R i G d

NHLA / NHPGA Winter Conference

Rain GardensA Natural and Aesthetic Approach toA Natural and Aesthetic Approach to

Stormwater Management

Jeffrey Hyland, ASLA, CLARB

landscape architecture | environmental planning | urban designwww.FeWood.com

What is a rain garden?What is a rain garden?A rain garden is specially constructed shallow depression designed to captureshallow depression designed to capture stormwater run-off and encourage its infiltration. A rain garden benefits the landscape visually and especiallylandscape visually and especially environmentally.

Why are rain gardens beneficial?y gReduce regional flooding, helps attenuate initial storm surgesurge

Storm surges carry nearly 70% of the pollution found in our streams and lakes

A properly designed rain garden can trap and retain up to 99% of

ll f d icommon pollutants found in stormwater runoffCan be used to improve siteCan be used to improve site drainageAdds visual interest and habitat diversity to the landscape

Rain garden detailsRain garden details…Can be designed to receive and filter runoff from a variety offilter runoff from a variety of drainage areas; paved areas, roofs, lawns, etc.C b d d i llCan be adapted to virtually any site condition.Most successful when native plants are utilizedUsing native plants enhances habitat value attracting birdshabitat value, attracting birds, insects and amphibiansExisting low areas are usually not the best area for a rain

d l t di t i t i th l tgarden unless standing water is never present in the low spotRain gardens are not mosquito breading areas

First StepSite analysis

Ob h l d h i i d i hObserve the landscape when it rains to determine how storm water naturally flowsMake note of sources of stormwater flow and/or potential pollution p psources such as:

Paved driveways, sidewalks, patios, and roadsRooftops downspouts drainpipesRooftops, downspouts, drainpipesAn area of concentrated stormwater (a swale along the driveway)Areas frequented by, pets, farm animals, geese, etc.

Locate leech field – make sure not place the rain garden directly over a leech fieldLocate drinking water well – it’s best not to place the rain garden

llnear a well

Design ConsiderationsgLocation

The rain garden should be a minimum of 10 feet from a structure with a basementPlace in full or partial sunlightSelect a flat area down gradient from the stormwater source, that appearsthe stormwater source, that appears to drain wellSelect an area away from tree rootsRain gardens are attractive additionsRain gardens are attractive additions to the landscape. Select an area that is visible

Design ConsiderationsSizing – detailed methodSizing detailed method

Problem:How big does a rain garden need to be to treat the stormwaterHow big does a rain garden need to be to treat the stormwater runoff from my driveway?Average design storm for NH is 1.25 inches of rain/2 hoursD i i 20 f t id b 50 f t l 1 000 f tDriveway is 20 feet wide by 50 feet long = 1,000 square feet

1.25 inches of rain = 0.104 feet of rain (average design storm for NH)

1,000 sq. ft. x 0.104 ft. = 104 cubic feet of wateri d d i ifi 6 i h dRain garden design specifies 6 inches deep

104 cubic feet ÷ .5 inches = 208 square feet

Answer:Answer: 11 ft wide x 20 ft long x 6 inches deep

Estimated volume treated and recharged, 25,000 gallons per year

A rain garden should be 20% of the surface area(s) from which the storm water originates (1000sf. roof = 200sf. rain garden)

Design ConsiderationsDesign ConsiderationsAesthetics goals

Determine the appropriate level of design (formal to informal)Consider existing and future planting and g p glandscapingCreate a cohesive design by incorporating elements found in the surrounding landscapeelements found in the surrounding landscape into the rain garden – particular plants, boulders, etc.Plant in drifts at least three of one type ofPlant in drifts, at least three of one type of plant creates a visually pleasing and cohesive design

ConstructionThe basics

Call Digsafe to get utilities “marked out” 1-888-344-7233. Conduct a percolation test by digging a test pitConduct a percolation test by digging a test pit 12” deep and fill it with water. When drained fill it again, this time water should drain completely in 12 hours or less. If it has then move on to the next step

ConstructionThe basics

Excavate the rain garden 12”-18” deepExcavate the rain garden 12 18 deepMix sand and compost with excavated material (50% sand, 30% compost, and 20% excavated material) and place in the bottom of excavation 6”-9” deepand place in the bottom of excavation 6 9 deep

Grade bottom of rain garden flat or with a slight pitchg pPlace excess soil around perimeter to create a berm and leave an area low to allow for overflowAt the point where higher velocity water enters the yrain garden place 2”-6” riverstone to slow water

Case Study

The roof area is approximately 1300sf.The driveway is 14’ wide and 50’ longThe septic system is directly in front of the residence at the high point on the propertyThe well is in the back yardRoughly half of the property slopes towards a small seasonal stream at edge of property

Case StudyD i l iDrainage analysis

Case StudyyDrainage calculation

How big does the rain garden need to be in order to treat the stormwater runoff from the drainage area?

