Known for our tree planting work, the Greenway Trust is now undertaking another type of restoration: improving the habitat in the river itself.
Since 2005, we have worked with Washington State Parks to restore more than 40 acres along Issaquah Creek in Lake Sammamish State Park. Efforts have focused on replacing invasive plants with tens of thousands of native plants to increase shade and lower stream temperatures for threatened salmon populations. Now it’s time to focus on the stream bed.
The lower mile of Issaquah Creek, which runs through the State Park before entering Lake Sammamish, needs help. Issaquah Creek has deeply incised banks in many locations, creating steep drop-offs and disconnecting the creek from the surrounding historic floodplain, creating an inhospitable environment for the many species of salmon and other fish that use the creek.
Large woody debris (LWD)—normally present in a healthy creek—is almost entirely absent from this stretch. LWD creates pools and other in-water features and provides spawning, rearing, resting, food production, and refuge habitat for salmon.
The Greenway Trust is working with State Parks, Northwest Hydraulic Consultants, and The Watershed Company to create a plan to add wood and plantings to increase hydraulic and geomorphic complexity and available cover for salmon, with an emphasis on improving rearing habitat for juvenile Chinook.
The LWD added to the stream will provide immediate benefits for salmon, while the young trees planted along the banks of Issaquah Creek will provide long-term wood supply as they grow and eventually fall into the creek.
With a project this big, partners are key. We are proud to be working with Washington State Parks, King County, local tribes, the City of Issaquah, and others, with funding from the King County Flood Control District and The Boeing Company.
This project builds on twelve years of past successes of restoration within Lake Sammamish State Park and will improve in-stream salmon habitat conditions. This is a multi-phase project, and will take two to three years to complete. This year, current conditions were analyzed and now conceptual design alternatives are being studied and evaluated. The next step will be developing a preliminary design, with project construction still a few years away.