Čakwab Levee Setback and Floodplain Restoration Project
Green River Watershed
The Levee atis located on the north side of the Middle Green River about four miles upstream of the State Route–18 bridge which crosses the river just east of the City of Auburn. The King County Department of Natural Resources and Parks (DNRP) owns the property.
- Increase quantity and diversity of salmon habitat.
- Maintain or improve existing level of off-site flood and erosion protection for agricultural land, private farms and residences and Green Valley Road.
- Restore natural river processes (channel migration, wood recruitment, etc.).
Fish and wildlife habitat
The removal of the existing damaged levee has reconnected off-channel habitat and increased channel migration, flow splitting, wood recruitment and other natural processes critical to the formation of high-quality, diverse salmon habitat. The result is expected to be increased productivity, abundance, diversity of Green River Chinook salmon and steelhead stocks.
As the reach continues to respond to levee removal, we expect to recover:
10 acres of high quality, off-channel habitat immediately landward of the levee that will be connected nearly year-round to the mainstem river;
30-45 acres of connected, forested floodplain within, upstream and downstream of the project area; and
20-25 acres of active river channel that will be: wider and shallower with finer substrate; potentially split into multiple threads with periodic mid-channel bars and islands; higher quality spawning habitat; and more frequently connected to adjacent floodplain areas at lower flows.
Many of these gains are already unfolding in the reach just one year after project completion in 2021.
Improved flooding and erosion protection
The removal of this aging flood facility and construction of a modern, setback flood facility in 2021 increases protection of existing property and farmland from channel migration and overbank flooding. The old levee was damaged and could have resulted in erosion and flooding of private property, structures and farmland if it failed. The construction of a new berm at the downstream end of the site reduced current levels of flooding on the adjacent two properties during large flood events. Mainstem river floodwater surface elevations will also be lower upstream of the site as a result of the levee removal. The new setback revetment reduces the risk of river bank erosion for adjacent landowners and protects existing farmland, residences and infrastructure from channel migration and overbank flooding.
Project actions completed in 2021
- Removed the 1,600 foot-long levee and constructed a setback facility.
- Removed >25,000 cubic yards of angular rock and native gravel from the levee;
- Removed 600-800 trees from the levee and oxbow area and distributed them throughout the adjacent river and floodplain areas to be recruited gradually to the river and promote natural river and floodplain processes.
- Constructed a 1,600 foot-long erosion protection facility that consists of:
- 600 linear feet of buried rock revetment; and
- 9 engineered log jams.
- Constructed a 600 foot-long gravel terrace to reduce flooding on private property.
- Constructed three side channels through the levee to convey water into the old 1950s river channel.
- Constructed a 650 foot-long (0.1 acres) gravel maintenance road.
The large rock that covered the river side of the levee has been removed and used to construct a new buried revetment. Removal of the rock has exposed the underlying native cobbles, gravels, sands and silts which make up the core of the levee. Some of this material was pushed into the floodplain to form gravel bars that can be eroded by the river and provide spawning gravel for salmon, and some has been trucked to an adjacent King County property where it was spread and planted with native trees and shrubs.
The new flood and erosion protection facility includes a buried rock revetment and engineered log jams comprised of large rock and interlocking logs. A gravel maintenance road has been installed landward of the revetment. A shallow gravel terrace has also been constructed to reduce overbank flooding across a farm field.
The 81.4 acre project site is owned by King County and is mostly within a forested floodplain of the middle Green River just downstream of its confluence with Burns Creek.
The 1,600 foot-long levee was built in 1960 with gravel from the river and imported, large rock (rip rap) to protect it from erosion. The levee formed a “T” shape with an access road to the levee that separates two riverine wetlands. The levee provided some minor flood protection to adjacent properties but did not contain flood water during moderate to large events. Its primary purpose was for erosion control.
The construction of Lones Levee limited channel migration and other habitat-forming processes in the more than 60 acres of floodplain areas adjacent to and downstream of the levee for the past 50 years. It was also a fish-passage barrier, preventing salmon from effectively using the 4.6 acres of riverine wetland habitat located behind the levee. The old levee trapped juvenile salmon behind it each spring, resulting in the death of salmon each summer as temperatures rise in the wetland.
The major earthwork was completed between May and October 2021. Initial replanting with native plants then took place between October 2021 and May 2022. Additional planting will continue into 2023. Project monitoring and maintenance will be ongoing for 10 years to ensure success of the project.
The mainstem Green River was historically very productive for Chinook and other salmon species. However, the habitat needed for salmonid spawning and rearing has been substantially reduced as a result of landscape and river changes, such as the construction of dams and levees to contain rivers. The 1999 listing of Chinook salmon as “threatened” under the federal Endangered Species Act triggered the need to develop a plan to increase productivity of the Green River Chinook population. The WRIA 9 Salmon Habitat Plan (2005) prioritized the need for juvenile salmon rearing in the mainstem of the Green River and identified specific projects to promote the creation of this habitat such as the Čakwab Levee Restoration Project. This project will restore critical rearing habitat and protect adjacent farmlands which are now vulnerable because Lones Levee, constructed over 50 years ago, is in disrepair.
Project documents, files, and video
Lones Levee Project Construction Photos (2.95 MB)
Lones Levee 40 percent design drawings (30.5 MB)
The Determination of Non-Significance and SEPA Environmental Checklist posted below were open for public comment through August 30, 2019.
Determination of Non-Significance (638Kb PDF)
Project funding comes from the following sources:
- King County Flood Control District
- King County Flood Control District Cooperative Watershed Management Grant
- King County Water and Land Resources Division
- Washington State Salmon Recovery Funding Board (Pacific Coast Salmon Recovery Funds from National Oceanic and Atmospheric Administration)
- King County Conservations Future Tax (Property acquisition)
- Puget Soundkeeper Alliance
- Puget Sound Acquisition and Restoration Fund (PSAR)
- Waste Action Project
For more information about the the Lones Levee Floodplain Restoration Project, please contact Dan Eastman, Project Manager, King County Ecological Restoration and Engineering Services.