RainGardens Laurie J. Fox Virginia Tech Hampton Roads AREC.
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Transcript of RainGardens Laurie J. Fox Virginia Tech Hampton Roads AREC.
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
NCSUNCSU
NCSUNCSU
NCSUNCSU
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
NCSUNCSU
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
NCSUNCSU
Marly-Holmes Marly-Holmes Neighborhood Assoc.Neighborhood Assoc.
Minneapolis, MNMinneapolis, MN
Rain Garden WorkshopRain Garden Workshop
Blacksburg, VABlacksburg, VA
NCSUNCSU
NCSUNCSU
Stoney Brook-Millestone Stoney Brook-Millestone Watershed Assoc.Watershed Assoc.
Pennington, NJPennington, NJ
VersiTankVersiTank
Old Dominion UniversityOld Dominion University
Norfolk, VANorfolk, VA
NCSUNCSU
NCSUNCSU
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