The Muddy River is a stream, about long, southeast of

Mount St. Helens Mount St. Helens (known as Lawetlat'la to the indigenous Cowlitz people, and Loowit or Louwala-Clough to the Klickitat) is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United St ...

in the U.S. state of

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

. The Muddy River flows south–southeast and joins the Lewis River just above the

Swift Reservoir Swift Reservoir is a reservoir on the Lewis River in the U.S. state of Washington. It is located in Skamania County. It was created in 1958 with the construction of Swift Dam. See also *List of lakes in Washington (state) *List of dams in the C ...

. The Lewis River flows west and is a tributary to the Columbia River. The east flank of Mount St. Helens is within the watershed of Muddy Creek. During the

1980 eruption of Mount St. Helens On March 27, 1980, a series of volcanic explosions and pyroclastic flows began at Mount St. Helens in Skamania County, Washington, United States. A series of phreatic blasts occurred from the summit and escalated until a major explosive er ...

, lahars (volcanically-induced mud and

debris flows Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generall ...

) swept through its channel. About of stream channels around the volcano were affected by lahars. The

United States Forest Service The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency in ...

maintains the Muddy River Picnic Site, next to the river and to Forest Road 25 in the

Gifford Pinchot National Forest Gifford Pinchot National Forest is a National Forest located in southern Washington, managed by the United States Forest Service. With an area of 1.32 million acres (5300 km2), it extends 116 km along the western slopes of Cascade Ran ...

. Trails cross the river on its upper reaches.

Course

Muddy River originates at about the level on the southeast side of Mount St. Helens in the Cascade Range. The river source is within Mount St. Helens National Volcanic Monument and Gifford Pinchot National Forest. Shoestring Glacier is to the

right Rights are legal, social, or ethical principles of freedom or entitlement; that is, rights are the fundamental normative rules about what is allowed of people or owed to people according to some legal system, social convention, or ethical ...

and East Dome is to the left. Flowing southeast down steep slopes, the river curves sharply to the northeast just beyond the level of the volcano. Here the river crosses Forest Road 83 and passes the Ape Canyon Trailhead and the Lava Canyon Interpretive Site, both on the left, before entering Muddy River Gorge.

River mile A river mile is a measure of distance in miles along a river from its mouth. River mile numbers begin at zero and increase further upstream. The corresponding metric unit using kilometers is the river kilometer. They are analogous to vehicle roa ...

s are marked on the map quadrangles for the lower Muddy River and the Lewis River. Flowing northeast through the gorge, the stream plunges over three waterfalls before emerging from the narrows and curving sharply again to the southeast. Here Crane Lake is on the left, Smith Creek enters from the left, and Smith Creek Trailhead is on the right. Slightly downstream of the trailhead, the river leaves the national volcanic monument but remains in the national forest. At about the level, Clearwater Creek enters from the left. Turning south, the river descends less rapidly, passing under Forest Road 25 and then receiving Clear Creek from the left about from the mouth. At the road crossing, Muddy Creek Picnic Site is on the left. Below the confluence with Clear Creek, the river meanders through Cedar Flats, leaves the national forest slightly more than a mile from the mouth, and passes a

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

(USGS) stream gauge, on the left from the mouth. Muddy River enters the Lewis River about from the larger stream's mouth on the Columbia River.

Discharge

The USGS monitors the flow of Muddy River at a station upstream of the confluence with the Lewis River. The average flow of the river during 54

water year A water year (also called ''hydrological year'', ''discharge year'' or ''flow year'') is a term commonly used in hydrology to describe a time period of 12 months for which precipitation totals are measured. Its beginning differs from the calendar ...

s, including 1984–2011, is . The maximum flow recorded was on February 8, 1996, and the minimum flow was on December 5–7, 1929. The high flow in 1996 was associated with general flooding in the Pacific Northwest during the Willamette Valley Flood of 1996. A flood destroyed an earlier version of the gauge in January 1974. The existing gauge began recording data in October 1983. The mudflow flood related to the eruption of Mount St. Helens in 1980 occurred outside the period of record for either gauge.

References

External links

USGS CVO maps, data, and resources related to the Muddy River and the eruption of Mt. St. Helens
{{authority control Rivers of Washington (state) Rivers of Skamania County, Washington Gifford Pinchot National Forest