Oak Creek | Corvallis Sustainability Coalition

Oak Creek is named for the Oregon White Oak savanna and woodlands that once flourished in this watershed.

Oak Creek is the least developed of the watersheds in Corvallis, even though portions of its downstream corridor are among its most highly developed. It is the largest watershed for Corvallis, even though most of it is outside of the municipal boundaries.

Watch this 4-minute video to learn where Oak Creek flows.

Pre-1800 – In the Kalapuya era, the Oak Creek watershed was burned annually or biannually. The extensive beaver-created wetlands and riparian zones did not burn from the low-impact burns, due to the high moisture levels of the soils and plants. Outside of those moist areas was dry prairie. The grasses and small woody plants burned while the large Oregon White Oak trees had evolved to resist low-impact burns. The upland forests of Oak Creek that are common today, did not exist prior to 1850 due to the burns. The lowlands were primarily dry prairie or wetlands controlled by beaver dams and ponds. Oak Creek was highly braided with many shallow corridors connecting a series of wetlands. There was no discernible single channel. The plentiful beaver dams kept the waterway full even during long, severe droughts.

1800s – With the settlement of Euro-Americans, the beavers were trapped to extinction, and the wetland-creating dams were destroyed. The creek beds were deeply incised by the faster flowing creek water and further trenched by farmers as drainage channels. As the creek beds were scoured and trenched, the water table dropped with it, further drying out the wetlands. Later in the 1800s, farmers installed agricultural tiles (underground drainage pipes) in their farmland to further dry out the land, leaving mostly arid land in the summer. Oak Creek had six water wheel-driven mills on what is now OSU agricultural land. In the late 19th century, development in lower Oak Creek around the OSU Campus transformed farmland into residential and institutional property. All of Oak Creek from McCulloch Peak (highest source of Oak Creek) was a hydrological system unrecognizable in its current form, function and ecological health from what it was in the 1700s.

1900s – The upper reaches of the watershed grew into forests. The sloping piedmont and flatland became mostly farmland or low-density residential. OSU gained ownership of 40% of the watershed for forestry, agriculture and the campus. Most of the watershed is in Benton County, with the lower portion in the City of Corvallis. The area around campus that was not agricultural land became dense residential and institutional development. Small dams were built along the single, deeply incised corridor. During this era, the lower portions of the creek became a quick-response, high-speed stormwater conveyance system, fed by stormwater pipes, which were, in turn fed by roads, buildings, paved sidewalks and other paved surfaces. The stormwater currently drains directly into Oak Creek from piped outfalls, untreated and unrestricted throughout the lower corridor. Many of the tributaries that existed in the 1800s downstream of what is now Walnut Blvd. and 53^rd have been filled in and built over. Many OSU buildings were built over filled in tributaries, including the Peavey Building and Gill Auditorium. Oak Creek further devolved in the 1900s into a hydrological system unrecognizable in its form, function and ecological health from what it was in the 1800s.

2000s – While there is growing understanding of the need to regenerate healthy, productive creeks, the top City priority for Lower Oak Creek is that it remains a rapid response, high-speed stormwater conveyance system. One dam was removed on Oak Creek in 2007 on the OSU campus near 35^th Street. One dam remains on Oak Creek to serve the OSU Dairy Farm. To learn more about dams on Oak Creek, watch this 9-minute video, “Dammed Oak Creek”.

Greater pressures to increase housing development, build more and wider roads and large-capacity stormwater pipes and culverts is a recipe for further degeneration of creek health and functionality. The City’s Long-term Transportation Plan has significantly more major arterial roads cutting through existing agricultural land, crossing Oak Creek in multiple places. Vegetated riparian zones have been slightly expanded with federal grants, and there have been two recent culvert enlargements installed to provide healthier creek flows. While there have been small regenerative gains, the larger hydrological and ecological health conditions of the creek continue to degrade from added development and impervious surfaces that feed polluted stormwater directly into the creek.

Oak Creek Stats

8,199 Acres – Oak Creek covers about 4% of the Marys River watershed.
15 Miles Long – The stream length is measured from its highest and furthest perennial flow at McCulloch Peak down to its outfall into the Marys River, plus the length of its main tributaries
Highest Point – McCulloch Peak at 2,155 above sea level
Lowest Point – Confluence with the Marys River across from Avery Park at 210 feet above sea level
Main Tributaries – Over 125 tributaries feed Oak Creek from the highlands. The principal tributaries are the West Branch, the East Branch, Alder, Skunk, Mulkey, Russian and Lamprey Creeks
Flow Rates – 0.5 cubic feet per second (CFS) in summer, 5 CFS in winter, more than 200 CFS at flood stage
Ownership – 40% OSU, 55% private, 5% City or County
Paved or built impervious surfaces – Seven percent of the watershed is covered with pavement or buildings, and 11% of the watershed is considered urban.
Forest Cover – 36% is covered with forest.
More than 25 creek bridges – Oak Creek is crossed by a road or pedestrian bridge about every one-half of a mile.
Pollution Status – State studies have found the creek has excessively high temperature and bacterial counts, resulting in 303d state-listed violations.

