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TIDAL LIFE | Never thought I’d say this: Please don’t rain on my rain garden
I was ready to start digging. I had the shovel in my hand, figuratively speaking. Actually, I was sitting in the commissioners’ hearing room in Coupeville listening to a presentation by Linda Lyshall of the Puget Sound Partnership about advances in the field of “low impact development.”
Low impact development is a set of methodologies for land management and building construction that focuses on reducing stormwater runoff. By leaving native soil and existing plant life undisturbed and working with the geology of the site, LID directs rainwater into the ground to recharge the aquifer rather than letting it run into Puget Sound.
While this is what the earth does naturally, in the built-environment, rain gardens can be used to mimic the process.
The idea of installing rain gardens on my property had interested me from the first moment I heard about them.
It seemed so simple. Rainwater from my home’s roof would run into a specially constructed low area — a swale — where it would irrigate water-loving, yet drought-tolerant plants and soak naturally into the earth, recharging our shared groundwater.
Plus, I wouldn’t have to pump water out of the ground to keep those plants alive. Bliss!
But when Lyshall said, “We don’t recommend them on a bluff,” a little cloud appeared, throwing a shadow across my inner landscape.
“The clay layer of the bluff structure is impervious, the water hits it and runs out horizontally and comes out the face of the bluff which can destabilize the slope,” she said.
There was a downpour in my soul. Edenic visions disappeared under the deluge.
Water running out
the face of the bluff was exactly what I’d been thinking I could avoid by planting rain gardens. Now I know they’re not for me. If I had a larger piece of property, things might be different, but this is just a small lot with a house taking up a good portion of it.
So those of you who have large lots, or live inland where the water has more time to percolate down to the aquifer, this one’s for you.
What is a rain garden? They’re talked about a lot these days as LID becomes increasingly popular.
For those who just returned from an extended stay in the Sahara, a rain garden is “a shallow, constructed depression that is planted with deep-rooted native plants and grasses. It is located in your landscape to receive runoff from hard surfaces such as a roof, a sidewalk or a driveway. Rain gardens slow down the rush of water from these hard surfaces, hold the water for a short period of time and allow it to naturally infiltrate into the ground,” according to The Rain Garden Network (www.raingardennetwork.com).
That definition is a little vague. Not just any depression will do, it needs to be the right size and it must be filled with an absorbent compost mix.
And “shallow” is a relative term; rain gardens come in all shapes and sizes.
In some Seattle neighborhoods, typical roadside drainage ditches have been replaced with long, narrow rain gardens. In parking lots, they are often more square. Some sites use several, linked together by underground pipe, to distribute runoff during severe storms.
Details of construction are available from a number of organizations, but there are a few rules of thumb to keep in mind when planning rain gardens.
First, to avoid inadvertently turning your crawl space into a holding tank, locate them several feet from the foundation.
Second, make sure the spot you choose is lower than the area you’re trying to drain.
Third, check on those utilities; underground electric lines and water don’t mix.
As in any garden, plant selection is dependent on each individual homeowner’s needs, soil type and sun exposure. Typical designs rely heavily on native plants and grasses which are best adapted to the amount of local rainfall, but some non-natives also do well in rain gardens.
Contrary to expectation, your rain garden will need watering during the first season while plants get settled. And it will require maintenance. You’ll have to weed, just like in any other garden.
With time, the soil mix will compact and must be replenished. But we do those garden tasks anyway, and those of you who put in rain gardens can do them with the knowledge that your efforts are not just beautifying your garden but also protecting our water supply and Puget Sound.
As for me, the disappointment will pass. I’ve got a new plan percolating; water harvesting, or as I prefer to call it, catchment and release.
For more information:
• Whidbey Conservation District is hosting a low impact development tour on April 17. Register at www.whidbeycd.org, “Calendar of Events” page, or call
• Puget Sound Partnership, www.psp.wa.gov
• Master Gardeners, www.island.wsu.edu/master
• Shore Stewards, www.shorestewards.org/island
Questions or comments for Tidal Life? E-mail me at email@example.com.