Green Stormwater Infrastructure (GSI)

What? Many downspouts connect our roof gutters to underground pipes that carry water to our local creeks and Lake Washington. Disconnecting your downspout from existing standpipes can be accomplished fairly easily with an elbow, pipe extension, and splash block.

Considerations: 

• Disconnect no more than 700 square feet of roof area to a single downspout or splash-block. 
• Downspouts should not be disconnected within 50 feet of steep slopes or landslide hazard areas. 
• Downspouts should discharge at least 5 feet from your house foundation. 

Resources:

• DIY Downspout Disconnection Guide(PDF, 4MB)

What? Native landscaping is the use of plants that are native to Western Washington, meaning they are adapted to our particular soils and climate. Native plants often have deeper root systems than non-native plants, which helps them survive in the dry summer months. Removing some of your less permeable surfaces – such as patios or lawns - and replacing them with native plants can help you save money and create a landscape that requires less maintenance over time. Native landscaping is more capable of absorbing rainwater runoff, and can add visual interest and wildlife benefit to your yard. 

Considerations:

• New and young plants need water to grow strong roots. Watering is essential during the first two to three summers after native landscaping installation. 

Resources:

• DIY Native Landscaping Guide(PDF, 6MB)
• Native Landscaping Maintenance Guide(PDF, 7MB)
• King County Native Plant Finder

Learn more about Natural Yard Care on your property.

What? Surfaces that do NOT allow water to soak in are called "impermeable" or "impervious." These surfaces shed water, usually to the storm system. Too many impervious surfaces can cause flooding issues and magnify pollution problems in local waterways. If a surface can allow water to pass through, it is called "permeable" or "pervious"

Permeable/pervious pavement can be used for walkways, parking areas, driveways, and patios. The pervious pavement reduces the amount of rainwater runoff by allowing rain to infiltrate through the surface and into the ground. Examples are pervious concrete, pervious asphalt, permeable pavers, and grass pavers.

Considerations:

• Permeable pavement is best on gentle slopes less than 12%
• Provide an overflow path for runoff from big storms to flow to street drains, landscaping, or a rain garden.

Resources:

• Permeable Pavement Maintenance Fact Sheet(PDF, 2MB)

What? Rain gardens are shallow, bowl-shaped gardens designed to collect and filter water from your roof, driveway, or other impervious surfaces. Rain gardens can be shaped and sized to fit your yard, are filled with a rich layer of mulch and compost to help water soak in, and are landscaped with a variety of plants that fit your yard, sun, and soil. 

Considerations:

• Your property needs a fairly level yard with a slope less than 5%. Rain gardens should also be located at least 50 feet away from steep slopes to reduce landslide hazard. 
• Rain gardens should be at least 10 feet from your house foundation. 
• Rain gardens need well-draining soil to function properly. This can sometimes require removing your existing soil and replacing it with a specialized rain garden soil mixture.

Resources:

• Western Washington Rain Garden Handbook - An excellent, comprehensive guide covering design, installation, and maintenance of a rain garden. 

What? A cistern is a large rain barrel that collects hundreds to thousands of gallons of water. Made of durable materials like metal, heavy plastic, or fiberglass, cisterns fill with water from your roof, gutters, and downspouts. Water can be stored until you need it for irrigation, or can be slowly released by hose to your landscape. 

Considerations: 

• Cistern overflow should be directed at least 5 feet from your house foundation. 
• Full cisterns can weigh thousands of pounds. Careful placement and a sturdy foundation will keep your cistern safe and secure. 
• A dark colored tank and shaded location will limit algae growth, reduce maintenance needs, and extend the lifespan of your cistern. 
• Cisterns come in a variety of sizes and shapes, and can often be fit on the side of a home out of sight. Shielding a cistern from view with trellis material or plants can also address aesthetic concerns. 

Resources:

• DIY Cistern Installation Guide from Seattle Public Utilities. 
• Cistern Maintenance Guide(PDF, 2MB)
• Cistern and rain barrel sources
• Using Cistern/Roof Water for Edible Vegetable Gardens

NEW: Receive rebates up to $500 for planting trees on your property. Learn more about our Tree Rebate Program.  

What? Planting trees creates a canopy, or "umbrella," of leaves that helps provide shade and reduces the intensity of rainfall before it hits the ground. Planting trees is an easy, affordable way to help the environment. 

Considerations:

• Trees should be planted 10 feet from underground utilities and permanent buildings, 20 feet from street lights or other trees, and 30 feet from street corners. Trees near power lines should grow to less than 25 feet tall.  

Resources:

• DIY Tree Planting Guide(PDF, 8MB)
• Tree Care and Maintenance(PDF, 3MB)
• Tree List - City of Kirkland Staff Recommendations(PDF, 912KB)
• City of Kirkland Tree Codes