Bank Stabilization and Riparian Restoration

Four important bank erosion sites were chosen for remediation based on field observations, landowner cooperation, the amount of sediment pollution prevented and the importance of reaches to threatened native salmon and steelhead.  Complete details of the site selection process and also photographs of other locations with bank erosion problems can be found in the Tenmile Creek Watershed Conservation and Restoration Action Plan.   

Boulder wing deflectors will be used to direct currents away from stream banks and to scour deep pools that will provide shelter for salmon and steelhead juveniles and adults.  Bioengineering will be used, with large amounts of living willow material embedded in the structures.  This will create shade, help cool water temperatures, and provide excellent cover for fish

Opposite the bioengineering project at the Hogan property is a large patch of invasive Himalaya blackberry plants that prevent other more desired trees from becoming established and provide very limited wildlife habitat. As part of the 319h project, this thicket will be removed and a diverse riparian gallery forest will be established in its place. Species will include alder, cottonwood, ash, bay laurel, and maple. These new trees will be grown to sapling size in a greenhouse by Dennis Hogan. After planting, trees will be caged to prevent deer browse. Air temperatures will be studied to gauge long term riparian air temperature changes with succession.

Cahto Creek – Kelley Property Just downstream of the Hogan property on Cahto Creek, and closer to the convergence of Tenmile Creek, is the Kelley project site. The stream bank here has been even more actively eroding, contributing sediment pollution that fills pools and clogs spawning gravels downstream. The Cahto Trail also borders the stream on the Kelley property and bank erosion is eating away at its bed. A similar shift in the channel occurred during last winter, where the pool at the base of the cut-bank filled and a riffle in the middle of the gravel bar formed. This reach of Cahto Creek has few pools deeper than 3 feet (see Monitoring), and the structures here will create pools likely four to six feet deep with excellent cover.

Mill Creek – Feigon Property The Feigon property is on Mill Creek above Little Case Creek and there is a 300-foot-long bank failure there. Mill Creek is known to harbor steelhead annually, except during severe drought, and Chinook salmon in high flow years. Coho have not been seen on the property, but likely occurred in Mill Creek historically based on National Marine Fisheries Service intrinsic potential maps. The bank erosion at this site was active during the winter of 2021-2022, and a shallow riffle next to the failing bank is exposed to the sun and contributes to stream warming. There are no pools over 3 feet deep in the reach upstream and downstream of the proposed project.