This presentation was created to provide property owners with an overview of rain garden construction that can be used to reduce the nonpoint source pollution coming from their property. The design guides in this presentation represent general guidelines for rain garden construction. To be eligible for the stormwater utility credit, rain gardens must be designed according to the standards of the Georgia Stormwater Management Manual and certified by a professional engineer. As with any construction, property owners should contact Athens-Clarke County to determine permitting requirements and address any other issues that may occur.
Bu Buil ild d You Your r Ow n Rai n Garden Rose Mary Seymour Engineering Extension Specialist CAES-Griffin Campus Ag Pollution Prevention Program Sponsored by P2AD of Georgia
What is a Rain Garden?
• An area in a man-made landscape landscape that that captures a shallow amount of water and and holds it for a short time period • Run Runoff off wat water er indented is cap captur tured ed an and dwhere iinfi nfilt ltra rate ted d iinto nto the soil in an area plants and soils utilize and filter the water • An at attr trac acti tive ve ad addi diti tion on to a llan ands dsca cape pe
Purpose of a Rain Garden • Capt Captur ures es runo runoff ff from from impe imperv rvio ious us areas such as roofs, driveways, patios • Redu Reduce ce runo runoff ff leav leavin ing g lan lands dsca cape pe to become stormwater • Pond Pondin ing g sho shoul uld d las lastt no no mor more e tha than n 48 48 hours after rain stops
Benefits of Rain Gardens • Lo Low wm mai aint nten enan ance ce,, llow ow wa wate terr u use se,, beautiful landscape feature
• In Incr crea ease ses s in infi filt ltra rati tion on o off ra rain inwa wate terr iin n landscapes with impervious surfaces –
- infiltrates as much as 30 % more water than a flat or sloped lawn area
• Re Redu duce ces s floo floodi ding ng risk risks s an and d st stre ream am bed destruction downstream • Diff ffe er ent k kiind o off h ha abita tatt in the landscape
Location of the Rain Garden • At leas leastt 10 10 ft ft fro from m a buil buildi ding ng foundation • Near Near pati patio o, d dri riv veway eways s roa roads ds • Area Area that that wate waterr wil willl nat natur ural ally ly move move to –low area •• Eas Ea s y vi v i e w ing in g fro f rom m in i n s ide id e Fitt Fittin ing g into into the the rest rest o off the the lan lands dsca cape pe
Locations to Avoid • Next Next to a bu builildi ding ng foun founda dati tion on • Over a septic system • Wher Where e wat water er stan stands ds for for lon long g per perio iods ds already – High
seasonal water table area
• Insi Inside de tthe he drip dripliline ne of any any larg large e tre trees es • Slopes greater 12%
Rain Garden Size • Depends on – Area
of drainage – Depth of ponding of rain garden – Soil
and Slope of location
Deciding the Size • Figure out the size of the area thatto will have runoff going the rain garden • For a house, draw a footprint • Break whole roof into areas going to each gutter • F igure areas for each gutter
Soil Testing • Infiltration Test Dig a hole 6-8 inches deep and wide – Fill hole with water – If water does not drain out of the hole in 12 hours, not a good location for a rain garden
–
• Soil C Ch hemistry T Te es t –
Take 2 cups of soil to the local county extension agent and have testto adjust pH tell whether limeaissoil needed • Results will •
and whether there is enough nutrients in the soil $8 fee, takes about two weeks for results
