The Cedar River, looking downstream, as it flows west past the Herzman Levee.
The Herzman Levee Setback and Trail Stabilization project will provide flood and erosion risk reduction along a stretch of the Cedar River about four miles east of the City 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, this revetment has been repeatedly undermined and repaired over the years. It is also at risk of the river cutting behind its upstream end, which could erode the unprotected bank of the Cedar River Trail. 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. These repairs were required to protect critical infrastructure against erosion and scour damage during high flows.
The project team has conducted an analysis of flooding patterns and topography within the project area and evaluated the feasibility of several alternatives to modify the existing Herzman Levee and CRT2 Revetment. The selected alternative will remove and set back the downstream portion of the levee, construct a side channel, and install flow deflectors on the left bank to push high-velocity water flows away from the CRT2 Revetment below the trail.
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 habitat and improved flood conveyance through this reach of the river.
The Herzman Project is located along the left and right banks of the Cedar River between Renton and Maple Valley, approximately four 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 which is currently in development. Due to their proximity, development of the Herzman Project is being coordinated with the Riverbend Project to maximize the flood risk reduction and habitat benefits of both projects.
Reduce the erosion risk to State Route 169, the Cedar River Trail, and the regional fiber optic trunk line buried within the State Route 169 right-of-way by stabilizing the over-steepened bank along the CRT2 Revetment and deflecting high-velocity flows away from the facility.
Reduce the erosion risk to the Herzman Levee and the CRT2 Revetment by setting back the levee and improving flood conveyance through the adjacent floodplain.
Reduce the frequency of future maintenance and repair needs by improving the resiliency of the Herzman Levee and CRT2 revetments.
Protect homes and SE Jones Road by reducing the erosion risk to the Herzman Levee.
Increase the amount of slow water and edge habitat available to juvenile salmonids for rearing and refuge by allowing the river to better access up to eight acres of floodplain area.
Maximize flood risk reduction and habitat benefits by coordinating the design with the Riverbend Floodplain Reconnection Project located immediately upstream.
Planning and Alternatives Selection
May 2017 to November 2018
Preliminary Design (30 percent)
November 2018 to October 2019
Final Design and Permits
October 2019 to February 2021
June 2021 to November 2021
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 were 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 Stabilization 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.