| Alsea River | |
| Name Etymology: | Alsea tribe of Native Americans[1] |
| Map Size: | 300 |
| Pushpin Map: | USA Oregon |
| Pushpin Map Size: | 300 |
| Pushpin Map Caption: | Location of the mouth of the Alsea River in Oregon |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | Oregon |
| Subdivision Type4: | County |
| Subdivision Name4: | Benton County, Lincoln County |
| Length: | 48.5miles |
| Discharge1 Location: | near Tidewater, Oregon, 21miles from mouth[2] [3] |
| Discharge1 Min: | 45cuft/s |
| Discharge1 Avg: | 1459cuft/s[4] [5] |
| Discharge1 Max: | 41800cuft/s |
| Source1 Location: | Lane County, Oregon |
| Source1 Coordinates: | 44.3761°N -123.6025°W |
| Source1 Elevation: | 278feet[6] |
| Mouth: | Alsea Bay, Pacific Ocean |
| Mouth Location: | Waldport, Lincoln County, Oregon |
| Mouth Coordinates: | 44.4225°N -124.0808°W |
| Mouth Elevation: | 0feet[7] |
| Basin Size: | 466sqmi[8] |
The Alsea River flows 48.5miles from Alsea, an unincorporated community in the coastal mountains of the U.S. state of Oregon, to the Pacific Ocean near the city of Waldport. It begins at the confluence of the North Fork Alsea River and the South Fork Alsea River and ends in Alsea Bay, a wide estuary at Waldport.[9] The river flows generally west-northwest in a winding course through the mountains of southern Benton and Lincoln counties, passing near the unincorporated community of Tidewater and through the Siuslaw National Forest. Its drainage basin extends into Lane County, along the headwaters of the South Fork Alsea River.
The Alsea River supports runs of chinook and coho salmon, as well as steelhead and coastal cutthroat trout. The Alsea River Fish Hatchery is along one of its tributaries, the North Fork Alsea River.
The Alsea River begins in the Central Oregon Coast Range near the unincorporated community of Alsea, and flows generally west about 48.5miles to the Pacific Ocean at Waldport, on the west coast of the United States. Formed by the confluence of the South Fork Alsea River and the North Fork Alsea River, the stream meanders through the Siuslaw National Forest for all but the last 6miles of its course. Oregon Route 34 follows the river closely, crossing it once about 8miles from the mouth.[9]
During its first 1miles or so, the river receives Cathcart Creek, Roberts Creek, and Mill Creek, all from the right, and passes Mill Creek Boat Landing on the right. Oregon Route 34 parallels the river on the north; that is, on the right facing downstream. Here the river begins a long, roughly U-shaped loop around the south end of Digger Mountain, which rises to 1220feet above sea level at coordinates 44.3573°N -123.7048°W.[10] Along this stretch, which is about 9miles long, the river passes under Hayden Covered Bridge; receives Schoolhouse Creek from the right, Birch Creek from the left, and Narrows Creek and Maltby Creek from the right, passes Campbell Boat Landing on the right and Salmonberry Boat Landing on the left, goes under Salmonberry Road, receives Salmonberry Creek from the left, passes Missouri Bend Recreation Site and Boat Ramp on the left, and receives Benner Creek from the left and Digger Creek from the right.[9] Slightly west of the mountain, about 33.5miles from the mouth, the river leaves Benton County, and enters Lincoln County.[9]
Passing Little Digger Mountain on the right, the river receives Fall Creek from the right, Cow Creek and Minotti Creek from the left, and Wolf Creek, Phillips Creek, Cedar Creek, and Butter Creek from the right as it passes Trenholm Saddle, a mountain gap at coordinates 44.3876°N -123.7523°W[11] on the right about 31miles from the mouth. About 2miles later, the river begins another U-shaped loop of about 9miles around the south end of Stoney Mountain, which rises to 1020feet above sea level.[9] [12]
Flowing around Stoney Mountain, the Alsea River receives Five Rivers and Lake Creek from the left, passes Blackberry Campground on the left, receives Grass Creek and Brush Creek from the left and Schoolhouse Creek from the right, passes Mike Bauer Picnic Grounds on the right and, shortly thereafter, a USGS gauging station on the right 21miles from the mouth. About 1miles further downstream, the river passes Slide Campground on the right before entering Hellion Rapids at coordinates 44.3923°N -123.8334°W.[13] Downstream of the rapids, the river receives Scott Creek, Slide Creek, and Hatchery Creek, all from the right, and Line Creek from the left before reaching the unincorporated community of Tidewater, about 12miles from the mouth.[9]
Between Tidewater and Alsea Bay, the river receives Mill Creek and Squaw Creek from the right, Canal Creek from the left, Risley Creek from the right, passes under Oregon Route 34, which then parallels the river on the south or left, and receives Arnold Creek from the left at about 8miles from the mouth. About 2miles later, it leaves the Siuslaw National Forest. Shortly thereafter, it receives Southworth Creek and Constantine Creek from the left and Drift Creek from the right. It receives Eckman Creek from the left, passes W. B. Nelson State Recreation Site on the left about 3miles from the mouth and enters Alsea Bay. As part of the bay, it receives Lint Creek from the left, passes Waldport on the left, flows under U.S. Route 101, and enters the Pacific Ocean at the mouth of the bay.[9]