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Stormwater & Natural Drainage Systems (NDS)

What is stormwater and why is it a problem?​

A car driving through a large pudde in a fooded road
A close up of a stormwater drain with dirty water flowing from the street into the drain
A group of 3 Orca whales swimming in the ouget soundwith the Downtown Seattle skyline in the background

Stormwater is water that falls during a rainstorm or when snow melts. In developed areas such as Seattle, we have many hard surfaces such as roadways and rooftops that do not allow water to soak into the ground. Flooding occurs when a lot of water runs over hard surfaces.

The runoff from drizzling or pounding rain also picks up fertilizers, pesticides, soaps, and other pollutants from the ground. It transports them to the nearest storm drain and local waterways, contaminating water quality and harming fish and other wildlife.

The City of Seattle is working to reduce the amount of pollution from runoff from flowing into Longfellow Creek, the Duwamish River, and Puget Sound.

Natural Drainage Systems (NDS)

Natural Drainage Systems (NDS)  hold and clean polluted stormwater from streets and sidewalks, removing pollutants before they can reach Longfellow Creek. NDS offer multiple benefits to local neighborhoods and ecosystems, including:

  • Increased landscaping

  • Lower risk of flooding

  • Creation of habitat along our streets

  • Healthier creek ecosystems

  • Traffic calming

  • More street trees

  • Pedestrian improvements


NDS installations include spongy soil and deep-rooted plants that clean and filter toxins in water. How a typical NDS planting installation changes over time: 

5 images of an NDS planting over a 5 year period. The first shows small plants and visible dirt in the planter strip, the final photo shows large green bushes, tall grasses, flowers, ad blooming trees in the planter strip.

For accessibility needs, please contact the Project Manager at to arrange to have this visually presented information described to you.

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