Transcript of "Austin Texas Rain Garden Fact Sheet"
earth-wise guide to Rain Gardens Keeping Water on the LandWhat is arain garden?A rain garden is a shallow, vegetateddepression designed to absorb andﬁlter runoff from hard (impervious)surfaces like roofs, sidewalks, anddriveways. Rain gardens are usuallyplanted with colorful native plantsand grasses. They not only providean attractive addition to the yard,but also help to conserve water andprotect our water quality.How does a raingarden help?As Austin becomes increasinglyurbanized, native landscapes arereplaced with impervious surfacesthat prevent rainwater from soak-ing into the ground. Stormwater Photo: Mary Ann Ryan - Master Gardenerquickly runs off these hard surfaces,picking up any pollutants from theland and carrying them to ourcreeks. This rapidly ﬂowing water Create A Rain Garden in Six Stepsalso increases the chances of ﬂood-ing and erosion.The goal of a rain garden is to keep Find the Right Select an area on gently sloping orwater on the land. Rain gardens, ﬂat landwith their shallow depressions, Location Verify the slope of your lawncapture stormwater and provide Observe the ﬂow of water (instructions on next page). Slopefor natural inﬁltration into the soil. from rooftops, driveways or should less than 10%This provides water for the plants other hard su surface and place the raingardenand helps maintain a constant ﬂow where this water collects If possible, pick a spot in full to partialof water in our streams through sun. Shady locations will still work, butgroundwater. They also help ﬁlter the options for attractive plants areout pollutants including fertilizers, more limited in the shadepesticides, oil, heavy metals and Make sure that any overﬂow does notother chemicals that would oth- cause unintended runoff to a neighbor’serwise reach our creeks through property or other structurestorm drains or drainage ditches.By reducing the quantity of water If you are experiencing drainage-relatedthat runs off your property, rain gar- problems (e.g. severe foundation prob-dens help lower the risk of ﬂooding lems, erosion or local ﬂooding), considerand erosion. placing the rain garden at least 10’ away from the structure Avoid areas with utility lines. Be sure to call 1-800-DIG-TESS (344-8377) to iden- tify the location of underground utilitieswww.growgreen.org – the service is free
How to Calculate the Slope of Your Lawn 6” 120” = .05 x 100 = 5% slope1. Pound one stake in the ground at the 4. Measure the distance in inches between uphill end of your rain garden site and the two stakes pound another stake in the ground at 5. Now measure the height in inches on the the downhill end. The stakes should be downhill stake between the ground and about 10’ apart string2. Tie a string to the bottom of the uphill 6. Divide the height between the ground stake and run the string to the and string by the distance between the downhill stake two stakes and multiply the result by 1003. Using a string or carpenter’s level, make to ﬁnd the lawn’s percent slope the string horizontal and tie the string to the downhill stake at that height Test the Soil Finally, divide this area by 6. This Calculate the Size When soil is saturated calculation tells you how large the (after you’ve irrigated and Shape of Your rain garden should be to hold 1” or it has rained,) dig a Garden of runoff in a rain garden that is 6” hole 6” in diameter and Through observation, locate the deep (see options below) 12” deep in the area you’d like to put roof area or other impervious the rain garden. (Ideally, you want to surface that will contribute runoff Impervious Surface Raingarden Size Options be sure there is at least the 12” of soil Area (sq. ft.) (sq. ft.) (ft. x ft.) to your rain garden above bedrock) 200 33 3x11or 4x9 Use a tape measure to estimate the size of the area. This doesn’t 400 67 5x14; 7x10 require climbing on the roof! 600 100 5x20; 8x12 Standing on the ground, measure 800 133 6x22; 10x13 the footprint of the area you are 1000 167 6x28; 10x17 interested in (the area taken up by your house if you were looking Remember more than one raingar- down from above) den might be needed to collect all Once you have estimated the length the run off from your roof and width, multiply the two mea- Rain gardens shouldn’t be just func- surements to get the area of the tional - they should be attractive, impervious surface in square feet creative and fun! Each Drainage Area = 1/4 of rooftop 60’ Downspout Total Rooftop = 1800 sq. ft. Insert a ruler and ﬁll the hole with 30’ water up to the 6” mark. Time how 30’ long it takes the water to be ab- sorbed into the ground 15’ 1/4 Rooftop = 450 sq. ft. 4 o t p 4 q The water should absorb in less than 24 hours. If there is still water in the hole after 24 hours, then the site is not suitable for a rain garden If your soils meet the inﬁltration test 75 sq. ft. 75 sq. ft. requirements, then you are ready to build the garden! Drainage = 30’ x 15’ : 6 = 75 sq.’