Problem Soils • If soil soils s are are high high in clay clay or have have been been compacted during development, they may not have the capacity to infiltrate well • The The rain rain gard garden en area area soil soil can can be be removed and replaced with a better draining soil
Problem Soils • Idea Ideall rai rain n gar garde den n soi soill mix mix – 5050-60 60% % sand, 20-30% topsoil, 20-30% compost – No
more than 10% of mix should be clay
• Be care carefu full of of the the nutr nutrie ient nt cont conten entt of of composts…lower nutrient concentrations is better for the rain garden soil
Deciding the Size • Sand Sandy ys soi oils ls – 5-8% 5-8% of runo runoff ff area area • Clay Clay soil soils s – 10-1 10-15% 5% of runo runoff ff area area • Exam Exampl ple e – Area Area = 1800 1800 sq.f sq.ftt – Sandy soil - .06 X 1800 – Clay soil - .12 X 1800 =
= 108 sq.ft 216 sq.ft
• If the the are area a of of the the rain rain gard garden en need needs s to to be > 300 sq ft, consider making two smaller ones or bring in the earth moving equipment
Deciding the Size A rain garden on a steeper slope can be smaller and deeper than a rain garden on a flatter slope Measuring Slope
Installing the Rain Garden
Layout of Rain Garden • Rain Rain gard garden ens s are are usua usualllly y not not squa square re or a perfect circle • The The long long leng length th shou should ld be perpendicular to the major slope • The The sho short rter er leng length th shou should ld go down down the major slope
Layout of Rain Garden • Thin Think k abou aboutt wher where e exce excess ss stor storm m water will go • You You can canno nott sen send dy you ourr o ove verf rflo low w ont onto o your neighbors property
• Loc al government has jurisdiction over land disturbing activities
Installing the Rain Garden • Pointers Bottom of the rain garden should be level – Top of berm should be about the same elevation as the uphill edge of the rain garden –
Overflow Area • Al Alwa ways ys ha have ve an ov over erflo flow wm met etho hod d ffor or la larg rger er st stor orms ms Lower area in the berm somewhere – Drain pipe within rain garden –
Connecting the Rain Garden • Create a shallow wide swale or bury a corrugated drain pipe carryinto flow from to gutter the rain garden • Line swales with turfgrass or gravel to prevent erosion
Installing the Rain Garden • La Lay you outt e ed dge of rrai ain ng ga ard rde en w wit ith h rope or garden hose • Set asi sid de tth he tto op 4 4-6 -6 in inch che es o of f soil (topsoil), excavate the hole thenplanting use thearea. top soil to backfill the • Move ove tthe he so soilil in the the ra rain gard garde en area down to the bottom edge of the rain garden
Installing the Rain Garden • Pre repa pare re th the e so soilil fo forr pl plan anti ting ng – Add
lime and fertilizer as recommended recommended by soil test – Spread 2 to 4 inches of compost and mix or till it into the whole area of the rain garden
• No Now w you a arre rre eady tto o plant
Plants • A wide wide v var arie iety ty of pl plan ants ts in bo both th si size ze tex textu ture re and color makes for an interesting rain garden • Ra Rain in ga gard rden ens sc can an be de desi sign gned ed to at attr trac actt butterflies and birds with the right plant choices • Mi Mix x tr tree ees, s, s shr hrub ubs, s, p per eren enni nial als, s, o orn rnam amen enta tall grasses and turfgrasses • Pl Plan ants ts mu must st be we wett a and nd dr drou ough ghtt ttol oler eran antt –
Really tough plants
Trees for Rain Gardens • • • •
Red Maple River Birch Crape Myrtle Black Gum
• • • •
Sweetbay Magnolia Dahoon Holly Winter King Hawthorn Sugar H Ha ackberry
• Bald Cypress • Green Ash • Willow Oak
• Fringetree • Gingko • Persimmon
• Serviceberry • Hornbeam
