Rain Gardens: 50 minute introduction for N. coast residents

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Presentation to Clatsop County gardeners and others during the Spring Garden seminar series, 4.17.10.

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Rain Gardens: 50 minute introduction for N. coast residents

  1. 1. Rain Gardens for Healthy Streams and Clean Water Robert Emanuel Oregon State University Extension Service Tillamook & Clatsop counties Oregon Sea Grant Extension
  2. 2. “ We forget that the water cycle and the life cycle are one.” --Jacques Cousteau
  3. 3. Where is your garden in the watershed?
  4. 4. Workshop Goals <ul><li>What is a rain garden & how does it work? </li></ul><ul><li>Why build a rain garden? </li></ul><ul><li>Assess your site for a rain garden </li></ul><ul><li>Steps to design and install a rain garden </li></ul><ul><li>More resources </li></ul>
  5. 5. what is a rain garden and why build one?
  6. 6. A rain garden is a “sunken garden bed” that collects & treats stormwater runoff from rooftops, driveways, sidewalks, parking lots & streets. Graphic: EMSWCD
  7. 7. © Good Nature Publishing
  8. 8. How a Rain Garden Works Graphic: EMSWCD
  9. 10. Photo Tom Liptan, City of Portland Environmental Services
  10. 12. http://www.asla.org/awards/2007/07winners/517_nna.html
  11. 13. <ul><li>you want to protect your local watershed </li></ul><ul><li>you like groundwater </li></ul><ul><li>you don’t like floods </li></ul><ul><li>you want to keep runoff & put it to work </li></ul><ul><li>you like native plants & wildlife </li></ul><ul><li>you have the rain to spare anyway…. </li></ul>why would you build one?
  12. 14. The Problem: Conventional Stormwater Management
  13. 15. Robert Emanuel, OSU Extension Service
  14. 16. Puget Sound Action Team, WSU Pierce County Extension
  15. 18. Puget Sound Action Team, WSU Pierce County Extension
  16. 19. Stormwater Pollutants <ul><li>Suspended solids/sediments </li></ul><ul><li>Nutrients (nitrogen, phosphorus) </li></ul><ul><li>Metals (copper, lead, zinc, cadmium, mercury) </li></ul><ul><li>Oils & grease </li></ul><ul><li>Bacteria </li></ul><ul><li>Pesticides & herbicides </li></ul><ul><li>Increased temperature </li></ul>
  17. 20. Flooding and Urban Development More Runoff Arriving Faster
  18. 21. Stream Degradation WSU Extension/Puget Sound Action Team
  19. 24. what are the steps to building a rain garden?
  20. 25. Steps to Assessing a Site <ul><li>Calculate how much water to treat </li></ul><ul><li>Decide where to put a garden </li></ul><ul><li>Calculate slope </li></ul><ul><li>Test soil </li></ul>
  21. 27. Calculate Impervious Surface
  22. 28. <ul><li>Calculate ft 2 of impervious area(s) </li></ul><ul><li>Calculate total rain garden area needed </li></ul><ul><li>Determine dimensions of each garden </li></ul>Sizing a Rain Garden
  23. 31. Sizing Factors <ul><li>Willamette Valley = 10% of impervious surface </li></ul><ul><li>Southwest Oregon = 10% of impervious surface </li></ul><ul><li>Central Oregon = 15-20 % of impervious surface (shallow) </li></ul><ul><li>Coast = 15-20% of impervious surface </li></ul>
  24. 32. width of surface x length of surface = area (ft 2 ) area x .18 = total rain garden area 12 ft x 30 ft = 360 ft 2 360 ft 2 x .18 = 65 ft 2 potential dimensions: 65 /10 = 6.5 x 10 ft
  25. 33. soil
  26. 34. <ul><li>Dig a hole to depth of rain garden </li></ul>2. Fill with water and let it drain 3. Fill with water again, measure depth, record time and depth 4. Record time after water drains 5. Calculate permeability = depth (inches) / time (hours)
  27. 36. Soil Percolation Test Interpretation Drainage Rate Suggested RG ponding depth Less than ½ inch/hour Do not build ½ to 1 inch/hour 12-24 inches 1 to 2 inches/hour 6-8 inches More than 2 inches/hour 6 inches
