South Thornton Creek Natural Drainage System (NDS) Project

Photo of a street with natural drainage system.
A natural drainage system project a few years after installation.

Project Description

Improving Our Communities with Natural Drainage Systems
Seattle Public Utilities (SPU) will construct natural drainage systems (NDS) at 4 sites in the south Thornton Creek basin. NDS consist of shallow depressions in the public right-of-way, or “planter strip,” filled with deep-rooted plants and spongy soils that temporarily hold and clean polluted stormwater from streets and sidewalks before the stormwater enters our waterways.

Natural drainage systems can offer multiple benefits to local neighborhoods and ecosystems, including:

  • Greener, more attractive neighborhoods
  • Lower risk of flooding
  • Creation of habitat along streets
  • Healthier creek ecosystems
  • Calmer traffic patterns
  • More street trees

The Project FAQ contains more information.


Seattle Public Utilities (SPU) will construct natural drainage systems (NDS) at 4 sites in the south Thornton Creek basin. Selected sites can be viewed on one of the maps below. 
Combination site map: view high level map with 4 sites shown (Northgate site: 23, Victory sites: 113 & 138, Wedgewood site: 139, and Meadowbrook site: 208)

What's Happening Now?

We completed our technical analysis and selected sites to move into the design phase. We selected sites based on a variety of factors that included community input, recurring drainage and flooding issues, existing soil conditions, and availability of off-street parking. The project FAQ has a complete list of factors weighed.

Throughout 2020, we will:

  • Design the natural drainage systems and pathway improvements
  • Continue to engage with residents, businesses, and community organizations around individual sites

Community Benefits

This project will improve water quality in Thornton Creek, as well as improve stormwater drainage, slow traffic, and beautify streets.
The project will also help the City of Seattle achieve its goal of managing 700 million gallons of stormwater runoff using green infrastructure.

 Community Engagement

If you're interested in learning more and finding out about upcoming community engagement events, please sign up to receive project email updates.


2017 - 2018

  • Early project planning and site selection
  • Outreach to residents about potential sites

2019 - 2020

  • Onboard design consultant
  • Design development for selected sites
  • Design phase outreach throughout 2020


  • Anticipated construction


  • Project closeout



Natural drainage systems slow stormwater and filter out pollutants before they can harm our creeks and other waterways. Keeping pollutants out of our water is important for fish, aquatic life, and people.
Building a natural drainage system in Thornton Creek basin is part of the Plan to Protect Seattle's Waterways. SPU used to call these "roadside rain gardens" but now calls them "natural drainage systems" or "NDS".
Why Thornton Creek? Thornton Creek is a salmon-bearing urban creek with degraded water quality. Stormwater picks up pollutants from streets—including oil, heavy metals, and fertilizers—and flows into the creek through ditches or pipes. This project will remove pollutants from the stormwater before it reaches the creek and reduce the quantity of stormwater going into the creek.