Mills – Six known mills were built in the Oak Creek watershed in the 1800s. Three were lumber mills, and three were carding mills.
Dams – There is one true dam remaining in Oak Creek. It is located to the SE of the intersection of Harrison Blvd. and 53^rd Street. It is a “Pop-Up” dam owned and operated under State permit by OSU to provide irrigation water to the OSU Dairy Farm during the dry months. Ironically, OSU has the permit to withdraw more water per day than Oak Creek normally flows in the summer. Fortunately, OSU has never used its full permitted use and allowed Oak Creek to run dry. The dam is lowered during the wet season to allow unobstructed creek flow.
Fish Barrier – The last remaining human-made fish barrier other than the OSU Dairy Farm Pop-Up dam is located in McDonald Forest, just upstream from the Oak Creek Drive entrance to the forest. It is a concrete structure that was built decades ago for testing purposes. It is rarely used for that purpose, but it still restricts fish passage. Other fish passages on Oak Creek have been removed in the past 15 years at great expense. An irrigation dam downstream of 35^th Street was removed on OSU property in 2007. A raised culvert was re-engineered for fish passage underneath Philomath Blvd. east of Brooklane Drive by ODOT. Another culvert adjacent to the covered Irish Bend Bridge and the OSU Dairy Farm was replaced to allow fish passage.
Fish in Oak Creek – Despite all of the human impact, small numbers of native fish continue to survive in this harsh environment, though in non-sustainable low populations. These species include cutthroat trout, Pacific lamprey, brook lamprey, mountain whitefish, rainbow trout, large-scale sucker, mountain sucker, speckled dace, redside shiners, reticulate sculpin and torrent sculpin. During Marys River flooding, chinook salmon juveniles find refuge in the lower Oak Creek floodplain.
Beaver – Beaver and beaver dams have been found in recent years and are common in the mid-corridor region of Oak Creek, where development is minimal and the topography is relatively level. Beaver dams are especially common on Oak Creek tributaries such as Mulkey and Lamprey Creeks.

Watershed Boundaries

Northern Boundary – McCulloch Peak east to Dimple Hill, south and then east towards the west and south sides of Witham Oaks Hill
Western Boundary – The western watershed boundary is Bald Hill, west and north sides to Mulkey Ridge, then north to McCulloch Peak
Southern Boundary – A barely discernable ridge borders the North Branch Dunawi Creek watershed from NW to SE.
Eastern Boundary – The eastern headwaters on the south side of Dimple Hill form a border with the Dixon Creek watershed, traversing from NW to SE toward Witham Hill. In the lowlands starting at Harrison Blvd., a barely discernable ridgeline continues to traverse from the NW to the SE through OSU Campus toward the Marys River, across from Avery Park.

Water Action Team Activities in Oak Creek

Partnered with OSU Engineering School to conduct studies and design mitigation strategies to improve water quality and reduce the impact of the unnatural rapid response stormwater system that drains into Oak Creek from OSU campus
Produced a 3-D glass model of the Oak Creek Watershed as an educational tool
Led two bike tours of Oak Creek, as well as two hiking tours to the highest source of Oak Creek on McCulloch Mountain
Published an article in “Wild in the Willamette” to familiarize readers with the wonders of Oak Creek
Discovered and researched the Lost Creeks of Oak Creek
Partnered with OSU, the Marys River Watershed Council, the Marys Peak Group of the Sierra Club, the Columbia River Inter-Tribal Watershed Council and Freshwaters Illustrated to have a previously named 3-mile Oak Creek tributary named as “Lamprey Creek” – the first creek in the United States names after this most ancient species of fish (450 million years old) and one which spawns in Oak Creek. We co-sponsored the Lamprey Creek Awakening Ceremony.
Produced two videos about Oak Creek – “Oak Creek in Corvallis: Journey of an Ancient Stream” and “Dammed Oak Creek”
Initiated surveys of unnamed tributaries upstream of Walnut Blvd. Seven of 25 surveys have been completed and will be posted on a digital GIS map.

Oak Creek Stats

Watershed Boundaries

Water Action Team Activities in Oak Creek

Resources

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