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Rain Garden Basics

What is a rain garden?

A rain garden is a beautiful and effective way to clean polluted stormwater runoff.  A rain garden acts like a miniature 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. They can be built at several scales and one may be just right for your home or neighborhood.

Rain Gardens are simply shallow depressions that:

  • Can be shaped and sized to fit your yard.
  • Use a special mix of sand and compost that allow water to soak in rapidly and supports healthy plant growth.
  • Can be landscaped with a variety of plants to fit the surroundings.

Rain garden illustration showing runoff coming from a house into the rain garden. Arrows show how the water infiltrates into the ground.


Small salmon fingerlings in a jar with treated stormwaterWhy do we need rain gardens?

Stormwater is nothing but rainfall after it falls on the earth’s surface and travels across the landscape to a nearby stream or other water body. In landscapes that have been altered by humans, this stormwater picks up everything we humans leave behind – things like oil and gas, heavy metals, fertilizers, and animal waste.

Scientists have confirmed that stormwater is harmful to humans, animals, and fish that come in contact with it. Eventually stormwater makes its way to Puget Sound impairing the Sound’s water quality, impacting our shellfish and fisheries industry, and limiting recreational opportunities.

WSU research and experiments have shown that stormwater collected from highways around Puget Sound is lethal to fish. However, when that same stormwater was filtered through a special rain garden soil mix – the fish lived. Rain gardens can be a important tool in limiting the amount of contaminated water reaching our streams and Puget Sound.

Examples of Rain Gardens

Rain garden. Garfield Street, Port Townsend. Photo: E. Guttman1009150938a

Rain garden. Photo: E. Guttman1009150834

Rain garden. Photo: EdmondsRGs2

Rain garden at Point Hudson, Jefferson County. Photo: E. Guttman1009150828b

Rain garden at Point Hudson, Jefferson County. Photo: E. Guttman1009150832f