Rain gardens
Build one that is the right size,
and it will run itself.
A rain garden is a shallow planted basin that takes runoff from a roof or driveway and lets it soak in. The design is simple. Almost every failure traces back to one of three things: wrong size, wrong soil, or wrong place.
Runoff calculator
Catchment area and soil type in, runoff volume and required garden size out. Start here.
Berms, swales and basins
Shaping the yard to hold rain where it falls, from a single basin to check dams on a slope.
Percolation testing
How to measure your real infiltration rate with a shovel, a bucket, and an afternoon. In progress.
Plant selection by region
Species that tolerate both a 48-hour soak and a dry August. In progress.
The build sequence
- Measure the catchment. Roof footprint in square feet, per downspout.
- Test the soil where the garden will go, not somewhere convenient nearby.
- Size the basin from those two numbers. Calculator.
- Site it at least 10 ft from the foundation, off the leach field, out of the water table.
- Excavate and level. The basin floor must be flat, or the whole garden drains to one end.
- Build the inlet and the overflow. Every rain garden needs somewhere safe for water to go when the storm exceeds the design.
- Plant, mulch, and water through the first two summers. After that it is on its own.
The one rule. Size before you dig. Resizing a finished basin means moving the same soil twice.
Rather have it built? Size it with the calculator, then get quotes from local installers.
About this section
Guides are being rebuilt and published progressively. The runoff calculator is live now. More on the project.
More from spawnusa.org
A rain garden handles the water that falls on your own roof and driveway. If the water is coming from a lake, canal or bay and taking the bank with it, start with the seawall cost guide instead.
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Choosing and costing shoreline armor, with the permit path.
Seawall cost
Per linear foot by material, with a calculator.
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What fails, what each repair involves, and when to replace instead.
French drains
Yard, foundation and basement drains: the same trench at three depths.
French drain cost calculator
Priced per foot by placement, depth and outlet.