RainGardens Laurie J. Fox Virginia Tech Hampton Roads AREC

By Any Other Name…  rain garden  rainscaping  catchwater garden  bioretention basin  infiltration trench or swale  BMP – best management practice  aesthetic opportunity

What Exactly? conservation & preservation tool water

Water Quantity  Most abundant resource  97% saltwater  Most of 3% in glaciers  Very small % in surface and groundwater for humans

Water Quantity  Surface - water on or near the earth’s surface (rivers, lakes, springs, storm water)  Ground - water in the saturated zone below the water table (aquifer)

Water Cycle

Water Quality The degree of excellence relative to: colorodor suspended solids nutrients dissolved oxygen pathogens (bacteria)

Threatened by: point and non-point source pollution through leaching and runoff of sediments, nutrients, toxics Water Quantity & Quality

 Sediments - organic & inorganic solid particles  Nutrients - N & P  Toxics - pesticides, gas, oil, heavy metals, weeds, & pathogens

Rain Gardens  Conserve water quantity  Preserve water quality

Why?  remove pollutants  prevent erosion  recharge groundwater  prevent flooding  provide wildlife habitat  less $ alternative to ponds

Pioneered in Prince George County, MD  $2-5K per lot savings  additional lots in lieu of storm water ponds  no BMP maintenance feesadded value  no BMP maintenance fees + added value landscape features landscape features

How?  catch rain and runoff water (6” deep)  temporarily hold it (< 4 days)  soil & plants filter sediments, nutrients, pollutants  water percolates down to recharge aquifers  water moves into atmosphere through transpiration and evaporation

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

 3 planting zones  4 days or less  5% of drainage area  6” water LowHighMiddle Adams County SWCD Quincy, IL

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Flow direction splash block extension pipe

rate per hour

Depth  Dimensions Ponding depth 6” – Divide Impermeable area by 20 Ponding Depth 3” – Divide impermeable area by 10 Impermeable Surface Area Required Size of Rain Garden (6” deep) Potential Rain Garden Dimensions (ftXft) Required Size of Rain Garden (3” deep) Potential Rain Garden Dimensions (ftXft) 800 ft 2 40 ft 2 4X10, 5X8, 6X7 80 ft 2 7X12, 8X10, 9X ft 2 50 ft 2 5X10, 6X8100 ft 2 7x15, 10X ft 2 60 ft 2 4X15, 5X12, 6X10, 8X8 120 ft 2 10X12, 8X ft 2 70 ft 2 5X14, 7X10140 ft 2 10X14, 7X ft 2 80 ft 2 7X12, 8X10, 9X9 160 ft 2 8X20, 10X ft 2 90 ft 2 6X15, 7X13, 8X12, 9X ft 2 9X20,10X18, 12X15 Sizing the rain garden NCSU

Sizing 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: = 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 NCSU

Marly-Holmes Neighborhood Assoc. Minneapolis, MN

Rain Garden Workshop Blacksburg, VA

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Stoney Brook-Millestone Watershed Assoc. Pennington, NJ

VersiTank

Old Dominion University Norfolk, VA

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Filtera

Virginia Tech Rain Garden  Virginia Tech  City of Virginia Beach HEC  Virginia Cooperative Extension  VB MG Water Stewards  Local Nurseries & SPSA  Local Media

2007

2.5” rain in 1 hour

2010

Rain Garden Plants