BUILDING YOUR RAIN GARDEN. Garden Location Where does water flow from? Where does water travel or collect? Observe your yard during a rainfall event.

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