetlandBackyard Wetland
Sizing your Rain GardenSizing your Rain Garden
How much runoff is coming from impervious areas?
Sizing Rain GardensSizing Rain Gardens Roof AreaRoof Area Driveway AreaDriveway Area Total Impermeable Drainage AreaTotal Impermeable Drainage Area
Depth Depth Dimensions Dimensions Ponding depth 6” – Divide Impermeable area by 20Ponding depth 6” – Divide Impermeable area by 20 Ponding Depth 3” – Divide impermeable area by 10Ponding Depth 3” – Divide impermeable area by 10
Use chart: Sizing Your Rain GardenUse chart: Sizing Your Rain Garden
Sizing ChartSizing ChartImpermeableSurface Area
Required Size
of Rain Garden
(6” deep)
Potential Rain Garden
Dimensions(ftXft)
Required Sizeof Rain
Garden (3” deep)
Potential RainGarden
Dimensions(ftXft)
800 ft2 40 ft2 4X10, 5X8, 6X7
80 ft2 7X12, 8X10,9X9
1000 ft2 50 ft2 5X10, 6X8 100 ft2 7x15, 10X10
1200 ft2 60 ft2 4X15, 5X12, 6X10, 8X8
120 ft2 10X12, 8X15
1400 ft2 70 ft2 5X14, 7X10 140 ft2 10X14, 7X20
1600 ft2 80 ft2 7X12, 8X10,9X9
160 ft2 8X20, 10X16
1800 ft2 90 ft2 6X15, 7X13,8X12, 9X10
180 ft2 9X20,10X18,12X15
Sizing ExampleSizing ExampleEXAMPLE: A house is 60 feet EXAMPLE: A house is 60 feet
by 60 feet. by 60 feet.
Based on owner estimation:Based on owner estimation:25% of the roof area 25% of the roof area is draining to the downspout. is draining to the downspout.
The driveway area draining The driveway area draining to the rain garden is 500 square feet. to the rain garden is 500 square feet.
For a desired 6 inch ponding depth, what size should For a desired 6 inch ponding depth, what size should the rain garden be?the rain garden be?
Sizing ExampleSizing Example
Roof area: Roof area: 60 X 60 = 3600 sq. ft. 60 X 60 = 3600 sq. ft. ¼ of the flow to ¼ of the flow to
downspouts:downspouts: (3600 sq.ft) X 25% = 900 (3600 sq.ft) X 25% = 900 sq.ftsq.ft
Roof area plus driveway: Roof area plus driveway: 900 + 500 = 1400 sq. ft 900 + 500 = 1400 sq. ft Divide square footage by 20: Divide square footage by 20: 1400/20 = 70 sq. 1400/20 = 70 sq.
ft.ft.
ANSWER:ANSWER: The water garden should be at least The water garden should be at least 70 square feet.70 square feet.
A A 5 x 145 x 14 or or 7 x 107 x 10 foot garden design foot garden design would be sufficientwould be sufficient
Rain Gardens can be SmallRain Gardens can be Small
Depth of 3 – 8 Depth of 3 – 8 inchesinches
Larger for clay Larger for clay soils, smaller for soils, smaller for sandy onessandy ones
Work with the area Work with the area you have!you have!
Size is flexibleSize is flexible
Rain Garden ConstructionRain Garden Construction
Rain Garden ConstructionRain Garden Construction
Potential Site
Define the boundary by using string or spray paint
Before digging, lay out the area
Digging Your Rain GardenDigging Your Rain Garden
Dig garden 4-6 inches, with a slight depression
in the center
Digging Your Rain Garden Digging Your Rain Garden
On sloped sites:
Use dug out soil to create a berm along one side of garden
This will serve to retain water during a storm
Planting and MulchingPlanting and Mulching
Berm
Cover the berm with grass or
mulch to prevent erosion
Planting and MulchingPlanting and Mulching
Planting and MulchingPlanting and Mulching
Mulch with 2-3 inches of hardwood mulch
Avoid Pine Straw and Lighter Mulches –
They Will Float!
MulchingMulching
Removes PollutantsRemoves Pollutants Maintains Soil Maintains Soil
MoistureMoisture Prevents ErosionPrevents Erosion