3500 f t d i3500 square feet drainage area (comprised of roof, driveway, walkway and lawn)

1.25 inches of rain = 0.104 feet of rain (average design storm for NH)NH)

3500 sq. ft. x 0.104 ft. = 364 cubic feet of waterAssume a rain garden depth of 6 inches deep (.5 feet)364 cubic feet ÷ .5 feet = 728 square feet

Answer: 21 ft wide x 35 ft long x 6 inches deep21 ft wide x 35 ft long x 6 inches deep

Case StudyConceptual design

Riverstone at pipe outfalls

Pipe from downspout

Snow storageSnow storage

B ldBoulders

Pipe from downspout

Case StudyC t l d i l tConceptual design enlargement

Small Tree

Seeded area wet

Low shrubs

Seeded area – wet meadow seed mix

Low hardy groundcover in snow storage area

Tall shrubs

Perennials

Design ConsiderationsPlantingPlanting

Use plant species that can tolerate periodic flooding as ll i d f d hwell as periods of drought

Native plants are more adaptable to the conditions found in a rain gardengPlace plants that prefer drier conditions at the higher or outer edge of your rain gardenPlant species that enhance your rain garden's value asPlant species that enhance your rain garden s value as wildlife habitatShady rain gardens - mimic the vertical layers found in a

l fnatural forestSunny rain gardens – mimic a wet meadow with a mix of prairie wildflowers and grassesp gWhen planting is complete seed, spread compost or place river stone

Design ConsiderationsgPlanting

Design ConsiderationsPlantingPlanting

Design ConsiderationsPlantingPlanting

Design ConsiderationsN ti l t S itNative plants – Sunny sites

Shrubs: (Most sun or shade)S i b A l hi l if li

Flowers: S fl A iServiceberry - Amelanchier alnifolia

False Indigo - Amorpha fruticosaBlack chokeberry - Aronia melanocarpaButtonbush - Cephalanthus occidentalis

Sweet flag - Acorus americanusNew England aster - Aster novae-angliaeMarsh marigold - Caltha palustrisTurtle head - Chelone glabra

Silky dogwood - Cornus amomumGrey dogwood - Cornus racemosaRed-osier dogwood - Cornus sericeaAmerican Hazelnut - Corylus americana

Boneset - Eupatorium perfoliatumJoe-pye weed - Eupatorium maculatumBedstraw - Galium boreale Bottle gentian - Gentiana andrewsiiAmerican Hazelnut - Corylus americana

Witch Hazel - Hamamelis virginianaWinterberry - Ilex verticillataFragrant sumac - Rhus aromatic

d ( d ) i lb

Bottle gentian - Gentiana andrewsii Oxeye sunflower - Helianthus helianthoidesBlue flag - Iris versicolorGreat blue lobelia Lobelia siphilitica

l d ld d lidMeadow sweet (needs sun) - Spirea albaSnowberry - Symphorocarpos albaNannyberry - Viburnum lentagoAmerican cranberry - Viburnum trilobum

Grass-leaved goldenrod - Solidago graminifoliaTall meadow rue - Thalictrum dasycarpum

yAmerican cranberry - Viburnum trilobum 'Compacta'

Design ConsiderationsNative plants – Shady sites

Shrubs: (see previous slide)

Ferns:

Flowering Perennials:Turtle head - Chelone glabraJoe Pye-weed - Eupatorium purpureumFerns:

Ostrich fern - Matteuccia struthiopterisSensitive fern - Onoclea sensibilisCinnamon fern - Osmunda cinnamomeaR l f O d li

Joe Pye weed Eupatorium purpureumVirginia waterleaf - Hydrophyllum virginianumCardinal flower - Lobelia cardinalisCanada mayflower - Maianthemum canadenseVi i i bl b ll M t i i i iRoyal fern - Osmunda regalis

Marsh fern - Thelypteris palustris

Sedges:

Virginia bluebells - Mertensia virginicaFalse dragonhead - Physostegia virginianaTall meadow rue - Thalictrum dasycarpum

Fringed - C. crinitaLake - C. lacustrisTussock - C. strictaFox - C vulpinoideaFox - C. vulpinoidea

Design ConsiderationsA few more plants…

Trees and Shrubs:Amelanchier laevis, ShadbushBetula nigra, River birch

Wildflowers, Ferns, Grasses, and Sedges:Asclepias incarnata, Swamp milkweedLupinus perennis, Wild Blue Lupineg ,

Cephalanthus occidentalis, ButtonbushClethra alnifolia, Sweet pepperbushFothergilla gardenii, Dwarf fothergillaHighbush Blueberry Highbush Blueberry

p p , pVernonia noveboracensis, Common ironweedAthyrium filix-femina, Lady fern Carex pendula, Drooping sedge

Highbush Blueberry, Highbush BlueberryIlex glabra, InkberryLindera benzoin, Spicebush Liquidambar styraciflua, Sweet gumSambucus canadensis, American elderberryRhododendron viscosum, Swamp AzaleaViburnum dentatum, Arrowwood

Rain Garden ExamplesR id ti lResidential

Rain Garden ExamplesCommercial / MunicipalCommercial / Municipal

Other ways to control stormwaterOther ways to control stormwater…

Water collection cisternsPermeable pavementsPermeable pavementsGreen roofs

Visit the Ironwood design group web sitefor links to additional rain garden resources.

www.FeWood.com

Questions?Questions?

R i G dRain GardensA Natural and Aesthetic Approach toA Natural and Aesthetic Approach to

Stormwater Management

Jeffrey Hyland, ASLA, CLARB

landscape architecture | environmental planning | urban designwww.FeWood.com