With the installation of large woody material Issaquah Creek will continue to re-establish a more meandering flow path, improving habitat for salmon and water quality and flood storage.

Lower Issaquah Creek

In-Stream Restoration at Lake Sammamish State Park

The Mountains to Sound Greenway Trust and the Washington State Parks and Recreation Commission are partnering to study in-stream habitat and natural process improvements along the lower 6,000 feet of Issaquah Creek that flows through Lake Sammamish State Park. With 1.3 million annual visitors to the State Park, this project will be highly visible with tremendous community outreach and education opportunity. When completed (phase 1 construction is currently planned for summer of 2024), along with other efforts underway by State Parks and the City of Issaquah, it will finish nearly all restoration that is proposed in the lower reach of Issaquah Creek in the 2005 Chinook Salmon Conservation Plan (WRIA 8, 2005) and the 2017 update to the Plan (WRIA 8, 2017).

Project Highlights:

  • 5 acres of new restoration ​
  • 50+ acres restoration buffer enhancement ​
  • 7,500+ native trees and shrubs planted
  • Open 0.3 miles of new side channels​
  • Creation of pilot channel and reconnected oxbow
  • Installation of over 400 pieces of large woody material

Project Goals:

The Lower Issaquah Creek In-Stream Restoration Project aims to improve juvenile Chinook rearing habitat (complexity and diversity)​ by…

  • Re-engaging the floodplain
  • Inserting large woody material (LWM) that will create pools; reduce and redirect flow; and increase scour and cooler, deeper pockets of water
  • Contributing riparian reforestation that will provide future LWM recruitment, shade, nutrients, and contribute food and vegetative matter

This project will also improve habitat conditions for other salmonid species like coho and sockeye.

Large cottonwood tree in Issaquah Creek improving channel complexity

Since 2005, the Greenway Trust has been leading incremental riparian restoration projects in the State Park, adding three-to-five acres annually along the banks of Issaquah Creek. In recent years, partners from the WRIA 8 Technical Committee encouraged the Greenway Trust to pursue a more comprehensive ecological in-stream restoration effort. Specifically, a restoration effort that would leverage the slowly maturing native forest (now 50+ acres of riparian buffer planted in the State Park) by completing an analysis of instream habitat conditions, evaluating opportunities for increased relict-channel and floodplain connections, and placement of large woody material (LWM) features to improve conditions for juvenile Chinook and other salmonid species. This project represents the assessment of this effort to date, and includes most of the final remaining A-, B-, and C-level projects from the 2005 Lake Sammamish State Park Wetland, Stream, and Lakeshore Restoration Plan.

The last 5 acres of riparian habitat still covered by blackberry (right side of creek) when this photo was taken in 2020. Restoration is underway, including the planting of 950 trees at the Greenway’s Annual Tree Celebration in 2022 (shown below)
2022 Tree Planting Celebration

Conceptual Design Report

The Lower Issaquah Creek Restoration at Lake Sammamish State Park Conceptual Design Report was completed in December of 2018. The report describes existing channel conditions, breaking down the project into four reaches defined by geomorphology and current habitat features. The report also outlines project objectives and presents two alternatives for in-stream restoration. The two alternatives were  shared with project partners and stakeholders, with Alternative 2 being the unanimous preferred alternative. After the selection of Alternative 2, further outreach was conducted to refine the Conceptual Design which is reflected in the Updated Conceptual Design Drawings.

Preliminary Design Report

The Lower Issaquah Creek Restoration at Lake Sammamish State Park Preliminary Design Report was completed in September of 2020. Following the Recreation and Conservation Office (RCO) Guidelines for Design and Restoration Project Deliverables, the report documents the following:

  1. Project history and background
  2. Project objectives for all four reaches
  3. Descriptions of infrastructure
  4. LWM Inventory
  5. Hydraulic modeling
  6. Channel migration zone analysis
  7. Outreach and engagement with interest groups
  8. Preliminary cost estimates

Preliminary Report

Preliminary Report with Appendices

Full Appendices

Project Construction

Phase 1 (Reach 2 and Reach 3) project construction is currently planned for the summer of 2024.

Project Funding

Funding for this effort comes through a King County Flood Control District Cooperative Watershed Management grant via the Lake Washington/Cedar/Sammamish Watershed (WRIA 8), the Washington State Salmon Recovery Funding Board (SRFB) through WRIA 8, the Washington State Recreation and Conservation Office (RCO), and a grant from The Boeing Company. The Greenway Trust has contracted with Northwest Hydraulic Consultants (NHC), and The Watershed Company to evaluate alternatives and develop a preliminary design to enhance this stretch of Issaquah Creek.

Additional funding announced!  

In December 2022, Congresswoman Kim Schrier, M.D. (WA-08) announced that this work is one of the 15 local projects that will receive over $22 million as part of the Community Project Funding program included in the FY23 government funding bill. Thank you Rep. Schrier for your support!

“I’m thrilled that I could go to bat for the 8th District and make sure all 15 of our district’s requested projects received funding,” said Rep. Schrier.” These projects are a unique opportunity to advocate for our community’s needs. Local governments and nonprofits know what our communities need best, and that is why I went directly to them for recommendations about what the federal budget should prioritize.”

For more information, please contact Mackenzie Dolstad at mackenzie.dolstad@mtsgreenway.org.