West Michigan: Rain Gardens


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Rain Gardens

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West Michigan: Rain Gardens

  1. 1. Rain gardens, or bioretention How to design and construct systems, are beautiful a successful professional landscaping features that manage rain garden stormwater on site. Their loose, deep soils absorb water and filter pollutants. Some rain gardens have under-drains that carry filtered water away. Rain gardens complement any style of landscape. Their size can vary, and they can fit into odd shapes and spaces. They are an excellent method of keeping stormwater on site and out of the sewer system.
  2. 2. Before You StartProfessional tools for designing rain gardens are free! Evaluate existing soils. You should replace soils with an absorbent soil mix to ensure water will soak in.You can get spreadsheets to calculate project size However, the characteristics of local soils also affect yourand price, engineering manuals, plant information, rain garden. The in-situ soils must be able to infiltrate at a speed that prevents saturation. If they do not, you willthe latest research, and more at the following URL: need to design an under-drain and overflow plan.www.raingardens.org/docs/bioretention_tools.pdf Special considerations apply in clay soils. Be sure to budget for necessary costs.Creating Contractors who have never designed and constructed a rain garden before will want to do things the waya Functional Design they have always done them. The project may requirePut your rain garden in the right place; additional supervision; plan for this expense. Groupdown-slope from building foundations and up-slope meetings are a good way to share informationfrom storm drain infrastructure. The most practical way with project managers, engineers, excavatorsto determine rain garden location is to visit the site. and landscapers.Re-grade to ensure stormwater goes into the rain garden.Direct overflow and under-drain flow to enter Create an attractive design.existing stormwater infrastructure. Rain gardens feature easy-care plants that are native to your region. Landscapers can create a planting layoutSize the rain garden correctly. that is both beautiful and functional, with attractiveDo not guess the amount of designs and drifts of color. Seeded or naturalistic rain stormwater going into your rain garden. gardens are economical and function well, but some Use the free tools to perform people find them inappropriate in formal settings. the necessary stormwater calculations. Give your rain garden a tended appearance (neatly defined borders, not weedy looking). Landscapers new to rain gardens or native plants may need guidance in plant selection. Do not choose aggressive species that you will need to divide frequently.
  3. 3. Constructinga Successful Rain Garden Stage construction carefully to avoid erosion.Seek contractors experienced with rain gardens, Protect the rain garden from erosion and sedimentor those open to acquiring new skills. during and after construction. Sediment can sealContractors unfamiliar with rain gardens maymisunderstand the concept. Be sure you are actually the surface. Install effective erosion controls, andcreating a rain garden. The goal of a rain garden leave them in place until all site construction,is to soak stormwater into the soil quickly, including other landscaping, is completed.not to create a pond. The most common cause of failure of a rain gardenReplace soil to a depth that insures infiltration. is soil compaction. It is essential to avoid compactionSoil preparation is essential for success. Replace of soils during all phases of construction.existing soils with a loose soil mix appropriate for your Do soil placement and grading from the side. Preventsite. In heavy clay areas, research and experience vehicles from driving on the rain garden. Place barriersindicate that a mix of sand and compost (no topsoil) to protect from foot and construction traffic.works well. Additional drainage infrastructure willcontribute to reliable infiltration. This prevents soil Retrofits can be successful if you applycompaction, soil saturation and standing water. all design considerations. You can sometimes convert existing detention or retentionAvoid soil saturation, especially in cold climates ponds into rain gardens. However, many smallerwhere the rain garden soil may freeze. rain gardens scattered throughout a developmentBe sure you have excellent infiltration and drainage. will function better than converting a large pondOverflow and under-drain plans are part of a successful at a remote location.project. A three-inch layer of shredded hardwoodmulch helps keep the soil from freezing. Do not usebark chips, which wash away.Stormwater Run-off Pooling Zone Detention/ Filtration Zone Retention/ Recharge Zone
  4. 4. Maintaininga Beautiful Rain GardenCare for your rain garden regularly. Get the free bioretention tools!Regular maintenance is required to keep your www.raingardens.org/docs/bioretention_tools.pdf.rain garden looking good and functioning well.Be sure to include this in your plan and your budget! www.raingardens.org Saving the Great Lakes,WAT E R : Water daily the first few weeks after planting, one garden at a timethen regularly until plants are established. Later on, waterin a drought if this is practical. You can install irrigation,and only turn it on manually as needed. Raingardens.org is a program of West MichiganW E E D : Weed on a regular basis, especially the first year. Environmental Action Council in Grand Rapids, Michigan.Educate people working in the rain garden. They mayidentify native plants as weeds.M U L C H : A rain garden planted with plugs or containerplants benefits from a layer of shredded hardwood mulch.This reduces weeding and watering and helps establish the We promote keeping stormwater on siteplants. It also prevents surface sealing of the rain garden, in the Great Lakes basin, and, thanks to our website,and removes specific pollutants from pavement runoff. everywhere else in the world.F E RT I L I Z E : Should not be necessary. Nativeplants should thrive in the prepared soil mix. Avoiduse of herbicides, pesticides, and fungicides in andaround the rain garden.K E E P S A LT O U T O F T H E R A I N G A R D E N :Salt destroys soil biology and damages plants. It buildsup in the soil, and, over time, you will need to replacesoil and plants. Use alternate deicers, but sparingly.If you cannot avoid salt, filter through therain garden and carry away salty waterwith an under-drain.