Page 32 - 7166 - Rain Garden Handbook

1 Determine the
26 PLAN

Shape of Your

Rain Garden OVERFLOW 16'

16' x 24.5' = 392 sf
The shape of the rain garden often is determined
by existing features such as the need to avoid
structures, trees, and utilities. Rain gardens
can be shaped to fit available space and site
conditions. For example, a long, narrow rain
garden works well on sloping ground. Position
the long dimension so it follows the contour of
the slope, creating a bench. This will reduce
the amount of excavation needed to keep the
bottom flat so water doesn’t flow to one end and
pool, leaving the rest dry. See page 37 for more INFLOW
information about construction on slopes. 24.5' TOP SURFACE OF
PONDING AREA

Remember to provide additional space for the
overflow containment area and plantings around
the ponding area.

Count the Grid Boxes OVERFLOW
CONTAINMENT AREA

When creating an irregular shape, lay out the rain garden on grid
paper to confirm the correct size. Use the grid paper to check if
your irregular-shaped ponding area is sized appropriately. After
drawing a square or rectangle with the calculated square footage
you need, draw your desired shape. Count the number of squares
inside the square or rectangle and the number of squares inside EXAMPLE RAIN GARDEN
the desired shape to make sure they match. Adjust your design if The example above shows an irregular shape
needed to get the number of squares to match. based on the sizing calculations on page 25.
This is just one example. Rain gardens can be
designed in many different sizes and shapes.
See 3-PLANT for other examples.