  28. 37. Steps to Assessing a Site <ul><li>Calculate how much water to treat </li></ul><ul><li>Decide where to put a garden </li></ul><ul><li>Calculate slope </li></ul><ul><li>Test soil </li></ul>
  29. 38. Setbacks Property lines Proximity to buildings Tree roots Basements, foundations Utilities Steep slopes
  30. 39. Graphic: EMSWCD
  31. 40. Rule of Thumb: conventional rain gardens are located on slopes <10% and >50 ft. from steep slopes; Seek professional help if needed!
  32. 42. Critical Elements <ul><li>Check out your plans w. authorities </li></ul><ul><li>Excavate & grade; prevent soil compaction </li></ul><ul><li>Plan for inflow and overflow </li></ul><ul><li>Disconnect downspouts </li></ul><ul><li>Channel water </li></ul><ul><li>Select and place your plants </li></ul><ul><li>Apply mulch </li></ul>
  33. 43. Legal issues <ul><li>Call your local community development office </li></ul><ul><li>Describe what you’re doing </li></ul><ul><li>Ask “Do I need a permit?” </li></ul><ul><li>Digsmart! Call 811 </li></ul>
  34. 46. Berms <ul><li>Use your excavation spoils to build berm </li></ul><ul><li>3:1 ratio is critical on any slope </li></ul><ul><li>Consider notching the berm for overflow </li></ul><ul><li>Arm the notch </li></ul><ul><li>Plant and mulch berm edges to prevent erosion </li></ul>
  35. 47. What does 3:1 really mean?
  36. 48. Disconnect Downspouts Photo courtesy of Portland Environmental Services
  37. 49. Channeling Flow <ul><li>Where piping, connect directly to downspouts </li></ul><ul><li>Grade pipes downhill </li></ul><ul><li>Grade garden away from inflow point </li></ul><ul><li>Slow the water at inflow areas </li></ul><ul><li>12” below surface, Schedule 40 ABS or PVC </li></ul>
  38. 50. Overland Channeling Photo: Judy Scott, OSU
  39. 51. Moving water across a sidewalk Photo courtesy of Portland Environmental Services
  40. 52. Moving water away from building Mt Tabor Middle School, Portland
  41. 53. Another creative overhead solution!
  42. 55. Inflow Outflow
  43. 56. Some Plants for Rain Gardens
  44. 57. It’s all about being in the ZONE … Slope Base Uplands = driest zone Base = wettest zone Slope = wet and dry Uplands
  45. 58. BASE Graphic: EMSWCD SLOPE SLOPE UPLANDS UPLANDS
  46. 59. The Zone is about Moist, Mesic, Dry Soil Mesic Moist Dry
  47. 60. Idaho blue-eyed grass ( Sisyrinchium idahoensis ) Western blue-eyed grass ( Sisyrinchium bellum ) Slope/Upland
  48. 61. Native Baldhip Rose (Rosa gymnocarpa) Upland
  49. 62. Red-flowering currant ( Ribes sanguineum ) Slope
  50. 63. Douglas Spirea ( Spirea douglasii ) Base/Slope/Upland
  51. 64. Spanish lavender ( Lavandula stoechas ) Slope/Upland
  52. 65. New Zealand bronze sedge ( Carex testacea ) Slope/Upland
  53. 66. Fernleaf yarrow ( Achillea filipendulina ) Slope/Upland Photo: Tennessee.edu
  54. 67. Kinnickinnik (Arctostaphyllos uva-ursi) Slope/Upland
  55. 68. Soft rush (Juncus gracilus var. pacificus) Base
  56. 69. Invasive Species
  57. 72. Rain Garden Maintenance <ul><li>Water in first year </li></ul><ul><li>Consider notching berm for first year </li></ul><ul><li>No fertilizer or garden chemicals </li></ul><ul><li>Maintain at least ½” of mulch (prefer 2”) </li></ul><ul><li>Keep clear of trash, sediment, debris </li></ul><ul><li>Prune, weed, and trim as needed </li></ul><ul><li>Clean out inflow and outflow structures </li></ul>
  58. 74. extension.oregonstate.edu/watershed/rain-gardens Publication: bit.ly/osgpub Presentation: bit.ly/rgforor
  59. 75. Full Day Rain Garden Training Friday, September 17 th , Ft. Clatsop, Netul Room, 8:30 AM -4:00 PM Online registration opens July
  60. 76. Contact Information Robert Emanuel, Ph.D. Water Resources & Community Development Specialist OSU Extension Service Clatsop & Tillamook counties (503) 842-5708 x 210 [email_address] blogs.oregonstate.edu/h2onc

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