Bank stabilization and levee setback projects
Typical bank stabilization projects involve reconstruction of flood damaged levee and revetment segments using a combination of large toe rock and large coniferous logs with intact root-wads placed below the ordinary high water mark (OHWM). Native vegetation and biodegradable geotextile fabrics are used above the OHWM, occasionally in combination with limited amounts of rock facing. Such repairs may include preventative action such as relocation of log or debris jams. These repairs are intended to stabilize eroding and/or slumping river banks as well as to provide fish habitat benefits. Some projects may also afford space for top of bank revegetation to provide additional riparian habitat for wildlife. Completed bank stabilization projects are monitored for several years to ensure that erosion control, revegetation and habitat enhancement goals are met.
Levee setback or slope back projects involves the reconstruction of a facility in a manner that maintains its flood hazard reduction function but substantially changes the footprint and facility cross section to allow increased conveyance, reduced environmental impacts of flood protection on the riparian corridor, improved shoreline habitat, reduced annual maintenance costs, and in some cases, partial reestablishment of fluvial processes. In a slope-back project, the toe alignment is maintained, but the middle and upper bank are regraded in a manner that moves the top-of-bank further from the channel, reducing both high-flow and low-flow constraints on the river and associated aquatic habitat.
Click on a major river basin to learn about specific projects:
For questions about projects on King County Rivers, please contact John Koon, Engineer, River and Floodplain Management Unit.