Project Background
Thornton Creek
Thornton Creek is made up of 18 miles of urban waterways running through southeast Shoreline through northeast Seattle where it enters Lake Washington. The Thornton Creek watershed is the largest in Seattle, covering approximately 12 square miles. Most of the water (including rainfall that picks up pollutants when it falls on roofs, streets, and parking lots) in that 12 square miles drains into Thornton Creek and its tributaries.
As Seattle has grown and developed, Thornton Creek has been altered from its original path. Much of the creek and its tributaries have been straightened and its surrounding wetlands filled. A few sections of Thornton Creek have even been redirected through pipes underground. As a result of these changes, the creek’s natural capacity to store water has been greatly decreased and it now suffers from frequent flooding and poor water quality. Over the years, this flooding has caused damage to public infrastructure such as roads and private property. In addition, decreased water quality has negatively impacted the health of the fish, birds, and other wildlife who live in the Thornton Creek watershed.
Climate change is predicted to cause increasingly larger rain events, meaning even more water in Thornton Creek during storms and even more frequent flooding.
A primary goal of this project is to restore Thornton Creek on the property to a more natural state to reduce large-scale flooding. Other completed projects in the area with a similar focus include the Kingfisher and Thornton Confluence Floodplain projects.
Learn more about the Thornton Creek watershed from King County’s Stream Report.
The Project Site
The land where the upcoming park will be was previously a privately-owned property, listed for sale in 2018. The community recognized it as an opportunity to create more green space in the Lake City community and to restore and protect Thornton Creek. In response to strong community advocacy and support, Seattle Parks and Recreation and Seattle Public Utilities jointly purchased the property to create a public park and restore the natural area.
The site area includes approximately 200 linear feet of stream, approximately 21,000 square feet of potential floodplain habitat, and approximately 19,000 square feet of upland habitat. Restoring the area will create multiple benefits, including reduced upstream and downstream flooding; improved water quality; improved creek habitat for fish, aquatic life, and birds; greater watershed resiliency; easier maintenance and future replacement of the undersized NE 125th Street culvert; and public access to a new park that connects the Lake City community to a restored natural area.
A former private residence
The project site, a former private residence, includes multiple structures that are slated for demolition due to flooding and safety concerns. Thornton Creek runs through the property and connects with a culvert under NE 125th Street.
A scenic place to walk, explore, and observe local wildlife…
A view of Thornton Creek passing by a structure on the park property.
Wildlife
Juvenile coastal cutthroat trout and rainbow trout are currently supported in Thornton Creek at the site. Photo by John McMillan.
Over time the site will become more important for fish habitat as the removal of barriers up and downstream allow for salmon passage. Coastal cutthroat trout, rainbow trout, and other aquatic life like stream insects are currently supported by the site and will also benefit from restoration.
Seattle Public Utilities anticipates removing and replacing the culvert at NE 125th Street as part of a separate, future project, allowing salmon to access a greater length of Thornton Creek.
Birds like herons and eagles as well as mammals like beavers and river otters will also benefit from the increased natural habitat, food sources, and water quality resulting from a culvert replacement.
What is involved in restoring a stream?
Restoring a stream with the goal of decreasing flooding often involves widening the stream and increasing its complexity. Stream complexity can be achieved by adding bends to the stream channel, as well as by adding wood and other obstacles. Stream complexity slows water and creates pools where stream insects and fish can gather to rest and shelter from predators. Widening and increasing complexity slows the flow of water, decreasing erosion, and allows a stream to hold more water, decreasing flooding.