Rock Creek Restoration

Rock Creek begins in the Corvallis Watershed and flows into the Marys. It is an important watershed for many Marys River watershed residents because it provides Corvallis with drinking water. Although Rock Creek has high habitat potential for resident cutthroat trout and migratory steelhead and Pacific lamprey, an upstream dam and fish passage barriers block fish migration and stop natural sediment transport through the watershed. The Watershed Council has worked to restore in-stream habitat and fish passage in Rock Creek by installing large woody debris structures, planting streamside trees, and addressing fish passage barriers.

The Marys River Watershed Council received support from the City of Corvallis, U.S. Forest Service, Siuslaw National Forest, Oregon Watershed Enhancement Board, Meyer Memorial Trust, U.S. Fish and Wildlife Service, Oregon Department of Fish and Wildlife, Shiver River LLC, Starker Forests, Bio-Surveys LLC, Trask Design and Construction, River Design Group, Benton County, and private landowners. The project increased habitat for aquatic species, improved water quality, and addressed extremes in flow and temperature for downstream neighbors.

Dams on Rock Creek prevent sediments and large woody debris from moving downstream to replace material lost through erosion and decay. Loss of upstream material inputs allows gravel beds to erode to bedrock, which significantly lowers habitat quality for aquatic species. Exposed bedrock increases water temperatures and does not have the nooks and crannies that slow flows, capture food, and provide shelter for aquatic organisms.

To address these concerns, the Watershed Council installed 44 large woody debris structures. The log placement will benefit aquatic species and downstream communities and address the effects of upstream sediment loss. These installations help address the downstream effects of the dam by providing flood mitigation, temperature control, and aquatic habitat. Woody debris structures help slow and spread water across the stream channel and floodplain, which can decrease flood impact and increase groundwater absorption. Large woody debris helps address habitat loss by capturing and retaining gravel to build more complex habitats for use by species like cutthroat trout and steelhead.

Alongside large woody debris placement, the Watershed Council planted 2 acres of riparian trees along the banks of the creek. These riparian plantings decrease water temperatures and provide habitat and forage for aquatic species. Riparian plantings decrease the water temperature by fully shading the creek and the surrounding floodplain. Trees also provide forage for aquatic macroinvertebrates, which benefits the rest of the aquatic food web. Riparian trees allow small creeks like Rock Creek to have a higher fish density per cubic foot of water than larger rivers like the Willamette because they can fully cover the streambed and provide proportionally more food. An additional benefit of the riparian plantings is that they become a source of new large woody debris as they mature and fall into the creek.

Four ineffective culverts and two impassable dams impede fish passage on Rock Creek. This hurts fish like cutthroat trout and steelhead who attempt to move upstream to lay eggs in the winter and to avoid rising water temperatures in the summer. Limitations on natural movement can artificially decrease population viability and size by isolating segments of the population from each other and from important winter and summer refugia The Watershed Council worked with our partners to reestablish fish passage by replacing culverts and installing fish ladders. The project opened an additional 8 miles of stream to migratory aquatic species. After the removal of passage barriers, cutthroat trout populations in the creek increased, and their distribution throughout the watershed normalized, indicating they were able to reach upstream reaches for thermal refugia and spawning. The fish passage barrier removal also helped maximize the benefits of riparian planting and large woody debris supplementation.