Beaver Creek Habitat Enhancement

Beaver Creek and its tributaries contain some of the highest quality cold-water habitat remaining in the Marys River watershed. Unfortunately, the stream is impacted by the legacy of riparian conifer removal and historic floodplain disconnection, which has decreased aquatic habitat quality and increased flood risks and water temperatures. To preserve and enhance Beaver Creek, the Watershed Council placed large woody debris structures, conducted riparian planting, and reconnected a historic stream alcove. These actions should increase in-stream habitat and increase ecosystem services provided by the creek and the nearby riparian area. The Watershed Council received support from the Oregon Watershed Enhancement Board, Benton County, the City of Corvallis, and private landowners.

Past land management practices have limited the quality of in-stream habitat in these creeks. Historically, loggers removed riparian conifers from streams throughout the Willamette Valley. Conifers were targeted for their high-quality wood which is larger, stronger, and more rot-resistant than that of many deciduous trees. Conifers’ unique qualities also make them excellent anchoring points for large woody debris structures when they mature and fall into the streambed. Structures anchored by conifers can maintain high-quality instream habitat for decades by sorting gravels, collecting new woody material, and slowing flows. Removal of riparian conifers in Beaver Creek limited the quality of salmonid habitat in the basin by stopping the cycle of adding woody debris to the stream. 

To address this habitat deficit, the Watershed Council installed 26 new large woody debris structures in Beaver Creek. To ensure that high-quality habitat will be maintained in the future, the Watershed Council also planted new riparian plants. As the young trees mature, they will continue building and maintaining in-stream habitat without the need for human intervention. The new large woody debris structures will provide habitat for native fish and amphibians like cutthroat trout and the Pacific giant salamander. 

Most rivers and streams in the Willamette Valley are disconnected from their former floodplains. This decreases habitat complexity and quality. Ash swales are seasonal wetland ecosystems that depend on periodic flooding. Wetland ecosystems can provide flood control, sequester carbon, and filter water, all of which benefit downstream communities. These wetlands also provide high-quality spawning and rearing habitat for Oregon amphibians.

Because Beaver Creek had dug into the streambed and was disconnected from its floodplain, it could not flood the wetland and maintain the ash swale. The Watershed Council chose to restore the area by digging a new path for the stream to seasonally flood the wetland. Species like the Pacific tree frog, rough-skinned newt, and swallowtail butterfly will use this new habitat. The new wetland also provides ecosystem services for downstream communities like mitigating extreme flows, filtering water, and stabilizing soil.

Unfortunately, Oregon ash trees have come under threat from the emerald ash borer (EAB). Researchers recently spotted EAB in the Portland Metro Area. EABs are likely to expand through the entire Willamette Valley. The EAB presents an existential threat to native ash trees. Widespread losses of riparian ash trees could increase stream temperatures and decrease the habitat quality in riparian ecosystems.

Recognizing the threat EABs pose, the Watershed Council has chosen not to include ash species in riparian plantings and is pursuing opportunities to plant new species in current ash groves to fill in gaps left by their future loss. By planting other tree species underneath current ash groves, they will be ready to replace riparian gaps left by dying ash trees. This proactive forest management will allow us to maintain high-quality forests that provide benefits like providing habitat, decreasing erosion, and lowering stream temperatures.