Willamette
Willamette is a mapped river in the YearMaps hydrographic index. River courses organise settlement, agriculture and frontier-making more durably than any political boundary, and this reach is indexed against the dams, lakes and cities within its catchment.
- Feature Class
- River
- Coordinates
- 44.67°, -123.06°
About Willamette
The Willamette River ( wi-LAM-it) is a major tributary of the Columbia River, accounting for 12 to 15 percent of the Columbia's flow. The Willamette's main stem is 187 miles (301 km) long, lying entirely in northwestern Oregon in the United States. Flowing northward between the Oregon Coast Range and the Cascade Range, the river and its tributaries form the Willamette Valley, a basin that contains two-thirds of Oregon's population, including the state capital, Salem, and the state's largest city, Portland, which surrounds the Willamette's mouth at the Columbia.
Originally created by plate tectonics about 35 million years ago and subsequently altered by volcanism and erosion, the river's drainage basin was significantly modified by the Missoula Floods at the end of the most recent ice age. Humans began living in the watershed over 10,000 years ago. There were once many tribal villages along the lower river and in the area around its mouth on the Columbia. Indigenous peoples lived throughout the upper reaches of the basin as well.
Encyclopedic summary adapted from Wikipedia: Willamette River (CC BY-SA 4.0).
Willamette in Depth
Course
The upper tributaries of the Willamette originate in the mountains south and southeast of Eugene, Oregon. Formed by the confluence of the Middle Fork Willamette River and the Coast Fork Willamette River near Springfield, the main stem Willamette meanders generally north for 187 miles (301 km) to the Columbia River. The river's two most significant course deviations occur at Newberg, where it turns sharply east, and Canby, where it turns north again. Near its mouth north of downtown Portland, the river splits into two channels that flow around Sauvie Island, both of which are navigable and maintained by the United States Army Corps of Engineers.
History
For at least 10,000 years, a variety of indigenous peoples populated the Willamette Valley. These included the Kalapuya, the Chinook, and the Clackamas. The territory of the Clackamas encompassed the northeastern portion of the basin, including the Clackamas River (with which their name is shared). Although it is unclear exactly when, the territory of the Chinook once extended across the northern part of the watershed, through the Columbia River valley.
Geology
The Willamette River basin was created primarily by plate tectonics and volcanism and was altered by erosion and sedimentation, including deposits from enormous glacial floods as recent as 13,000 years ago. The oldest rocks beneath the Willamette Valley are the Siletz River Volcanics. About 35 million years ago, these rocks were subducted by the Farallon Plate beneath the North American Plate, creating the forearc basin that would later become the Willamette Valley. The valley was initially part of the continental shelf, rather than a separate inland sea. Many layers of marine deposits formed in the forearc basin and cover the older Siletz River Volcanics. About 20 to 16 million years ago, uplift formed the Coast Range and separated the basin from the Pacific Ocean.
Sections adapted from Wikipedia: Willamette River (CC BY-SA 4.0).
Willamette: Key Facts
| Length | 301 km |
|---|---|
| Average discharge | 900 m³/s |
| Drainage basin | 29,730 km² |
| Mouth | Columbia River |
| Drainage system | Willamette River basin |
| Tributaries | Santiam River, Columbia Slough, Molalla River, Luckiamute River, Clackamas River, McKenzie River, Calapooia River, Middle Fork Willamette River |
Facts from Wikidata Q131071 (CC0).
Major River Dossiers
Hand-written studies of the great river systems of history.
Connected Reaches
Nearby watercourses in the same drainage network.
Water Bodies in the Catchment
Settlements Along the Reach
Hydraulic Infrastructure Nearby
Surrounding Terrain
Willamette: Quick Answers
- Where is Willamette?
- Willamette is located in United States, at 44.6662° N, 123.0600° W.
- Are there dams on the Willamette?
- No dam on the Willamette is recorded in the YearMaps dam index, which covers major structures only.