Georgia Rain Garden Manual

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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

 

Planning Your Rain Garden • Location • Size • Plant Mix

 

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

 

Black Gum

 

Willow Oak • Winter King Hawthorn

 

Shrubs for Rain Gardens • Winterberry • Arrowwood • Buttonbush • Summersweet Clethra • Wax Myrtle

• American Beautyberry • Bottlebrush Buckeye • Inkberry • Oakleaf Hydrangea

• Chokeberry

• Virginia Sweetspire

 

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

• < 30 ft to gutter   –   only

the roof area needs to be included in sizing

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