Riverbend Levee Setback and Floodplain Restoration
Cedar River - Lake Washington Watershed
The Riverbend Levee Setback and Floodplain Restoration Project will now be constructed in two phases due to the significant changes that occurred during the flood in February 2020. Phase 1 construction will begin as soon as August 31, 2020, and last approximately 3 months. Phase 2 alternatives are in development.
During the construction period, SR169 will be reduced to one lane of travel in the westbound direction from approximately MP 19.5 until MP 21.4, and the Cedar River Trail will be diverted around the work area.
Fall 2020 construction activities will include:
- Extension of a setback revetment on the western (downstream) end of the project area to protect the Cedar River Trail and State Route 169;
- Construction of a buried setback revetment south of the previous location of the mobile home and RV park, on the upstream end of the project area; and
- Surface and underground demolition of the mobile home park, including septic tank, utility, road, and concrete pad removal.
On Feb. 9, Phase 4 flooding on the Cedar River resulted in a breach of the Riverbend Lower Levee at Cavanaugh Pond in unincorporated King County.
The avulsion of the river through the levee has resulted in the river occupying the pond previously protected by the levee and pulling away from the right bank downstream of the avulsion. The Riverbend Lower Levee is on the site of the larger Riverbend Levee Setback and Floodplain Restoration Project being managed by the Water and Land Resources Division of King County’s Dept. of Natural Resources and Parks. The levee breach will obviously necessitate some modifications of the project plans, but the shift has resulted in a number of benefits including an ecological boost to the area that was intended to be achieved by the project’s design. Impacts of the channel realignment are being reviewed and next steps will be forthcoming. In the meantime, Water and Land Resources Division employees are carefully monitoring the area and actively assessing what needs to be done for both flood safety and project adjustments.
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The Riverbend Levee Setback and Floodplain Restoration Project builds upon a long-term effort to protect public safety and restore salmon habitat by acquiring property and relocating residents from a flood-prone portion of the Cedar River floodplain.
The project goals are to:
- Restore riverine processes and functions in the Cedar River and its floodplain in order to improve the quality, quantity, and sustainability of salmonid spawning and rearing habitat;
- Reduce flood and erosion risks to people, property, and infrastructure;
- Accommodate public use consistent with future ecological conditions at the site; and
- Balance flood and ecological benefits and other objectives with project costs.
The project will reconnect approximately 52 acres of floodplain, enhance connection to existing off-channel habitats and create new side-channel habitat on the site. This will be accomplished by removing portions of existing levee/revetment, excavating side channels, raising the bottom elevation of a relic gravel mine (Cavanaugh Pond) to surrounding floodplain elevation and placing wood. The project will also include new buried setback revetments outside of the floodplain that will protect SR 169, the Cedar River Trail and adjacent private property from potential future channel migration.
The project is expected to significantly increase off-channel habitat availability and improve existing juvenile and adult salmon habitat. The loss of these types of habitat features due to bank armoring and disconnection of off-channel habitat has been identified as a primary factor limiting Chinook salmon productivity in the Cedar River. This project is prioritized in the WRIA 8 Chinook Salmon Conservation Plan and will bring the watershed 40% closer to its goal of 130 acres of floodplain reconnection by 2025.
The project site is located on public property along the left bank of the Cedar River between River Miles 6.5 and 7.5 east of Renton in unincorporated King County. The project site encompasses Cavanaugh Pond Natural Area and the previous site of the Riverbend Mobile Home and RV Park, which King County purchased in 2013.
|Acquisition and Resident Relocation
|Planning and Preliminary Design||2015-2016|
|Final design and permitting
Project design and implementation funding
- Floodplains by Design Partnership
- King County Water and Land Resources Division
- Washington State Salmon Recovery Funding Board
- City of Seattle
For more information about the Cedar River Riverbend Project, please contact Jon Hansen, Project Manager, Ecological Restoration and Engineering Services Unit.