Rain gardens a sound solution to pollution

Published on Thu, May 1, 2008 by Sonia Hurt

Read More News

Rain gardens a sound solution to pollution

By Sonia Hurt

WSU Master Gardeners, in conjunction with the Watershed Master/Beach Watcher volunteers, have a new project on their shovels – rain gardens.

Our marine waters may still look as beautiful as ever, but if we look below the surface we find troubling facts. In the past few decades we have lost thousands of acres of commercial shellfish beds due to human and animal waste. In the last 10 years the list of shellfish beds on the brink of closure has doubled. Stormwater runoff is now one of our biggest threats to water quality, and according to the Washington State Department of Ecology, has polluted more than 30 percent of our state’s waters.

Our native soils and forests store, filter, and slowly release cool, clean water to streams, wetlands, and the largest estuary on the west coast – Puget Sound. This is extremely important because the rich diversity of life in marine and fresh water, as well as on land, depends on clean water to thrive.

As any region grows, forests are replaced with roads, houses, shopping centers and parking lots.

When it rains or snows, more water flows from these surfaces than undisturbed areas, carrying oil, fertilizers, pesticides, sediment and other pollutants downstream. Much of the pollution in our streams, wetlands and Puget Sound now comes from stormwater runoff.

In forested areas, surface water runoff is less than 1 percent. Once the natural cover is removed and development begins the runoff increases to more than 30 percent. This runoff and contaminants (called non-point pollution) are damaging our water resources and harming aquatic life here in Drayton Harbor and Birch Bay.

One way to significantly reduce the amount of stormwater and pollutants coming from your property is to create a rain garden in your yard. Rain gardens are one of the most versatile and effective tools in a new approach to managing stormwater called low impact development (LID). A LID project may incorporate several tools to soak up rain water, reduce stormwater runoff, and filter pollutants. Some examples of these tools include permeable paving which allows water to soak in, compost-amended soils, vegetated roofs, rainwater collection systems, and rain gardens.

A rain garden acts like a native forest by collecting, absorbing, and filtering stormwater runoff from roof tops, driveways, patios, and other areas that don’t allow water to soak in. Rain gardens are designed as shallow depressions, filled with compost-amended soil, that can be shaped and sized to fit your yard and landscaped with a variety of plants to fit the surroundings and complement your home.

Rain gardens provide multiple benefits. They filter oil and grease from driveways, pesticides and fertilizers from lawns, and other pollutants before they reach the storm drain and eventually streams, wetlands and marine waters. They reduce flooding on neighboring property, reduce erosion in streams, and provide habitat for beneficial insects and birds.

Rain gardens, just like any garden area, need maintenance to perform well and look good. While mulching, watering and weeding will keep your rain garden looking great and working to its maximum potential, a well-designed rain garden needs minimum care.

Most plants will need deep watering during the dry season for the first two to three years to establish healthy root systems. If you have selected the appropriate natives or plants adapted to Western Washington, then the rain garden will need little or no watering after that.

Do not apply fertilizers to your rain garden. The rain garden soil mix provides plenty of nutrients and if you have selected the appropriate natives or plants adapted to this region, no fertilizing is needed.

A note of caution. Rain gardens should not be located near the edge of steep slopes or bluffs. The additional water could result in landslides. Additionally, they shouldn’t be placed over septic drain fields, shallow utilities or in areas that do not drain well.

Within the next few months the Master Gardeners and Watershed Master/Beach Watcher volunteers will be creating a demonstration rain garden.

Small changes in the way we live and enjoy our land can add up to huge conservation benefits for our water, our wildlife and our grandchildren. For more information about designing and installing a rain garden, Washington State University’s Pierce County Extension has created an excellent publication: Rain Garden – Handbook for Western Washington Homeowners. This handbook shows how to design and locate a rain garden. It also provides a nice list of plants for different exposures as well as several sample planting plans.

Copies of the Rain Garden Handbook are also available at: www.pierce.wsu.edu.
For more information about the Whatcom County Extension program, call 360/676-6736.