Molalla River Watershed Restoration

The Molalla River watershed was burned by both the Beachie Creek and Riverside fires in the 2020 Labor Day fires. Increased instream summer temperatures, sedimentation, and winter high flow events are some of the main anticipated effects of the fires. High summer water temperatures and a lack of spawning habitat were already identified as limitations before the fires, particularly for ESA-listed spring Chinook and winter steelhead. The long-term effects of the fires are expected to exacerbate these pre-existing limiting conditions in the Molalla watershed.
This project added large wood to Copper Creek, a major tributary of the Molalla River that was also identified as being particularly vulnerable to hillslope failure, due to the severity of the burn in the area and steep slopes. The length of stream treated was lower than proposed due to difficulties obtaining adequate wood to fully stock the proposed stream miles. Channel structure placement was a proposed activity that was incorrectly omitted. By adding large wood to the channel, this project has increased areas of slower-moving water that are able to retain sediment in the case of a landslide. Upland vegetation management was also a proposed activity that was incorrectly omitted. Partners in this restoration plan included Native Fish Society, the Oregon Department of Fish and Wildlife, the US Bureau of Land Management, and Fruit Growers Supply Company.

Located in Clackamas County, on the traditional homelands of the Confederated Tribes of the Grand Ronde, the Molalla River provides habitat for ESA-listed spring-run Chinook and winter steelhead. Habitat limitations due to the widespread continuing effects of historical logging practices and agriculture in the Molalla River watershed remain the biggest factor limiting the recovery of Chinook and steelhead in the basin. Restoration locations were identified in the 2012 Rapid Bioassessment of the basin; redd locations of winter steelhead indicate that a large number of redd sites are located on the mainstem, where a number of small tributaries enter the Molalla. The addition of large wood jams will aid in the creation of spawning and rearing habitat, selectively placed where distinct riparian areas exist to anchor the wood. These sections of stream also tend to be of a gentler gradient, where more complex stream habitats (a mixture of pools, riffles, and glides) exist, indicating that added wood will be able to create distinct areas of scour and deposition, increasing the availability of spawning and rearing habitat. Replanting the riparian area following the construction of large wood placement will further reduce bank erosion, thereby reducing turbidity. Shading provided by riparian plants will decrease solar radiation and reduce water temperatures. Streamside vegetation will also increase food availability in the stream through contributions of leaf litter and terrestrial insects.