Rain Garden Definition

Transcription

1 Rain Garden Definition A shallow depression to capture, temporarily pond, and absorbs run-off water from impervious surfaces (roofs, pavement) Rain gardens slow down rainfall run-off on the way to surface water

2 Rain Gardens for Bioretention Rain gardens utilize water from impervious streets, driveways and rooftops and put the water back in the ground. Manage water on-site and provide beauty

3 Rain Gardens (Key detain water and infiltrate) - Shallow (6 to 9 max. deep) Depressions - Surface should be dry in 24 hours (or less) - Soil amendments sometimes needed (compost and/or sand) - Planted with deep-rooting Plants (natives work well) - Design as a Landscape Feature ( natural, formal, or in-between) - Design to Integrate into Landscaping - Select plants to attract Wildlife (for multiple benefits)

4 Locate a Rain Garden Understand where the water flows on a site Where soils will infiltrate impounded water Not Upslope from a home Closer than 10 from house foundation Under heavy tree canopy On unstable slopes On sites with high water tables Where water stands long enough to kill grass On active construction sites

5 Where would you put a raingarden?

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7 Soils First! Knowing rate of water movement is first step in design Percolation is the rate water moves through the soil (inches/hour) Minimum rate 0.5 in/hr Optimum is 1 in/hr Water should drain through the soil in hours Soil texture is a measure of the percent of sand, silt or clay

8 Perc test hole to measure rate that water moves into the soils first call one call to locate utilities

9 Call one call and locate utilites. Dig hole with post hole digger 1 ft below floor of rain garden about 1.5 ft (min) in center of rain garden. Dig another hole in center at the upslope side at about 3 ft depth below rain garden floor PERCOLATION TEST PAGE 4-5 OF MANUAL

10 Fill test holes with 12 inches of water, if drains away in hours may be fine After 24 hours fill with another 12 inches of water, if drains away in 12 hours, percolation rates should be 1 inch/hour If drains down in 24 hours should be.5 inches/hour If it does not drain in 24 hours try other practices such as soil quality restoration and/or native landscaping

11 Area 20 ft X 25 Feet = 500 square feet. More than 1 per hour multiply by 10% 500 x.10 = 50 sq ft with 6 inches of depth 10 ft L x 5 ft W More than.5 per hour but less than 1 per hour multiply by 20% 500 x.20 = 50 sq ft with 6 inches of depth 10 ft L x 5 ft W

12 Rain Garden Shapes

13 Rain Garden Shapes

14 Rain Garden Shapes

15 Installation Techniques Lay out with flags, a hose, or rope Install it on the contour (across the slope) Longer and narrow if it fits the site

16 Procedure After Iowa One Call and percolation Kill and/or remove turf grass Remove and stockpile topsoil

17 Removing sod in rain garden

18 Installation Techniques Cut & Fill Process Build a small berm on the lower edge Use excavated soils from up-hill side of rain garden Stockpile surface soils and use subsurface soil in berms

19 Procedure Use subsoil to build a berm Compact berm as its built (2 lifts) Check berm for level Build the center 2 higher than a side to create overflow Leave overflow low until plants establish

20 Over-excavate your garden Depth should be 6 of ponding and 6-12 amended soil. Amended soil mix is one part each Topsoil from your garden area Compost Sand

21 Soil Amendments Amending rain garden with bagged compost Minimum requirements: 30% topsoil 30% compost 30% sand Use washed sand not masonry sand Order amended soil mix 50% compost-50% sand t mix with excavated soil Rototill amended soil mix in garden area, or shovelmix

22 Protect Inlet location from scour Watch for scour from concentrated flows Sheet flow Tile Line Downspout Swale

23 Level Bottom Level from end to end and side to side Infiltrate water uniformly across bottom Maximizes capacity and storage

24 Check the berm for level and choose the overflow area to leave lower

25 Preparing inlet to rain garden from plastic drain tile delivering roof water

26 Checking capacity of rain garden and berm height

27 BORDERS Bullet Edging Brick Edging Trench-Master (Edging Trencher) Designed & Installed by: Natural Shore Technologies

28 Iowa Native Plants Native plants grew in Iowa before European settlement Tallgrass prairie ecosystems developed 10,000 years ago Developed a deep fibrous root system reaching 6-12 feet deep Created the best soils in the world

29 What to Plant? Native plant species Adapted to climate and conditions Drought tolerant Disease resistant Deep root systems Build porosity and increase organic matter Thrive with less care than non-native species Attract wildlife with nectar, berries, seeds

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32 Native Plant Favorites Blue Grama Bottle gentian Butterfly milkweed Columbine Culver s root Fox sedge Golden alexander Little bluestem Mountain mint Nodding onion Pale purple coneflower Prairie blazing star Prairie smoke Sideoats grama Silky aster

33 Native Plants Right Plant for the Right Place plugs $ ea. 3-4 pots $3-4 each

34 Prairie Smoke Butterfly Milkweed

35 Planting and Maintenance

36 Rain garden four months after planting with native plugs

37 Distribute mulch over planting area prior to planting (small) plugs Native Landscaping

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39 Caring for Your Rain Garden Watering Young plants susceptible to stress Water regularly until established One inch of water per week in first growing season After establishment not much water needed for native plants

40 Caring for Your Rain Garden Annual Maintenance Spring Prune or burn dead vegetation in early spring (Local ordinance may prohibit burning) Weed garden Add mulch if needed Summer Weed garden Water during establishment or extreme situations Non-native plants may need more attention

41 Maintenance Options Keeping rain gardens looking good is key for acceptance Most people want something that looks orderly and well kept

42 Arranging plants and reviewing layout

43 Try not to step in the rain garden reduce compaction Adding plants to rain garden

44 Mulching-shredded or chipped wood 2 mulch layer required; 3 suggested Mulch plants Keep them cool Retain moisture Create weed barrier

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