• Loblolly Pine
Birch ch • River Bir
Cypress ress • Bald Cyp Loblolly Loblol ly P Pine ine
Map ple • Red Ma Gingko
Myrtl tle e • Crape Myr Swee weetb tba ay Magn gnol olia ia
Deci cidu duou ous s Shr Shrub ubs s • Provide Seasonal Interest – – –
Flowers Berries Fall Color
• More Natural Growth Form • Majority of of We Wetland Pl Plants ar are Deciduous
• Inkberry
Arrow wood
Yaup upon on Hol olly ly
Sou outh the ern Wax Myr yrtl tle e
Bottlebrush Bucke Buc keye ye
Oakleaf Hydrangea
American Beauty Berry
Virginia Sweetspire
Spic pice e Bush
Winterberry
Buttonbush
Herbaceous Plants for Rain Gardens • Asters • Blackeyed Susan • Lobelia • Northern Sea Oats • Cardinal F Fllower • Goldenrod • Ironweed • Joe Pye Weed • Rose or Swamp Mallow
• • • •
Swamp Milkweed Royal Fern Cinnamon Fern Netted Chain Fern
• • • • • • •
Broad Beech Fern Canna Lilies Yellow Flag Iris Rushes St. Johns Wort Foam Flower White Arrow Arum
• Jack-in-the-Pulpit
Herbaceous Plants for Rain Gardens- Groundcovers • S huttleworth ginger • Partridge berry
• Zoysia • Lir iop e • Mondograss
Canna Lilies
St. Johns Wort
Ironweed
Cinnamon Fern
• Royal Fern
Swamp Milkweed
Asters J oe Py Py e Weed
Liriope
Blackeyed Susan
Chasmanthium latifolium Northern Sea Oats
Miscanthus sinensis Silver Grass
Phalaris arundinace arundinaceae ae Ribbon Grass
Festuca cinerea Silver Fescue
Pennisetum alopecuroides Fountain Grass
lants nts to Avo Avoid id Pla • Those Su Susceptible to to Ro Root Ro Rots –
Most coniferous shrubs
Azaleas – Indian Hawthorn – Camelias –
Maintenance • No spec specia iall main mainte ten nan ance ce requ requir ired ed.. .... • Routine ine periodic landscaping maintenance – – – – –
Weeding Pruning Replacing plants Plant Division Replacement of mulch
Credits •
Photo Photos s of of C Com ompl plet eted ed Ra Rain in Garde Garden nE Exa xamp mple les s cou court rtes esy yo of f
City of Maplewood http://www.ci.maplewood.mn.us/index.asp?Type=B_BASIC& SEC={F2C03470-D6B5-4572-98F0-F79819643C2A}} SEC={F2C03470-D6B5-4572-98F0-F79819643C2A • Plan Plantt ph phot otos os ffro rom m Ve Vege geta tati tion on ffor or Bio Biore rete tent ntio ion n Area Areas, s, All Allen en Caldwell, CED, NC State CES or from Todd Hurt, GCES, Cherokee County and Gary Wade, GCES, Horticulture Specialist • Rain Gardens A How-to Manual for Homeowners University of Wisconsin Extension Pub #GWQ037 http://clean-water.uwex.edu/pubs/raingarden/rgmanual.pdf •
Iwww.raingardens.org ntro Picture - Rain Gardens of West Michigan
GCES Recommended Resources • A Co Comp mpila ilatio tion no off L Low ow Ma Main inte tena nanc nce e Plan Plants ts for for Georgia Landscapes http://pubs.caes.uga.edu/caespub a.edu/caespubs/Agriculture/horticult s/Agriculture/horticult http://pubs.caes.ug ure/H-91-009.htm • En Envi viro ronm nmen enta talllly y Fri Frien endl dly yL Lan ands dsca cape pe Pr Prac acti tice ces s http://pubs.caes.uga.edu/caespub s/Agriculture/horticult http://pubs.caes.uga.edu/caespubs/Agriculture/horticult ure/H-00-060.htm • La Lan nds dsca cape pe Pla lan nts fo forr Geo eorg rgia ia http://pubs.caes.uga.edu/caespu bs/pubcd/B625.htm 5.htm http://pubs.caes.uga.edu/caespubs/pubcd/B62 • So Soilil Pr Prep epar arat atio ion na and nd Pl Plan anti ting ng Pr Proc oced edur ures es fo for r Ornamental Plants in the Landscape http://www.ces.uga.edu/pubcd/B932-w.htm • Soi oill T Te est stin ing g ffor or Hom ome ea and nd Ga Gard rde ens http://pubs.caes.u http://pubs.caes.uga.edu/caespu ga.edu/caespubs/pubs/PDF/L bs/pubs/PDF/L387.pdf 387.pdf
Questions and Thoughts
Deciding the Size • – > include 30 ft frolawn m guarea tter between house and rain garden for sizing rain garden