RainRain

GardensGardensLaurie J. FoxLaurie J. Fox

Virginia Tech Hampton Roads ARECVirginia Tech Hampton Roads AREC

By Any Other By Any Other Name…Name…

rain gardenrain garden rainscapingrainscaping catchwater gardencatchwater garden bioretention basinbioretention basin infiltration trench or swaleinfiltration trench or swale BMP – best management practiceBMP – best management practice aesthetic opportunityaesthetic opportunity

What Exactly?What Exactly?

conservation & preservation toolconservation & preservation tool

water

Water QuantityWater Quantity Most abundant resourceMost abundant resource 97% saltwater97% saltwater Most of 3% in glaciersMost of 3% in glaciers Very small % in surface and Very small % in surface and

groundwater for humansgroundwater for humans

Water QuantityWater Quantity SurfaceSurface - water on or near the - water on or near the

earth’s surface (rivers, lakes, earth’s surface (rivers, lakes, springs, storm water)springs, storm water)

GroundGround - water in the - water in the saturated zone below the saturated zone below the water table (aquifer)water table (aquifer)

Water CycleWater Cycle

Water Water QualityQualityThe degree of excellence relative to:The degree of excellence relative to:

colorcolorodorodor

suspended solidssuspended solidsnutrientsnutrients

dissolved oxygendissolved oxygenpathogens (bacteria)pathogens (bacteria)

Threatened by:Threatened by:point and non-point source point and non-point source

pollutionpollutionthroughthrough

leaching and runoffleaching and runoffofof

sediments, nutrients, toxicssediments, nutrients, toxics

Water Quantity & QualityWater Quantity & Quality

SedimentsSediments - organic & inorganic - organic & inorganic solid particlessolid particles

NutrientsNutrients - N & P - N & P ToxicsToxics - - pesticides,pesticides, gas, oil, gas, oil,

heavy metals, weeds, & heavy metals, weeds, & pathogenspathogens

RainRain Gardens Gardens

Conserve water Conserve water quantityquantity

Preserve water Preserve water qualityquality

Why?Why? remove pollutantsremove pollutants prevent erosionprevent erosion recharge groundwaterrecharge groundwater prevent floodingprevent flooding provide wildlife habitatprovide wildlife habitat less $ alternative to pondsless $ alternative to ponds

Pioneered in Prince George County, MDPioneered in Prince George County, MD$2-5K per lot savings$2-5K per lot savingsadditional lots in lieu of storm water pondsadditional lots in lieu of storm water pondsno BMP maintenance feesno BMP maintenance fees + added valueadded value

landscape featureslandscape features

How?How? catch rain and runoff water (6” deep)catch rain and runoff water (6” deep) temporarily hold it (< 4 days)temporarily hold it (< 4 days) soil & plants filter sediments, nutrients, soil & plants filter sediments, nutrients,

pollutantspollutants water percolates down to recharge water percolates down to recharge

aquifersaquifers water moves into atmosphere through water moves into atmosphere through

transpiration and evaporationtranspiration and evaporation

How?How? existing or created depressionexisting or created depression > 10’ house, 25’ septic field> 10’ house, 25’ septic field high organic sandy loam soilhigh organic sandy loam soil flood & drought tolerant plantsflood & drought tolerant plants mulch, mulch, mulchmulch, mulch, mulch Voila! Instant Rain Garden!Voila! Instant Rain Garden!

3 planting zones4 days or less5% of drainage area6” water

Low HighMiddleAdams County SWCDQuincy, IL

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Flow direction

•splash block

•extension pipe

rate per hour

Depth Depth Dimensions DimensionsPonding depth 6” – Divide Impermeable area by 20Ponding depth 6” – Divide Impermeable area by 20Ponding Depth 3” – Divide impermeable area by 10Ponding Depth 3” – Divide impermeable area by 10

ImpermeableSurface Area

Required Sizeof RainGarden (6” deep)

Potential Rain Garden

Dimensions(ftXft)

Required Sizeof RainGarden (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 the rain gardenSizing the rain garden

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Sizing ExampleSizing Example Roof area: 60 X 60 = 3600 sq. ft. ¼ of the flow to

downspouts: (3600 sq.ft) X 25% = 900 sq.ft Roof area plus driveway: 900 + 500 = 1400 sq. ft Divide square footage by 20: 1400/20 = 70 sq. ft.

ANSWER: The water garden should be at least 70 square feet.

A 5 x 14 or 7 x 10 foot garden design would be sufficient

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Marly-Holmes Marly-Holmes Neighborhood Assoc.Neighborhood Assoc.

Minneapolis, MNMinneapolis, MN

Rain Garden WorkshopRain Garden Workshop

Blacksburg, VABlacksburg, VA

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Stoney Brook-Millestone Stoney Brook-Millestone Watershed Assoc.Watershed Assoc.

Pennington, NJPennington, NJ

VersiTankVersiTank

Old Dominion UniversityOld Dominion University

Norfolk, VANorfolk, VA

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FilteraFiltera

Virginia Tech Rain GardenVirginia Tech Rain Garden

Virginia TechVirginia TechCity of Virginia Beach HECCity of Virginia Beach HECVirginia Cooperative ExtensionVirginia Cooperative ExtensionVB MG Water StewardsVB MG Water StewardsLocal Nurseries & SPSALocal Nurseries & SPSALocal MediaLocal Media

2007

2.5” rain in 1 hour2.5” rain in 1 hour

2010

Rain Garden PlantsRain Garden Plants