Longfellow Creek Floodplain Project

Existing floodplain habitat along Longfellow Creek at Graham St. Beaver ponds.

Existing floodplain habitat along Longfellow Creek at Graham St. Beaver ponds.

Project description

Promoting a healthy, accessible, and resilient urban watershed in your neighborhood.

Seattle Public Utilities (SPU) is working to reduce flooding and improve the health of Longfellow Creek in the North Delridge neighborhood.

Through the Longfellow Creek Floodplain project, SPU will evaluate the potential for creek and floodplain restoration at five locations along Longfellow Creek between the West Seattle Golf Course and Sylvan Way.

A floodplain is the flat area next to a stream or river that temporarily stores floodwater when high stream flows overtop their banks during storms. Within the project area, much of Longfellow Creek’s historic floodplain habitat has been lost or degraded, leading to erosion, loss of natural flood storage, and poor habitat for fish, wildlife, and streamside forests.

As a floodplain reconnection project, the Longfellow Creek Floodplain project aims to ease flooding and improve water quality by removing pollutants and slowing the flow of water to improve the health of the creek and wildlife habitats.

SPU will collaborate with North Delridge communities, the Longfellow Creek Network, the Office of Planning and Community Development (OPCD), the Department of Neighborhoods (DON), Seattle Parks and Recreation (SPR), and SPU's consultant team to center racial and social equity throughout this work.


This project will focus on five reaches along Longfellow Creek between the northern end of the West Seattle Golf Course (Genesee St) and Sylvan Way. SPU plans to select one to two sites within these reaches, on the basis of their potential to slow and store high flows during storms.

Aerial map of Longfellow Creek area showing potential floodplain restoration sites. A, West Seattle Golf Course. B, Southwest Juneau Street Bypass and Upstream of Southwest Juneau Street. C, Southwest Graham Street Beaver Ponds upstream to 24th Avenue Southwest. D, 24th Avenue SW to Southwest Willow Street. E, Southwest Myrtle Street to Sylvan Way Southwest Creek Daylighting.
SPU is currently evaluating the five sites shown in this map to determine their potential for floodplain restoration.

What's happening now?

The Longfellow Creek Floodplain project is in the planning and options analysis phase. During this phase of the project, SPU explores a range of different approaches to select sites and project(s) for design and construction.

SPU has identified five potential sites along Longfellow Creek and is currently evaluating their potential for floodplain restoration and developing concepts for each of the sites. From these concepts, we will develop several restoration options. Each restoration option may include one or more sites. These restoration options will be further evaluated with input from community and City partners, and one option will be selected to move forward into the project’s design phase.

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Community benefits

Historically, Longfellow Creek was an important natural drainage system that provided valuable habitat for fish and wildlife, green space for community recreation and forest health, and water quality protection. Unfortunately, historic land use development has dismantled, and in some places eliminated, parts of the creek, degrading this important ecosystem.

Existing problems in Longfellow Creek include:

  • Excess stormwater and high storm flows due to historic development
  • Flooding from channel constrictions and the loss of floodplain connections
  • Erosion and channel incision
  • Habitat degradation
  • Water quality concerns

Through this project, we have a chance to reconnect pieces of the creek in a way that improves drainage, adds resiliency to the creek, and invests in community needs and interests, such as improved access to Longfellow Creek and green recreation areas. Depending on the site(s) selected for restoration, there may also be opportunities for better trail connectivity along and across Longfellow Creek that will connect to the new transit improvements along Delridge Way.

What options are we looking at?

We are currently evaluating the potential for floodplain restoration at five sites. In addition to floodplain restoration, there may also be opportunities to address other habitat or infrastructure needs such as fish passage and culvert replacement or creek daylighting. We will package the site concepts into several options for further evaluation. We anticipate advancing design and construction at 1-2 sites.

Community involvement

Community input will play an important role in this project’s planning and design. As SPU develops concepts for the project, we will engage with the community to gather feedback and evaluate which options can best address community interests and needs. We recognize that there are already a number of City-led projects taking place in the Delridge Corridor, and we aim to incorporate themes we have heard during community engagement for these other projects into our project concepts. Sign up to receive email updates when public input opportunities become available.

  • 2023: Assess five potential sites and develop high-level concept for two sites
  • Early 2024: Analyze the draft concepts for two potential sites
  • Late 2024: Develop floodplain restoration options based on the results of the assessments and draft concepts

The Longfellow Creek watershed has experienced extensive industrial, commercial, and residential development. This development has fundamentally changed the watershed as wetlands and floodplains have been filled in, buildings have been constructed in the floodplain, and large sections of the creek have been piped and moved underground.

As creek floodplains have been eliminated and disconnected, peak flows in the creek have increased and channelization (straightening and confining the creek) and erosion have narrowed and deepened the creek channel. These changes have caused flooding and property damage, fish habitat loss, and barriers to fish passage. The negative impacts of land use development and urbanization have degraded habitat and human connectivity to the watershed and eliminated many of the drainage benefits that a well-functioning creek can provide.

Through the Longfellow Creek Floodplain project, the City aims to make significant investments in the Longfellow Creek watershed, bringing multiple benefits to the watershed and the nearby neighborhood. Funding for this project was made available by SDOT and King County Metro, both of whom are required to provide stormwater flow control because of their work in the Delridge Corridor.

Rather than building costly underground detention vaults or pipes to manage stormwater, SDOT and King County Metro have entered into an agreement with SPU to develop an alternative approach to meeting these stormwater flow control requirements. The Longfellow Creek Floodplain project comes out of this agreement, as a project that will increase natural flood storage in the Longfellow Creek watershed while also providing multiple benefits to the ecosystem and community.

Public Utilities

Andrew Lee, General Manager and CEO
Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000

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Seattle Public Utilities (SPU) is comprised of three major direct-service providing utilities: the Water Utility, the Drainage and Wastewater Utility, and the Solid Waste Utility.