Here’s how to sequester your rainwater runoff and reduce your ecological footprint.
YOU MAY FIND yourself in a beautiful house. With a beautiful wife. You may ask yourself, “Where does my rainwater go?” Even if you aren’t a Talking Heads fan, you should be asking that question. It’s important because if you live in the Seattle region, the runoff from your roof probably is affecting the water quality of Puget Sound.
In many neighborhoods, runoff goes into an antiquated sewer system that overflows into the Sound during heavy storms. In other areas, it runs down the street directly into the Sound, after picking up some engine oil and garbage along the way. Both of these scenarios present hazards to the ecosystem. In fact, storm runoff is the largest source of pollution in the Sound, creating problems for fish, birds, vegetation and every other living thing that depends on fresh water.
Fortunately, a rain garden can beautify your landscape and turn you into an environmental hero at the same time. Finding a way to sequester your rainwater runoff is a great way to reduce your ecological footprint.
The concept of a rain garden is simple. The downspouts on your home are directed into a shallow basin that holds the runoff from your roof while it slowly percolates into the soil. This prevents your rainwater from becoming a source of pollution. It also provides excellent habitat for plant, animal and insect species in your yard. The homes in certain neighborhoods of Seattle are eligible for rebates from the county when they install a new rain garden. However, regardless of your location, sequestering rainwater at home makes a lot of sense. If done properly, rain gardens can be superb additions to the home landscape, providing an entirely new ecological zone on your property.
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The design and construction of a rain garden are a bit more involved than we have room to discuss today. Fortunately, there are many qualified rain-garden installers in the area, and plenty of detailed instructions for DIY gardens online. So we’ll just cover a couple of general guidelines here.
Most important, please make sure you leave plenty of space between the runoff basin and your home (a minimum of 10 feet from the foundation is recommended). After all, you’ll be directing a large amount of water into a concentrated area. Also, remember that the water will need to move downhill, away from the house to the basin. Overly steep slopes can cause erosion, and very flat areas will require trenching to move the water effectively. That being said, a rain garden is generally a small landscape project, and most yards can easily be adapted to accommodate one.
A rain garden typically has three planting zones. The closer you get to the bottom of the basin, the more tolerant the plants need to be of water saturation and submersion.
• Zone 1: the bottom of the basin
• Zone 2: the sloping sides of the basin
• Zone 3: the top of the basin and the surrounding area
Due to variations in sun exposure and other site conditions, it’s not possible to prescribe a specific planting plan for your site, but here are a few of my favorite selections for each area:
Zone 1: Common Sedge (Juncus effusus), Biokovo Hardy Geranium (Geranium cantabrigiense ‘Biokovo’), Red-Twig Dogwood (Cornus sericea).
Zone 2: Deer Fern (Blechnum spicant), Lady Fern (Athyrium filix-femina), Orange New Zealand Sedge (Carex testacea), Tufted Hair Grass (Deschampsia cespitosa).
Zone 3: Wild Ginger (Asarum caudatum), Blue Oat Grass (Helictotrichon sempervirens), Salal (Gaultheria shallon), Oakleaf Hydrangea (Hydrangea quercifolia), Red-Flowering Currant (Ribes sanguineum), Vine Maple (Acer circinatum).
Because there are so many plants that thrive in and around a rain garden, it is easy to plant too many species. This can lead to a chaotic and unruly appearance. If you’d like to strive for a more seamless integration into your landscape, I recommend selecting only one to three species for each zone.