Page 26 - 7166 - Rain Garden Handbook

20 PLAN
1

B. Identify the row with the rainfall region where your rain garden will be installed
by looking at the maps on pages 22 and 23. Match the color and region
number shown in the map to the color and number in the sizing chart.

C. Find your soil drainage rate in the sizing chart based on your soil drainage test.
If your selected performance level is Best, be sure to pick the right row for your
ponding depth, either 6 inches or 12 inches.

D. Referencing soil drainage rate, rainfall region, and desired performance
level, find the “sizing factor” to determine the area in square feet of the top
surface of the ponding area of your rain garden. The sizing factor is shown
as a percentage of the total amount of contributing areas. Multiply the total
contributing area by the sizing factor to get the top surface of the ponding area. Mandi Roberts
Total Contributing Area x Sizing Factor Percentage = Top Surface of Ponding Area

5. HOW MUCH ROOM DO YOU HAVE FOR YOUR
RAIN GARDEN?

Measure how much space is available for the rain
garden. If it does not fit in the selected location,
consider the following options:
Erica Guttman • Reduce the size of the rain garden by reducing the

size of the contributing area.
• Reduce your performance level (from Best to Better
or Better to Good).

• Consider a different shape—rain gardens can be
long and narrow. See page 26 for more information.

Erica Guttman Erica Guttman • Divide the rain garden into more than one location
with separate drainage areas.

• Find another location.