RainSmart Rain Garden Design Submittal Form

This form will ask you questions about your rain garden site and design, as described in the Royal Oak Rain Garden Program: DIY Residential Rain Garden Guidebook. 

Please be prepared to:
  1. Identify your imperious area 
  2. Determine the slope 
  3. List the results of your soil infiltration test (click to view video or click to view worksheet)
  4. Upload a copy of your rain garden design and plant list.

Contact Information:


Step 1: Impervious Surface Area Calculations
Calculate the total amount of impervious surface area (rooftop and/or driveway/sidewalk) that will flow into the rain garden. Select all that apply:
Length(ft) 
x Width (ft) 
= Area (ft2) 

Rooftop:

 
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Sidewalk:

 
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Driveway:

 
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Step 2: Slope Calculations

To accurately size your rain garden, you must also determine the slope of the garden area as described in the Royal Oak Rain Garden Program: DIY Residential Rain Garden Guidebook:

  1. Hammer a stake in the uphill end of the rain garden location and another one at the downhill end. The stakes should be about 12 to 15 feet apart.
  2. Tie a string at the bottom of the uphill stake and extend it to the downhill stake.
  3. Using a string level (available at most hardware stores), level the string and tie it to the downhill stake.
  4. Measure the width (in inches) between the two stakes. Measure the height (in inches) on the downhill stake between the ground and string (see Figure A).
  5. Divide the height by the width and multiply the result by 100 to find the lawn’s percent slope (this will be automatically calculated for you).


Graph to illustrate how to calculate a slope


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Depending on your infiltration test and soil type, you may need to dig you rain garden 2 inches deeper than the final elevation to allow for added soil amendments.


For slopes greater than 12%, it is recommended that you find a different location or consider other stormwater management techniques.
Step 3: Infiltration Test

For detailed instructions click to view video or click to view worksheet:

  1. Dig a hole that is the width of your shovel and 18” deep.
  2. Fill with water and wait until it’s dry.
  3. Fill the hole again with 12” of water and time how long it takes to infiltrate. 

Drain Time (hours) Water Depth In Inches (2nd Fill)

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Sizing Multiplier chart

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Step 4: Rain Garden Size Calculation

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Depending on your infiltration test and soil type, you may need to dig your rain garden 2 inches deeper than the final elevation to allow for added soil amendments.
Step 5: Recommended Number of Plants

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Recommended number of plants

As a basic guide, it’s recommended that your garden includes:
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Step 6: Upload Drawing
Please upload your rain garden design and planting list. Be sure to include the following in your design:
  1. Scale (if using graph paper, one block should equal 1 square foot)
  2. Location of the house and any pertinent property lines, trees, driveways, sidewalks, etc.
  3. Identify how the water will get to the rain garden (overland swale or underground pipe).
  4. Identify the overflow outlet location for when the garden fills up and spills over. Make sure it flows away from any buildings.
  5. Identify the number of plants, species, and where they will go in the garden.

Include link to template and example  

Contact Information