The Cedar River as it flows west past the Herzman Levee.
The Herzman Levee Setback and Trail Stabilization Project will provide flood and erosion risk prevention along a stretch of the Cedar River about four miles east of Renton. The need for the project was identified in the Cedar River Capital Investment Strategy, completed in 2017, which identified flood and erosion risks and potential solutions throughout the lower Cedar River valley.
The Herzman Project area contains two important flood protection facilities: the Herzman Levee, which extends 800 feet along the right bank, and the Cedar River Trail 2 (CRT2) Revetment, extending 500 feet along the left bank (see map, below). The Herzman Levee reduces risks due to channel migration for SE Jones Road and for several homes landward of the levee. The CRT2 Revetment provides protection for State Route 169 (SR 169), the Cedar River Trail, and underground utilities.
The Herzman Levee artificially constrains the Cedar River, forcing it to flow directly at the CRT2 Revetment. As a result, the CRT2 revetment has been repeatedly undermined; it is also at risk of the river cutting behind its upstream end, which could erode the remaining bank between the revetment and the Cedar River Trail. The top of the revetment’s left bank is within five feet of the trail, providing very little buffer. The Herzman Levee has also been damaged over the years and is prone to scour due to its overly steep riverward bank.
Since 1990, the Herzman Levee has been repaired twice and the CRT2 Revetment has been repaired four times. All repairs were required to address erosion and scour damage due to high flows.
The project team will conduct an analysis of flooding patterns and topography within the project area and evaluate the feasibility of several alternatives to modify the existing Herzman Levee. One possible approach is to remove and set back a portion of the levee and construct a side channel to convey high water flows away from the CRT2 Revetment. The project could also entail upgrades to the CRT2 revetment.
The goal is to enable both facilities to provide greater resilience against erosion and channel migration and better protect homes and infrastructure, while saving taxpayer dollars over the long term. Setting back the Herzman Levee will also open nearly eight acres of floodplain to more natural river processes, improving habitat and increasing the conveyance capacity of the river at this location.
The Herzman Project is located along the left and right banks of the Cedar River between Renton and Maple Valley, approximately 4 miles east of the I-405/SR 169 interchange in unincorporated King County. It is adjacent to the
Riverbend Levee Setback and Floodplain Restoration Project (Riverbend Project), a county project focused on both flood hazard reduction and habitat restoration. Due to their proximity, the analysis of the Herzman Project is being coordinated with the Riverbend Project and the two projects will be designed to complement one another.
Improve the ability of the CRT2 revetment to provide protection for State Route 169, the Cedar River Trail, and the regional fiber optic trunk line buried within the State Route 169 right-of-way.
Reduce the angle of attack and the erosive energy of the river against the Herzman Levee and the CRT2 Revetment, thereby increasing their resiliency and reducing future maintenance and repair needs.
Reduce adjacent and upstream water surface elevations during large-scale flood events by reconnecting the river to the adjacent floodplain, thus increasing the conveyance capacity of the river at this location.
Protect homes and SE Jones Road.
Improve riparian and aquatic habitat conditions in the area by opening up to eight acres of floodplain to more natural river processes and increasing the amount of slow water and edge habitat available to juvenile salmonids for rearing and refuge.
Coordinate the design with the current Riverbend Floodplain Reconnection Project located immediately upstream.
Planning and Alternatives Selection
May 2017 to November 2018
Preliminary Design (30 percent)
November 2018 to April 2019
Final Design and Permits
April 2019 to March 2020
June to November 2020
The Cedar River flows directly towards the Cedar River Trail and SR 169, as shown here.
The alternatives analysis and preliminary design of the project are funded by a Floodplains by Design grant from the State Department of Ecology. Subsequent phases, including final design and construction, are to be funded by the
King County Flood Control District, partner agencies, and grants. Project Documents
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For more information about the Herzman Levee Setback and Trail Stabilizaton Project, please contact
Nancy Sandford (formerly Nancy Faegenburg), Project Manager, King County River and Floodplain Management Section, Water and Land Resources Division, Department of Natural Resources and Parks.