The Rainbow Bend Levee Removal and Floodplain Reconnection Project, completed in 2013, was a multi-partner, multi-objective effort to reduce flood risks and improve salmon habitat in the lower Cedar River. The work was done in two phases spanning more than ten years.
In the first phase, King County successfully helped move residents out of harm’s way. Single-family homes and a mobile-home park were threatened with chronic flooding, requiring emergency response and evacuations. King County purchased the flood-prone properties, helped residents relocate to homes in safer places, and then removed the unoccupied dwellings, creating a 40-acre open space.
In the second phase of the project the levee was removed, four logjams were constructed, two new channels and backwater habitat were created, and tens of thousands of native plants were installed. The goal was to improve salmon habitat and floodplain functions and diminish long-term maintenance costs along the trail.
Watch the project video: Restoring Rainbow Bend — Good for People and Fish
Large-scale, multi-objective projects like Rainbow Bend, where old levees are removed or set back, are central to restoring the viability of threatened Puget Sound fall Chinook salmon. At the same time, these projects can reduce flood risks to residents and infrastructure. Following a multi-objective project such as this, effectiveness monitoring is critical to improving the design and outcomes of future projects.
A comprehensive, 10-year monitoring project is underway to determine whether project goals and objectives are being met effectively and efficiently. The monitoring work is focused on changes in the river, large wood, fish habitat, and plant performance. Early results indicate that the project is working well. The channel is migrating again and the river is becoming more complex and suitable for juvenile and adult salmon. The number of juvenile Chinook salmon that can reside in the project site has increased. Adult salmon are spawning at high densities in the largest of the two side channels.
One of the ways King County monitors fish use in project sites is through the use of underwater video. Watching fish underwater allows us to directly observe how they are using their habitat and interacting with each other. In short, it allows us to enter their world and lets them show us what habitats are important.
For an in-depth look at the monitoring details, check out the Monitoring and Maintenance Report, Rainbow Bend Levee Removal and Floodplain Reconnection Project: Monitoring and Maintenance Report.