Lower Nehalem Tributary Junctions Large Wood Engineering Designs

The proposed projects are located at 7 high priority cool water tributary confluences within the lower Nehalem River Watershed. The project goal was to develop engineering design alternatives to evaluate options for installing large wood to restore salmonid habitat complexity at 7 cool water tributary junctions with the mainstem Nehalem River. The goal was to develop a permit-level engineering plan set (30% drawings) and construction cost estimates with which to obtain project permits and implementation funding for Phase I construction in 2020. Due to the number and complexity of the sites and concerns of project partners we were unable to develop permit ready designs. A 30% design level was achieved for the Cook Creek (tributary option), Salmonberry River, and Spruce Run Creek sites. These 30% designs include conceptual level designs that describe the placement and types of structures intended for each anticipated wood structure. They also include typicals of the various structure types showing how structures of each type are typically constructed. Permit ready designs could not be achieved for the sites because fill/removal volumes and the necessity of anchoring structures could not be determined. This will also allow for more stability calculations to be done prior to project implementation as well as other concerns to be addressed. Project partners include: Wild Salmon Center, Oregon Department of Fish & Wildlife, Oregon Parks and Recreation Department, Oregon Department of Forestry and NOAA Fisheries.

The proposed technical assistance project will provide the Lower Nehalem Watershed Council with 30% engineering designs for large wood placement that have been reviewed and vetted by a Technical Team. The project to install large wood will benefit juvenile salmon at up to 7 tributary stream confluences with the Nehalem River. These confluence zones have been identified as cool water refugia zones with summer water temperatures significant cooler than the mainstem Nehalem, which is DEQ 303(d) listed for temperature. At all of the proposed sites, due to past land management practices, there is no large wood and no cover for juvenile fish, making them highly susceptible to predation. By installing large wood at these confluence zones, the project will address this deficiency and potentially allow for future large wood accumulation in this zone by slowing flows and accumulating gravels and cobbles, locally aggrading the channel, reducing the energy and allowing large wood to deposit.