Overview
Rain gardens
A rain garden intercepts runoff from a roof, driveway, or patio and holds it in a shallow basin long enough for it to infiltrate — typically within 24 to 48 hours, which is short enough that it never breeds mosquitoes.
The four decisions
- Catchment. Which surfaces drain into it, and how many square feet do they cover.
- Soil. How fast water moves through your ground, measured with a percolation test you can do with a shovel and a bucket.
- Size. Derived from the first two. This is where most projects go wrong.
- Plants. Species that tolerate both saturation and drought, chosen for your region.
The detailed guides, the plant selector, and the sizing calculator live on the rain garden section of this site:
When a rain garden is the wrong tool
A rain garden handles water that falls on the parcel. If water is already coming through the wall or the floor, start with foundation and basement water. If it is pooling in the yard or running off a slope faster than it can soak in, a French drain carries it away. And if a lake, canal or bay is taking the bank itself, no amount of infiltration helps: see the seawall and riprap guide.