Global InformationCourse of the Willamette River information
| Willamette | |
|---|---|
 Oregon City Bridge and Willamette Falls | |
 A map of the Willamette River, its drainage basin, major tributaries and major cities | |
  Location of the mouth of the Willamette River in Oregon | |
| Etymology | From a Clackamas Indian village name[2] |
| Location | |
| Country | United States |
| State | Oregon |
| Physical characteristics | |
| Source | Confluence of Middle Fork Willamette River and Coast Fork Willamette River |
| • location | near Eugene, Lane County, Oregon |
| • coordinates | 44°01′23″N 123°01′25″W / 44.02306°N 123.02361°W[1] |
| • elevation | 438 ft (134 m)[1] |
| Mouth | Columbia River |
• location | Portland, Multnomah County, Oregon |
• coordinates | 45°39′10″N 122°45′53″W / 45.65278°N 122.76472°W[1] |
• elevation | 10 ft (3.0 m)[1] |
| Length | 187 mi (301 km)[3] |
| Basin size | 11,100 sq mi (29,000 km2)[4] |
| Discharge | |
| • location | Morrison Bridge, Portland, 12.8 miles (20.6 km) from mouth[5] |
| • average | 33,800 cu ft/s (960 m3/s)[5] |
The Willamette River is a 187-mile (301 km) tributary of the Columbia River in the U.S. state of Oregon. The upper tributaries of the Willamette originate in mountains south and southeast of the twin cities of Eugene and Springfield. Formed by the confluence of the Middle Fork Willamette River and Coast Fork Willamette River near Springfield, the main stem meanders generally north from source to mouth. The river's two most significant course deviations occur at Newberg, where the stream turns sharply east, and about 18 miles (29 km) downriver from Newberg, where it turns north again. Near its mouth, the river splits into two channels that flow around Sauvie Island. The main channel enters the Columbia about 101 miles (163 km) from the larger stream's mouth on the Pacific Ocean, and the smaller Multnomah Channel enters the Columbia about 14.5 miles (23.3 km) further downstream near St. Helens in Columbia County.
Incorporated Cities along the Willamette's course include Springfield and Eugene in Lane County; Harrisburg in Linn County; Corvallis in Benton County; Albany in Linn and Benton counties; Independence in Polk County; Salem in Marion and Polk Counties; Keizer in Marion County; Newberg in Yamhill County; Oregon City, West Linn, Milwaukie, and Lake Oswego in Clackamas County (Small portions of the later two extend into Multnomah County), and Portland in Multnomah County. (Parts of Portland are also in Washington County, but the Willamette never makes contact with Washington County.) Significant tributaries include the McKenzie, Long Tom, Marys, Calapooia, Santiam, Luckiamute, Yamhill, Molalla, Tualatin, and Clackamas rivers.
Arising at 438 feet (134 m) above sea level, the river loses 428 feet (130 m) in elevation between source and mouth or about 2.3 feet per mile (43 cm per km). The gradient is slightly steeper from the source to Albany than from Albany to Oregon City. At Willamette Falls, the river plunges about 40 feet (12 m). For the rest of its course, the river is extremely low-gradient and is influenced by Pacific Ocean tidal effects from the Columbia. The main stem of the Willamette varies in width from about 330 to 660 feet (100 to 200 m).
- ^ a b c d Cite error: The named reference
gniswas invoked but never defined (see the help page). - ^ Bright, p. 567
- ^ "The River". Willamette Riverkeeper. Archived from the original on October 8, 2006. Retrieved June 26, 2010.
- ^ "National Water Information System: USGS 14211720 Willamette River at Portland". United States Geological Survey. 2008. Retrieved June 26, 2010.
- ^ a b Loy, et al., pp. 164–65