Rain Gardens
What are the dangers of storm water runoff?
With urbanization, city roads, roofs and parking lots have replaced grasslands and forests that traditionally absorbed rainfall. Now, very little of the rain that falls in a city is actually absorbed by the ground. Instead, rainwater carries trash and pollutants into storm drains and deposits it, untreated, into nearby lakes and rivers. This jeopardizes clean drinking water, harms fish and wildlife and damages property. Over-applied fertilizer, made up of nitrogen and phosphorous, also washes into drains during a rainstorm. These chemicals create algal blooms that raise water temperatures and deplete water’s oxygen, leading to dangerous conditions for both animals and humans.
Considering Seattle’s rainy climate, storm water runoff is of particular concern. Excess rainwater can back up and flood homes, overflow sewers, and erode hillsides and stream banks. It also carries dirt, oil and metal from cars, lawn chemicals, cleaners and pet waste into Seattle’s salmon-spawning streams and swimming beaches.
Fortunately, there are many solutions, such as rain gardens, to address this issue.
What national and local action has been taken?
On a national level, the “Only Rain down the Drain” campaign has sought to educate people about the dangers of dumping polluting materials into storm drains.
As part of the Clean Water Act, Congress enacted the National Pollution Discharge Elimination System (NPDES) to control the negative effects of storm water runoff. Most neighborhood storm drains and sewers are owned and operated by the local town or county, and they must comply with the NPDES. Therefore, many communities (including Seattle) encourage residents to control runoff at its source by offering rebates for those who install rain gardens.
Rain gardens as the solution:
Rain gardens are a win-win solution; they capture storm water and keep it on site, while also providing a beautiful landscape. Through a pipe connected to a downspout, excess rain water from your roof, driveway or patio is conducted to your rain garden, which quickly absorbs water into its soil and irrigates your trees and shrubs.
Rain gardens are built on a slight depression, usually about 6-8 inches deep, which allows the garden to hold water for a short period of time while it absorbs it into the soil. Unlike a pond or a wetland, rain gardens typically hold water for less than 24-hours, even after a heavy storm. Rain gardens are easy to maintain, and those with native plants should not require fertilizers or pesticides in order to thrive. In the summer, rain gardens can attract colorful birds, butterflies and honey bees, and they provide habitat for predatory insects that eat harmful bugs. Rain gardens make good use of water by reusing water that would normally run off to the storm drain. Therefore, in addition to being beautiful and protecting the environment, rain gardens can save you money on your water bill!
Incentives for Rain Gardens in Seattle:
The City of Seattle is helping residents reduce storm water runoff in areas with “CSO” (combined sewer overflow) by providing “RainWise Rebates” for rain gardens! If you live on a property within a CSO area, the City will pay up to 100% of the costs of installing a rain garden or a cistern, based on how many square feet of runoff is controlled.
To qualify for RainWise Residential Rebates:
1. The property must be within a CSO target area
2. Work must be done by a contractor who is trained and licensed with RainWise
3. Pre and post-construction inspections must be done by a Seattle Public Utilities inspector.
4. Rebate request forms must be submitted within 90 days of approval by the SPU inspector.
To find out if you’re eligible for a rebate and choose a contractor, click here:
https://rainwise.seattle.gov/city/seattle/rainwise_solutions
You can also create a “My RainWise” account to play with different configurations of storm water management projects and evaluate their costs and benefits:
https://rainwise.seattle.gov/city/seattle/user_properties/new
For more information, email rainwise@seattle.gov or call Seattle Public Utilities’ Garden Hotline at 206-633-0224.
Here is a great pdf created by the Seattle Public Utilities office called “Building a Rain Garden”:
http://www.seattle.gov/util/groups/public/@spu/@usm/documents/webcontent/spu01_006287.pdf
Northwest Native Rain Garden Plants:
Better Living provides a good list of native Northwest rain garden plants on their website:”Choosing Plants for Pacific Northwest Rain Gardens:”
http://www.betterlivingshow.org/blog.choosing-plants-for-pacific-northwest-rain-gardens.htm
Native Plants for Rain Gardens in the Sun:
Coastal Strawberry, Fragaria chiloensis
Common Camas, Camassia quamash
Dense Sedge, Carex densa
Douglas Aster, Aster subspicatus
Northwest Cinquefoil, Potentilla gracilis
Oregon Iris, Iris tenax
Slough Sedge, Carex obnupto
Tufted Hair-grass, Deschampsia cespitosa
Western Columbine, Aquilegia formosa
Yarrow, Achillea millefolium
Native Plants for Rain Gardens in the Shade
Coastal Strawberry, Fragaria chiloensis
Creeping Oregon Grape, Mahonia nervosa
Dagger-leaved Rush, Juncus ensifolius
Deer Fern, Blechnum spicant
False Solomon’s Seal, Smilacina racemosa
Fringecup, Tellima grandiflora
Large-leaved Avens, Geum macrophyllum
Piggyback Plant, Tolmiea menziesii
Salal, Gaultheria shallon
Stream Violet, Viola glabella
Sword Fern, Polystichum munitum
Wood Sorrel, Oxalis oregano
Western Bleeding Heart, Dicentra formosa
Washington State University also has a good pdf entitled: “Reusing Rain in the Pacific Northwest: Rain Gardens” that provides lots of useful information about rain gardens, including a list of native plants: http://clark.wsu.edu/volunteer/ws/ws-raingardens-8-08.pdf
Finally, the King County Northwest Yard and Garden website is also a helpful resource:
http://www.kingcounty.gov/environment/stewardship/nw-yard-and-garden.aspx
Additional Resources:
Rain Gardens by Lynn M. Steiner and Robert W. Domm
This post was written by Risa Waldoks, “wwoofer” at the Village Green, November, 2012