Rain Gardens Laurie J. Fox Virginia Tech Hampton Roads AREC - PowerPoint PPT Presentation

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Rain Gardens Laurie J. Fox Virginia Tech Hampton Roads AREC

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  1. Rain Gardens Laurie J. Fox Virginia Tech Hampton Roads AREC

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

  3. What Exactly? conservation & preservation tool water

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

  5. 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)

  6. Water Cycle

  7. Water Quality The degree of excellence relative to: color odor suspended solids nutrients dissolved oxygen pathogens (bacteria)

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

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

  10. Rain Gardens • Conserve water quantity • Preserve water quality

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

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

  13. 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

  14. 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!

  15. Low Middle High Adams County SWCD Quincy, IL • 3 planting zones • 4 days or less • 5% of drainage area • 6” water

  16. NCSU

  17. NCSU

  18. NCSU

  19. Flow direction • splash block • extension pipe

  20. rate per hour

  21. Sizing the rain garden • Depth  Dimensions • Ponding depth 6” – Divide Impermeable area by 20 • Ponding Depth 3” – Divide impermeable area by 10 NCSU

  22. 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: 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 NCSU

  23. Marly-Holmes Neighborhood Assoc. Minneapolis, MN

  24. Rain Garden Workshop Blacksburg, VA

  25. NCSU

  26. NCSU

  27. Stoney Brook-Millestone Watershed Assoc. Pennington, NJ

  28. VersiTank

  29. Old Dominion University Norfolk, VA

  30. NCSU

  31. NCSU

  32. Filtera

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

  34. 2007

  35. 2.5” rain in 1 hour

  36. 2010