R Rain Garden C Construction Once you feel conﬁdent in theplacement of the garden, lay out the l f hshape using string or tape to deﬁnewhere to digNow you are ready to dig!!! - If the yard is fairly level (ﬂat), just Pick dig out the garden to a depth up the City of of 6” Austin’s Grow Green landscaping material (like stone or fact sheets and plant guide - If the yard is on a gentle slope, timber). This will distribute over- you may need to dig out soil at most areas nurseries or ﬂow evenly across the perimeter visit www.growgreen.org from the upslope area to con- of the rain garden struct a small berm (mound for proper installation of compacted soil) at the Loosen the soil in the bottom of and establishment downslope side of the garden the rain garden to a depth of 3 tips inches. Top dress the loosened soilMaintain a depth of 6 inches with compost so the soil is readythroughout the bottom of the rain for plantinggarden. A string level can help youmaintain a consistent depth If water ﬂows quickly into the rain Plant SelectionSlope the sides of the rain garden garden, you will need to construct and Installation a “splash pad” to guide the water 6HOHFW SODQWV WKDW KDYHusing a shovel to create a gentle to the rain garden. Splash pads areside slope D ZHOOHVWDEOLVKHG URRW VVWHP FRQ- OO typically constructed with rock and WDLQHUL]HG SODQWV YV VHHG
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Maintenance Water regularly until plants are established (usually one growing season) Weed as needed Avoid fertilizing - it’s usually unnec- essary for most native plants If your rain garden is located near a gutter downspout or roof val- ley, consider adding rain barrels so that you will have an extra store of water for irrigating the rain gar- den plants during dry weather. The City of Austin Water Utility offers rebates for the purchase of qualify- ing rain barrels. http://www.ci.austin. tx.us/watercon/rainbarrelprogram.htm Observe the performance of your rain garden over time to make sure it functions as planned. If the wa- Suggested Plants for Central Texas Raingardens ter remains for longer than 2 days, amend the soil by gently cultivating the top 4” to 6“ to break-up any Base of the garden Sides of the garden surface crust. Add sand or compost to create a more free-draining soil Bushy Bluestem Big Bluestem and then re-apply mulch to Cardinal Flower Big Muhly the surface Eastern Gamagrass Black-eyed Susan Fall Obedient Plant Brazos Penstemon Frogfruit Clasping Coneﬂower If there is Gregg’s Mistﬂower Cut-leaf Daisy standing water, will Horsetail Deer Muhly mosquitoes be a problem? Inland Sea Oats Eastern Gamagrass Mosquitoes should not be a Marsh Obedient Plant Gulf Coast Muhly problem because a rain garden is Maximilian Sunﬂower Illinois Bundleﬂower designed to only hold water for a day or two – not long enough Salt Marsh Mallow Marsh Fleabane for mosquitoes to complete Scarlet Rose Mallow Pink Evening Primrose their breeding cycle. Slender Rush Pitcher Sage Soft Rush Plains Coreopsis Swamp Milkweed Prairie Wildrye Swamp Sunﬂower Scarlet Sage Switchgrass For more earth-wise Water Clover gardening tips, visit Find a Grow Water Daisy Green Landscape Design Template towww.growgreen.org White-topped Sedge match your needs and style. Wooly Rose-Mallow For water conserving tips and rebates, visitwww.waterwiseaustin.org www.ci.austin.tx.us/ 974-2550 854-9600 growgreen/landscape_templates.htm