North Fork Toutle River
Encyclopedia
Toutle River
The Toutle River is a river in southwestern Washington State, in the Pacific Northwest region of the United States. It rises in two forks on the flanks of Mount St. Helens and joins the Cowlitz River near Castle Rock.-Eruption of Mount St. Helens:...
in the southwestern Washington in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. The river has its headwaters near Spirit Lake
Spirit Lake (Washington)
Spirit Lake is a lake north of Mount St. Helens in Washington State. The lake was a popular tourist destination for many years until the 1980 eruption of Mount St. Helens. With the eruption and resulting megatsunami, thousands of trees were torn from the surrounding hillside after lake water was...
, on the north side of Mount St. Helens
Mount St. Helens
Mount St. Helens is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It is south of Seattle, Washington and northeast of Portland, Oregon. Mount St. Helens takes its English name from the British diplomat Lord St Helens, a...
, and flows about 30 miles (48.3 km) to the Toutle River, 22 miles (35.4 km) upstream of its confluence with the Columbia River
Columbia River
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...
. The largest tributary is the Green River
Green River (North Fork Toutle River)
The Green River is the largest tributary of the North Fork Toutle River in the U.S. state of Washington. Situated near Mount Saint Helens in the Cascade Range in the southern part of the state, it flows generally west through wild forested valleys for...
, which joins near the unincorporated town of Toutle
Toutle, Washington
Toutle is an unincorporated community in Cowlitz County, Washington, United States. Toutle is located approximately ten miles east on SR 504 from exit 49 of I-5. Toutle is not very far from the well-known Mount St. Helens...
.
1980 eruption of Mount St. Helens
The 1980 eruption of Mount St. Helens, a stratovolcano located in Washington state, in the United States, was a major volcanic eruption. The eruption was the only significant one to occur in the contiguous 48 U.S. states since the 1915 eruption of Lassen Peak in California...
, which coated the valley with ash and filled it with successive mudflows. The result of the eruption was that many hillsides were stripped of forest, and as a result erosion has increased dramatically and the North Fork is now extremely laden with sediment. Previously, Spirit Lake was the source of the river, but eruptions blocked the outlet and Spirit Lake no longer drains directly into the North Fork; instead, a tunnel was excavated in 1985 to connect the lake with South Coldwater Creek, a tributary of the North Fork. Once a mature river, the North Fork has transformed into a braided stream of relatively young origin, and its valley floor is less than three decades old. The Toutle River Sediment Retention Structure
Toutle River Sediment Retention Structure
The Sediment Retention Structure is a , earthen dam on the North Fork of the Toutle River in Washington. Its construction was completed by the US Army Corps of Engineers in 1989. Its purpose is to retain sediment created since the 1980 eruption of Mount St...
was built by the U.S. Army Corps of Engineers on the river in 1989 to prevent this sediment from traveling downstream and clogging the shipping channel of the Columbia River
Columbia River
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...
.
The upper part of the North Fork Toutle River watershed was redirected to the crater of Mount St. Helens itself until 1982. The river's headstreams begin on a volcanic ash deposit roughly 3 miles (4.8 km) long and 200 feet (61 m) deep, which is the source of much of the excess sediment.