So what is a revetment?
Revetments are used to line the banks of freshwater rivers, lakes, and man-made reservoirs, especially to prevent damage during periods of floods or heavy seasonal rains. Typically they are placed on the outside banks of the bends in the river where the river can be the most damaging. Unlike the construction of a dike, which is basically a large earthen pile, this revetment will consist of large rocks buried below the river bottom to inhibit undermining of the riverbank, more rock on the lower part of the riverbank to resist bank erosion, and vegetated “soil wraps” above the rock to stabilize the upper river bank.
According to the City of North Bend, the Reinig Road Revetment was originally constructed in 1966 to protect the roadway from erosion, but it now also protects power lines and a water supply pipeline. During Snoqualmie River flood events, high flows have undermined the revetment and stripped away large rock protection which has left the riverbank exposed to erosion.
In recent years, high river flows have damaged portions of the revetment. In total, the damaged portions extend approximately 775 feet and are situated across from where the South Fork Snoqualmie River joins the Snoqualmie River. These sections have little armor rock remaining at the face, and erosion continues to widen the damaged areas and is advancing into the riverbank toward the road.
The project goals, according to the Washington State Department of Transportation, are to repair damages and improve stability of the revetment, reducing the potential for further erosion, to do the repair in a manner that minimizes long-term maintenance needs and associated costs and to protect the surrounding habitats as much as possible. This project will also protect the two utilities that run parallel to the river; the Puget Sound Energy Transmission line and the Canyon Springs water supply main.
Repairs to the Reinig Road Revetment will begin between approximately June 15 and Oct. 30, 2021. Southeast Reinig Road will be closed near the project site for construction. The westbound lane will reopen by Sept. 6, 2021. The closure area will be limited to Southeast 81st Street to 428th Avenue Southeast. Local access for emergency vehicles and residents living along this stretch of road will be provided.
You can read more about the project here.