Fish & Water
Walk through your yard and identify potential locations. Note any strong slopes or low spots. It is helpful to watch water flow patterns on the landscape during a rainy day.
- Avoid areas with poorly drained soils. Rain gardens should not be constructed in locations that stay wet throughout the rainy season. Sediment deposits may reveal where water frequently ponds.
- Note soil color. The presence of water modifies soil color by affecting the oxidation rate, making soil color a helpful indicator of a soil’s ability to drain water. Higher water content in the soil leaves less room for air, specifically less oxygen.
- In well-drained (and therefore oxygen-rich) soils, red and brown colors caused by oxidation are more common. These are good soils for rain gardens.
- Wet (low-oxygen) soils usually appear gray or greenish due to the presence of reduced (ferrous) iron oxide (figure 12). Avoid these sites for your rain garden.
- Note areas where water might drain to your neighbors’ or public property. You don’t want to inadvertently harm adjacent property with rain garden overflow.
- Identify potential locations about 10 feet away from your downspouts where water tends to flow (figure 13). Keep in mind that you can redirect water from your downspouts toward a rain garden site (figure 14).
- Gutters and other topographical features will sometimes push water toward a pinch point or an area where most of the water is directed. Consider this a potential area for a rain garden (figure 15).
- Avoid placing your rain garden in a location higher than your yard’s water collection points.
- Look for areas nearby where overflow from a rain garden can be absorbed or safely directed into an approved stormwater collection point, such as a street-side gutter or storm drain. Place your garden between the runoff source and its destination—your rain garden.
Where Not to Place Your Rain Garden
- Do not place your rain garden on top of a septic system drain field. When uphill from a septic system, allow at least 50 feet between a rain garden and the septic system.
- If capturing roof water runoff, place your rain garden at least 10 feet downslope of a roof downspout to avoid impacting existing structures. You can direct water from your downspout to a rain garden by creating a swale or by using rocks or tiles. Avoid placing rain gardens uphill of a house.
- A rain garden should be the final feature installed as part of a larger landscape or architectural project. Sediment flowing into your rain garden from construction or loose soil may limit infiltration.
- To prevent slumping and to protect concrete structures, make sure the outer edge of your rain garden is at least the following distance from a structure:
- 3 feet from a sidewalk
- 6 feet from a basement
- 2 feet from a crawl space or slab
- 10 feet from a retaining wall
- Just because there is ponding water in your yard does not mean it is a good place for a rain garden. Your soils need to have good percolation rates to avoid standing water for more than 2 or 3 days.
- Avoid areas such as wetlands, natural springs, or seeps that stay wet during the rainy season.
- Avoid placing a rain garden under large trees. The tree roots can be damaged by the excavation and may also be overwhelmed by the amount of water that pools beneath them.
- Avoid soils that have been contaminated by chemicals or other toxic substances.
- To prevent surface erosion, do not place rain gardens on slopes steeper than 10 percent. If you have sloped property, consider contacting a licensed landscape professional or engineer to design site-specific safe ways to store and route water off-site without damage.
- Don’t make your neighbors angry! During large storms, it is normal for rain gardens to overflow. Make sure to route the overflow to a safe location away from steep slopes, structures, and neighbors’ properties.
This is an excerpt from How to Install a Rain Garden, ANR-2768.
Laura Bell, Project Coordinator; Eve Brantley, Water Resources Specialist and Professor; Caitlin Sweeney, Assistant Coordinator; and Naomi Pitts, Assistant Coordinator, all with Alabama Extension Water Program at Auburn University