by Charlene Burgi
Last week I left you with the promise of more to come regarding passive rainwater catchment systems. In the past, I briefly described rain gardens as a method for capturing rainwater, but abbreviated how these gardens work.
On the surface, rain gardens can appear as a formal landscape feature or a picturesque part of your garden. But they are also very functional, serving to capture rain and prevent runoff by diverting the water into a porous pond-like basin filled with layers of rock and organic matter.
It is important to build the rain garden at least ten feet away from the foundation of your house. Be certain to direct the downspouts of your house into the rain garden. One method of doing so is by designing dry creek beds that lead to the garden. On the downhill side of the pond away from the house, use berms—or bioretention cells—built of organic material to finish the self-contained ponds and stop the water from running off.
The basin should be back-filled with a minimum of 12 inches of porous soil. Use plants that can take adverse wet to dry conditions. Plant water-wise plants on the berms you create. Install deep fibrous rooted plants such as agapanthus or native plants for the greatest success.
Ideally the rain garden will hold the captured rain water for about four hours after an inch of rain fall. Besides preventing the rain water from entering storm drains, the garden will filter runoff and help to recharge ground water. And don’t be surprised if your garden also becomes a haven for birds and butterflies!