DESCRIPTION
This project will manipulate Lones Levee to facilitate the restoration of natural channel migration processes, consistent with current flow regimes of the Green River, at river mile 38, right bank. Manipulating the levee would promote the re-occupation of the river into remnant meander bends and channel migration zones, improving the habitat diversity for salmonids and other species.
The project may be implemented through the following activities:
*Manipulate Lones Levee by removing face rock (veneer rock), exposing the unconsolidated material of the levee's core to the hydraulic energy of the river. In time, this exposed material, much of which was originally excavated from the river, would be transported back into the river;
*Construct setback protection structures to protect adjacent private property from potential channel migration;
*Realign lower Burns Creek, if needed;
*Install engineered log jams and large woody debris near the upper end of the levee removal area and within the old meander bend/channel migration zone; and
*Remove the existing levee access road that crosses the old meander bend perpendicular to the levee
King County completed a conceptual design and additional site investigations for the Lones Levee setback located on the Middle Green River. This conceptual design maximizes habitat benefits and protects agricultural lands adjacent to the project. Currently, Lones Levee prevents the river from traversing the floodplain and connecting isolated lateral habitats. Future restoration will free the river to traverse the floodplain in an unconstrained manner for over a mile in length across 85 acres when the river exceeds 8,800 cfs, providing significant ecological lift for salmon habitat. Setting the levee back will facilitate fish access to side channels, riverine wetlands, and an abandoned oxbow channel; the extent, frequency, and duration of connection to these habitats will significantly increase post-project.
Conceptual designs initially diagrammed the: 1) removal of two levees: Lones and Turley. As part of the conceptual design process, King County became aware that removing Lones Levee was more feasible than Turley, due to landowner willingness. Consequently most of the focus of the conceptual design (and final design) process pertains to Lones Levee. King County provided the following deliverables: 1) conceptual plan drawings and design report which also includes an underground revetment at Lones; 2) wetland assessment; 3) geotechnical study; 4) hydrologic analysis; 5) engineering construction cost estimate. This project was prioritized for restoration in 2013, when King County completed a feasibility study of 10 potential levee setback projects adjacent to the Middle Green River. This future restoration project will be constructed in a King County-designated Agricultural Production District.
